Symposium Organizers
Raz Jelinek, Ben Gurion University
Petras Juzenas, Oslo University Hospital
Ya-Ping Sun, Clemson University
Bai Yang, Jilin University
NM01.01: Carbon Dot Basics
Session Chairs
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 305
8:30 AM - *NM01.01.01
Graphene Quantum Dots from Coal
James Tour 1
1 , Rice University, Houston, Texas, United States
Show AbstractDiscussed willl be routes to prepare graphene quantum dots from coal, their use in composites, energy devices and medicine.
9:00 AM - *NM01.01.02
Strongly Emitting Carbon Dots—Synthesis, Luminescence Properties and Application in Nanothermometry
Andrey Rogach 1
1 , City University of Hong Kong, Kowloon Hong Kong
Show AbstractChemically synthesized carbon dots have emerged over the recent years as a new class of efficient light emitting materials [1]. After presenting our recent synthetic strategies leading to highly luminescent carbon dot based phosphors with improved stability and the emission extended towards the red part of the spectrum [2,3], I will present optical spectroscopic studies focused on elucidating the role of molecular fluorophores on the emission characteristics of carbon dot species chemically synthesized from the commonly used precursors citric acid and a variety of amines [4,5]. I will conclude my talk with an example on how temperate dependent emission of carbon dots can be employed for intracellular photoluminescence lifetime thermal sensing [6].
[1] C. J. Reckmeier, J. Schneider, A. S. Susha, A. L. Rogach. Luminescent Colloidal Carbon Dots: Optical Properties and Effects of Doping. Optics Express 2016, 24, A313.
[2] D. Zhou, Y. Zhai, S. Qu, D. Li, P. Jing, W. Ji, D. Shen, A. L. Rogach. Electrostatic Assembly Guided Synthesis of Highly Luminescent Carbon-Nanodots@BaSO4 Hybrid Phosphors with Improved Stability. Small 2017, 13, 1602055.
[3] D. Zhou, D. Li, P. Jing, Y. Zhai, D. Shen, S. Qu, A. L. Rogach. Conquering Aggregation-Induced Solid-State Luminescence Quenching of Carbon Dots through a Carbon Dots-Triggered Silica Gelation Process. Chem. Mater. 2017, 29, 1779.
[4] C. J. Reckmeier, Y. Wang, R. Zboril, A. L. Rogach. Influence of Doping and Temperature on Solvatochromic Shifts in Optical Spectra of Carbon Dots. J. Phys. Chem. C 2016, 120, 10591.
[5] J. Schneider, C. J. Reckmeier, Y. Xiong, M. von Seckendorff, A. S. Susha, P. Kasak, A. L. Rogach. Molecular Fluorescence in Citric Acid Based Carbon Dots. J. Phys. Chem. C, 2017, 121, 2014.
[6] S. Kalytchuk, K. Polakova, Y. Wang, J. P. Froning, K. Cepe, A. L. Rogach, R. Zboril. Carbon Dots Nanothermometry: Intracellular Photoluminescence Lifetime Thermal Sensing. ACS Nano 2017, 11, 1432.
9:30 AM - NM01.01.03
Bottom-Up and Top-Down Synthesized Carbon Quantum Dots—Structure-Function Relationship and Photodynamic Anti-Cancer Effect
Tim Pillar-Little 1 , Namal Wanninayake 1 , Doo Young Kim 1
1 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractCarbon quantum dots (CQDs) show great promise for bio-imaging and photo-induced therapeutics due to their low cost, facile synthesis and controllable optical properties. In this study, two types of CQDs were synthesized and their chemical structure and property relations were compared. A top-down approach utilizes the harsh oxidation of bulk carbons to produce graphene quantum dots (GQDs) whereas a bottom-up approach produces carbon nanodots (CNDs) by the condensation of small organic molecules like glucose or citric acid. With a unique balance of low dark cytotoxicity and strong photodynamic effect, CQDs can be employed as antibacterial and anti-cancer agents. However, their potential cannot be fully realized without understanding the mechanism for photodynamic activity. Spectroscopic and chemical methods were employed to differentiate the chemical structure of CQD produced by the two approaches. In viability tests with A549 and HL60 cells, both GQD and CND demonstrated excellent biocompatibility in dark. After exposure to blue light, GQD showed a superior PDT effect compared to CND. Based on the chemical structure of GQD and CND, we hypothesize this originates from the varied sp2:sp3 carbon content and vastly different functional group distributions. Interestingly, the incorporation of nitrogen atoms into the carbon network enhanced PDT efficiency in CND but GQD was negatively impacted. Our results suggest that the collapse of the surface passivation layer of CND upon the addition of nitrogen atoms is the cause of this enhancement. For GQD, the substitution of oxygenated functional groups with nitrogen-containing functional groups seems to alter the attraction of O2 to the photo-excited core, which is a prerequisite for the production of reactive oxygen species (ROS). Singlet oxygen (1O2) was quantitatively measured and found to be a primary factor for the observed photodynamic effect. Plasmid samples of known size were irradiated with light and the fragments were separated by gel electrophoresis to determine the presence of other ROS like hydroxyl radical or superoxide ion. Specific 1O2 and radical quenching agents such as (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO) and catalase were also studied. From these results, it is concluded that 1O2 production is the dominant pathway with minor contribution from other ROS. This presentation underlines the significance of understanding CQD structure-function relations in order to develop low-cost, photodynamic anti-cancer and anti-bacterial agents.
9:45 AM - NM01.01.04
Sensitive, Selective Detection and Differentiation of Nitro-Explosives Using Fluorescent Carbon Dots
Xiangcheng Sun 1 , Yu Lei 1
1 Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractInstant, sensitive and selective detection of nitro-explosives has gained increasing attention in recent years because of the implications for homeland security, global demining and environmental safety. Here we applied a series of fluorescent carbon dots (CDs) to sensitive and selective detection and differentiation of nitro-explosives. Firstly, blue fluorescent carbon dots were prepared through a single precursor and worked as trinitrophenol (TNP) sensors. It was found that TNP could sensitively and selectively quench the emission of carbon dots. The excellent sensing performance to TNP was attributed to the synergistic effect on TNP's low molecular orbitals, the presence of energy transfer as well as acid-base interactions. Later on, CDs-Au NPs complex was used to determination of TNT through a fluorescence-on mode. Au NPs could quench the emission of CDs due to energy transfer and the interactions. Addition of TNT sensitively and selectively restored the emission of CDs. Finally, we prepared nitrogen and phosphorus co-doped carbon dots with dual wavelength FL emission, which demonstrated ratiometric sensing and differentiation between different explosives targets (e.g., TNT and TNP).
9:45 AM - NM01.01.04
Sensitive, Selective Detection and Differentiation of Nitro-Explosives Using Fluorescent Carbon Dots
Xiangcheng Sun 1 , Yu Lei 1
1 Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractInstant, sensitive and selective detection of nitro-explosives has gained increasing attention in recent years because of the implications for homeland security, global demining and environmental safety. Here we applied a series of fluorescent carbon dots (CDs) to sensitive and selective detection and differentiation of nitro-explosives. Firstly, blue fluorescent carbon dots were prepared through a single precursor and worked as trinitrophenol (TNP) sensors. It was found that TNP could sensitively and selectively quench the emission of carbon dots. The excellent sensing performance to TNP was attributed to the synergistic effect on TNP's low molecular orbitals, the presence of energy transfer as well as acid-base interactions. Later on, CDs-Au NPs complex was used to determination of TNT through a fluorescence-on mode. Au NPs could quench the emission of CDs due to energy transfer and the interactions. Addition of TNT sensitively and selectively restored the emission of CDs. Finally, we prepared nitrogen and phosphorus co-doped carbon dots with dual wavelength FL emission, which demonstrated ratiometric sensing and differentiation between different explosives targets (e.g., TNT and TNP).
NM01.02: Properties and Applications I
Session Chairs
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 305
10:30 AM - *NM01.02.01
Chiral Nanocarbons
Nicholas Kotov 1
1 , University of Michigan, Ann Arbor, Michigan, United States
Show AbstractOne of the rapidly expanding fields of inorganic materials is chiral inorganic nanostructures. This talk will cover both experiment and theory of chiral nanostructures as applied to chiral nanocarbons and in particular to carbon/graphene quantum dots, their assemblies with distinct mirror asymmetries, and composite materials from carbon nanotunbes, graphene and other nanocarbons with strong rotatory optical activity. The origin and multiple components of mirror asymmetry of individual chiral inorganic carbons and their assemblies represent the fountation of this talk. Differences and similarities with chiral structures known from other fields of chemistry will be discussed as well.
Developement of the field of chiral inorganic nanostructures started from the observation of strong circular dichroism for simple nanoparticles and their assemblies, and expanded to sophisticated constructs including nanocarbons. Besides the well-established chirality transfer from bioorganic molecules extensively used in organic chemistry, other methods to impart handedness to nanoscale matter specific to inorganic materials were discovered. They include multiphoton chirality transfer, polarization effects in nanoscale assemblies, lithography and others. Multiple chiral geometries were observed with characteristic scales from ångströms to microns. One of the representative examples is the graphene quantum dots with either left or right twist of the entire nanoscale sheet that generates circular dichroism peaks with opposite polarity. The latter should be attributed to resonances of incident electromagnetic radiation with plasmonic and excitonic states of nanoscale carbons.
Distinct similarities with chiral supramolecular and biological systems also emerged. The analysis of these similarities with known biological, supramolecular, and and other materials help us understand in greater depth the role of chiral nanostructures in Nature and accelerate the development of technologies based on chiral nanocarbons. Their technological prospects in drug delivery and chiral photonics will be discussed.
11:00 AM - NM01.02.02
Structural and Electronic Properties of Nitro-Fullerenes Using Density Functional Theory (DFT)
Wagner Pequeno 1 2 , David Azevedo 2 3 , Edvan Moreira 4
1 , Secretaria de Estado de educação do Distrito Feder, Brasília Brazil, 2 Campus Planaltina, Universidade de Brasília, Brasília, DF, Brazil, 3 Física, Universidade de Brasília, Brasília, DF, Brazil, 4 Física, Universidade Estadual do Maranhão, São Luís, MA, Brazil
Show AbstractRecently, Cabban et al [1] proposed (from a theoretical point of view) nitrofullerene C60[NO2]n (n ranging from 1 to 12) decomposition based on reactive molecular dynamics[2]. In that case, the focus was the fragmentation of the molecular system under temperature increasing, where the authors clearly showed a big amount of energy liberation in an explosion form. In this work, after an extensive conformal search analysis to obtain structures of low-energy using Universal Force Field(UFF) as implemented in Forcite module[3,4], we report for the first time results for Density Functional Theory(DFT) with DMol3 code[5, 6] of energetics of nitrofullerene C60[NO2]1 (NF1) and C60[NO2]2 (NF2) compared with nitroglycerine. From these results, we obtained the Gibbs free energy, for NF1 and NF2, and observed that is almost four times bigger than nitroglycerine at room temperature.
This indicates a very strong potential application for explosives or pyrolysis products.
[1] V.V. Chaban, E.E. Fileti, O.V. Prezhdo, Buckybomb: Reactive Molecular Dynamics Simulation, Journal of Physical Chemistry Letters, 6 (2015) 913-917.
[2] A.C.T. van Duin, S. Dasgupta, F. Lorant, W.A. Goddard, ReaxFF: A reactive force field for hydrocarbons, Journal of Physical Chemistry A, 105 (2001) 9396-9409.
[3] A.K. Rappe, C.J. Casewit, K.S. Colwell, W.A. Goddard, III, and W.M. Skiff, J. Am. Chem. Soc. 114 (1992), pp. 10024–10035.
[4] D. Root, C. Landis, and T. Cleveland, J. Am. Chem. Soc. 115 (1993), pp. 4201–4209
[5] B. Delley, J. Chem. Phys., 2000, 113, 7756-7764, DOI: 10.1063/1.1316015.
[6] P. Hohenberg and W. Kohn, Phys. Rev., 1964, 136, B864-B871, DOI:10.1103/PhysRev.136.B864
11:15 AM - NM01.02.03
Synthesis and Optical Properties of Graphene Quantum Dots
Julien Lavie 1 , Shen Zhao 2 , Lucile Orcin-Chaix 2 , A. Narita 3 , Klaus Müllen 3 , Jean-Sebastien Lauret 2 , Stéphane Campidelli 1
1 , CEA Saclay, Gif sur yvette France, 2 Laboratoire Aimé Cotton, Centre National de la Recherche Scientifique (CNRS), Orsay France, 3 , Max Planck Institute for Polymer Reserach, Mainz Germany
Show AbstractThe outstanding electronic, optical and mechanical properties of graphene strongly inspire the scientific community at both the fundamental and applicative levels. However, along this way several key scientific issues have to be addressed and one of the main challenges of the field is the control and modification of graphene electronic properties, and notably the controlled opening of a sizable bandgap. It is well known that when a material is reduced to nanoscale dimensions, the electronic confinement induces original size-dependent properties. For the last decade, a great attention has been paid to the size reduction of graphene using conventional top-down approaches (lithography and etching, thermal treatments and oxidation of bulk materials) to fabricate graphene quantum dots (GQDs)[1] or graphene nanoribbons (GNRs) [2]. However, top-down approaches do not permit to manipulate the structure of the material at the atomic scale. In particular, they do not allow a sufficient control of the morphology and oxidation state of the edges, which drastically impact the properties. In order to truly control, with the required level of precision, the morphology and the composition of the materials and of its edges, the bottom-up approach is the relevant way to proceed[3],[4].
With the aim to study and understand the optical properties of GQD materials, we performed the bottom-up synthesis[5] of different families of nanoparticles exhibiting controlled shapes and edges. Because of their strong aromatic character graphene nanoparticles tend to aggregate in solution; however, for future application it is of high interest to be able to discriminate the intrinsic absorption and emission of the GQDs from those of aggregates. For example, we observed that by STM and by polarized microscopy that GQDs bearing alkyl chains are forming columnar structures with liquid crystal properties in solvents. Here, we study the optical properties of graphene quantum dots as a function of their individualization. Using absorption, steady-state and time-resolved photoluminescence and photoluminescence excitation (PLE) spectroscopy, we try to establish the intrinsic optical properties of the GQDs and understand how the structure influences the properties.
[1]M. Bacon, S.J. Bradley, T. Nann Part. Part. Syst. Charact. 2014, 31, 415-428.
[2] M. Terrones, A.R. Botello-Méndez, J. Campos-Delgado, F. Lopez-Urias, Y.I. Vega-Cantu, F.J. Rodriguez-Marcias, A L. Elias, E. Munoz-Sandoval, A.G. Cano-Marquez, J.C. Charlier, H. Terrones, Nano Today 2010, 5, 351-372.
[3] A.C. Grimsdale, K. Müllen, Angew. Chem. Int. Ed. 2005, 44, 5592 – 5629.
[4] A. Narita, X.Y. Wang, X. Feng, K. Müllen Surname Chem. Soc. Rev. 2015, 44, 6616.
[5] Z. Tomović, M.D. Watson, K. Müllen, Angew. Chem. Int. Ed. 2004, 17, 755 –758.
11:30 AM - NM01.02.05
Photo-Active Hollow Carbon Dots for Visible Light-Driven Oxidative Coupling Reactions of Amines
Jung Hyun Park 1 , DaBin Yim 1 , Tae Woog Kang 1 , Juhee Han 1 , In-Jun Hwang 1 , Sin Lee 1 , Jong-Ho Kim 1
1 , Hanyang Univ, Ansan Korea (the Republic of)
Show AbstractRecently, optically active carbon-based materials including carbon dots have gained a lot of interest in the field of sensing and photocatalysis. For improvement of the catalytic activity of carbon nanomaterials, it is very important to control their atomic composition and nanostructure. Herein, we report a novel approach for the synthesis of Mo and S atoms co-doped hollow carbon dots (MoS_HCDs) for visible light-driven oxidative coupling reactions of amines. MoS_HCDs were effectively obtained by the solvothermal reaction of MoS2 nanosheets/NMP dispersion at 140oC under the oxygen atmosphere. As-prepared MoS_HCDs had 22 nm in lateral size with a hollow interior of 7 nm. MoS_HCDs exhibited very intense fluorescence emission in the visible region of electromagnetic spectrum (2.7 eV band gap), and showed great photocatalytic activity for the oxidative coupling reaction of various primary and secondary benzylamines under visible light irradiation.
NM01.03: Synthesis and Mechanisms
Session Chairs
Tuesday PM, November 28, 2017
Hynes, Level 3, Room 305
1:45 PM - *NM01.03.01
Fluorescent Carbon Dots—From Mechanistic Studies to Applications
Doo Young Kim 1 , Yiyang Liu 1 , Timothy Little 1 , Somes Das 1 , Chris Richards 1
1 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractFluorescent carbon dots (FCDs) are a new class of carbon-based nanomaterials suitable for various applications including bioimaging, photodynamic therapeutics, sensing, catalysis, and photovoltaics. Despite of extensive studies, structure-property relations and photophysical mechanisms of FCDs remain unclear. Emission mechanism and photophysics of FCDs have been masked in previous ensemble fluorescence studies due to significant inhomogeneity in size, shape, and chemical defects. We employed various structural characterizations and single-molecule spectroscopy to unveil structure-property relations and photophysical pathway. Our observation strongly suggests that single carbon dots can possess multiple chromophoric units associated with the core of FCD and oxygenated defect-related emissive traps. Interestingly, the majority of the chemically-reduced FCD particles showed multiple levels in fluorescence intermittency profiles, while the oxidized particles predominantly showed a single level. It was also found that heteroatom significantly influences single-molecule photo-blinking behavior. Nitrogen-doped carbon dots show a larger proportion of particles with near-IR emission as compared to un-doped particles. Doping of FCDs also resulted in changes in the photo-stability and the fluorescence intermittency seen in single FCD particles. While milliseconds to seconds time scale blinking was regularly observed for red-emitting nondoped carbon dots, nitrogen doping significantly reduced blinking. The spectral range was extended to red wavelength under strong alkaline condition. In this talk, time-resolved fluorescence lifetime results of top-down and bottom-up synthesized FCDs will be discussed. In addition to results from fundamental studies, our recent progresses in applying FCDs for bio-imaging, photodynamic anti-cancer therapy, surface-modified water-purification membrane, and electro- and photo-catalysis will be also presented.
2:15 PM - NM01.03.02
Synthesis, Properties and Applications of Nitrogen-Doped Carbon Nanodots
Maurizio Prato 1 2
1 , Univ di Trieste, Trieste Italy, 2 , CIC biomaGune, San Sebastian Spain
Show AbstractWe have recently described a simple, scalable, reliable and cost-effective synthetic process for producing high-quality nitrogen-doped carbon nanodots (NCNDs), by employing arginine and ethylenediamine as precursors (1). The new material displays among the smallest size and the highest fluorescence quantum yields reported so far. Moreover, they can be easily post-functionalized, due to the abundant presence of amino groups.
These new NCNDs can act as powerful alternative to the conventional co-reactant species for electro-chemiluminescence generation (2). We have also presented a rational synthetic design for mastering CND properties, showing the importance in the choice of the precursors. By using properly designed functional units, the desired properties can be modulated, from the molecular to the nanoscale level in a controlled fashion. CNDs with customized emission can therefore be approached. Green, red and finally white-emitting CNDs were synthesized (3).
Finally, preliminary investigation on their cytotoxicity, cell uptake and imaging capability, and on their employment for LED fabrication, suggested their potential for various applications.
During this talk, we will communicate our latest results in this fast developing field.
References
(1) Synthesis, Separation, and Characterization of Small and Highly Fluorescent Nitrogen-Doped Carbon NanoDots
Arcudi, F.; Dordevic, L.; Prato, M.
ANGEW. CHEM. INT. ED. Volume: 55 Issue: 6 Pages: 2107-2112 Published: FEB 5 2016
(2) Amine-Rich Nitrogen-Doped Carbon Nanodots as a Platform for Self-Enhancing Electrochemiluminescence
Carrara, S.; Arcudi, F.; Prato, M.; et al.
ANGEW. CHEM. INT. ED. Volume: 56 Issue: 17 Pages: 4757-4761 Published: APR 18 2017
(3) Rationally Designed Carbon Nanodots towards Pure White-Light Emission
Arcudi, F.; Dordevic, L.; Prato, M.
ANGEW. CHEM. INT. ED. Volume: 56 Issue: 15 Pages: 4170-4173 Published: APR 3 2017
3:00 PM - *NM01.03.04
Carbon Dots—The Complex Interplay between Morphology and Optical Properties
Alexander Urban 1
1 , LMU Munich, Munchen Germany
Show AbstractCarbon dots (CDs) have attracted rapidly growing interest in recent years due to their unique and tunable optical properties, the low cost of fabrication and their wide-spread uses. However, due to the complex structure of CDs and the various synthetic strategies employed, both the internal morphology and the intrinsic mechanisms governing the photoluminescence of CDs are still poorly understood.
In this talk I will discuss the latest results on the origin of photoluminescence in CDs. Using the hydrothermal growth method, we find that both molecular fluorophores and polyaromatic hydrocarbons (PAHs) are involved in the emission process. We also look into the role that heteroatoms play in the tuning of the optical properties. Depending on the dopant atoms used, we can tune the absorption and emission of the carbon dots. Moreover, we can shift the relaxation between radiative decay (light emission) and non-radiative charge carrier-splitting, which can be used for photocatalysis. These results highlight how the detailed understanding of the underlying morphology and photophysics of carbon dots can be used to specifically tailor their functionality.
3:30 PM - NM01.03.05
Wisdom from Basil Seeds—Facilitating Role of Phenolic Molecules in Polysaccharide-Based Carbon Dots Formation
Kyueui Lee 1 , Eunsook Park 1 , Caroline Sugnaux 2 , Chan Jin Jeong 3 , Phillip Messersmith 2 4 , Sung Young Park 3 5 , Haeshin Lee 1
1 Chemistry, KAIST, Daejeon Korea (the Republic of), 2 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 3 IT Convergence, Korea National University of Transportation, Chungju Korea (the Republic of), 4 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 5 Chemical and Biological Engineering, Korea National University of Transportation, Chungju Korea (the Republic of)
Show AbstractFluorescent carbon nanoparticles, in other words carbon dots, have been extensively studied for their applications. It has been previously demonstrated that the carbon dots can be easily prepared by sulfuric acid-induced carbonization reaction using various natural polysaccharides (e.g. birch kraft pulp, mango fruit, sweet pepper, grass, pomelo peel, soy bean, grapefruit, banana, cabbage and so on) as chemical sources. However, the chemical mechanism of carbon dots formation with natural polysaccharides has poorly been studied despite the extensive studies of carbon dots. Herein, we found that small amounts of ester-linked ferulic acid to the polysaccharide chains of basil (Ocimum basilium) seeds (mainly composed of glucomannan) induce local condensation of polysaccharides more efficiently, resulting in carbon dot production. Compare to the carbonized glucomannan, the sample with glucomannan and trace amounts of ferulic acid (0.4 wt% of glucomannan) exhibited doubly enhanced photoluminescence after the carbonization reaction, demonstrating the distinctive roles of ferulic acids as a chemical seed for facilitated carbon dot growth. Presumably, carbon dots generated from natural sources might share the similar mechanism of phenolic compound mediated nanoscale condensation followed by core carbonization. Our study indicates that the unavoidable trace amounts of phenolic compound in polysaccharides plays a significant role in catalytic seeds for carbon dot formation.
3:45 PM - NM01.03.06
A New Graphene Quantum Dot Sensor for Estimating an Antibiotic Concentration
Nuzhet Ahamed 1 , W Fan 1 , P. Wong 1 , M. Schrlau 1 , Kalathur Santhanam 1
1 , Rochester Institute of Technology, Rochester, New York, United States
Show Abstract
Recently, there has been concern on antibiotics like ciprofloxacin (CPFX) entering into the environment through different sources such as live stocks, agricultural run off and domestic water effluents that would result in antibiotic resistant bacteria (1). Consequently, there has been need to have a sensor that would enable us to measure the concentration of CPFX so that adequate steps could be taken to remove CPFX in the environment. A number of methods have been examined for this purpose. However, none of them have the sensitivity and reliability as the methods employ the oxidative property of CPFX; CPFX oxidation occurs at potentials greater than 1.0 V. We wish to report here the construction of ferric ion modified graphene quantum dot senor that senses CPFX with high accuracy and reliability. The sensor development is based on the principle that Ferric ion binds to CPFX and the bound species is reduced by differential pulse voltammetry. Ferric ion undergoes a well defined one electron reduction in sodium sulfate solution (pH=6.5) at graphene quantum dot electrode (GQD) in differential pulse voltammetry (DPV) at 0.31V vs Saturated Calomel Electrode (SCE) with a peak width of 0.10 V. The ferric ion reduction in the bath containing nanomolar to micromolar concentrations of ciprofloxacin shows a distinct reduction in the cathodic peak and the appearance of three cathodic peaks in DPV at EI pc=0.160 V, EIIpc=0.200V and EIII pc= -0.10V. At a concentration of ciprofloxacin in the solution that is in excess of the binding, only the above three peaks are observed. The decrease in the cathodic peak at Epc =0.31 V is linear with the concentration of ciprofloxacin and hence has been used as an electrochemical sensor in the potential pulse method for the estimation. Due to the large surface area of graphene (2), the CPFX bound ferric species shows enhanced peak currents. The sensor is fabricated by depositing graphene quantum dot containing known concentration of ferric ion (3). The sensor response to different concentrations of CPFX is measured by monitoring the integrated current flow in the potential step experiment from 0.60 V to 0.20V. The sensor response from nanomolar to micromolar concentrations have been measured successfully suggesting the feasibility of the sensor for its use in aqueous environmental analysis.
1) P. Gayen and B. P. Chaplin, ACS Appl. Mater. Interfaces, 8 (3),1615–1626 (2016).
2) A.K. Geim and K.S. Novoselov, Nat. Mater., 6, 183–191 (2007).
3) Z. Protich, P. Wong, and K. S. V. Santhanam, ACS Sustainable Chem. Eng., 4 (11), 6177–6185 (2016).
NM01.04: Poster Session
Session Chairs
Wednesday AM, November 29, 2017
Hynes, Level 1, Hall B
8:00 PM - NM01.04.01
Size Fractionation of Graphene Quantum Dots Using Cross-Flow Membrane Filtration
Sang-Gu Yim 1 , Yong Jin Kim 2 , Ye-Eun Kang 1 , Byung Kee Moon 3 , Eun Sang Jung 4 , Seung Yun Yang 1
1 Biomaterial Science, Pusan National University, Miryang-si Korea (the Republic of), 2 , Institute of Basic Sciences Center , Ulsan-si Korea (the Republic of), 3 , Pukyong National University, Busan-si Korea (the Republic of), 4 , Pusan National University, Miryang-si Korea (the Republic of)
Show AbstractGraphene quantum dots (GQDs) have received a great attention as a promising material for biological, opto-electronics, and energy applications due to its low toxicity, stable photoluminescence (PL) in moderate pH solutions, and high chemical resistance. Especially, unique PL features of GQDs depending on its size and shape make it possible to exploit in bio-imaging applications. Although many synthetic or manufacturing routes have been proposed to produce a GQD solution, the broad size distribution in GQD solutions limits its use as efficient optical agents. Several separation methods such as centrifuge and dead-end filtration have been used to get a narrow size distribution of GQD but more scalable and efficient separation method need to be developed. Here we present a new method for the separation of GQDs dispersed in water by using cross-flow filtration system with track-etched membranes having uniform and cylindrical nanopores. The aqueous GQD solutions mainly consisting of blue-emitting GQDs (B-GQDs) and green-emitting GQDs (G-GQDs) were introduced to the track-etched membrane and fractionated with a constant permeate flow of 7.8 L/m2hr at 0.1 bar. After membrane filtration, we observed a clear blue fluorescence in the permeate side attributed by selective permeation of relatively small B-GQD molecules. The selectivity in terms of separation factor between B-GQD and G-GQD was 0.74, indicating B-GQDs were enriched in the permeate side. Our results demonstrated a simple method for the size fractionation of two-dimensional nanostructures including GQDs using cross-flow filtration system with membranes having uniform pore size. Since the membrane process for separation of molecules is cost-effective and scalable, our approach can be applied to obtain a large amount of size-controlled GQDs.
8:00 PM - NM01.04.02
Tunable Morphology and Photoluminescence of Hybrid Carbon Nanocomposites Depending on Solvent Polarity
Yuri Choi 1 , Byeong-Su Kim 1
1 , UNIST, Ulsan Korea (the Republic of)
Show AbstractThe tunable photoluminescence (PL) of carbon nanodots has received much attention for a wide range of applications. However, despite significant progress in the development of carbon nanomaterials showing solvent-dependent PL, only few example of the tunability covering the wide range of colors has been reported. Toward this end, graphene oxide (GO), an oxidized analogue of graphene, has been proposed for the modulation of the molecular configuration of carbon nanomaterials because of its surface functional groups together with its high specific surface area. Herein, we report a unique design and synthesis of hybrid carbon nanosheets (CNSs), which show strong solvatochromic behavior with wide emission tunability ranging from blue to orange and even to white in various solvents. The hybrid CNS hosts clusters of carbon nanorings on the surface of GO nanosheets as the product of the hydrothermal reaction of small molecular precursors in the presence of GO nanosheets. Unlike the typical formation of spherical carbon nanodots in the absence of a GO template, the molecular precursors turned into concentric carbon nanorings with the aid of the GO template during carbonization. Under UV and visible-light excitation, the prepared CNS displayed highly tunable emission covering the visible ranges depending on the solvent and the excitation wavelength. A detailed mechanistic framework was carefully developed through a series of spectroscopic analyses, including UV/Vis, PL, FT-IR, X-ray photoelectron spectroscopy, and time-resolved electronic spectroscopy. Toward the realization of wide emission of hybrid carbon nanomaterials, this study revealed the origin of solvatochromic PL, which is accompanied by a morphological transition of CNS from 2-dimensional sheets to 3-dimensional crumpled morphologies depending on the solvent. We found that the different degrees of the exposure of surface functional groups to the solvent and the solute-solvent hydrogen (H)-bonding interactions are responsible for the morphological changes. Upon switching from water to DMF, an aprotic solvent, the folded and crumpled structure of CNS showed owing to the maximized intra H-bonding. These factors affect the non-radiative relaxation of the photoexcited surface functional groups causing the steady-state spectral modulation of PL. We anticipate that this solvatochromic CNS poses promising opportunities in optoelectronic devices and sensors.
8:00 PM - NM01.04.03
A Study on Photophysical Property on Graphene Quantum Dots Containing Electron Accepting Moieties
Jongwan Choi 1
1 , Sahmyook University, Seoul Korea (the Republic of)
Show AbstractGraphene quantum dots (GQDs) have been receiving much attraction in various research fields due to their unique physical properties including strong and stable photoluminescence. Furthermore, GQD can be good for making optoelectronic device, sensor, and bioimaging application that has excellent solubility and low cytotoxicity. Recent studies have investigated band gap tuning of GQD through size control. Doping with heteroatoms is effective method to tune their optical property by changing electron density of GQD.
In this work, GQD with electron acceptor moieties were synthesized through chemical reaction. The structural characterization of functionalized GQD was performed through spectroscopic and microscopic studies. Band gap of the GQD was controlled by chemical functionalization, as the shift of the emission color from blue to green was observed with functionalization.
8:00 PM - NM01.04.04
Graphene Quantum Dots Electrochemistry and Development of Sensitive Electrochemical Biosensor
Sanju Gupta 1 , Tyler Smith 1 , Alexander Banaszak 1
1 , Western Kentucky University, Bowling Green, Kentucky, United States
Show AbstractGraphene quantum dots (GQDs) are zero-dimensional material derived from graphene derivatives with characteristics from the structure of graphene with quantum confinement and edge effects possessing unique properties. Intense research activity in GQDs is attributed to their novel physical-chemical phenomena arising from the sp2-bonded carbon core surrounded with edge functional moieties. In this work, GQDs of optimal 5-7 nm size are investigated for their fundamental electrochemical properties and use in electrochemical sensing including enzyme-based glucose biosensor. Glucose oxidase (GOx) was immobilized on GQDs modified glassy carbon (GC) and the UV-Vis absorption and fluorescence spectroscopy, electron microscopy, cyclic and differential pulse voltammetry and electrochemical impedance spectroscopy, techniques were used for characterizing the electrochemical biosensor. The well-defined quasi-reversible redox peaks were observed under various electrochemical conditions (pH, concentration, scan rate) to determine diffusion coefficient and heterogeneous electron transfer rate constant. The developed biosensor based on GOx/GQD responds efficiently to glucose presence over the concentration range 10 mM - 3 mM with limit of detection 4.57 mM. The relatively high-performance is attributed to large surface-to-volume ratio, excellent biocompatibility of GQDs, mesoporous GQD/GC and abundant hydrophilic edges and hydrophobic plane in GQDs that favors the GOx adsorption on electrode surface. We also carried out similar studies with other graphene-based electrode surfaces and biomolecules for electrochemical comparison opening ways for potential sensing applications in medicine as well as biotechnology. The work is supported in parts by NSF KY EPSCoR RSP Award, NASA KY EPSCoR RIDG Award and internal FUSE Grant.
8:00 PM - NM01.04.05
Facile Synthesis of Water-Soluble Graphene Quantum Dots/Graphene Oxide Composites for Efficient Photodetector
Sanju Gupta 1 , J. Walden 1
1 , Western Kentucky University, Bowling Green, Kentucky, United States
Show AbstractGraphene quantum dots (GQDs) are a kind of 0D material with characteristics derived from both graphene and carbon dots (CDs). Combining the structure of graphene with the quantum confinement and edge effects of CDs, GQDs possess unique properties. Intense research activity in GQDs is attributed to their novel phenomena of charge transport and light absorption/ emission. The optical transitions are known to be available up to 6 eV in GQDs, applicable for photonics and biomedical technologies. We present a facile hydrothermal method for synthesizing uniform sized GQDs with a strong greenish and violet blue emission at ~ 10-14% quantum yield. This approach enables a large-scale production of aqueous GQD solution without the need for stabilizers. The structure and emission mechanism of the GQDs have been studied by combining extensive characterization techniques and rigorous control experiments. We further demonstrate the distinctive advantages of such GQDs as high-performance photodetectors (PDs). We report high-efficient photocurrent (PC) behaviors consisting of multilayer GQDs sandwiched between monolayer graphene sheets. The observed unique PD characteristics prove to be dominated by the tunneling of charge carriers through the energy states in GQDs, based on bias-dependent variations of the band profiles, resulting in novel dark current and PC behaviors. We gratefully acknowledge financial support from NSF-DMR, NSF KY EPSCoR, NASA KY EPSCoR and WKU Research Foundation grants.
8:00 PM - NM01.04.06
Synthesis Optimization of Absorption-Tuned Carbon Nanodots for Application as Optoelectronic Hybrid Nano Devices
Frank Dissinger 1 , Kseniia Zimmermann 2 , Davide Cammi 2 , Tobias Voss 2 , Siegfried Waldvogel 1
1 , Johannes Gutenberg-University, Mainz, Mainz Germany, 2 , TU-Braunschweig, Braunschweig Germany
Show AbstractDue to their excellent surface-to-volume ratio in combination with unique electronic characteristics, semiconductor nanowires allow the realization of highly potent optoelectronic devices and sensors.[1] By functionalizing these semiconductor nanowires with quantum dots using organic linker molecules, luminescence dynamics and electron tunneling processes of the resulting hybrid nano devices could be elucidated.[2,3]
Unfortunately, the well-known toxicity of the nanodot compounds (such as CdSe) restrains the fabrication of larger scale devices, thus utilization of carbon nanodots as “green” light harvesters should be considered. These are non-toxic and easily synthesized starting from simple chemicals. Therefore these and optically potent “C-Dots” have been in the focus of research over the last 10 years. Optimization of their luminescence, quantum efficiency and different optical and sensing applications have been reported.[4]
In our work we demonstrate the fabrication and analyzation of a nanoscale hybrid photosensor, where the usage of CdSe has been successfully replaced by carbon nanodots, based on a synthesis with citric acid.
To increase the light harvesting capabilities of the applied nanodots, their absorption characteristics have to be adjusted from the UV-region to lower energetic light. As the different absorption phenomena of the particles are not in a broad research focus and still lack of systematic classification and elucidation, this has to be investigated. [5]
The formation of an organic fluorophore compound is proposed to be a key step in the formation of the photoactive particles and could furthermore be the reason for some observed absorption phenomena. [6]
Using this information, we report the tuning of citric acid based C-Dots for a red shift of their absorption by changing synthetic conditions and varying nitrogen containing stabilizing agents (forming different fluorophore intermediates). Furthermore, the effect on the photoconductivity of resulting hybrid nanostructures consisting of different types of C-Dots and nanowires will be presented.
References:
[1] Joyce, H. J.; Gao, Q.; Hoe Tan, H.; Jagadish, C.; Kim, Y.; Zou, J.; Johnston, M. B., Progr. Quantum Electron. 2011, 35 (2-3), 23-75.
[2] Bley, S.; Albrecht, F.; Resch, S.; Waldvogel, S.R.; Menzel, A.; Zacharias, M.; Voss, T.; Gutowski, J.; Phys. Status Solidi C 2016, 13, 606-609.
[3] Bley, S.; Diez, M.; Albrecht, F.; Resch, S.; Waldvogel, S.R.; Menzel, A.; Zacharias, M.; Gutowski, J.; Voss, J., J. Phys. Chem. C 2015, 119, 15627-15635.
[4] Li, H.; Kang, Z.; Liu, Y.; Lee, S.-T., J. Mater. Chem. 2012, 22, 24230-24253.
[5] Cayuela, A.; Soriano, M.L.; Carillo-Carión, C.; Valcárcel, M., Chem. Commun. 2016, 52, 1211-1326.
[6] Song, Y.; Zhu, S.; Zhang, S.; Fu, Y.; Wang, L.; Zhao, X.; Yang, B., J. Mater. Chem. C, 2015, 3, 5976-5984.
8:00 PM - NM01.04.07
Synthesis of Carbon Quantum Dots under Microwave Irradiation from Biomass Waste
Philippe Pierrat 1 , Pierre Magri 1 , Jean Gaumet 1
1 , University of Lorraine, Metz France
Show AbstractCarbon quantum dots (CQDs) a relative newcomer in material science are fascinating in that they have similar properties as more extensively-developed regular quantum dots, but have greater potential as they are not limited by the presence of heavy metals. CQDs electronic and luminescent properties (e.g. wavelength-tunable emission, excellent photostability and a potential high quantum fluorescence yield) are advantageously combined with chemical stability, biocompatibility and low toxicity.
Syntheses of CQDs are easier to carry out than with quantum dots and they can be elaborated from simple molecules such as citric acid or glucose.[1] Much effort has been devoted to preparing CQDs from raw materials such as citrus fruit peels, ground coffee, orange juice, overcooked meat.[2,3] The synthesis of CQDs usually consist of three steps: carbonization, passivation and functionalization. Microwave irradiation is a relatively new, fast and efficient synthesis method for preparing CQDs as it incorporate all three steps, as opposed to other methods, which require carrying out each step separately.[4] This is a considerable advancement towards more economical synthesis methods, greener chemistry and diversifying sustainable source materials.
We report herein, the synthesis of CQDs from biomass waste materials with the use of a monomode microwave reactor. The accurate verification of temperature, time, pressure and power helps to provide reproducible batches of CQDs with size controlled particles. Various source materials, such as banana and orange peels, vegetables food waste, compost and methanization sludge were first dried at 60°C for 24h then crushed and ground. The prepared samples were diluted in various media (H2O, NH4OH, HNO3) then poured into vials and inserted in the microwave reactor. The numerous polar groups derived from these source materials enable CQDs solubility in water. Different synthesis parameters were studied: the reaction temperature, the reaction time and the concentration of the reactants. Larger particles were removed and the supernatant was purified by dialysis on membrane cut-off at 1000 Da against ultrapure water. The prepared CQDs were then systematically characterized in terms of size (DLS, TEM and AFM), optical properties (absorbance and luminescence spectroscopies), and structure (DRIFT, Raman spectroscopy, IR, NMR, elemental analysis, TGA and XPS).
In conclusion, highly reactive CQDs can be developed from biomass waste via a fast and green microwave method. This is a new means to improving waste biomass upgrading.
References:
[1] P. Pierrat, R. Wang, D. Kereselidze, M. Lux, P. Didier, A. Kichler, F. Pons, L. Lebeau, Biomaterials, 2015, 51, 290-302.
[2] A. Prasannan, T. Imae, Ind. Eng. Chem. Res. 2013, 52, 15673–15678.
[3] C. Jiang, H. Wu, X. Song, X. Ma, J. Wang, M. Tan, Talanta, 2014, 127, 68-74.
[4] I.Y. Goryacheva, A.V. Sapelkin, G.B. Sukhorukov, Trends in Analytical Chemistry, 2017, 90, 27-37.
8:00 PM - NM01.04.08
Hydrothermal Synthesis of Fluorescent L-Cysteine-Derived Carbon Dots by Microwave-Assisted Autoclave Treatment
Taishu Yoshinaga 1 , Yoshiki Iso 1 , Tetsuhiko Isobe 1
1 , Keio University, Kanagawa Japan
Show AbstractFluorescent carbon dots (CDs) are expected as an alternative to compound semiconductor quantum dots containing heavy metals, owing to attractive properties of visible emission, low toxicity, and water solubility. Doping of hetero atoms such as B, N, S, P, and Si, into CDs can improve their photoluminescence (PL) quantum yield. Therefore, we focused on biocompatible L-cysteine containing N and S as a carbon source. We prepared CDs from L-cysteine through hydrothermal synthesis. Here we report that L-cysteine concentration is a key factor to determine particle size, elemental composition, and optical properties of CDs.
L-cysteine was dissolved in ultrapure water at concentrations ranging from 17 to 133 mmol L−1. The solution was purged with argon gas and transferred into a polytetrafluoroethylene (PTFE) vessel. The sealed PTFE vessel was heated at 230 °C for 30 min using an autoclave with a microwave heating system. The resulting suspension was centrifuged at ~16,000 × g (12,000 rpm using a rotor with a diameter of 10 cm) for 15 min to remove a large by-product. The supernatant was passed through a membrane filter (pore size: 0.2 µm) to yield a dispersion of CDs. A powder sample was also prepared by freeze-drying the dispersion for 24 h.
According to TEM observation, mean particle size of CDs decreased with increasing L-cysteine concentration. When the L-cysteine concentration increased from 17 to 133 mmol L−1, N/C molar ratio increased from 0.32 to 0.54, while S/C molar ratio decreased from 0.27 to 0.11. FT-IR absorption peaks were observed at 1401 and 1600 cm−1 corresponding to C-N and C=N bonds, respectively. CD dispersions exhibited PL peak at 434 nm under 360 nm excitation. With increasing the L-cysteine concentration, the PL quantum yield increased from 0.33 to 4.5%. This improvement is possibly attributed to the increase in the N content. Dependence of CD properties on the L-cysteine concentration implies that L-cysteine concentration changes reaction process, such as decomposition reaction of molecule, cross-linking reaction between molecules, and so on.
8:00 PM - NM01.04.09
Controlled Photoluminescence of Graphene Quantum Dots through Liquid-Phase Laser Ablation
Rosemary Calabro 1 , Dong-Sheng Yang 1 , Doo Young Kim 1
1 , University of Kentucky, Lexington, Kentucky, United States
Show AbstractGraphene quantum dots (GQDs) are an emerging class of carbon nanomaterials that exhibit interesting optical properties making them desirable for applications such as photovoltaics, photocatalysis, biosensing, bioimaging and photodynamic therapy. It has been shown that the optical properties of GQDs are influenced by both the size of the particles through the quantum confinement effect as well as defect states affected by chemical functional groups. However, traditional methods to produce GQDs, such as chemical oxidation, present several limitations including the use of harsh chemicals, formation of toxic side products, and inhomogeneity in the size and surface functional groups. Liquid-phase laser ablation is an alternative method to produce GQDs which utilizes fewer chemicals, forms fewer side products, requires simple purification methods, and allows for improved control over their sizes and functional groups. During liquid-phase laser ablation, a solid target of carbon precursor is irradiated with a high-power nanosecond pulsed laser source, forming plasma plumes that expand and are cooled by the surrounding liquid and condense into carbon nanoparticles. It was found GQDs produced through liquid-phase laser ablation of carbon nano-onions in water resulted in a blue shifted photoluminescence, smaller particle size, and a larger concentration of surface hydroxyl groups, as compared to those produced through chemical oxidation. Additionally, it was found that by laser ablating in different solvents or solutions with organic solutes, the size, functional groups and optical properties could be tuned. The laser parameters such as pulse energy, wavelength, and repetition rate can also be used to control the mechanism of GQD formation and alter the product. The structure and optical properties of resultant GQDs are characterized by UV-vis absorbance, fluorescence, Fourier-transform infrared absorption, and x-ray photoelectron spectroscopic measurements, and atomic force and transmission electron microscopic measurements.
Symposium Organizers
Raz Jelinek, Ben Gurion University
Petras Juzenas, Oslo University Hospital
Ya-Ping Sun, Clemson University
Bai Yang, Jilin University
NM01.05: Carbon Dot Composites
Session Chairs
Wednesday AM, November 29, 2017
Hynes, Level 3, Room 305
9:00 AM - *NM01.05.01
Development and Bio-Applications of Nontoxic Carbon Dots
Roger Leblanc 1 , Zhili Peng 1
1 , University of Miami, Coral Gables, Florida, United States
Show AbstractCarbon dots (C-dots) have recently attracted enormous attention due to their unique properties. In this talk, the preparation, characterization and bio-applications of a new type of nontoxic, water-soluble C-dots will be presented. The C-dots were prepared from carbon nanopowders with an average size of 4 nm, and have been applied in various bio-relevant applications.
One prevention and therapeutic strategy for diseases associated with peptide or protein fibrillation is to inhibit or delay the fibrillation process. In our study we have shown that C-dots could significantly inhibit the fibrillation formation of both insulin and amyloids. Simulation study indicated that the presence of rich surface carboxyl groups played an important role in the fibrillation inhibition. A major medical challenge one faces to treat central nervous system (CNS) related diseases is to cross the tight junctions between endothelial cells, which are known as blood–brain barrier (BBB). Recently, our experiment suggested that the transferrin conjugated C-dots could enter the CNS of Zebrafish while C-dots alone could not. In another study, C-dots were applied as a drug delivery system by conjugating with transferrin and anticancer drug doxorubicin. In vitro study showed greater uptake of the conjugates compared to free doxorubicin, the conjugates at 10 nM was significantly more cytotoxic than doxorubicin alone, reducing viability by 14~45 %, across multiple pediatric brain tumor cell lines. Accidents, disease and aging compromise the structural and physiological functions of bones, and in vivo bone imaging test is critical to identify, detect and diagnose bone related development and dysfunctions. Here we show that C-dots with low quantum yield (“dark”) bind to calcified bone structures of live Zebrafish larvae with high affinity and selectivity. Binding resulted in a strong enhancement of luminescence that was not observed in other tissues, including non-calcified endochondral elements. Retention of C-dots by bones was very stable, long lasting, and with no detectable toxicity. Further, we have shown that this high affinity and specificity binding property towards bone is unique to the C-dots developed in our lab, selective C-dots in literature did not show any interaction with the bone. These observations support a novel and revolutionary use of C-Dots as highly specific bioagents for bone imaging and diagnosis, and as a potential bone-specific drug delivery carrier.
In our C-dots biomacromolecules conjugation studies, we realized that using traditional analytical methods, quantification of biomacromolecules (i.e., proteins and nucleic acids) concentration in their C-dots conjugates is difficult due to the interference of C-dots. To this end, a simple, yet reliable analytical method based on circular dichroism spectroscopy to quantify biomacromolecule concentration in their C-dots conjugates was developed.
9:30 AM - *NM01.05.02
Carbon Dots—A New Class of Light-Activated Antimicrobial Agents
Liju Yang 1 , Ya-Ping Sun 2
1 Pharmaceutical Sciences, North Carolina Central University, Durham, North Carolina, United States, 2 Chemistry, Clemson University, Clemson, South Carolina, United States
Show AbstractPhoto-activated antimicrobial technology is a rapidly developing field in response to the demand in development of effective treatments, control and prevention of bacterial infectious diseases. While colloidal TiO2 has been the traditional photo-activated antimicrobial agent for years, novel materials are discovered and added to this field rapidly. Recently, carbon dots (CDots) have been demonstrated for their great potential in serving as effective light-activated antimicrobial agents.
CDots are generally small carbon nanoparticles with various surface passivation schemes, their unique optical properties and photocatalytic functions have been explored for a wide range of biological applications. This study reported CDots’ photoinduced bactericidal functions, with the results suggesting that the dots were highly effective in bacteria-killing with visible light illumination. Property-function correlations were explored. Several important factors that are associated with the light-activated bactericidal efficiency, including surface modification, fluorescence quantum yield, and others, have been investigated. Mechanistic implications of the results, challenges and opportunities in further development of CDots into a new class of effective, low cost, low to non-toxic visible/natural light-responsive bactericidal agents for bacteria control and other potential antimicrobial applications are discussed.
Acknowledgement: This research was supported NIH grant R15GM114752.
10:30 AM - *NM01.05.03
Interaction between Surface Plasmons and Cdots—Towards Hybrid Materials
Adi Salomon 2 , Lihi Efremshkin 3 , Susanta Kumar Bhunia 2 , Raz Jelinek 2
2 Department of Chemistry, Ben Gurion University of the Negev, Beer Sheva Israel, 3 Department of Chemistry, Institute of Nanotechnology and Advanced Materials (BINA) Bar-Ilan University, Ramat-Gan Israel
Show AbstractPlasmonic nanostructures and carbon dots (C-dots) are fascinating optical materials, utilized in imaging, sensing, and color generation. Interaction between plasmonic materials and C-dots may lead to new hybrid materials with controllable optical properties. Herein, we demonstrate for the first time coupling between plasmonic modes and C-dots deposited upon a plasmonic silver hole array. We show that this coupling leads to remarkable visual attenuation and shifts of the plasmonic wavelengths (i.e. color tuning). In particular, the C-dots-plasmon couplings and pertinent color transformations depend both upon the C-dots' fluorescence emission wavelengths and functional residues displayed upon the C-dots' surface. This optical modulation corresponds to energy level alignment and consequent energy transfer between the C-dots and the plasmonic silver hole array. Notably, the energy coupling observed in the C-dot/plasmonic system hybrid system allows to distinguish between C-dots exhibiting similar optical properties in solution, albeit displaying different functional residues. Thus, the chemical signature of the C-dots system plays an important role in determining the optical properties of the hybrid C-dots/plasmonic system.
11:00 AM - *NM01.05.04
Carbon Quantum Dots Contribution to Optoelectronic Devices
Lucia Veca 1
1 , IMT - Bucharest, Bucharest Romania
Show AbstractThe compelling combination of distinctive photophysical properties, low production costs, and absence of toxic elements envisioned carbon-dots (C-dots) as an attractive alternative to the semiconductor QD-based technologies. Hence, since their first designed synthesis, C-dots have witnessed expanding research efforts towards diverse applications.
Aiming to explore the usage of these new materials as emissive/photoactive layer in optoelectronic devices we have synthesized C-dots by passivation of carboxylated carbon nanoparticles surface with various diamines.
Newly designed C-dots exhibit high photo-emission efficiency and depending upon the surface functionality they display either green emission or emission spectra covering the entire visible domain, corresponding to multiple excitation wavelengths.
Finally, the advances made to date regarding the benefits which these C-dots have been able to bring to the optoelectronic devices will be underlined.
11:30 AM - NM01.05.06
Charge-Carrier Dynamics in Carbon Nanodots with Different Ligand Shells under Photo-Excitation
Kseniia Zimmermann 1 , Angelina Vogt 1 , Frank Dissinger 2 , Siegfried Waldvogel 2 , Tobias Voss 1
1 Institute of Semiconductor Technology, University of Technology Braunschweig, Braunschweig Germany, 2 Institute of Organic Chemistry, Johannes-Guttenberg University Mainz, Mainz Germany
Show AbstractThanks to their remarkable properties such as low toxicity, easy manufacturing and tunable optical properties, carbon nanodots (C-dots), can potentially be used to replace colloidal semiconductor quantum dots in nanoscale optoelectronic devices. Spectral tailoring of the absorption and emission of semiconductor quantum dots can be achieved by changing their size and exploiting quantum-size effects. In the C-dots, the interplay of transitions involving C-C bonds and surface/interface states allows for a spectral tuning via exchanging the surface ligands.
Here, we study the ultrafast luminescence dynamics of C-dots in order to analyze the recombination channels of the photo-excited electron-hole pairs. The C-dots were prepared by means of hydrothermal pyrolysis or a microwave assisted synthesis of citric acid with stabilizing agents. Four different C-dot suspensions with selected stabilizing molecules were studied: polyethylenimine encapped (PEI-EC), diethylenetriamine (DETA), ethylenedioxy-bis-ethyleneamine (EDA) and urea. After cleansing with column chromatography, the obtained particles were dissolved in suitable solvents. The C-dots were photo excited with an OPA pumped by a femtosecond amplifier (100 fs, 1 kHz) and the time- and spectrally resolved luminescence was detected with a streak-camera coupled to a spectrometer (time resolution < 30 ps).
For all C-dots studied, we find luminescence decay times between 4 and 14 ns. In most cases, the luminescence exhibits a mono-exponential decay. The decay time and the Stokes shift of the C-dots capped with PEI-EC show only small variations when different solvents (water, ethylene glycol, ethanol) are used or the pH-values of the aqueous solution is changed (pH 3, 6, 9). In contrast, the Stokes shift of C-dots stabilized with Urea shows a strong linear variation with the dipole factor Δf of the solvent, and the decay time of C-dots stabilized with DETA is very sensitive to the pH value of the aqueous solution (Δt=13.5 ns at pH 6 vs. Δt=10.5 ns at pH 9). We will discuss the results in terms of the interaction of the solvent molecules with the C-dot shell with a particular emphasis on the tunability and stability of their optical properties. The results underline the importance of the interface states between C-dots and the ligand shell for the optical properties of the C-dots and their charge-carrier dynamics under photo-excitation.
11:45 AM - NM01.05.07
Photothermal Carbon Nanodots for Cancer Theranostics
Woosung Kwon 1 , Yoonsang Park 2
1 , Sookmyung Women's University, Seoul Korea (the Republic of), 2 Chemical Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractMultifunctional nanoparticles have been widely investigated for biomedical applications, such as imaging, therapy, and drug delivery. Especially, photothermal nanoparticles have received great attention as theranostic agents because of their heat-generating abilities after exposure to laser irradiation. However, photostability and safety issues have been the technical hurdles for further clinical applications. In this regard, photothermal carbon nanodots (P-CNDs) can be a strong candidate due to their biocompatibility and photostability. Here, we design an efficient synthetic route to P-CNDs and demonstrate their biomedical applications in photoacoustic imaging (PA) and photothermal therapy (PT). We perform in vivo/ex vivo PA imaging of sentinel lymph nodes via intravenous injection. The renal clearance of P-CNDs is confirmed by the whole-body PA monitoring. P-CNDs are then conjugated with hyaluronic acid to detect early hepatocellular carcinoma. Finally, tumors are treated by PT with intratumorally injected P-CNDs and the size of the tumors are monitored to evaluate the therapeutic efficacy of PT.
NM01.06: Properties and Applications II
Session Chairs
Wednesday PM, November 29, 2017
Hynes, Level 3, Room 305
1:30 PM - *NM01.06.01
A Carbon-Carbon Hybrid—Immobilizing Carbon Nanodots and Carbon Nanotubes
Dirk Guldi 1
1 , University of Erlangen, Erlangen Germany
Show AbstractThe thrust of this work is to integrate small and uniformly sized carbon nanodots (CND) with single-walled carbon nanotubes of different diameters as electron acceptors and electron donors, respectively, and to test their synergetic interactions in terms of optoelectronic devices. CNDs were prepared by pressure-controlled microwave decomposition of citric acid and urea. CNDs were immobilized on single-walled carbon nanotubes by wrapping the latter with poly(4-vinylbenzyl trimethylamine) (PVBTA), which features positively charged ammonium groups in the backbone. Negatively charged surface groups on the CNDs lead to attractive electrostatic interactions. Ground state interactions between CNDs and SWCNTs were confirmed by a full-fledged photophysical investigation based on steady-state and time-resolved techniques. As a complement charge injection into the SWCNTs upon photoexcitation was investigated by ultra-short time-resolved spectroscopy.
2:00 PM - NM01.06.02
White-Light Emitting Carbonaceous Species from Acetylene Carbonization in Zeolite Nanoreactor
Seung Hyeon Ko 1 , Hongjun Park 1 2 , Taekyoung Lee 1 2 , Ryong Ryoo 1 2
1 , Institute for Basic Science, Daejeon Korea (the Republic of), 2 Chemistry, Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of)
Show AbstractOver the last few years, extensive research efforts have focused on development of solid-state white-light-emitting materials because of their potential for energy-efficient illumination. Common approaches to generate white light emission are either by properly mixing red, green, and blue-emitting semiconductor quantum dots or integrating them with traditional organic phosphors. However, semiconductor nanocrystals containing Cd or other heavy metals have serious toxicity as well as high costs, which considerably limits their practical applications. In recent years, compared to the quantum dots, carbon-based fluorescent nanodots including carbon dots and graphene quantum dots have emerged as promising substitutes for the present fluorescent nanomaterials because of their competitive optical performance - high photostability, non-blinking photoluminescence and versatile tunability of optical properties.
Herein we report on a facile synthesis of carbonaceous species from acetylene carbonization using Ca2+ ion catalyst embedded in zeolite nanoreactor. The resulting product directly exhibits strong white-fluorescence in N-methyl-2-pyrrolidone (NMP) solution under a single wavelength excitation. The photoluminescence quantum yield of the white emission was determined to be 13.7 % under 340 nm excitation in NMP solution. The current synthesis method is a reliable low-cost synthetic technique, rendering potential various scientific and industrial applications.
2:15 PM - NM01.06.03
One-Step Synthesis of N-Doped Graphene Quantum Dots from Chitosan as a Sole Precursor Using Chemical Vapor Deposition
Subodh Kumar 1 , Gilbert Daniel Nessim 1
1 Chemistry Department, Bar Ilan University, Ramat Gan Israel
Show AbstractWe describe a simple, environment friendly, and fast synthesis of nitrogen doped graphene quantum dots (N-GQDs) on copper foil by chemical vapor deposition using only chitosan, a cheap and non-toxic biopolymer, as a carbon and nitrogen precursor. In this method, chitosan is thermally decomposed into volatile nitrogen containing heterocyclic compounds (N-HC) which recombine into N-graphene quantum dots by means of precipitation on the surface of a copper foil. We characterized the synthesized N-doped graphene quantum dots by Raman spectroscopy, XPS, AFM and HR-SEM and found them to be in the range 10-15 nm diameter and 2-5 nm thick with 4.19 % of nitrogen content. We also show that by varying the growth time we can modulate the size and number of graphene layers in the N-GQDs. Moreover, the synthesized N GQDs were found to exhibited photoluminescence (PL) emission in the visible band region rendering them suitable for applications in nano optoelectronics.
3:30 PM - *NM01.06.04
Synthesis of Functional Carbon Nanospheres for Energy-Related Applications
Sheng Dai 1 2
1 Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Chemistry, University of Tennessee, Knoxville, Knoxville, Tennessee, United States
Show Abstract
Carbon-based materials are the most popular material types in both fundamental research and industrial applications, partly because of their well-controlled nanomorphologies. Carbon nanospheres are attracting more and more attention worldwide because of their excellent performance in various fields: drug delivery, sensing, heterogeneous catalysis, encapsulation of electrode materials. Actually, spherical carbon is an old material, whereas controlling carbon spheres in the nanometer range is a recent story. Recently, it has become possible to precisely control the particle size, surface area, pore size, chemical composition, and dispersity of carbon nanospheres. Toward this end, a number of synthetic strategies are emerging, such as hydrothermal carbonization of biomass-based resources, extended Stöber synthesis, and organic–organic self-assembly via different binding methods. In this presentation, we will summarize recent routes for carbon nanospheres and briefly touch on their applications to shed light on the great potential of this field. A special emphasis is placed on the possible modulation of spherical structures at the nanoscale.
4:00 PM - *NM01.06.05
Colloidal, Fluorescent, Functional Carbon Nanoparticle for Biomedical Applications
Nikhil Jana 1
1 , Indian Association for the Cultivation of Science, West Bengal India
Show Abstract4:30 PM - NM01.06.06
Glucose-Derived Graphene Quantum Dots for High Performance Optoelectronic Devices
Shu Ping Lau 1 , Jr-Hau He 2
1 Department of Applied Physics, Hong Kong Polytechnic University, Kowloon Hong Kong, 2 Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah, University of Science and Technology, Thuwal Saudi Arabia
Show AbstractGraphene quantum dots (GQDs) prepared by microwave assisted hydrothermal method using glucose as precursor have attracted great attention [1]. The GQDs could emit in the ultraviolet, visible as well as near-infrared spectral range [2]. The photon downconversion behavior of the GQD can be utilized to harvest additional ultraviolet photons to improve the absorption of the device. In the meantime, the highly conductive GQD also improves the conductivity of the organic layer. By employing GQDs in n-type Si heterojunction, dye-sensitized and Si/PEDOT:PSS hybrid solar cells, the conversion efficiency of these solar cells could be enhanced significantly [3-5]. The efficiency enhancement is based on the photon downconversion phenomenon of GQDs to make more photons absorbed in the depletion region for effective carrier separation, leading to the enhanced photovoltaic effect. GQDs are the promising materials for developing photon-managing, low-cost, and highly efficient photovoltaic devices.
[1] Tang et al. , ACS Nano 6 (2012) 5102.
[2] Tang et al., ACS Nano 8 (2014) 6312.
[3] Tsai et al., Nano Letts. 16 (2015) 309.
[4] Tsai et al., ACS Nano 11 (2017) 4564.
[5] Lee et al., Nano Energy 36 (2017) 260.
4:45 PM - NM01.06.07
Effect of Surface Chemistry on Optical, Chemical and Electronic Properties of Blue Luminescent Graphene Quantum Dots
Jian Ren 1 2 , Fabian Weber 1 3 , Sneha Choudhury 1 3 , Florian Weigert 4 , Eglof Ritter 5 , Dawei Cao 1 3 , Annika Bande 1 , Ljiljana Puskar 1 , Ulrich Schade 1 , Ute Resch-Genger 4 , Emad Aziz 1 2 , Tristan Petit 1
1 Institute of Methods for Material Development, Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), Berlin Germany, 2 Department of Physics, Freie Universität Berlin, Berlin Germany, 3 Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Berlin Germany, 4 Division 1.10 Biophotonics, Bundesanstalt für Materialforschung und -prüfung (BAM), Berlin Germany, 5 Institute of Biology, Humboldt-Universität zu Berlin, Berlin Germany
Show AbstractDue to their unique physical properties, particularly their electronic and luminescent properties, graphene quantum dots (GQDs) are expected to be suitable for a wide range of applications in bioimaging, electro-optical and photonic materials or energy harvesting among others.1 Tuning the surface chemistry provides an efficient approach to modulate the fluorescence and distinct electronic properties of GQDs.2 Nevertheless, the role of surface chemistry on the electronic structure of GQDs remains poorly understood.
In this presentation, we will compare systematically the electronic and chemical structures of GQDs functionalized with carboxylic and aminated groups to those of non-functionalized GQDs, combining experimental and theoretical approaches. First, the electronic structure of GQDs was characterized by soft X-ray absorption (XA) and X-ray emission (XE) spectroscopies at the BESSY II synchrotron radiation source, probing unoccupied and occupied electronic states, respectively, at the carbon K edge for the first time. The interpretation of XA/XE spectra was discussed based on theoretical calculations. Subsequently, the chemical structure of the GQDs was characterized by ATR-FTIR. Since the interface between GQDs and water is believed to play a central role in the chemical reactivity and the optical properties in aqueous environments, the GQDs–water interface was probed by in situ attenuated total reflection Fourier transform infrared (ATR-FTIR). We previously demonstrated that monitoring the OH vibrations of water molecules during exposure to humid air was a powerful method to probe H-bonding environment around carbon nanomaterials.3 For GQDs, clear surface-dependent water adsorption profiles are observed and discussed. Finally, the optical properties of these GQDs were characterized by UV/Vis absorption and photoluminescence measurements.
Our results, from both experiment and theory, suggest that the surface chemistry of the GQDs significantly affects their electronic structures and optical properties. Moreover, these findings will contribute to an improved understanding of the structure–activity relationship of GQDs and other carbon nanomaterials with surface modifications.
1. LeCroy, GE. et al. Functionalized carbon nanoparticles: Syntheses and applications in optical bioimaging and energy conversion. Coord. Chem. Rev. 320-321, 2016.
2. Zhu, S. et al. Investigating the surface state of graphene quantum dots. Nanoscale 7, 2015.
3. Petit, T. et al. Unusual water hydrogen bond network around hydrogenated nanodiamonds. J. Phys. Chem. C 121, 2017.
Symposium Organizers
Raz Jelinek, Ben Gurion University
Petras Juzenas, Oslo University Hospital
Ya-Ping Sun, Clemson University
Bai Yang, Jilin University
NM01.07: Properties and Applications III
Session Chairs
Thursday AM, November 30, 2017
Hynes, Level 3, Room 305
8:30 AM - *NM01.07.01
Graphene Quantum Dots for Precise Cancer Theranostics
Junjie Zhu 1 , Fenfen Zheng 1
1 , Nanjing University, Nanjing China
Show AbstractGraphene quantum dots (GQDs), deriving from graphene, have unique two-dimensional honeycomb structure and photoluminescence properties due to quantum confinement effect and boundary effect, as well as excellent biocompatibility, and thus have been explored for applications in biomedicine in recent years. With every atom exposed on its surface, GQDs show ultra-high surface area available for efficient molecular binding via noncovalent binding such as π-π stacking or hydrophobic-hydrophobic interaction. Moreover, the hydrophobic basal plane endows the GQDs super-high membrane permeability in cells, thus GQDs could easily enter the cells and traverse the nuclear pores, enhancing molecule accumulation in nucleus. Inspired by these, we are pursuing to combine different nanomaterials and biomolecules to fabricate GQD-based nanocarriers for precise cancer theranostics. Here, we fabricated a smart drug nanocarrier based on fluorescence resonance energy transfer by capping graphene quantum dots onto fluorescent mesoporous silica nanoparticles via ATP aptamer for real-time monitoring of ATP-triggered drug release. By virtue of the precision and flexibility of laser manipulation, a multifunctional nanocarrier consisting of graphene quantum dots co-embedded with gold nanorods in a mesoporous silica matrix was designed for NIR and biodegradation synergistically triggered drug release and integrated chemo-photothermal therapy. These GQD-based stimuli-responsive nanocarriers are potential for the next generation cancer theranostics.
9:00 AM - NM01.07.02
Subwavelength-Structure-Induced Strong Hot Electron Absorption in the Carbon Aerogels
Ai Du 1 , Ming Gao 1 , Wei Sun 1 , Mingfang Liu 1 , Hongqiang Wang 1 , Jun Shen 1 , Bin Zhou 1
1 , Tongji University, Shanghai China
Show AbstractOwing to its diverse chemical compositions and unique properties which could fill the gap between condensed- and gas-state matter aerogels are now regarded as a new state of matter.[1] Much work discussed the influence of density on the physical properties, but rare work talks clearly about the microstructure/properties relationship. Recently, we found that subwavelength microstructure obviously affect the diffuse reflectivity of the carbon aerogels.[2] These were prepared with different nanostructure by carbonizing the resorcinol-formaldehyde (RF) aerogels and showed ultralow reflectivity in the UV-Vis-NIR spectra. Modifying concentration (W%) and catalyst ratios (R/C) of the RF colloid, leads to a roughly positive correlation between reflectivity and density (42~328 mg/cm3). Moreover, R/C parameter which determined the microstructure of the aerogels affected significantly the reflectivity. By tuning their nanostructure, we got the minimum at about 0.19 % which approached the measuring limit of our equipment. We attribute this behavior to the indirect interactions including electromagnetic-electron interaction and electron-microstructure interaction. The subwavelength structure of the conductor strongly decreases the mean free path of the electrons inside, leading to an extra hot electron absorption besides considering the Joule’s heating. The structure much smaller than the wavelength (< 2 nm) could affect the light propagation greatly. Thus we designed an experiment to study the photoelectric effect of the ultra-black carbon aerogels. The visible light could induce strong light current, while the infrared could not. The light current is in direct proportion to the intensity of the lights but saturated when the light power is higher than ~80 mW. The saturated current has been demonstrated to be induced by the producing of plasmas. The strong photoelectric and plasmas effects may attribute to the high energy of the electrons and the active surface of tiny carbon skeletons.
Keyboard: Carbon aerogels, Subwavelength structure, Hot electron, Photoelectric effect
References
1. A. Du, B. Zhou, Z. Zhang, et al. Materials, 2013, 6(3), 941-968.
2. W. Sun, A. Du, Y. Feng, et al. ACS Nano, 2016, 10(10), 9123–9128.
9:15 AM - NM01.07.03
Novel Route to Large-Scale Synthesis of Phosphorus-Doped Graphene Quantum Dots
Muhammad Shehzad Sultan 1 , Bibek Thapa 1 , Frank Mendoza 1 , Vladimir Makarov 1 , Brad Weiner 2 , Gerardo Morell 1
1 Physics, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States, 2 Chemistry, University of Puerto Rico at Río Piedras, San Juan, Puerto Rico, United States
Show AbstractThe graphene quantum dots (GQDs), a zero-dimensional graphene quantum structure, have triggered the intense research worldwide. Owing to their remarkable properties like high transparency, large surface area, high conductivity, tunable fluorescence, and excellent dispersibility in an aqueous medium, they have been substantially exploited in the energy storage, optoelectronics, and biomedical applications. The doping of GQDs with heteroatoms is the effective way to tune their band gap and the electronic density. In this study, we develop a novel route for the large-scale synthesis of Phosphorus-doped Graphene Quantum Dots (P-GQDs) using pulse laser fission method. The absolute yield of P-GQDs is about 24–30 mg per trail. This yield was estimated using absorption spectra of GQD. The absorption and emission spectra of P-GQDs are significantly different from that of the pristine GQDs indicating the successful doping. We discuss the qualitative model to elucidate the observed data based on perturbation of the carbon conjugated π-system by Phosphorus atoms, which partially substitute carbon atoms of GQDs. These outcomes result in an ample opportunity for the optoelectronic applications.
10:00 AM - NM01.07.04
Unusual Light Absorption Caused by Lowly Oxidized Graphene Quantum Dots
Seokwoo Jeon 1
1 , Korea Advanced Institute of Science and Technology, Daejon Korea (the Republic of)
Show AbstractGraphene quantum dots (GQDs), simply making graphene typically under 10 nm, and the change of emission behavior from known fluorescents on graphene draws huge interest for potential applications to display, lighting, and optoelectronic devices. Our group has developed unique exfoliation and dispersion methods of 2D materials by the intercalation of alkali metal/organics. With the advantage of the methods generally excluding, or controlling, the oxidation of 2D materials, we have studied the origin of intrinsic emission (~ 400 nm) of GQDs and found low oxidized GQDs possess discrete bandgap ~3.1 eV due to the formation of subdomain which is a cluster of 4-7 isolated sp2 carbon hexagons. The discrete bandgap is not only good for emission but also good for enhanced absorption. Two examples, one is an extraordinary enhancement of UV absorption in TiO2 nanoparticles (NPs) incorporated with GQDs of low oxygen concentration and the other is OPV improvement via GQD-induced charge-transfer kinetics and P3HT absorption resulting in significant improvement to active layer absorption, will be presented. Especially, chemically-bonded TiO2 NPs/GQDs composites exhibit highly tunable UV absorption, achieving over 280% enhancement of optical density at the absorption band around 338 nm due to the direct charge transfer from the lowest unoccupied molecular orbitals (LUMOs) of GQDs to the conduction bands (CBs) of TiO2.
10:15 AM - NM01.07.05
Carbon Quantum Dot—Photosensitizer Conjugates in Photodynamic Therapy
Jose Aguilar Cosme 1 , Helen Bryant 2 , Frederik Claeyssens 1
1 Materials Science and Engineering, The University of Sheffield, Sheffield, South Yorkshire, United Kingdom, 2 Oncology & Metabolism, The University of Sheffield, Sheffield, South Yorkshire, United Kingdom
Show AbstractPhotodynamic therapy (PDT) has seen wide clinical application for treatment of skin cancers using photosensitizers (PS) to produce singlet oxygen leading to cell death. However, effectiveness is limited by low solubility and inefficient accumulation in target tissue. While therapies utilising sensitizer precursors have seen success, they are limited by low uptake and solubility in the target tissue. Carbon quantum dots (CQDs) are nanoparticles which have been previously used in bioimaging applications, and may be utilised to perform efficient energy transfer towards conjugated photosensitizers. CQDs have been found to have high biocompatibility and no photobleaching. These properties are quite important as many photosensitizers, such as protoporphyrin IX, have dark toxicity (LC50 25 ug/ml) and rapid bleaching upon contact with light. CQDs have also been reported as being capable of inmobilizing various molecules such as dyes, which conserve their luminescent properties while embedded in the carbon core.
In this work, PDT was evaluated using CQD-PS conjugates excited via laser irradiation in C8161 melanoma cells. CQDs were synthesized through microwave-assisted pyrolysis of citric acid and ethane-1,2-diamine . In a similar synthesis method, host-guest encapsulation of protoporphyrin IX was attempted through its pyrolysis alongside the previous reagents. A modified carbodiimide-based crosslinking protocol was used to bind the CQD-PS conjugates, which were purified through dialysis and characterized by UV/Vis spectroscopy, fluorescence spectroscopy, FTIR, and TEM. Internalization of CQD-PS particles was confirmed by confocal two-photon microscopy using U2OS osteosacroma cells, co-staining with DAPI. Toxicity was evaluated utilising Alamar Blue to determine metabolic activity with varying concentrations of the CQD-PS, CQD and PS.
The CQD-PS conjugate crosslinking was confirmed with changes in the absorption and emission spectra of the CQD. Cell viability assays focused on dark toxicity indicate CQD-PS conjugates are less toxic than unbound photosensitizer, though the conjugate shows increased toxicity compared to unbound nanoparticles. Although solubility was increased, aggregation can still be seen in the CQD-PS solution in TEM images, which limits the concentrations of CQD-PS that may be used. In summary, the use of CQDs as carriers for photosensitizers allows higher drug concentrations without significantly compromising cell viability before activation, improving the efficiency of treatment.
10:45 AM - NM01.07.07
One-Pot Synthesis of Single-Crystalline Graphene Quantum Dots and Its Application
Seok Hwan Lee 1 , Tae-Ho Kim 1 , Seul Bi Lee 2 , Hyeon Han 2 , Young Yun Kim 1 2 , Sung Cik Mun 1 3 , Jeong Eun Won 1 , Do Youb Kim 2 , Jaemin Lee 2 , Sang Hyuk Im 4 , O OK Park 1
1 Department of Chemical and Biomolecular Engineering (BK21+ graduate Program), Korea Advanced Institute of Science and Technology, Daejeon Korea (the Republic of), 2 Division of Advanced Materials, Korea Research Institute of Chemical Technology, Daejeon Korea (the Republic of), 3 Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota, United States, 4 Department of Chemical and Biological Engineering, Korea University, Seoul Korea (the Republic of)
Show AbstractRecently graphene quantum dots (GQDs) have been of great interest because of their excellent properties such as excitation wavelength dependent emission, high photo-stability, strong chemical stability, good biocompatibility and excellent charge transport. So far, GQDs have been successfully synthesized by hydrothermal, emulsion templating, and Hummer’s method. However, it is still challenging to synthesize GQDs with high quality graphitic structure and controllable size via solution chemistry because the convention bottom-up process such as hydrothermal and emulsion templating methods produced carbon dots with low crystallinity and the top-down process such as Hummer’s method yielded GQDs with broad size distribution, broad photoluminescence (PL) spectrum and low quantum yield. Here, we synthesized GQDs with high quality crystallinity and uniform controllable size via one-pot single-phase solution chemistry. It is based on dehydration of d-glucose under amine and acetic acid catalytic condition on the basis of taking in-situ proton nuclear magnetic resonance (1H NMR) spectroscopy during the reaction. Electro-microscopic analysis such as transmission electron microscopy (TEM) and atomic force microscopy (AFM) images of GQDs showed that it have hexagonal crystal structure with 0.241 nm lattice distance of (100) graphitic crystal plan and it have hexagonal plate in shape and have perfect crystalline structure, as well. The thicknesses of GQDs were under 1 nm. Respectively, which means that GQDs are constructed by bi-layered to triple-layered graphite, It should be noted that the bi-layered or triple-layered GQDs were synthesized by one-pot single-phase solution chemistry because the carbon dots and the exfoliated reduced graphene oxide are thicker than ~ 3000 pm and such thin graphene could be obtainable via chemical vapor deposition method (CVD). Spectroscopic characterization showed that GQDs exhibited clear excitation dependent PL spectrum with regular interval spectrum. Regardless of its size, they showed a strong blue emission at 420nm and narrow emission spectrum and short-exciton lifetime. In addition, various analytical methods were performed to analysis structure of GQDs. Consequently, based on several analysis results, we can conclude that the single crystalline GQDs were formed through dehydrolysis of glucose under amine and acetic acid catalytic condition. Finally, GQDs fabricated into emitting layer on electroluminescence (EL) device and it has stable deep blue emission with low turn-on voltage.
11:00 AM - NM01.07.08
Direct Synthesis of Carbon Quantum Dots in Aqueous Polymer Solution—One-Pot Reaction and Preparation of Transparent UV-Blocking Films
Samuel Hess 1 , Elia Schneider 1 , Takashi Ogi 2 , Wendelin Stark 1
1 , ETH Zürich, Zürich Switzerland, 2 , University of Hiroshima, Hiroshima Japan
Show AbstractPackaging is omnipresent and allows expanding the lifetime of many products such as food, drugs, electronics, furniture, etc. Because of good processability, recyclability, and economical attractiveness, polymers are widely applied for every kind of packaging. Unfortunately, no polymer can block gas completely and most of them allow UV light to pass through, limiting the shelf life of products. One of the most prominent gas shielding polymers is polyvinyl alcohol (PVA) and its copolymer ethylene vinyl alcohol (EVOH), which is industrially applied as a separate layer within PET bottles. Additionally, many products need to be shielded not only from gas, but also from UV-light. Because customers prefer to see products through packaging, which creates an additional requirement, there is a high demand for transparent UV-blocking materials.
Fluorescent carbon quantum dots (CQDs), a class of carbon nanomaterials, have gained strong attention in research over the last few years. Due to their low toxicity, environmental sustainability, low synthesis costs, and simple synthesis routes, CQDs have become promising materials in the areas of bioimaging, biosensing and drug delivery. As CQDs possess light-shieling performance, they are treated as promising candidates to be applied in photovoltaics too. CQDs were applied in different polymer composite materials by dispersing pre-synthesized and purified CQDs within a polymeric matrix such as epoxide, polystyrene, polyvinylchloride, polycarbonate, polyamide, polyurea-urethane, polyester, polymethylmetacrylate or PVA. CQD composite films were often produced by hydrothermal synthesis of the CQDs in a first step and the resulting nanoparticles purified in a second step, followed by their dispersion within a polymer solution. Complex procedures for quantum dot separation, purification, and functionalization usually lead to low synthesis yields, thus limiting their applicability, especially in low cost industrial applications such as packaging.
Herein, we present a simple route for producing a UV-blocking polymer composite film from a one-pot synthesis in aqueous PVA solution (Hess et al., 2017) This one step CQDs synthesis, which does not require any time consuming or yield reducing work-up steps, was conducted with the cheap precursor materials citric acid (CA) and branched polyethylene imine (b-PEI). Aqueous CQDs–PVA solutions, as well as cast CQDs containing PVA films, were analyzed for their UV absorbance and light transmission. Analysis of solutions and films allowed elucidating important variations in performance between the solution vs. film states of the synthesized CQDs–PVA mixture. Interestingly, the aqueous CQDs–PVA solution, as well as the CQDs–PVA films, had surprisingly high UV-A absorption and transparency for visible light wavelengths, and led to well performing CQDs–PVA–PET composite films.