April 9-13, 2012 | San Francisco
Meeting Chairs: Lara A. Estroff, Jun Liu, Kornelius Nielsch, Kazumi Wada
Nanodiamond (ND) with stable and high-yield photoluminescence from color centers is considered as an advanced material for production of both single photon emitters  as well as bright biolables , depending on the number of centers in a single diamond particle. The development of luminescent NDs for these applications is mostly focusing on high-pressure high-temperature (HPHT) diamonds containing nitrogen-vacancy (NV) color centers. An â?oindirectâ? production of the luminescent NDs is used for this purpose, i.e. micro-scale diamond crystals are synthesized fist, and then are milled down to required nano-sized particles. A NV luminescence intensity in ND particles is controlled by special post-synthesis treatments of the HPHT diamond crystals enabling to increase the NV concentration in them. In our work we have studied aspects of controllable formation of luminescent centers in direct production of nanodiamond particles using detonation shock-wave-assisted synthesis as well as CVD synthesis. Representative classes of NDs produced by detonation shock wave conversion of diferent carbon precursor materials have been systematically studied. We demonstrate that the density of NV centers in nanodiamond particles can be controlled through a proper selection of the carbon precursor material. A controllable production of SiV color centers during microwave-plasma CVD growth of isolated diamond nanoparticles on Cu substrate was realized using a plasma-etched Si plate as a dopant source. This work was supported by Russian Ministry of Education and Science under the Contract no. P925, and RFBR grant no. 11-02-01432.  J. Tisler, G. Balasubramanian, B. Naydenov, R. Kolesov, B. Grotz, R. Reuter, J.-P. Boudou, P. A. Curmi, M. Sennour, A. Thorel, M. Borsch, K. Aulenbacher, R. Erdmann, P. R. Hemmer, F. Jelezko, J.Wrachtrup, ACS Nano 2009, 3, 1959-1965.  A. M. Schrand, S. C. Hens, and O. A. Shenderova, Critical Reviews in Solid State and Materials Sciences 2009, 34, 18â?"74.
Fluorescent Nanodiamond (FND) offers a promising platform for many biological applications including imaging probes and drug delivery. This is due to the potential to encapsulate photostable luminescent vacancy related defects into nanoscale diamond crystals which are biologically compatible and easy to functionalize. Density functional tight binding simulations have predicted the preferable positioning of nitrogen at the surface of NDs, where formation of NV defects is unlikely to occur. In this study, we investigate the silicon-vacancy (SiV) defect an alternative center in ND. SiV has been investigated primarily in the form of thin chemical vapor deposited (CVD) films and single crystal NDs, with much less attention in the form of isolated nanocrystals which are particularly relevant as biolabels or as a drug-delivery platform. Moreover, the development of biosensing or drug-delivery platforms may benefit from precise spatial control of FNDs for very specific therapeutic dosing or release kinetics. FNDs were produced by incorporation of Si-V defect color centers using microwave plasma chemical vapor deposition technique in weakly agglomerated sub-10nm NDs. The direct placement and manipulation (control of size, shape and chemical functionality) of brightly fluorescent NDs was done by scanning probe â?oDip Penâ? Nanolithography (DPN). Raman and room temperature photoluminescence measurements were used to confirm ND and the corresponding defect centers. Particle size was characterized by atomic force microscopy (AFM). Fluorescence microscopy combined with AFM will be used to map the fluorescence for isolated ND particles. We explore the mechanism of ink transport, suitable ND inks, and parameters (such as temperature, humidity, dwell time etc) that affect the ND writing. The ND array was characterized by Raman mapping. The SiV incorporated NDs readily exhibit strong narrow band room temperature fluorescence, even for sub-10 nm size particles. This is in contrast to the well-studied nitrogen-vacancy center (NV) in diamond which is reported to be relatively unstable and have low probability for incorporation of centers in sub-10 nm ND. The potential for further enhancement of SiV emission in diamond nanocrystals is demonstrated through controlled doping of nitrogen. The concentration of SiV centers was estimated by integrated intensity of the absorption peak obtained by UV-Vis spectroscopy. Electron paramagnetic resonance is used to measure the concentration and provide identification of the charged states of Si and N-related defect centers. In conclusion, enhanced room temperature photostable luminescence of SiV center offers a viable alternative to nitrogen-related defects as a fluorescent biomarker of clinically-relevant sub-10 nm size regime. We expect the DPN technique will allow superior ND feature size and pattern resolution, thus potentially providing more precise control of therapeutic dosing, single-particle tracking.
Nanodiamods (NDs) are considered to be a promising candidate for cellular marker applications . For practical use as a cellular marker there is the need for a high yield production method of small highly luminescent NDs. NV centres are commonly created by high energy beam irradiation and subsequent annealing . In this work, we optimized the process for the creation of highly luminescent NDs We used high-pressure high-temperature (HPHT) NDs with an average size of 35 and 110 nm. Several implantation strategies with various energies were compared. Irradiation parameters were optimized for high yield production of up to 500 mg of NDs per irradiation. The effect of annealing was consequently studied on proton-irradiated samples using a wide range of temperatures and annealing times from 0.5 to 8 hours. After annealing, all samples were oxidized using a mixture of H2SO4 and HNO3 to remove graphite from the surface and to stabilize the NV- luminescence. Raman and photoluminescence properties were studied during each step of the process to monitor creation of GR1 centres, N-V centres, N-V-N centres and nondiamond carbon phases. We discuss the most suitable energy for NV production. Annealing showed to have significant effect on the NV luminescence. Samples showed correlation between NV PL intensity and the Raman quality. This study of various irradiation and annealing strategies shows the optimal conditions for high yield fabrication of highly luminescent NDs. Finally, we demonstrate optical detectability of NDs in living cell environment.  Y. Y. Hui, C. L. Cheng, H. C. Change, J. Phys. D: Appl. Phys., 2010, 43, 374021  V. M. Acosta, E. Bauch et al. Phys. Rev. B, 2009, 80, 115202
ND particles with colour centres are very promising for a wide range of applications. In order to construct a ND luminescence centre for a specific purpose, it is necessary to know as much as possible about the parameters influencing the NDsâ?T optical properties. We studied (using time dependent density functional theory) such parameters which mainly affect optical centresâ?T behaviour. We focused on the relevance of surface chemistry (hydrogen vs. oxygen/hydrogen termination) and the kind of the strange/defect atom in the centre (transition metals (Ni, Cr) vs. nonmetals (N)). For ND particles with NV- centres close to the hydrogen terminated surface region (resulting in a positive electrostatic potential of the surface layer), excited triplet electrons are localised on C atoms. In this configuration, the luminescence probability is significantly reduced or/and the NV- centres in hydrogen terminated ND particles are converted into NV0 centres. In the case of oxygen containing a ND termination, the layer with an excess of electrons is created (resulting in negative electrostatic potential of the surface layer). Electrons excited from NV- centres are partly localised at high-electronegative oxygen atoms preserving higher luminescence probability. ND particle NV0 centre luminiscence is practically not affected by the particleâ?Ts termination. Based on the mentioned phenomenon, we can expect the significance of nanodiamond particlesâ?T terminations on their functionality in spintronic applications. The excitations of non-metal atoms (nitrogen) containing centres are of 2p origin. In the case of NV centres, the number of states for deactivation between the ground state and the excited state is low. Metal atom containing centre excitations were of 3d origin and the number of states lying between basic and excited state is relatively large. This great variety of excited states can interact via spin-orbit coupling and lead to shorter lifetimes and deactivation. Luminescence is a very complex phenomenon. Generally, it holds true that after a charge transfer to the excited state, its surrounding is more or less deformed so that the excited state is affected by its vicinity, the state and luminescence properties depend on the local structure (bonding, states) particularities. Finally, we should stress that all of the systems examined were calculated by density functional theory (DFT) methods. From the agreement of the theoretically and experimentally obtained parameters, we can conclude that ND colour centres have a strongly local character. Working in this way with point effects (colour-centre luminescence), we were able to describe (using DFT methods) details of the systems on a truly fundamental level yielding very useful information about the systems.
Bright, nontoxic, photoluminescent (PL) nanoparticles are needed for bioimaging and biomedical diagnostics. The photoluminescent nanoparticles of nanodiamonds and carbon dots are alternatives to cytotoxic quantum dots and metallic nanoparticles. It has previously been shown by others that high energy bombardment of nanodiamonds produces photoluminescence emission colors that are either red or green. While it has been shown that carbon dots can be formed by graphite oxidation that photoluminescence in the visible range. In this work, we will explore PL nanostructures derived from graphitic species. For example, carbon-dot decorated nanodiamonds are formed by oxidizing detonation soot, while nanoplatelets and nanoribbons are formed by oxidizing graphitic carbon. Oxidizing micrographite, nanographite, highly oriented pyrolytic graphite, and onion-like-carbon produce colloidal supernatant solutions that photoluminesce across the visible wavelength range. These suspensions exhibit a blue-shift with either increasing reaction time or temperature. Transmission electron microscopy shows structural changes for different PL colored product suspensions.
For many years the practical applications of nanodiamond, ranging from uses as optical markers for biological imaging and drug delivery to quantum encryption and magnetometry [1,2], have fascinated the scientific community. Many of these applications call for specific structures like nitrogen or boron dopants in the diamond lattice, a tailored surface structure, well-defined diamond morphology or a lack of defects in the diamond lattice. The ability to characterize these structure in nanosized objects like nanodiamond at the atomic scale is therefore of extreme importance. Transmission electron microscopy (TEM) is in principle well-suited to this challenge, however, the problems of characterizing these minute particles (1-5 nm) are well known; nanodiamond can graphitize under high-intensity electron beam conditions, causing variations in the (surface) structure of the particles. On top of this, technical challenges make that only a small amount of work has combined atomic-resolution structural characterization of nanodiamond particles with local spectroscopy or elemental quantification [3,4]. By switching to lower microscope acceleration voltages in an aberration-corrected instrument, the (surface) structure of the nanodiamond particles remains stable, allowing both microscopy and spectroscopy to be performed at atomic resolution without the potential for damaging the particles during the measurement process. In this contribution, the possibilities of spatially resolved electron energy-loss spectroscopy (EELS) and high-resolution transmission electron microscopy (HRTEM) imaging performed at low acceleration voltage (80-120kV) in an aberration-corrected instrument will be demonstrated through several recent studies of nitrogen and boron doping in detonation nanodiamond and boron doping in CVD grown diamond. To investigate the local coordination of the dopants in the nanodiamond species, EELS fine structure analysis is combined with detailed density functional theory (DFT) calculations where needed. 1) Smith B.R. et al. (2007) Journal of Luminescence, 127, 260-263 2) Balasubramanian, G. et al. (2008) Nature 455, 648-U46 3) Iakoubovskii et al. (2008) Nanotechnology 19, 15 4) Turner, S. et al. (2009) Advanced Functional Materials, 19 (13), 2116-2124 5) S.T. gratefully acknowledges financial support from the Fund for Scientific Research Flanders (FWO).
Nanodiamond was the first material identified that carries an isotopic signature of formation prior to the solar system. However, the 2-nm average particle size has, to-date, precluded measurements of the isotopic composition of individual cosmic nanodiamonds. Thus, the specific formation conditions, e.g., shock transformation versus vapor condensation, remain controversial. In order to better constrain the origin of the nanodiamonds, we performed atom-by-atom analysis, using low voltage, aberration-corrected scanning transmission electron microscopy (STEM). Our results show that the nanodiamond residues, prepared by acid dissolution of meteorites, are actually two-phase mixtures of nanodiamond and glassy carbon. Dark-field STEM images reveal the disordered ring structure of the glassy carbon, and show that the spatial extent is well beyond the nanodiamond surfaces. This is confirmed by electron energy loss spectrum imaging at the C K-edge, which shows the spatially-resolved sp3 and sp2 bonding of the nanodiamonds and glassy carbon, respectively. Individual impurity atoms are also observed in the dark-field STEM images. The image intensity allows quantitative determination of the atomic number of individual impurities , which can in principle help constrain the particle origins. However, the majority of these impurities are observed to diffuse rapidly under the electron beam, and are likely surface impurities from the acid dissolution treatments, and not associated with the isotopic anomalies indicative of the extrasolar origin. The discovery of the co-existence of glassy carbon with nanodiamond raises the possibility a new formation scenario in which the two phases had a common origin as shockwave transformation products of preexisting organic molecules in the interstellar medium . Additional STEM imaging is planned to look for structural impurities related to the diamond and glassy carbon formation that might confirm this scenario. STEM imaging of synthetic detonation nanodiamonds for comparison is also planned.  Krivanek et al., Nature 464 (2010).  Stroud, et al., Astrophysical Journal Letters, 738:L27 (2011).
In the light of future nanodiamond (ND) applications it is important to investigate the surface functionalization. We therefore conducted a systematic quantum chemical study on the molecular structure and vibrational spectroscopy of hydroxylated NDs, and predicted isomer energies based on a combined molecular dynamics/Monte Carlo (MD/MC) method. As model system we chose octahedral NDs with 0, 1, 2, â?¦, 35 OH groups. As in our previous study on hydrogenated ND models , we found that isomer energies predicted by the self-consistent-charge density-functional tight-binding (SCC-DFTB) are in good quantitative agreement with B3LYP/6-31G(d) energies. For series showing a specific trimer patterns, IR spectra exhibit periodicity. The obtained structures and IR spectra will be discussed in detail. References  W. Li et al. ACS Nano 2010, 8, 4475-4486.
Novel nanocarbons such as fullerenes, nanotubes, and nanodiamonds reside at the cutting edge of nanoscience and technology. Along with chemical functionalization, geometrical constraints such defects within or at the surfaces of detonation nanodiamond crystallites, can modify the electronic states of the nanocarbon material. Understanding the effects of steric strain on electronic structure is critical to developing nanoelectronic applications based on these materials. This paper presents a fundamental study of how bond strain affects electronic structure in a benchmark series of novel sp3 carbon cage compounds. Adamantane, C10H16, the smallest diamondoid, and arguably the smallest nanodiamond crystallite, has carbon atoms essentially commensurate with diamond lattice positions and possesses by far the least bond strain of the series. We have systematically studied how small chemical and structural differences to the adamantane cage affect electronic structure. Twistane, like adamantane, is a C10H16 isomer, but the fixed twist conformation of the central ring introduces some strain into the cage. Octahedrane (CH)12 and cubane (CH)8 are considerably more strained, culminating in cubane where carbon-carbon bonds lie either parallel, or orthogonal to one another. Using gas-phase near-edge X-ray absorption fine structure spectroscopy to probe the unoccupied electronic states, we observe two major progressions across this series. First, a broad C-C Ïf* resonance in the absorption splits into two more narrow and intense resonances with increasing strain. Second, the first manifold of states previously associated with tertiary C-H Ïf* in the diamondoid series appears to broaden and shift to lower energy. This feature is more than twice as intense in cubane as in octahedrane, even though these two molecules have similar local carbon chemical environments, i.e. tertiary carbon, (CH)x. Thus, differences are entirely due to the shape of the molecules, and we suggest the larger intensity indicates a high degree of p-p interaction between parallel C-C bonds in cubane.
Diamond defect centers in nanodiamonds or close to surfaces turn out to be exquisite probes for external fields. Defect centers in nanodiamonds, for example, show efficient energy transfer when acceptor molecules are in closed proximity. As a result, nearly 100% energy transfer between NV centers in small nanodiamonds and acceptor molecules attached to the surface of those diamonds can be detected. At the same time, the spin of those defects is a sensitive measure for external electric and magnetic field fluctuations. By this e.g. paramagnetic species in microfluidic channels or cells can be sensed. Even thin water layers of diamond or nanodiamond surfaces create a sizable signal. When put into cells, defect doped nanocrystals thus do have the potential for efficient detection of cellular signals and provide an entirely unique collection of sensor capabilities.
In the last decade, the realization of controlled quantum systems has become one of the major research topics in physics . Defect centers in diamond nanocrystals are promising candidates for a robust and scalable solid state quantum technology platform. Many different defect centers in diamond are known. Among them, the nitrogen vacancy (N-V) center has been intensely studied on the single center level in the recent years. N-V centers are long-time stable and occur naturally in bulk diamond and nanocrystals. Apart from a triplet ground state with ultra long coherence times they provide an optical transition at about 637 nm, which is capable to emit single photons even at room temperature . We will present recent results with single diamond nanocrystals. With a size of about 30 nm and containing a single N-V center they are ideal to build quantum hybrid structures in a bottom-up approach. Using cutting-edge nano manipulation techniques we show how preselected nanodiamonds can be positioned on prefabricated plasmonic or photonic structures  with nm precision, e.g. to enhance single photon emission rates [4, 5]. In order to realize more advanced quantum optical experiments directed towards a scalable integrated quantum technology platform several obstacles have to be overcome. As a major problem, we address the issue of spectral diffusion of single N-V centers in diamond nanocrystals. Additionally, the feasibility of two photon quantum interference of photons is discussed and a first experimental approach is introduced.  Ladd, T. D., Jelezko, F., Laflamme, R., Nakamura, Y., Monroe, C., O'Brien, J. L. (2010). Quantum computers. Nature, 464(7285), 45-53.  Wrachtrup, J., Jelezko, F. (2006). Processing quantum information in diamond. Journal of Physics: Condensed Matter, 18(21), S807-S824.  Schell, A. W., Kewes, G., SchrÃ¶der, T., Wolters, J., Aichele, T., Benson, O. (2011). A scanning probe-based pick-and-place procedure for assembly of integrated quantum optical hybrid devices, Review of Scientific Instruments 82(7), 073709.  Wolters, J., Schell, A. W., Kewes, G., NÃ¼sse, N., Schoengen, M., DÃ¶scher, H., Hannappel, T., LÃ¶chel, B., Barth, M., Benson, O., (2010). Enhancement of the zero phonon line emission from a single nitrogen vacancy center in a nanodiamond via coupling to a photonic crystal cavity. Applied Physics Letters, 97(14), 141108.  SchrÃ¶der, T., Schell, A. W., Kewes, G., Aichele, T., Benson, O. (2011). Fiber-integrated diamond-based single photon source. Nano letters, 11(1), 198-202.
Entanglement of two qubits by using surface plasmons (SPs)  would be the starting point for long-distance 2D quantum computing or processing with SPs fully compatible with integrated-photonics technology. Here, we present a first original step in this direction. Using an all-optical scheme, we can reproducibly attach a well-selected single nanodiamond (ND) of â?^ 25 nm in size with single or double nitrogen-vacancy (NV) occupancy onto the apex of optical fiber-tips for near-field scanning optical microscopy (NSOM). This achieves single-ND-based active optical tips. We have implemented such tips in a NSOM environment. Illuminating the grafted ND with a laser light guided by the fiber itself and using only the fluorescence light generated by the ND as nanosource of light achieves a genuine scanning single-photon microscopy  that can be run on a long term thanks to the exceptional photostability of the NV . We have further shown that the ND-based active tip efficiently launches SPs into gold films, either homogenous or nanostructured, that are dipped into its optical near field . Since the ND is a quantum source of light, one, or at most two SPs, depending on the actual NV occupancy, forms the experimental images. This is a first successful step towards a â?odeterministicâ? quantum plasmonics where single plasmons can be optically launched at any freely chosen position in a plasmonic receptacle. In this talk, we will first review our grafting protocol and our demonstration, assisted by suitable microscopy (for example leakage radiation microscopy), of quantum SP launching. We will comment on the spatial resolution offered by our single-photon tips  and on the wave-particle duality for SPs  revealed by our experiments. Then, we will present some prospects to our work in the extension of groundbreaking concepts of quantum optics to the plasmonics world as well as in the plasmonic entanglement of qubits.  A. Gonzalez-Tudela et al, PRL 106, 020501(2011)  A. Cuche et al, Opt. Express 17, 19969 (2009)  R. Brouri et al, Opt. Lett. 25, 1294 (2000)  A. Cuche et al, Nano Lett. 10, 4566 (2010)  A. Drezet et al, Opt. Commun. 284, 1444 (2011)  R. Kolesov et al, Nat. Phys. 5, 470 (2009)
Colloidal diamond nanoparticles (nanodiamonds) are a remarkable material that has emerged as an ideal platform for a diverse range of applications from biomedicine to microelectronics. While many of these applications are facilitated by their specific area, high adsorption capacity, high mechanical stability and lack of cytotoxicity, it is the luminescent properties that have attracted considerable attention in recent years. The optical emission in the visible spectrum is associated with specific types of functional point defects (also called â?ocolor centresâ?) that consist of complexes of impurities and lattice vacancies. The structure and morphology of nanodiamond has been studied extensively over the past decade, both computationally and experimentally, and these activities have been extended to include more detailed analyses of the stability of different functional defects within individual particles. For example, recent computational studies have proven useful in highlighting the relationship between the location of a given defect and its mechanical and optical stability; something that is challenging to probe experimentally. In this presentation we continue this line for research, and compare the location-dependent stability for a range of defects containing different combinations of nitrogen and vacancies. By calculating the energy barrier for vacancy-assisted bulk diffusion, these results are also used to predict the size-dependent probability of observation of different defects, and discuss the implications for optical stability.
The applications of nitrogen-vacancy (NV) centers in diamond can really benefit from an enhanced single-photon emission. In this work we discuss coupling of NV centers to metamaterials with hyperbolic dispersion (HMM). This class of metamaterials has a unique broadband singularity in photonic density of states (PDOS), unlike any other conventional system. Spontaneous emission depends on the available PDOS and can be enhanced when an emitter is inside or close to the surface of the HMM. Here we demonstrate the possibility of the enhancement of spontaneous emission from NV-centers by HMM in a broad spectral range.
Effective luminescent centers in nanodiamonds could be very important candidates in many important applications ranging from quantum information processes to bioimaging. The basic physical process in these color centers is the absorption of light, radiative and non-radiative decay of the excited states. Ab-initio studies could be very beneficial in understanding these key properties of color centers, however, it is highly non-trivial to study these phenomena at ab-initio level. Recent advances in methodology have made available to investigate the absorption and emission of light at ab-initio level in nanostructures. Time-dependent density functional theory (TDDFT) has become a powerful method to attack this problem. We applied this method with hybrid density functional in the kernel to study the absorption properties of nitrogen-vacancy center in a small nanodiamonds. We found that the quantum confinement effect is small. TDDFT method allows calculation of the forces in the excited state, thus, the calculation of zero-phonon line energies is feasible. We found that TDDFT method is able to quantitatively predict the zero-phonon line as well as the Stokes-shift of nitrogen-vacancy (N-V) center. We applied this method for the less known color centers in nanodiamonds. Recently, luminescent silicon-vacancy (Si-V) centers in ultrasmall nanodiamonds of diameter of 1.8 nm have been found that can be potentially a photostable substitution of recent unstable dye molecules applied for in vivo biological studies. However, it is not yet clear how the quantum confinement affect the luminescence of this defect. We considered both the neutral and negatively charged defects in our TDDFT studies where we modeled the nanodiamond with hydrogen termination and up to experimental sizes. We found that the quantum confinement effect is relatively small but should be clearly detectable in PL spectra and the Stokes-shift is much smaller than for N-V center. We give a theory for the Ni-related color center too in nanodiamonds which can be an important alternative candidate for efficient single emitter in the desired wave length of bio-applications.
Nitrogen-vacancy center (NVC) in diamond has attracted much attention in quantum computing of manipulating an ensemble of spins and nano-scale imaging with NVC used as an extremely sensitive magnetic sensor. The experimental foundation relies on a successful detection of the spin state even for single NVC through optical measurement. Notably, NVC contained nano-diamond is reported to be less toxic, anticipating new application of magneto-optical spectroscopy to single molecule fluorescence observation embedded into biological live samples. In this talk, we present a potential method to extract the fluorescence only from NVCs in a mixture of bright extrinsic fluorescence signals, by means of a synchronization of microwave irradiation and data acquisition via a high-speed electron multiplied CCD (EMCCD) camera for scope view observation. A couple of the experimental results applied to biological samples, live HeLa cell and C.elegans, indicated significant performance able to completely eliminate auto-fluorescence background originating from ingredient of feeds. Also confirmed was that this protocol works well in a real time observation of clear image only displaying NVCs at a conventional video rate. Together with the excellent photo-stability of NVC fluorescence, the method is highly applicable for obtaining new insight in observation of biological live samples, which has not been readily acquired in the conventional fluorescence microscopy due to luminous background frequently encountered and unstable properties of fluorescent dye. The similar protocol was adopted for investigating rotational dynamics of diamond particles. Some of the recent results will be presented.
Nanodiamond powder produced by detonation synthesis is the most promising nanofiller for (bio)composite applications . It is made of diamond particles of ~5 nm in diameter, combining fully accessible surface of 300 â?" 400 m2/g with a rich and tailorable surface chemistry. Nanodiamond has unique properties including optical, electrical, thermal, and mechanical ones, and is biocompatible and non-toxic material. In order to fully benefit from the potential of nanodiamond in nanocomposites, special attention must be paid to: 1) uniformity of nanodiamond dispersion in the matrix, 2) the design of nanodiamond-matrix interface on a molecular level, and 3) the properties of the polymer interphase formed in the vicinity of nanoparticles as a result of matrix-nanofiller interactions. We address these issues with different surface modification strategies. Covalent linking of octadecylamine , improves dispersions of nanodiamond in hydrophobic polymers. Reactions of nanodiamond's functional groups bring the nanocomposite design to a conceptually new level, where covalent interactions of nanodiamond with the matrix can be used to create a nanofiller-matrix interface with desired properties . Covalent incorporation of aminated nanodiamond into epoxy via reaction of nanodiamondâ?Ts aminogroups with epoxy groups of the resin results in a significant improvement in mechanical properties of the composites. The role of interphase should also be taken into consideration. Nanodiamond also has great potential to improve thermal conductivity , UV protection , and other properties of composites. For biomedical applications non-toxic fluorescent nanodiamond introduced into biodegradable polymers provides options for visual monitoring the nanocomposite performance, enhanced biomineralization, and delivery of cell growth factors and drugs attached to its surface. These multifunctional nanodiamond composites have a great potential for manufacturing tissue engineering scaffolds, bone fixation devices, and other biomedical applications. 1. Zhang, Q.; Mochalin, V. N.; Neitzel I., et al. Fluorescent PLLA-nanodiamond composites for bone tissue engineering. Biomaterials 2011, 32, 87-94. 2. Mochalin, V. N.; Gogotsi, Y. Wet Chemistry Route to Hydrophobic Blue Fluorescent Nanodiamond. Journal Of The American Chemical Society 2009, 131, 4594-4595. 3. Mochalin, V. N.; Neitzel, I.; Etzold B. J. M., et al. Covalent Incorporation of Aminated Nanodiamond into an Epoxy Polymer Network. ACS Nano 2011, 5, 7494-7502. 4. Neitzel, I.; Mochalin, V.; Knoke, I., et al. Mechanical properties of epoxy composites with high contents of nanodiamond. Compos. Sci. Technol. 2011, 71, 710-716. 5. Behler, K. D.; Stravato, A.; Mochalin, V., et al. Nanodiamond-Polymer Composite Fibers and Coatings. ACS Nano 2009, 3, 363-369.
The surface reactivity of nanodiamonds (NDs) can be tuned by changing their surface terminations. In this talk, we will present the intrinsic surface properties of hydrogenated (H-NDs) and surface graphitised nanodiamonds. We previously reported an efficient surface hydrogenation of NDs using a home-made Microwave Plasma Chemical Vapour Deposition (MPCVD) allowing the production of quantities usable for chemistry . Kinetics of this hydrogenation technique was studied by sequential surface analysis using XPS and AES . The proper surface reactivity of H-NDs will be discussed from different grafting experiments as photochemical reaction with alkenes or UV hydroxylation. We will show that our results strongly support electronic surface properties for H-NDs very similar to those of hydrogenated diamond films . The early stages of NDs surface graphitisation will be then presented with a sequential XPS study. Indeed, a specific reactivity was recently reported on surface graphitised NDs . Our results support two different mechanisms depending on the UHV annealing temperature . For T < 900Â°C, reconstruction into graphitic domains occurs at the NDs surface while for T > 900Â°C, graphitisation of the diamond core starts. This is further confirmed by HRTEM investigations. These results are in well agreement with a graphitisation model recently reported  which emphasises the major role played by dangling bonds at the diamond / graphite interface. NDs were also treated using an ex situ furnace with previous optimised conditions. Their reactivity at air exposure will be discussed using XPS, DLS and Zeta potential measurements. References  H. A. Girard et al., Diam. and Relat. Mater. 19 (2011) 1117.  J. C. Arnault et al., Phys. Chem. Phys. Chem. 13 (2011) 11481.  T. Strother et al., Langmuir18 (2002) 968.  D. Lang et al., DRM 20 (2011) 101  T. Petit et al., (submitted)  L. S. Li et al., The Journal of Chemical Physics 134 (2011) 044711
Nanodiamond particles (ND) stimulate broad interest among science and industry. The advantage of using ND arises mainly due to the versatility of carbon and the high external surface area of ~350 m2/g. After production and subsequent gas or liquid phase purification, ND shows a rich surface chemistry, consisting of different oxygen containing groups. It is of outmost importance to control the surface functionalization for its specific applications. Carboxylic groups can be used directly for further wet chemical modification, e.g. amination . Nevertheless, a control of oxygen group density or complete removal of functional groups can be aspired. In this work the modification of NDs surface chemistry by a stepwise layer by layer approach is reported. Commercially available detonation ND (Nanoblox, Inc., grade UD90, air and HCl purified as reported previously ) was used for this study. The repetitive steps we used are a) desorption of surface groups in inert gas (Ar or N2) or hydrogen at higher temperatures (up to 700 Â°C) and b) oxidation of the surface with air at lower temperatures (up to 300 Â°C). Thus, the surface of ND is constantly â?~cleanedâ?T on each step during desorption and new oxygen groups are introduced during the oxidation step. Crucial for the process is temperature control at each step. The oxidation temperature must be low enough to avoid diamond burn off, at the same time it must be high enough to ensure oxygen chemisorption. Temperatures during the desorption step must be low enough to avoid reconstruction of the metastable diamond phase. The temperature ranges were determined by TGA experiments in different atmospheres. Layer by layer experiments were carried out in a tube furnace and TGA with Characterization by FTIR, Raman, TEM, TGA and DLS. FTIR spectra of the starting material show a strong C=O stretch at 1760 1/cm. Heating of the starting material in N2 with a ramp of 5 Â°C/min shows a weight loss due to desorption of 5.2 wt.-% till 600 Â°C and 17.9 wt.-% till 1000 Â°C in total. After 9 air oxidation steps (300Â°C, 1h) and 10 desorption steps in Ar atmosphere (600Â°C, 5 min) FTIR confirms a reduction of carboxylic group number and shows a shift of the C=O peak to 1727 1/cm. Carrying out the same experiment in a H2 atmosphere results in nearly no detectable oxygen groups, despite the short treatment time of 5 minutes and low temperature. Stopping experiments after an air oxidation step results in a high content of carboxylic groups and also a shift of the C=O stretch to 1725 1/cm. To conclude, a stepwise layer by layer approach allows to reduce treatment time and temperatures for effective surface modification of ND, minimizing undesirable diamond carbon removal.  V. N. Mochalin et. al., ACS Nano 5 (2011) 7494.  S. Osswald et al., J. Am. Chem. Soc. 128 (2006) 11635
Nanocomposites comprising of carbon nanotubes (CNTs) in a polymer matrix can find several applications, ranging from transparent conductive polymers to high modulus skins. The density of the CNTs in the polymer mixture can be tuned to impart various properties to the composite, such as increased mechanical stiffness, electrical and thermal conductivity, and absorption of visible and infrared (IR) radiation. In this project, CNT-polymer nanocomposites are used as efficient infrared absorbers. For this application, the absorber layer needs to be thin (<1 Âµm), uniform, and the density of CNTs in the polymer should be high to efficiently absorb infrared. One of the major challenges to the fabrication of these films is the tendency of the CNTs to agglomerate in the mixture when its density is increased to above 1%. Traditional dispersants like dimethylformamide (DMF) and mixing methods like ultrasonication have only limited success for achieving uniform CNT based thin films. In this work, we demonstrate the fabrication of thin film nanocomposites using CNTs/nano-diamond (ND) in poly-(methylmethacrylate) (PMMA) for use as thin film infrared absorbers. Nanodiamond particles are added to the mixture in order to reduce the agglomeration of CNT bundles, leading to a marked improvement in the quality of the dispersion. The positively charged nanodiamonds debundle the CNT agglomerates which are held together electrostatically, and allow the formation of a stable colloidal suspension. Using this approach, thin film CNT/ND/PMMA layers ranging from 300 nm to 2 Âµm have been obtained by a spin coating process, which is a lower cost and more scalable alternative to the electro-spraying technique commonly used to form thin layers of CNTs on a substrate. The films are uniform, exhibit good dispersion and surface roughness, and form excellent porous layers with IR absorptivity of more than 90%. As compared to metal blacks, the conventional IR absorbers; reported CNT/ND based nanocomposite exhibits comparable absorption coefficient and are less susceptible to aging and can undergo much higher thermal budget.
I will report on the recent NMR studies of (1) fluorinated, chlorinated, hydroxylated and Cu- and Co-decorated diamonds nanoparticles; (2) nanodiamond suspension; (3) surface structure and composition and de-agglomeration of the diamond nanoparticles; (4) size-dependent properties of nanodiamonds and nitrogen centers; potential of nanodiamonds for quantum computing. The results will be discussed along with the data of HRTEM, EPR, XPS and Raman measurements.
Today the nanocomposites based on the conductive Polyaniline (PANI) polymer are at the forefront of industrial applications and the engineering of composites incorporating nanocarbons as filler is a fundamental research task. Searching for a way to produce PANI-based nanocomposites where the guest nanoparticles not only act as a filler able to modify some functional properties of the material, but help in the structural organization of the host polymer matrix, we have focused our attention on PANI-nanodiamond systems. A series of detonation nanodiamond (DND) â?" PANI composite samples have been prepared by using different polymerization methods, i.e. chemical (precipitation polimerization) and electrochemical (cyclic voltammetry and chronoamperometry), controlling the amount and the degree of dispersion of DND in the reaction environment. The results obtained using the different techniques allowed us to evidence the influence of DND particles on the nucleation mechanisms of the conducting polymer. In particular, the presence of DND has proven to modulate the organization of the aniline nucleates into stacked aggregates by a â?oseedingâ? mechanism, and to induce the production of unexpected one-dimensional nanostructures. FE-SEM and TEM observations evidenced in all the samples the prominent growth of fibril-like structures, that in some cases are found assembled in 2-D networks of tightly woven, partially oriented fibers. As evidenced by micro-Raman spectroscopy, such interesting PANI-DND fibers show the protonated emeraldine form typical of the conductive state of PANI. Moreover the XRD measurements, beyond confirming the insertion of DND inside the polymeric network, reveal that the packing of the polymeric chains leads to the formation of a long-range order into these one-dimensional systems. Electrical conductivity measurements on isolated fibers have been carried by means of an AFM apparatus whereas the electrocatalytic properties of these composite fibers have been tested toward the iodine reduction in organic solvent. Finally, a noticeable increase of the thermal stability and the decrease of the temperature-induced decomposition of the PANI backbone have been found for the composite material.
Due to their favorable strength to weight ratio and low friction coefficients, polymer composite materials find numerous applications in structural, tribological, biomedical, sports and other industries. A nanocomposite by definition contains filler smaller than 100 nm in diameter. At these small length scales, the specific surface area becomes large and polymer-filler interactions become increasingly important, changing polymer properties in the vicinity of the surface and forming a new phase called interphase. Tailoring the properties of the interphase allows for engineering the properties of composite materials. The small 5 nm diameter of detonation nanodiamond (ND) particles in combination with their superior mechanical properties (diamond properties) and rich surface chemistry, makes ND an optimal candidate for reinforcing polymer matrices 1. Multifunctional composites can be designed due to its various properties as well: in the case of an epoxy matrix 2, ultimate mechanical reinforcement has been achieved by using high loadings of ND powder, along with an increased thermal conductivity and reduced friction coefficients. The effect of functionalized (aminated) ND-NH2 on the epoxy stoichiometry and the resulting mechanical and tribological properties have been investigated and demonstrated the advantages of covalent incorporation of ND into the structure of epoxy, resulting in a strong nanofiller-matrix interface 3. To reinforce a thermoplastic biodegradable polymer, poly(L-lactic) acid (PLLA), NDâ?Ts surface has been hydrophobized to match this hydrophobic polymer, resulting in improved dispersion of ND in the matrix and better mechanical properties, along with biocompatibility and fluorescence 4. Several complementary mechanical characterization techniques have been used to study the reinforcing mechanisms of ND. Results of compression, fracture toughness, wear and frictional measurements have been compared. This research provides new insights in the reinforcing mechanisms of ND in polymer matrices on molecular level. 1. Behler, K. D.; Stravato, A.; Mochalin, V.; Korneva, G.; Yushin, G.; Gogotsi, Y., Nanodiamond-Polymer Composite Fibers and Coatings. ACS Nano 2009, 3, 363-369. 2. Neitzel, I.; Mochalin, V.; Knoke, I.; Palmese, G. R.; Gogotsi, Y., Mechanical properties of epoxy composites with high contents of nanodiamond. Compos. Sci. Technol. 2011, 71, 710-716. 3. Mochalin, V. N.; Neitzel, I.; Etzold, B. J. M.; Peterson, A.; Palmese, G.; Gogotsi, Y., Covalent Incorporation of Aminated Nanodiamond into an Epoxy Polymer Network. ACS Nano 2011, 5, 7494-7502. 4. Zhang, Q.; Mochalin, V. N.; Neitzel, I.; Knoke, I. Y.; Han, J.; Klug, C. A.; Zhou, J. G.; Lelkes, P. I.; Gogotsi, Y., Fluorescent PLLA-nanodiamond composites for bone tissue engineering. Biomaterials 2011, 32, 87-94.
Ultrananocrystalline diamond (UNCD) films were developed and patented in the past by researchers at Argonne National Laboratory. This novel form of diamond exhibits mutifunctionalities that are being utilized in a range of devices or system components, such as UNCD coated mechanical pump seals and more recently UNCD electrodes for water purification now in the market. In this paper, we present evidence for another form of UNCD produced by the synthesis of agglomerated nanodiamond clusters on Si substrates forming a highly porous and continuous nanostructure of UNCD. Microwave plasma-enhanced chemical vapor (MPCVD) deposition was used to grow this porous UNCD structure using H2+CH4 gas chemistry and bias-enhanced nucleation-bias enhanced growth (BEN-BEG). The nucleation layer was produced by exposing a virgin surface of a Si substrate to a H2-rich/CH4 plasma while applying a negative bias voltage to the substrate to accelerate H+ and C+ ions towards the Si surface, previously exposed to a pure hydrogen plasma to etch the native silicon oxide layer. The subplantation of energetic C+ atom forms the UNCD nucleation layer, followed by film growth enhanced by the continuous application of a negative bias to the substrate surface. While this process has been reported to produce dense and uniform films in our previous work, the highly porous structure with nanodiamond clusters was obtained through the modification of BEN-BEG process. Raman spectra indicate that the porous UNCD clusters have similar Raman signature as those of conventional UNCD films. Cross-sectional scanning electron microscopy (SEM) revealed that the modified BEN-BEG process results in 40% porosity with few tens of nm diameter clusters. The structure is under investigation using high-resolution transmission electron microscopy (HRTEM) to determine the nanostructure and the diamond-silicon interface. In conclusion, a new BEN-BEG process appears to be very promising to produce porous UNCD layers.
Nanoparticle adsorption properties are connected with charge presence on their surface in expense of the functional groups ionization at a surface, and also as result of reaction complex formation due to surface active centers interaction with ions or molecules from the solution. Adsorption ability of a surface of ultra-disperse diamond (UDD) of detonation synthesis depends on a way of its chemical processing after synthesis. The research objective contained in revealing different type UDDâ?Ts behavior in relation to water, simple and complex salts water solutions, organic molecules and some metal nanoparticles. Suspensions of several types UDD in NaCl water solution have pH (3.4â?"2.7) well below (5-6) measured in initial solutions caused by own acidity of the UDD surface and due to equilibrium exchange of metal ions with the surface protons. Techniques of quantitative determination of the protonogenic surface groupsâ?T by pH-potentiometry are used. According to alkali titration of UDD suspensions in 0.9 M NaCl solution and desorption kinetics of protons from UDD the desorption constants (pK1) of acid groups are estimated. Adsorption from chloride solutions of H[AuCl4], RhCl3, and also a methylene blue are ruled by Freundlich's equation. It was shown, that with reduction of the protonogene groups content both Rh(III) sorption and UV-absorption of the clarified UDD suspensions reduced. The adsorption on UDD of gold nanoparticles with various concentrations and the size of particles is defined. The final size distribution by SEM and appropriate calculation program was determined. The relatively low particle sorption value can be explained by identical charge sign both gold hydrosol surface and the UDD one.
New high-energy electric discharge technologies for production of carbon nanomaterials (CNM), containing fullerene-like clusters of the C60-C70 type, nanotubes, nanodiamonds and amorphous carbon (AC), using the methods of electrical explosion of graphite rods and electric breakdown of organic liquids (EBOL) are recently developed [1,2]. The EBOL technology gives an opportunity to produce AC in amounts required for industrial application. The EBOL technique consists in a high-energy electric discharge processing of liquid or gaseous organic media â?" source of carbon. Electric discharge is initiated by strong electric field in the coaxial electrode system with a pulse current generator. A destruction of hydrocarbon molecules into separate fragments occurs during this processing, what results in CNM formation in the process of ultra-fast cooling of the clusters. To investigate the influence of chemical nature of working media organic liquids from the class of arenes (benzene â?" C6H6) with sp2-hybridisation of carbon atoms in planar ring molecule and alkanes (cyclohexane â?" C6H12) with sp3-hybridisation of carbon atoms in nonplanar ring molecule were used. Performed comprehensive studies (XRD, electron microscopy and Raman spectroscopy) showed that produced powders are typical amorphous materials with a significant degree of disorder. XRD patterns of the powders have an amorphous halo at ~26Â° in Cu KÎ± radiation. Raman spectra (Î»=514.5 nm) are characterized by intense and broad D- and G-bands around 1360 and ~ 1610 cm-1 with value of ID/IG ratio ~ 0.9. This indicates a significant fraction of carbon atoms in sp2 state regardless of class of hydrocarbons used. But only in the case of EBOL of alkanes, CNM with developed surface (SBET=150 g/cm3) and complex core-shell structure were discovered. Individual particles of onion-like carbon consist of core about 5 nm surrounded by graphitic shell up to 5 layers with interlayer spacing of ~ 0.36-0.37 nm. In the case of other hydrocarbons, layered structure with interlayer spacing of ~0.35 nm is present on HRTEM images. So, a possibility of onion-like carbon synthesis in a large scale by the method of electrical breakdown of organic liquids (alkanes) is established. (chemical nature of working media significantly affects on structural state of produced CNM). Synthesized AC is used as an additive to electrolytes in the process of electro-chemical coating formation, what led to an increase in wear characteristics of the coating, and for electromagnetic waves shielding. This work was partially supported by the joint projects of SFBR of Ukraine (F41/139-2011)â?" RFBR of Belarus (T11K-130). 1. Rud A.D., Kuskova N.I., Ivaschuk L.I., Zelinskaya G.M. and Biliy N.M. Fullerenes, Nanotubes and Carbon Nanostructures. Vol. 19, Is. 1, P. 1536 (2010). 2. Rud A.D., Kuskova N.I., Baklar V.Yu., Ivaschuk L.I., Boguslavskii L.Z., Kiryan I.M. Bulletin of the Russian Academy of Sciences. Physics, Vol. 75, n. 11, P. 1435 (2011).
Gas phase surface treatment of nanodiamond (ND) particles is technical easy to implement and thus of high practical interest. E.g., partial oxidation in air is used to purify ND and selectively burn off sp2 carbon . Additionally, oxygen groups are introduced which can be used to further modify NDâ?Ts surface chemistry. The major disadvantage of oxidation in air is a high activation energy resulting in a narrow temperature window between partial and complete oxidation. At the same time, the exothermic heat of reaction can lead to a thermal run-away, making a controlled process difficult. The later one is assumed to be responsible for a pronounced oxidation of smaller ND particles within the sample . Thus, for a better control of the partial oxidation, the usage of other oxidation agents can be beneficial. In this work, endothermic oxidation of ND was studied using carbon dioxide as the oxidation agent. The carbon dioxide oxidation of commercially available ND (Nanoblox, Inc., grade UD90) was studied at different temperatures in isothermal TGA experiments and a tube furnace to verify the scalability of our process. The obtained ND was characterized by FTIR, Raman, TEM and TGA. Isothermal TGA experiments show that the process can be controlled over a wide temperature range, the mass loss after 7 h at 700 Â°C being approx. 25 wt.-% and 80 wt.-% at 800 Â°C. Due to the higher reaction temperature in carbon dioxide atmosphere, when compared to oxidation in air, a desorption of surface groups takes place during the heating phase. A weight loss of 9 wt.-% was measured when heating up to 700Â°C at a heating rate of 10 Â°C/min. Thus, for a kinetic evaluation of the mass loss signal, a pre desorption in an inert gas atmosphere is necessary. We found that the time depended mass loss after pre desorption follows a spherical shrinking core model, if the particle size distribution measured by TEM is taken into account. The sp2 carbon content was determined using Raman spectroscopy and shows nearly no change for samples treated at 700 Â°C, while powders oxidized at 800 Â°C show a pronounced D and G band, indicating an increase in sp2 carbon content. The desorption profile of CO2-oxidized ND obtained by TGA in nitrogen shows a slight shift towards functional groups desorbing at higher temperatures. FTIR measurements confirm a change in NDâ?Ts surface chemistry, the C=O stretch shifting from 1760 to 1710 1/cm accompanied by a loss in intensity, while the broad hydroxyl peak shifts from 2900 - 3600 1/cm, increasing in intensity.  S. Osswald et al., J. Am. Chem. Soc. 128 (2006) 11635  S. Osswald et al., Diamond Relat. Mater. 17 (2008) 1122
Knowledge about carbon hybrid films comprising both sp2 and sp3 bonding structures is of great importance for innovation applications of diamond-based nanostructures. Unfortunately, little is known about the mixed hybridization forms in the same nanomaterial, especially for the two-dimensional nanostructures. The structural properties of zero-dimensional nanodiamonds (NDs) and two-dimensional diamond nano-flakes (DNFs) are explored using density functional theory (DFT) simulations. The DFT results indicate that dangling bonds (DBs) on the ND surfaces play an important role in graphitization process, and the orientation of DBs on different ND surfaces determines whether there will be a graphitization process or not, resulting in the phase transformation from ND into bucky-diamond. Moreover, similar phase transition does occur in two-dimensional DNFs, leading to the coexistence of sp2 and sp3 bonding structures in the same diamond-based nanomaterial. Such a transition process in DNFs is proposed to depend on the crystallographic direction of the principal axis. These outcomes indicate that the stability of diamond-based nanomaterials relies on both the surface morphology and the principal axis. In addition, two kinds of reconstruction processes (including row and zigzag type) are observed on the (100) surfaces in both ND and DNF cases. Although these two kinds of reconstruction processes have been discovered and reported by a great number of elegant studies during the past few decades, both experimentally and theoretically, deeper information and detailed description of them are still not well understood. Hence, further investigation on such a topic is required in order to decipher the puzzle: in which situation will the row and zigzag reconstruction take place, respectively. Throughout our preliminary research, energy contribution and statistical perspective of C-C dimers on the (100) surfaces are proposed to be taken into account when discussing these two reconstruction types. Further intensive investigation is now ongoing.
Boron atoms seem to be efficient dopant atom in bulk diamond. Specially, for B doped diamond p-type bulk conduction and a p-type surface conductance was reported [1,2]. B can be incorporated with high reproducibility and high enough concentration to be useful for electronic devices. During the doping of diamond, boron can be incorporated in diamond lattice mostly in the single substitution form in case of lower concentrations. However, when boron concentration is increasing it is probable, that boron can be built into the lattice in a large variety of sites, which can be energetically favorable. It has been mentioned on the existence of coupled boron atoms in the diamond lattice passivated by hydrogen atoms. Also, it is favorable for boron to be placed near the carbon vacancy, though vacancies surrounded by boron atoms can be found in the heavily doped diamond. These centers are located on different positions in the band gap and thus have different influence on the material charge transfer properties. All the specific B/diamond systems were modeled using Density Functional Theory methods. It was shown, that resistivity is decreasing when the boron content increases in the diamond film. As the number of doped boron an atom in diamond lattice increase to critical values the acceptor level starts to broaden into a band; and starts to overlap with the valence band resulting in a metal to insulator transition. Nevertheless, after reaching plateau, conductivity of the highly boron doped diamond decreases. To describe such phenomenon, boron diamond films with a wide range on boron concentration have been studied. Quantum chemistry calculations have been performed to analyze the boron point defects and its vicinity in the diamond. To touch on more aspects of the complicated processes periodical systems as well as diamond particles have been modeled. As a result of these calculations were obtained data on the lattice structural bonding, energy structure, character of electronic transitions, bandgap values and position of the interlaying energy levels in highly boron doped diamond.  T. Yokoya, T. Nakamura, T. Matsushita, T. Muro, Y. Takano, M. Nagao, T. Takenouchi, H. Kawarada and T. Oguchi, Nature 438, 647-650 (1 December 2005) doi:10.1038/nature04278  E. Bustarret, P. Achatz, B. SacÃ©pÃ©, C. Chapelier, C. Marcenat, L. OrtÃ©ga and T. Klein, doi: 10.1098/rsta.2007.2151 Phil. Trans. R. Soc. A 28 January 2008 vol. 366 no. 1863 267-279
We report a systematic investigation of the effect of substrate temperature and methane feeding in Hot Filament Chemical Vapor Deposition (HFCVD) of diamond. We performed this study using either a mixture without or with a high concentration of argon. The standard HFCVD used has an independent substrate temperature control, adjustable between 823 to 1173 K. For the first set of experiments the gas mixture was composed only by methane and hydrogen. Methane content varied in the range 1 to 18 vol.%, balanced with hydrogen. For the second set of experiments, in an argon rich environment, methane and hydrogen concentrations were the only parameters changed. The feed gas mixture varied with 0.125 to 2 vol.% methane balanced to 10 vol.% with hydrogen, and 90 vol.% argon. Scanning electron microscopy (SEM) images showed the morphologies. Raman scattering spectroscopy was used to estimate the degree of order in the clustered aromatic sp2 phase and sp2/sp3 relative concentrations. X-ray Philips PW-1840 difractometer allowed measurements of diamond crystallite size to estimate renucleation rate. The dependence of the renucleation rates with temperature shows typical activation energies, indicating that renucleation may be correlated with some particular thermally activated chemical process. As in the case for the growth activation energy, there are two typical values, one during microcrystalline diamond growth (>20kcal/mol) and other during ultrananocrystalline diamond growth (~12kcal/mol). This behavior depends on concentration of methane and hydrogen. It is nearly independent of the argon presence in the feeding gas mixture.
Synchrotron radiation sources are important tools in the study of materials in different fields of physics, chemistry and biology. Due to the high-intensity beam, attenuators use some sources as a means to protect the optical components in front of the beam. In line of LNLS (National Laboratory of Synchrotron Light - Brazil) attenuators are normally made of pyrolytic graphite. One of the problems of these filters is related to graphitic sublimation because of the high beam energy. In this paper, we develop filter's attenuators based in microcrystalline (MCD) and nanocrystalline (NCD) diamond with a high concentration of sp2 carbon. Although diamond is transparent to radiation, we varied the concentrations of methane in the gas mixture in order to get MCD and NCD diamond with high attenuation. The substrate for the growth of diamond films was p-type silicon (100). In this work, we functionalized the surface of silicon with a polymer to promote surface seeding with nanodiamond particles and then deposited CVD diamond films with high nucleation density, in a hot filament reactor. The substrate was functionalized using the polymer PDDA â?" Poly (diallyldimethylamonium chloride - Mw 40000). The seeding was performed in water slurry containing 4 nm diamond particles dispersed by PSS â?" Poly (sodium4-styrenesulfonate) polymer. Film morphology was characterized by Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). Diamond film quality was determined by Raman Spectroscopy.
Nanodiamond has exceptional properties such as a low friction coefficient, high thermal conductivity, and high hardness; all of which make it an ideal candidate as a lubricant additive. Since the average diameter of a single nanodiamond particle is 5nm, the particles can be dispersed in oils to create colloidal solutions. Nanodiamond also has a very high volume to surface area due to its small particle size and spherical structure; it is a combination of this and the highly tunable surface chemistry which makes nanodiamond an ideal candidate for surface modification. Long chain hydrocarbons can be bonded to the surface of nanodiamond to increase its stability in oil and improve lubricating properties. Studies have shown that the use of nanodiamond as a lubricant additive will reduce the coefficient of friction of the oil and decrease the amount of wear that occurs. Although these properties are proven, there is no true explanation for the mechanism of lubrication. It is theorized that the spherical nanodiamond particles roll along the lubricated surface and provide a boundary layer, thus reducing the contact area of the two wear surfaces. A second theory is that the surface of the material adsorbs the nanodiamond particles and creates a thin film which provides lubricating properties while increasing the hardness of the surface. We prepared dispersions of nanodiamond in several different solvents such as Polyalphaolefin and Decane to test the optimal concentration and solution stability. Particle size reduction methods of ball milling and attrition milling were performed on the nanodiamond and were found to significantly increase the solution stability; this was confirmed by particle size measurements using a Zetasizer. Chemical syntheses were performed to bond long chain hydrocarbons such as octadectylamine to the surface of nanodiamond. Using this modified powder, colloidal solutions were formed at a much higher concentration than was possible with as received nanodiamond. We propose to use these solutions to determine the mechanism of lubrication of nanodiamond by the analysis of the wear surface after tribological testing. SEM-EDS studies of the wear surface before and after lubrication as well as TEM, AFM and Raman spectroscopy studies will be performed to determine the true mechanism of lubrication.
Nanodiamond has attracted much attention over the past decade. Studies of this novel nanomaterial aim to understand and tailor its unique properties rooted in the combination of an inert diamond core with a surface rich in functional groups. Raman and IR spectroscopy, being complementary techniques, provide valuable insights into phase composition and surface terminations of nanodiamond. Recently, using a combination of in situ Raman and FTIR spectroscopy and TGA, we have shown that the broad, asymmetric peak in the Raman spectrum of nanodiamond with a maximum at ~1640 cm-1 contains large contribution from O-H vibrations . However, the source of the O-H vibrations remains unidentified, suggesting that it can be either nanodiamond surface functional groups or adsorbed water. There are many hydroxyl and carboxyl functional groups covalently attached to nanodiamond surface, which could give rise to the O-H signals in IR or Raman spectrum. On the other hand, thermal analysis data show that nanodiamond is capable of adsorbing and retaining large amounts of water from the environment. However, Raman, IR spectroscopy, and thermal analysis have limited capabilities and cannot provide critical information to discriminate between the possible sources of O-H vibrations in nanodiamond. In this presentation we report on the results of inelastic neutron scattering to characterize surface chemistry of nanodiamond. Due to anomalously large incoherent neutron scattering cross-section of hydrogen, the inelastic neutron scattering mainly represents vibrational spectra of hydrogen in the hydroxyl groups and water molecules adsorbed on the nanodiamond surface. The inelastic neutron scattering spectra of nanodiamond recorded with Fine-Resolution Fermi Chopper Spectrometer (SEQUOIA) at Oak Ridge National Laboratory will be discussed, in particular, with the aim to answer the long-standing question about the origin of 1640 cm-1 (205 meV) mode observed in vibrational spectrum of nanodiamond. 1. V. Mochalin, S. Osswald, and Y. Gogotsi, Contribution of Functional Groups to the Raman Spectrum of Nanodiamond Powders. Chemistry of Materials, 2009. 21(2): p. 273-279.
Nanodiamond particles combine a spectrum of properties that make them promising as potential drug delivery and imaging agents with translational significance. For example, their faceted architecture enables remarkably potent drug and water interaction that have markedly enhanced chemotherapeutic efficacy with reduced toxicity over clinical standards, as well as major improvements in imaging efficiency. Nanodiamonds can also be scalably processed, where methodologies such as ultrasonication, ball milling, and acid washing yield uniform particles that are between 4-6 nanometers in diameter. In addition, nanodiamonds can be used to deliver virtually any type of therapeutic compound, ranging from hydrophilic/hydrophobic small molecules, to therapeutic proteins (e.g. insulin) and antibodies (e.g. anti-TGF beta), as well as DNA/siRNA, among others. Furthermore, in vitro and in vivo analysis of nanodiamond safety biocompatibility demonstrate that at therapeutically-relevant dosages, they appear to be safe materials for intravenous administration. Recent studies have shown that nanodiamond-doxorubicin (NDX) complexes can be rapidly synthesized with significantly reduced myelosuppression, which is typically the dose-limiting side effect of chemotherapy, compared to clinical standards [1,2]. Furthermore, the NDX complexes were capable of enhancing therapeutic efficacy towards a drug-resistant liver and breast tumor model in vivo. Importantly, this work showed that when normally lethal dosages of doxorubicin were bound to the nanodiamonds and administered as NDX, all of the animals survived and the tumors observed were the smallest in the study, demonstrating nanodiamond-mediated improvements in drug tolerance as well. In addition to mediating 10-fold increases in circulation half-life and improved tumor retention, recent studies pertaining to multimodal nanodiamond platforms for targeted imaging and therapy will also be discussed. 1. E.K. Chow, X-Q. Zhang, M. Chen, R. Lam, E. Robinson, H. Huang, D. Schaffer, E. Osawa, A. Goga, and D. Ho, Science Translational Medicine, 3, 73ra21, 2011. 2. H. Huang, E. Pierstorff, E. Osawa, and D. Ho, Nano Letters, 7, 3305, 2007.
Nanodiamonds (NDs) serve as a potentially ideal drug delivery platform because of a number of unique characteristics. The uniformity and stability of NDs, as well as their small size (~4nm), promote biocompatibility which we have demonstrated in vitro and in vivo. Because nanodiamonds can be functionalized with a broad array of molecules, including small molecules, proteins, antibodies and genetic material, NDs as a drug delivery platform can be used to treat a wide range of diseases. We have previously demonstrated that ND-doxorubicin (NDX) drug complexes could enhance the efficacy of chemotherapy in chemoresistant breast cancer and liver cancer mouse models while lowering the toxic effects of these drugs. While this work represents a promising initial step towards the utilization of NDs in cancer therapy, targeted therapy against specific forms and subtypes of cancer is becoming an important method of treatment. As such, we analyzed if cancer-targeting ND-drug complexes can improve treatment efficacy and lower drug toxicity compared to standard drug treatments and non-targeted ND-drug complexes. In particular, we evaluated epidermal growth factor receptor (EGFR)-targeting ND-drug complexes in human triple-negative breast cancer (TNBC) xenograft mouse model using the human TNBC cell line, MDA-MB-231. While known to express high levels of EGFR, TNBCs are associated with greater risks of metastases, recurrence and higher mortality rates than other subtypes of breast cancer. As such, developing better treatments against this form of cancer is important. EGFR-targeting of TNBCs was performed through multiple indirect and direct targeting ND-drug complex strategies. Successful homing of EGFR-targeting ND-drug complexes was first evaluated by conjugation of Xenofluor750 NIR esters to NDs in vitro and in vivo. These experiments demonstrated enhanced delivery of ND-drug complexes to EGFR-expressing breast cancer tumors and also demonstrated a potential for NDs as targeted tumor imaging reagents as well. Long-term tumor treatment experiments with anti-EGFR ND-drug complexes delivery of anthracyclines demonstrated enhanced drug treatment efficacy compared to non-targeted and standard drug treatment. Standard anthracycline treatment resulted in early mortality due to the toxic effects of chemotherapy. Conjugation of anthracyclines to NDs resulted in lower toxicity and increased survival. Non-targeted ND-drug treatment of TNBC tumors significantly impaired growth of tumors. EGFR-targeted ND-drug treatment resulted in an even more pronounced impairment of tumor growth and in fact led to complete regression of tumors in some cases. These translationally-driven studies demonstrate that ND conjugates can be effective as targeted drug-delivery and tumor imaging reagents.
Fluorescent nanodiamonds (FNDs), containing negatively charged nitrogen-vacancy (NVâ?") centers as fluorophores, have recently emerged as a promising biomarker for in vitro and in vivo applications. The carbon-based nanomaterial is biocompatible, non-toxic, and can be easily conjugated with biomolecules. Moreover, when excited by green-yellow light, the built-in NVâ?" fluorophores emit photostable far-red fluorescence (Î» = 600 â^' 800 nm), making it well suited for long-term labeling/tracking of cancer and stem cells. To prove the concepts, we have studied in detail the exocytosis of FNDs (size ~ 100 nm) from three different cell lines, HeLa cervical cancer cells, 3T3-L1 pre-adipocytes, and 489-2.1 multipotent stromal cells, with fluorescence microscopy and flow cytometry. No alteration in growth and proliferation of the FND-labeled cells was observed for up to 8 days and no substantial excretion of the endocytosed FND particles was found after 6 days of cell labeling. We have applied the same techniques to whole model organisms such as zebrafish and nude mice. In vivo imaging of nude mice intradermally injected with FNDs revealed that most of the nanoparticles are accumulated in lymph modes, as confirmed by ex vivo imaging and biodistribution measurements. We have also acquired transverse section images of the lymph nodes by fluorescence lifetime imaging microscopy to visualize the individual particles in tissues. We summarize in this talk our recent progress towards the development of FNDs for optical bioimaging with single particle sensitivity and long-term tracking capability in cells as well as in whole organisms.
The method of obtaining drug delivery system based on detonation nanodiamonds (NDs) was developed. NDs with covalently bound chlorine on the surface â?" chemical basis for creating drug delivery system were obtained. In comparison with fluorinated NDs chlorine atoms more than 1,5 times are readily eliminated from the surface during their substitution for drug molecules. On this basis conjugate NDs with glycine (ND-Gly) was synthesized. The method of semiquantitative evaluation of drug content on the surface of NDs based on the method of quantitative IR spectroscopy is suggested. This method is applicable for liquid and solid samples. The basic principle of method is plotting calibration curves of correlation Â«intensity IR-signal vs mass of drugÂ» for model mixture of NDs and identified drug. Using developed method evaluation of glycine content in ND-Gly conjugate was obtained and was 21Â±3% wt. The diffusion through the synthetic and natural (inverted rat's intestine) membranes of original and modified NDs of different dispersion was studied with/without ultrasonic treatment. It was shown that the ND particles start to penetrate through the membrane after 1 h. Afler 24 h 6.4% of the total amount of ND particles were passed through the membrane and after 48 h the NDs transition was almost over. The total amount of ND particles that penetrated through the membrane was ca. 8%. Under additional ultrasonic treatment the diffusion of particles is essentially increased. It was shown that up to 50% of ND particles diffuse for 24 h. It was observed that the diffusion curves were symbatic for 3 h when inverted rat's intestine was used as a membrane (then the destruction of biological membrane started). This experimental data allowed us to use the synthetic membrane for the NDs diffusion process modeling ex vivo. The influence of ND particles on respiratory activity of mitochondria was studied in vitro. It was found that NDs decrease the membrane potential of mitochondria. It was shown that conjugate ND-Gly action on the respiratory function of mitochondria considerably differs from the similar action of glycine while the dosage was equal. Biodistribution of modified NDs was studied on rabbits different methods with incubation time 1, 6, 24 h, 15 and 30 days. It was found that NDs accumulate in all essential organs and cumulate in excretory system of the organism. This work is a part of our preclinical trial of the drug delivery systems on the basis of detonation NDs created by us for the first time. This work was supported by RFBR (grant 11-03-00543).
The aim of this work is to develop the luminescencent nanodiamond platform for drug delivery systems, where the delivery event would be optically monitored by the change in the NV luminescence. Nanodiamond particles were recently suggested as a novel platform for gene delivery. Nanodiamonds coated with polyethylenimine (PEI 800) were successfully used as an efficient platform for siRNA delivery . Its high biocompatibility and content of stable luminescence centres makes them attractive for long term tracking in cells. In our recent works we have demonstrated that photoluminescence (PL) can be driven chemically by changing the occupation of NV- and NV0 states by H-, O- and F-termination, where F- and O- termination stabilizes the NV- luminescence and H-termination leads to quenching of luminescence. F-terminated ND also exhibited a high sensitivity to non-covalent bonding of charged polymers. In this work we show that this effect can be used for in vitro monitoring of RNA transfection in cells. Hydrogenated, oxidised and fluorinated HPHT ND with a size distribution of 15-20 nm were used in this study. Fluorination was performed on both hydrogenated and oxidized ND. Raman and PL (514 nm) spectra were taken from a colloidal dispersion of treated ND and after attachment of PEI800 and miRNA in cell medium and after internalization in IC21 cells. Confocal images were also recorded. We have recorded NV0/NVâ?" PL spectral contributions, induced by the interaction with PEI and miRNA depending on the type of surface termination. Spectra were recorded of ND outside and inside of cells.  X. Q. Zhang et al., ACS Nano, 2009, 3, 9, 2609-2616
Detonation nanodiamonds (ND) and soot, since they were discovered in 1960s, draw a lot of attention of scientists of the world for their unique physical-chemical properties. ND have a variety of the applications in different areas, and, due to their large specific surface, good adsorption ability, stability and non toxicity they are very perspective for biomedical application including virology (1). Influenza viruses were chosen for this investigation as they are widely-spread around the world and infect birds and mammals. The main ways of transmission of influenza A and B viruses are airborne way and water way (for bird viruses). In this investigation we have examined whether nanodiamond materials can adsorb influenza A and B viruses from water solutions. The following epidemic reference strains have been taken for survey : A(H1N1, H3N2) and B, isolated in 1999-2010, pandemic strain A(H1N1)v, influenza bird A(H5N2) viruses and reassortant A(H5N2) between human and bird viruses. The viruses were grown in chicken embryonic eggs and tissue culture cell MDCK, concentrated by ultracentrifugation, then diluted in physiological solution (PS). The interaction between viruses and adsorbents was analyzed by the method described (2). As the result of the adsorption, hemagglutination (HA) titers of virus solutions decreased in â?¤4000 times for concentrated viruses diluted in PS and in â?¤8 times for allantoises viruses. Adsorption efficiency depended on degree of virus purity, HA titers before adsorption and the sorbent mass. The soot was approx. 2,5 times more effective than ND.The adsorption of influenza viruses did not depend on antigenic structure of virus surface proteins. The interaction between virus and nanodiamonds materials occurred in the different solutions at 4-37Â°C during 10-20 min. The desorption of viruses from nanodiamonds into PS in 48 h were not observed. Adsorption result of fragments of cDNA,obtained in PCR reaction for influenza A virus (T= 22Â°C ): cDNA fragments with size>190 b.p were adsorbed by both adsorbents, fragments more 560 b.p. were fully adsorbed by soot and partly-by ND. The toxicity of ND and soot both concentrations â?¤ 1 mg/ml for cell MDCK was not observed. So,we established that nanodiamonds materials can be used as the sorbents for influenza A and B viruses for decontamination of these viruses from water solutions as polyaniline and carbon nanotubes (2). This work and publication was supported by the Cooperative Agreement Number 1U51â",P000527-01 above from The Centers for Disease Control and Prevention, USA, grant of President RF YC 882.2011.3. 1. A.M.Schrand, S.A.C. Hensens, O.A.Shenerova Critical reviews in solid and materials science,34:(1-2), (2009),18-74. 2. V.F. Ivanov, V.T. Ivanova, Y.E. Kurochkina, et all. Virus Sorbents on Polyaniline Interpolymer Complexes, Composites and their Sorption Properties. AIP Conference Proceedings, 1255, (2010), 46-48.
Nanodiamond is a highly versatile carbon nanomaterial which exhibits excellent mechanical strength, chemical stability, biocompatibility, and rich, tailorable surface chemistry. With its high and fully accessible surface as well as its unique surface chemistry, nanodiamond also exhibits great adsorptive properties. Furthermore, nanodiamond surface chemistry can be tuned to selectively increase the adsorption capacity of different compounds. In this work, we have created a controlled-release drug delivery system in which the model antibiotic tetracycline is adsorbed onto the surface of nanodiamond. Adsorption isotherms for tetracycline were generated for four different types of as received and modified nanodiamond and both optimal adsorption and release conditions were determined. For desorption, tetracycline release was measured as a function of passive diffusion and measured after ultrasound agitation. We plan to use these results as a first step towards creation of an optimized delivery system that can be used to prevent bacterial biofilm formation on the surface of titanium alloy implants. Such contamination results in periprosthetic infection, a very dangerous complication resulting from orthopaedic surgery that can result in implant removal, general infection, and sometimes even death.
Gold nanoparticles and nanodiamonds are two classes of materials that are receiving great attention in several emerging research areas, such as nanophotonics, nanomedicine and nano-biochemistry. These and other connected research fields are presently converging toward common goals and their synergistic action is expected to offer practical solutions to technological problems related to optical labelling, imaging, molecular loading and biosensing. In this context it is thought that the coupling on nanodiamonds with Au nanostructures and the investigation of the properties of these exciting hybrid systems could open a new fascinating scenario to the applied scientist community. In this paper we describe the preparation of Au nanoparticles loaded on detonation nanodiamond (ND) and the investigations carried out to test the optical behaviour of the coupled nanostructures. The generation and deposition of the Au nanoparticles is achieved by an electroless route, taking advantage of an innovative Au(III)-aminoethil imidazolium aurate salt, that is mixed with aqueous dispersions of nanodiamond. Our synthetic approach presents several interesting aspects with respect to the conventional preparation of Au nanoparticles for decoration purposes, because the process is carried out in the absence of any reducing agent or heat treatment. Moreover the process allows us to modulate the sizes of the Au nanoparticles and the features of the coating in terms of particle density and coverage degree of the diamond phase, thus allowing to selectively produce hybrid systems with different chemical an optical properties. Structure and morphology at the nanoscale of the Au-on-nanodiamond deposits have been deeply investigate by microscopy ( HR-TEM ) and diffraction ( TED ) techniques. The partial coating of the nanodiamond, together with the reduced size of the Au nanoparticles, enable to preserve the chemical properties of the ND. Optical properties of these systems have been determined by performing scattering and UV-Vis absorption measurements, and by comparing the experimental data with simulated extinction spectra. The results highlighted very interesting plasmonic and scattering behaviours, mainly related to the high refractive index of diamond. These innovative Au/ND materials are of paramount interest for basic photonic research and could easily find applications in bio-related research areas. We are presently exploring a series of Au-on-nanodiamond systems as platforms for surface enhancement of Raman signals and as novel nanosources for light amplification.
The detonation nanodiamond (ND) is a versatile low-cost nanomaterial with specific surface area in the range of 400-600 m2/g, particle size in the range of 4-10 nm, tunable properties and surface chemistry. ND soot is produced on a large scale by a controlled detonation of carbon-containing explosives . Selective oxidation of sp2 carbon in detonation ND soot by treatments with acids  or annealing in an oxygen-containing gaseous environment  allows for the fabrication of high sp3-content ND powder. Annealing of ND powder in an inert atmosphere at temperatures above 1400 C leads to their graphitization and formation of sp2 onion-like carbon (OLC), also called â?ocarbon onionsâ? and â?omulti-walled fullerenesâ? . The high surface area, good mechanical properties, low cost, the absence of micropores and relatively high electrical conductivity of as-produced ND soot and OLC combined with their ability to disperse well in both polar and none-polar solvents, make them attractive for many energy storage applications, such as components of electrodes for electrochemical capacitors [3-5] and Li-ion batteries. This talk will discuss the key characteristics of these versatile carbon nanomaterials affecting their performance in electrodes and the synergetic features ND and OLC may offer to other nanomaterials based on conductive polymers, ceramic nanoparticles and carbon nanomaterials having different geometry. Additionally, the talk will discuss ND- and OLC- composite synthesis routes as well as unique opportunities offered by various electrode fabrication techniques, including electrophoretic deposition, co-deposition with a polymer, preparation and casting of aqueous and organic suspensions. References: 1. Shenderova, O., C. Jones, V. Borjanovic, S. Hens, G. Cunningham, S. Moseenkov, V. Kuznetsov, and G. McGuire, Detonation nanodiamond and onion-like carbon: applications in composites. Physica Status Solidi a-Applications and Materials Science, 2008. 205(9): p. 2245-2251. 2. Osswald, S., G. Yushin, V. Mochalin, S.O. Kucheyev, and Y. Gogotsi, Control of sp(2)/sp(3) carbon ratio and surface chemistry of nanodiamond powders by selective oxidation in air. Journal of the American Chemical Society, 2006. 128(35): p. 11635-11642. 3. Portet, C., G. Yushin, and Y. Gogotsi, Electrochemical performance of carbon onions, nanodiamonds, carbon black and multiwalled nanotubes in electrical double layer capacitors. Carbon, 2007. 45(13): p. 2511-2518. 4. Pech, D., M. Brunet, H. Durou, P.H. Huang, V. Mochalin, Y. Gogotsi, P.L. Taberna, and P. Simon, Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon. Nature Nanotechnology, 2010. 5(9): p. 651-654. 5. Kovalenko, I., D. Bucknall, and G. Yushin, Detonation Nanodiamond and Onion-like Carbon - Embedded Polyaniline for Supercapacitors. Advanced Functional Materials, 2010: p. DOI: 10.1002/adfm.201000906.
Carbon onions was treated in the Shear Diamond Anvil Cell (SDAC) up to 35 GPa. Recovered samples was investigated with Transmission Electron Microscopy (TEM) and Raman. Carbon onions was stable in our experiments up to 17 GPa pressure. Raman spectra of these samples did not changes much. Using of shear deformation and pressure exceeded 25 GPa leads to destruction of carbon onions. TEM revealed appearance of amorphous carbon and onions with different shapes and sizes. Raman observed broadening of D and G bands of graphite. Moreover we observed downshift of G band to 1560 cm-1 which may be connected with sp3 C-C bonds formation.
Nanocarbons have attracted a great interest due to their potential applications in nanoscale devices, lubrication and composite materials. Recently, nanocarbons with a variety of morphologies are reported to have been obtained after annealing nanodiamonds above 1200 K. Here, we have investigated the transformation of 2-5 nm nanodiamond particles upon annealing using molecular dynamics simulations. The simulations show that nanodiamonds undergo annealing-induced graphitization by a progressive sp3 to sp2 conversion of carbon atoms that begins at the surface. The extent of this conversion depends on the size and morphology of the nanodiamond. It is found that graphitization easily proceeds from (111) surfaces towards the core, whereas the presence of (100) surfaces leads to residual sp3 carbon atoms. We will also discuss different steps involved in nanodiamond graphitization, the formation of onion-like carbon and vibrational spectra of these structures.
Common materials for supercapacitors have a porous structure, which leads to a high surface area and high capacitance. While they are able to store a significant amount of charge on their surface, limited ion mobility prohibit the use of high charge-discharge rates. The capacitive behavior of typical supercapacitor materials, such as activated carbon or carbide-derived carbon, can only be used for scan rates up to ~100 mV/s and the material tends to a resistive behavior at higher scan rates. Carbon onions are 5-10 nm sized spherical particles consisting of concentric graphitic shells. They can be considered as large multi-shell fullerenes. Particularly attractive is the combination of high conductivity and a moderate surface area (400-600 m2/g) resulting in a gravimetric capacitance of ~30 F/g.[2, 3] Carbon onion based devices can be used at ultra-high rates up to 200 V/s which is attributed to their high conductivity and exohedral structure. The closed surface of the carbon onion reduces any ion diffusion limitations at high scan rates that are associated with a porous structure. At an attempt to increase the surface area, and hence capacitance, KOH activation of the carbon onions was investigated. It was found that activation destroyed the outer shells of the particle, creating a rougher surface with surface micropores. From gas sorption, it was found that the non-activated carbon onions had a broad mesoporous pore size distribution (PSD). As the degree of activation increased, either by increasing the activation time or temperature, the resultant activated material became more microporous with a higher surface area and a more narrow PSD. The activated carbon onions were characterized electrochemically using cyclic voltammetry and electrochemical impedance spectroscopy. It was found that all the samples retained a capacitive behavior at charge / discharge rates up to 1 V/s, indicating the micropores are truly surface micropores, and not a porous network as in activated carbon or CDC. It was also found that for a more activated sample, the rate performance decreases; however the material is able to store more charge at the lower charge / discharge rates. At rates as high as 15 V/s, the activated onions were able to store almost three times the charge of the non-activated carbon onions. References: 1. KrÃ¼ger, A., Carbon Materials and Nanotechnology 2010, Weinheim: Wiley VCH. 490. 2. Portet, C., G. Yushin, and Y. Gogotsi, Electrochemical performance of carbon onions, nanodiamonds, carbon black and multiwalled nanotubes in electrical double layer capacitors. Carbon, 2007. 45(13): p. 2511 - 2518. 3. Pech, D., et al., Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon. Nature Nanotechnology, 2010. 5(9): p. 641 - 654.
Recently, certain nanomaterials in powder and colloidal forms have emerged as potential anti-friction and anti-wear additives to a variety of base lubricants. Among them detonation nanodiamond (DND) and onion-like carbon (OLC) are very promising nano-colloidal additives . Field test experiments on passenger cars demonstrated fuel efficiency improvement due to DND-based additives by 5% and higher. In order to optimize additive composition and expand a range of applications of DND nanolubricants, mechanisms of DND action need to be elucidated. In the current work, we focused on understanding of the role of friction surfaces properties (relative microhardness) as well as exploitation parameters of the test (external load, rotational velocity, duration of the test). Tribological experiments were performed using a universal tribology tester UMT-3, CETR, block-on-ring module. Transparent suspensions of 20nm DND and suspensions of 100nm OLC in a commercial oil Pure Mobil Super SAE 5W30 (ILSAC GF-5 â?" API SN, SM, SL) were investigated. Friction surfaces were inspected with SEM and EDX techniques. It was concluded, that depending on the relative microhardness of the friction surfaces and exploitation parameters, addition of DND can provide from modest to significant improvements in reduction of friction coefficient or wear, or both characteristics. Possible mechanisms of action of DND and OLC will be discussed.  M. G. Ivanov, S. V. Pavlyshko, D. M. Ivanov, I. Petrov, and O. Shenderova, JVST B, v. 28, 4, p.869, 2010
Diamond nanoparticles are exciting candidates for a diverse array of applications from single photon sources, through drug delivery and bio-labelling to the nucleation sites for growth of nanocrystalline diamond films. The apparent lack of toxicity, facile functionalisation strategies and stability makes them ideal bio-markers and drug delivery agents. The high quantum yield, photostability and fluorescence in the visible range are highly desirable optical properties for both bio-labelling and solid-state single photon sources. Unfortunately, the smallest diamond nanoparticles available are produced by a detonation process, which renders the individual particles tightly bound in aggregates that are difficult to separate into mono-disperse particle colloids. The aggregate size can be up to 100 nm in solution, far in excess of the ~5 nm core particle sizes, rendering the dispersions inadequate for the majority of the aforementioned applications. Simple wet chemical purification and ultrasound approaches are insufficient for the dispersion of these aggregates. In this work we will show that these aggregates can be efficiently broken down into their core particles and dispersed into stable colloids by simple annealing in hydrogen or oxygen gas. The hydrogenated particles exhibit strong positive zeta potentials whereas the oxygenated particles are negatively charged in water. The hydrogenated particles show stability over a wide range of pH below 8 whereas the oxygenated are stable at higher pH values. We will show that the electrostatic self assembly of diamond particles on different surfaces can be controlled by pH and the particles surface termination.
After half a century since its serendipitous discovery by Danilenko and his coworkers in 1963, the primary particles of detonation nanodiamond have been dispersed by attrition milling, fully purified and characterized. Preliminary results of beads milling have been communicated several times in the past but the full results are presented here for the first time. Purification and characterization became possible only after the satisfactory conditions have been found for the attrition milling. 1. Attrition milling. The most tenacious problem in the past when performing attrition milling onto tight agglutinates of the crude detonation product was extensive contamination of the disintegrated nanodiamond particles with the scraped media of attrition milling (zirconia). The latter could be readily identified as the broad second peak that appears at 20-60 nm range in the particle-size distribution obtained by dynamic light scattering method. Due to a large number of factors influencing the outcome of attrition milling, an optimum set of conditions has been determined by applying the analysis by the design of experiment method. In the course of improving conditions, the contamination level with zirconia nanoparticles dropped from the initial 1% to less than 0.002% according to semi-quantitative ICP analysis. To our knowledge, attrition milling is still the only way to mass produce primary particles of detonation nanodiamond within reasonable work load. To our surprise, average diameter of the primary particles has dropped from the long-believed 4-5 nm to 3.7Â±0.6 nm (DLS, vol-based). Work is in progress to understand this large decrease. 2. Purification. Complete dispersion and isolation of primary crystals of a nanoparticle is the first step toward the long-dreamed purification to a chemically acceptable level. We noticed high electrochemical response of the primary particles of detonation nanodiamond and found preparative electrophoresis led to significant progress towards understanding many enigmatic behaviors of detonation nanodiamond. So far our results agree well with theoretical predictions by Barnard and coworkers: the structure is complex core-shell type with sp2+x disordered domain in significant proportion near the surface. 3. Characterization. By the same logic, meaningful spectra and other physical characteristics could be obtained only after reaching acceptable purity in nanodiamond. We will mainly discuss Raman, XPS and other spectral information obtained from our latest samples.
Carbon nanodiamond is a promising candidate for a range of targeted therapeutic and imaging applications in medicine. One obstacle to realizing these goals is the fact that nanodiamonds have a propensity to aggregate in solution; hence there is a desire to find ways of generating stable suspensions of these nanoparticles in aqueous media. By considering various surface functionalizations of small carbon nanodiamonds, we have used potential of mean force calculations, alongside molecular dynamics simulations, to calculate the free energy of nanoparticle association in liquid water. We construct the required force-fields for this work based on density-functional tight-binding calculations. We probe how various surface functionalizations of the nanodiamonds affect the propensity to aggregate, and also examine the effects of surface charge density and distribution on this aggregation.
Diamond in nanoparticle form is a promising material that can be used as a robust and chemically stable catalyst support in fuel cells. It has been studied and characterized physically and electrochemically, in its thin film and powder forms, as reported in the literature. In the present work, the electrochemical properties of undoped and boron-doped diamond nanoparticle (BDDNP) electrodes, fabricated using the ink-paste method, were investigated. The route used to prepare the suspensions (inks) of diamond nanoparticles (DNP) and BDDNPs for the electrochemical studies was shown to be well-suited to obtain useful electrochemical information on these nanoparticle diamond supported systems. The cyclic voltammetry results showed that there were significant differences between the DNP and BDDNPs samples, with the latter exhibiting superior characteristics in terms of various electrochemical applications, including that of catalyst support. For the latter application, perhaps the most important consequence of the observed low capacitance and wide potential window might be the expected stability, particularly at higher potentials. Chemical reduction of metal nanoparticles at the nanometer scale was successfully performed using DNPs and BDDNPs as support materials by using an excess of a mild reducing agent (NaBH4) and a surfactant (SDBS). X-ray diffraction peaks for the metallic nanoparticles were clearly observed. The XPS and DRIFTS results provided important information about the type of surface functional groups on the diamond involved in the metal deposition. These techniques indicated that platinum ions interact, become reduced, and are deposited as metal on sites containing mainly -OH and CH2 (or â?"CH3) groups. TEM micrographs showed that the nanosize metals were crystals of less than 5 nm, which exhibited lattice fringes for the atomic planes of metal material, indicating good crystallinity, as well as of those of diamond. The distribution and dispersion of diamond and reduced metal nanoparticles were also clearly observed. Enhanced dispersion of some samples obtained through the use of SDBS surfactant was also observed. Homogeneous layers of catalyst systems on GDLs were obtained by the brush painting technique. This process was reproducible, as evidenced by the similarity of thicknesses of the layers prepared for anodes and cathodes, as determined by SEM. Metal loadings were close to the expected values. Drying and weighing steps were also important, as well as the humidity control at the conclusion of the painting process. Anodic polarization results for methanol oxidation demonstrated that respectable current densities, in the range of mA cm-2, could be obtained with both DNPs and BDDNPs decorated with Pt and Pt-Ru catalysts prepared using excess reducing agent and surfactant. The power densities obtained from the best catalytic system (ca. 55 mW cm-2 for Pt-Ru/BDDNP) were comparable to those obtained with amorphous carbon-supported catalytic systems, which are typically around 60 and 70 mW cm-2 at the same temperature.48 Based on the single fuel cell testing, it can be concluded that DNPs and BDDNPs can be used as practical electrocatalyst supports for Pt and Pt-Ru in direct methanol fuel cells or hydrogen-fueled polymer electrolyte fuel cells. Acknowledgements This work was supported by the NSF Center for Hierarchical Manufacturing at the University of Massachusetts Grant No. CMMI-0531171, NASA-URC Center for Advanced Nanoscale Materials Grant No. NNX10AQ17A and NSF-EPSCoR Institute for Functional Nanomaterials Grant No. OIA-0701525 and EPS-1002410. The authors acknowledge The Cornell Center for Materials Research (CCMR) for the TEM Analyses. The CCMR is funded by the National Science Foundation as part of the Materials Research Science and Engineering Centers program under Award Number DMR-0520404.
A laser irridiation technique was utilized for the synthesis, dispersion and functionalization of nanodiamonds here by us. Firstly, ultrafine nanodiamonds with sizes of 3â?"6 nm were prepared by irradiating graphite suspension using a long-pulse-width 1.2 ms laser at room temperature and normal pressure. The low power density and long pulse laser generated a lower temperature and a lower pressure, which determine the stable size of nanodiamonds. On the other hand, the low degree of supercooling allows a rather low growth velocity, and a disordered structure formed at the diamond surface retards the epitaxy growth. The above two factors dynamically limit the final size of nanodiamonds. Our results suggest that the growth of nanodiamonds follows the Wilson-Frenkel law, and the long pulse laser is propitious to producing fine nanodiamonds. Secondly, detonation nanodiamonds were found that can be deaggregated by laser irradiation in liquid. The amorphous carbon could absorb the laser energy and be heated; however the primary nanodiamonds are transparent to the laser. The explosive of amorphous carbon further destroy the covalent bonds between primary nanodiamonds and thereby release the nanodiamonds. The deaggregated nanodiamonds with size of about 6.3 nm were well-dispersed and stable in many none polar solvents. The surface of nanodiamonds could be modified by the liquid molecules during the laser ablation, which endows the nanodiamonds with visible light emission. Thirdly, by using the laser irradiation of carbon powders in organic solvents, the surface modification on the nanodiamonds occurred simultaneously with the formation of the nanodiamonds, and effective surface states for luminescence could be generated by selecting appropriate solvents. The present method is not limited to carbon materials, the extreme conditions created by laser ablation should be conducive to obtaining semiconductor (such as Si, Ge, and GaN) nanoparticles with unusual structures. On the other hand, the surface ligands and then luminescent properties could be modified conveniently by adopting different organic solvents. Therefore, this method shows high potential for fabricating new luminescent materials.
Nanodiamond powder (ND) has become one of the most promising and well-studied nanomaterials applied in various fields of science, technology and medicine. Recent achievements in the development of advanced ND applications present new demands to ND quality: purity, homogeneity of primary particle dimensions and surface area chemistry. ND produced by well-known detonation synthesis needs additional purification and fractionation which significantly increases the cost. Therefore, alternative methods of ND synthesis from pure carbon raw materials enabling to control the process are of especial importance. The novel technology for ND laser synthesis has been developed by Ray Techniques Ltd. The method is based on high-intensive laser radiation treatment of a specially prepared target containing non-diamond carbon soot placed in a liquid media. As a result, carbon atoms collect to form a cubic diamond crystalline lattice. This happens due to thermo-mechanical instability characterized by highly inhomogeneous space distribution of both the pressure (P) and the temperature (T) of the target mixture. As the duration of laser pulses is rather short, the time derivatives of both pressure (dP/dt) and temperature (dT/dt) are extremely high. Both P and T also rise dramatically in certain micro-regions reaching the values in which the thermodynamically stable form of carbon is a diamond. Thus, the key idea of the method is creation of very high local rates of both dP/dt and dT/dt. To do that, RT determined the appropriate parameters of the laser radiation, special composition of the target and the liquid media, as well as the treatment procedures. The â?owinningâ? combination of these factors enables to obtain pure monodispersed nanodiamonds (RayND). Changing some of parameters can cause changes of properties affecting further applicability: ND dimensions, structure and surface chemistry, as well as the productivity. In contrast to the existing technology, the RT method is highly controllable, environment-friendly and non-hazardous. It is also shown that it will be highly efficient in industrial production. RayNDs obtained under different conditions were studied and compared with detonation ND currently available at the market. It is shown that the higher level of purity and homogeneity of RayND, as well as a better diamond structure constitutes significant advantages for most ND applications. Using RayND opens new frontiers in biomedicine (drug- and gene-delivery and bio-imaging agents), electronic industry (abrasives for wafer polishing, heat-conductivity, electrical-insulating compounds, CVD coatings, emitters, etc) and optics (protective transparent films, laser lenses, optical windows and filters).
Nanodiamonds (NDs), most commonly made by a detonation process, have attracted considerable interest recently, in part because of the unique surface chemical and electrical properties they possess when compared to thin-film or bulk diamond. It has been widely demonstrated that NDs support a mixture of OH, COOH, O, NH and H surface terminations, following the purification processes used subsequent to their formation. It is also possible to chemically treat NDs to impart a single dominant termination type. In this paper, procedures for doing this will be mentioned, and the electrical and biological properties of the resultant NDs considered. For example, we have extensively studied the ability of neurons, the most difficult of cell types when it comes to regeneration, to attach and grow into fully operational networks in the presence of NDs, whilst other forms of diamond (and non-diamond substrates) are ineffective in this way. The mechanism behind this observation will be considered in terms of protein expression and adsorption. A particularly interesting application for biologically active NDs is their incorporation within polymeric scaffolds used as implants for nerve regeneration. The use of such devices, both permanent and biodegradable will also be considered.
The first approach to utilize nanodiamond particles for surface machining process is ELID (Electrolytic In-process Dressing)-Grinding with specific bonding grinding wheel with nanodiamond as abrasive grains, and nanometric surface smoothness has been achieved in finish grinding of such brittle materials as semiconductor and optical materials. A surface roughness of 0.3nm in Ra has successfully achieved for monocrystalline silicon. This process is particularly effective for finishing of difficult-to-machine materials. The second approach to utilize nanodiamond particles for surface machining process is combination of coarser diamond and nanodiamond abrasive grains for ELID-grinding wheels. Dramatic improvement in surface smoothness has been proved with a same grinding rate as that without nanodiamond abrasive grains. The combination such as #2000 and nanodiamond abraisve grains, #8000 and nanodiamond abrasive grains have been attempted to be used for optical glasses, tungsten carbide and sapphire. This presentation gives introductions of those research activities.
The use of nanodiamond is as diverse as its users. One area that can be described is in polishing of ceramic and glass substrates. Two types of polishing vehicles exist. Water and oil. The addition of nanodiamond to existing polishing systems is somewhat of a new concept. Depending on the substrate, Silicon Carbide, Sapphire, Fused Silica,etc,small amounts of nanosized or submicron sized hybrid diamond can produce spectacular results. Refering to Table 1 we can see that either with Pad or Pitch tables small additions to the total system produces pronounced efficiencies in productivity or finish. Depending on the accuracy of the process measurement between 30 and 70% productivity improvements have been seen. In almost all cases quality has been improved, i.e. flatness, surface roughness,etc. We see these results because nanodiamond consists of a primary pure polycrystalline diamond particle of 2 â?" 10 nm surrounded by a cluster of complex carbon compounds. SUMMARY The complexity of the surface of nanodiamond may never be completely understood. However one can state that precise surface modification and grading is required for consistent quality in use. The finer distribution of nanodiamond the less reactive the surface becomes without additional surface functionalization. This might explain why a 100nm nanodiamond will only achieve 20 to 30% productivity increase on Silicon Carbide wafer polishing while an 80 nm nanodiamond will achieve a 50% increase in productivity for essentially the same activity on â?~Râ?T Plane sapphire. The closer the cluster size gets to the primary particle the greater the carbon to carbon double bonding exist. The further from the primary particle or larger the Particle Size Distribution the bonding becomes infused with oxygen,carbon and hydrogen,oxygen,bonds. The binding energy is less suggesting a lowering of cluster strength. CONCLUSION The selection of nanodiamond sizing is dependant on what is to be accomplished. It is however counterintuitive to select a 60 nanometer nanodiamond when for example 100 nm colloidal silica is being used. While this may work it may not be the optimum solution. A complete analysis of the mediums used in polishing asspeeds,drip rate,recirculation, pad hardness, and so. In other situations where most of the variables have been accounted for,a simple addition of various weight percents of nanodiamond will achieve the desired results of increased productivity, reduction of rejects and/or increased in surface finish.
Recently, there is a great interest in the synthesis of ultrathin (100 nm and below) nanocrystalline diamond films, for various applications in nanoelectronics, nanoelectromechanical systems (NEMS)  and as a conformal coating for electrodes in bio-medical applications. Use of nanodiamond particles either produced by detonation (DND) or by mechanical grinding of HPHT diamond have been shown to be very useful in seeding the substrate surface to produce thin diamond films with thickness down to 70 nm. It has been observed that in order to produce a continuous, pinhole-free UNCD thin film, an initial nucleation density in excess of 10E11 cm-2 is required with average particle size in the range of 20 to 30 nm . The most common method used for the seeding is ultrasonic agitation in an alcohol solution. Water-based solution containing nanodiamond is more attractive since it eliminates waste containing alcohol. In the case of water-based solution, however, the sample surface often needs to be treated with appropriate chemical treatment to create a hydrophilic surface to achieve uniform wetting of the surface for better results. We present a method involving the use of water-based solution with nanodiamond (agglomeration size 5-15 nm), where no chemical activation of the wafer surface is required. We show that a very thin (5-10 nm) layer of tungsten not only helps to reduce incubation time but also helps to spread nanodiamond particles uniformly due to the nano-scale roughness of the film resulting in partial embedding of DND particles in to the tungsten film. We have achieved pinhole-free UNCD thin films on 150-mm and 100-mm diameter silicon wafers with a film thickness less than 50 nm and on high-aspect-ratio structures such as AFM tips with film thickness down to 30 nm. We further demonstrate versatility of the water based selective seeding technique in fabricating various functional nanostructures in ultrananocrystalline diamond (UNCD) including nanoporous membranes, micro-resonators, nanowire and nanodots. We present detailed characterization of the substrate surface by using SEM, AFM, TEM/EELS, and XPS techniques and discuss the critical role played by the DND particles surface chemistry when dispersed onto the substrate surface, and the role of substrate morphology. 1.A. V. Sumant et al., MRS Bulletin, 35(4), 281 (2010). 2.J.E. Butler and A. V. Sumant., Chem. Vap. Deposition, 14, 145 (2008). Use of the Center for Nanoscale Materials was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. We appreciate getting Nanodiamond seeding solution from Olga Shenderova from ITC Inc and collaboration.
In this work we address a novel concept of a hybrid nanocomposite, constituted of a nanocrystalline diamond (NCD) thin film incorporating magnetic nanoparticles (MNPs). Ultrananocrystalline diamond (UNCD) and nanocrystalline (NCD) diamond nanostructures have attracted more and more interest due to their unique electrical, optical and mechanical properties, which make them widely suitable for different applications, such as: MEMS devices, lateral field emission diodes, biosensors, thermoelectric constituents, etc. Also magnetic nanoparticles (MNPs) have been intensively investigated due to their applications in biomedicine (contrast agents for MRI, drug carriers, hyperthermia etc.), magnetic storage, magnetic separation and so on. The NCD and MNPs nanocomposites therefore combine functional properties of both unique classes of materials. For the fabrication, the NCD deposition technique using a high frequency pulsed microwave plasma CVD, working at low pressure has been employed. Initially we seeded silicon and fused silica substrates by a spin-coating with colloid consisting of a mixture of NCD and MNPs, dispersed in water. The concentration of the MNPs and the NCD in the seeding colloid was varied in order to obtain homogeneous seeding. In our study we used iron oxide and cobalt ferrite nanoparticles with the size ranging from 5 to 20 nm, prepared by different methods and stabilized with different surface coating. For the depositions a mixture H2/CH4/CO2 and low temperatures below 300Â°C were used. Morphology of the grown nanocomposites was studied by Atomic Force Microscopy and Scanning Electron Microscopy. The phase composition and the nanoparticles sizes (by means of the coherently scattering domain) were probed by glancing-angle X-ray diffraction. The nature of the carbon phase has been also examined by the Raman spectroscopy. Magnetic response of the samples was studied using a SQUID magnetometer, and subsequently by Magnetic Force Microscopy. The results of the detailed characterization and investigation of magnetic properties will be presented and the best preparation approach of the NCD and MNPs nanocomposites will be suggested.
Lubricants contain many additives in base oils which are organic compounds and the components can react at sliding contacts resulting in the degradation of lubricants and shortening their life. The additives containing phosphorus, sulfur and heavy metals have been used widely, however, they should reduce to use because of environmental problems. We are interested in nano-diamond as a lubricant additive, because it is non-toxic and stable physically and chemically. Since hydrophilic nano-diamond can disperse in water, it expects to be used as a lubricant additive in water as a base fluid instead of oil. On the other hand, lubrication with water has been demanded widely because water has many advantages such as environmentally-friendly liquid, high thermal capacity and chemical stability. Since water has a low viscosity, a certain interface-structure is needed to obtain lubricating performance with water. In this paper, we focused on hydrophilic nano-diamonds as a lubricant additive in water without any additives. Hydrophilic nano-diamonds were produced by a detonation method and disintegration by milling in water and they can disperse in water. Nano-diamond with 4 nm in diameter was dispersed in distilled water and the concentration was controlled. The solution was supplied at the sliding interface as a lubricant. Silicon wafer and several hydrogels were used as a sliding disk. Two friction testers were employed for evaluation of lubricating properties. Friction coefficient was monitored during friction tests. The surface morphology was observed by an optical microscope after friction tests. Low friction coefficient was obtained with a nano-diamond solution in water, however, scratched mark on silicon and sapphire surfaces was observed when silicon wafer was used as a substrate. Abrasive wear of the substrate and the ball was occurred by aggregated nano-diamond particles. On the other hand, low friction coefficient of 0.03 was obtained and no wear was observed on substrate and slider when hydrophilic gel substrates were used. The lubricating property can be continued more than 500 min by applying only water to the sliding interface. In the case of hydrophobic gel, higher friction coefficient was observed compared to hydrophilic gels. It can be concluded that hydrophilic interface structure is principle to obtain low friction coefficient. A mechanism of the water lubrication with hydrophilic nano-diamond will be discussed.
The tribological properties of anti-wear additive containing nanodiamond powder in lubricating oil were studied using a tester. The experimental results revealed that the anti-wear additive containing nanodiamond powder possessed better anti-wear and friction and temperature reduction properties in comparison with some commercial additives.
Detonation nanodiamond possesses high thermal conductivity (2000 W m-1 K-1), a small primary particle size (< 10 nm) and a low aspect ratio (quasi-spherical)â?" all ideal attributes for enhancing the functionality of thermal fluids and lubricants. Nanofluids containing diamond and using water, water-glycol, oils, or synthetic esters as the base fluid were prepared for thermal and tribological characterization. The thermal conductivity and heat transfer coefficient of fluids containing nanodiamond additives were measured via hot-wire probe and a custom test stand designed to replicate cooling conditions for dense electronics packaging. The nanodiamond additive improves both thermal conductivity and heat transfer coefficient. The relationship between nanodiamond concentration and property enhancement is dependent upon both temperature and surface chemistries. Current theories regarding thermal conductivity enhancement will be discussed in terms of this experimental data. Nanodiamondâ?Ts application as a lubricant additive is investigated using a range of relevant tribological tests. Nanolubricants are tested using a four-ball tester, a block-on-ring tester, and a High Speed Load Capacity test. Fluids containing the nanodiamond additive demonstrate reduced operating temperatures, reduced friction, reduced wear, and enhanced scuffing resistance.