Symposium Organizers
Hongshan He, Eastern Illinois University
Paola Deplano, University of Cagliari
Nobuhiko Iki, Tohoku University
Xingqiang Lv, Northwest University
MD7.1: Synthesis, Sensing and Imaging I
Session Chairs
Wednesday PM, March 30, 2016
PCC West, 100 Level, Room 106 A
9:30 AM - *MD7.1.01
Nanoscopic Lanthanide-Containing Clusters: Exploratory Synthesis and Materials Properties
Zhiping Zheng 1
1 University of Arizona Tucson United States,
Show AbstractIn this talk, our research directed toward developing new paradigms of lanthanide coordination chemistry and producing nanoscopic lanthanide-containing clusters with interesting materials properties will be presented. Inspired by the potential applications of polynuclear lanthanide hydroxide complexes, we developed the rational synthesis of these otherwise synthetically elusive species by the approach of ligand-controlled hydrolysis of the lanthanide ions. Nanoscopic and structurally pleasing lanthanide-hydroxo cluster motifs have been uncovered. Extension of this approach to mixed d-f systems affords giant heterometallic clusters. Properties of these cluster compounds pertinent to their potential applications in fuel technology and magnetic cooling will be discussed.
10:00 AM - MD7.1.02
Hyperspectral Imaging of Single Upconversion Nanocrystals within Individual Cavities of a Gold Micro-Cavity Array
Aravind Baride 1,Mary Berry 1,P. Stanley May 1
1 Univ of South Dakota Vermillion United States,
Show AbstractLanthanide-activated upconversion (UC) materials have the remarkable ability to generate visible or UV light upon NIR excitation. However, the poor efficiency of UC, particularly at low excitation power densities, is the major limitation for many potential applications of these materials. Because upconversion is a multi-photon process, UC intensity has a greater-than-linear dependence on excitation power density. It is common practice, therefore, to focus the excitation beam within a small sample volume to achieve high excitation power densities, resulting in brighter, more efficient upconversion. This often precludes large-area UC imaging in the absence of either powerful unfocused excitation or tightly-focused, rastered excitation. Plasmonic enhancement is a major strategy being pursued to improve the efficiency of upconversion. Properly designed plasmonic surfaces can generate patterned regions of highly-focused electric fields upon large-area illumination with excitation light. However, significant fundamental questions still remain with regard to the interaction of UC nanocrystals with plasmonic particles and surfaces. One difficulty in characterizing this interaction is that the observed enhancement is very sensitive to the position of the UC nanocrystal relative to the plasmonic architecture. Enhancements observed from ensembles of UC nanocrystals can be dramatically affected by the inhomogeneity of the particle distribution relative to the field ‘hot spots.’ In the study presented here, however, the geometry of the UC nanocrystals relative to the plasmonic surfaces is carefully controlled and the spectral data acquired with high spatial resolution, extending even to the single particle level. A model plasmonic architecture is used consisting of Au micro-cavity arrays. Single crystals of NaYF4: Yb, Ln (Ln=Er, Tm) of uniform size are imaged in the hemispherical cavity wells. UC images of the crystals is captured with a hyperspectral microscope, exciting the arrays with 980 nm light, using full field illumination. Single crystal orientation is confirmed by comparing the optical and hyperspectral images with the scanning electron microscope images. The project introduces a new approach for evaluating the effects of a plasmonic surface on UC efficiency.
10:15 AM - MD7.1.03
Toward Highly Luminescent Lanthanide-Organic Polymers for LED Applications
Jennifer Weimmerskirch-Aubatin 2,Christophe Labbe 2,Jean-Louis Doualan 2,Fabrice Gourbilleau 2,Sara El Hanbali 1,Olivier Perez 1,Sophie Boudin 1
2 CIMAP, NIMPH CNRS/CEA/ENSICAEN/UCBN Caen France,1 CRISMAT, UMR 6508 - ENSICAEN Caen France
Show AbstractMetal phosphonates are widely studied since the last decades due to their potential applications in several domains such as ion exchangers, proton conductors or opto-electronics and non-linear optical materials. Lanthanide aryl and alkyl phosphonates LnH(O3PR)2 (Ln = La, Y, Eu, Tb; R = CH3, C2H5, C3H7, C6H5) are particularly interesting for several reasons : (i) they exhibit an intense luminescence comparable to commercial phosphors like Y2O3:Eu3+ 1,2,3 ; (ii) they are easy to produce from cheap organic precursors by low temperatures processes and (iii) they are stable up to 400°C – 500°C. All these reasons make them competitive candidates for phosphors materials in LED applications.
Recently the R = C6H5 members of the LnH(O3PR)2 series have been successfully nanostructured to enhance luminescence4,5,6. We propose here another route to improve and control the luminescent properties of these materials, by selecting the most efficient host matrices and lanthanide doping rates. Based on this approach, the La1-xLnxH(O3PR)2 (0 ≤ x ≤ 1; Ln = Eu, Tb) series have been synthesized by hydrothermal methods at 180°C and studied.
The crystal structures have been analyzed by X ray diffraction, and the microstructures by scanning electron microscopy. The LaH(O3PR)2 structures are composed of alternating organic and inorganic layers. Within the inorganic layers, the lanthanum ions are disposed in chains of LaO8 polyhedra linked by opposite edges. Crystal structures and microstructures of La1-xLnxH(O3PR)2 compounds will be compared and presented.
The photophysical properties were investigated by photoluminescence (PL), PL excitation and time resolved PL spectroscopies. The La1-xEuxH(O3PR)2 phosphonates exhibit typical Eu3+ red luminescence, due to 4f-4f transitions. The La1-xTbxH(O3PR)2 phosphonates exhibit, under 4f-4f and 4f-5d excitations, 4f-4f blue to green emissions, which can be tuned by the lanthanide doping rates and the excitation wavelengths. Weakly Eu3+ / Tb3+ codoped materials exhibit a white emission under lexc = 378 nm ; giving alternative candidates for white phosphors applications. Whereas heavily Eu3+ or Tb3+ doped materials exhibit red and green emissions which can be optimized by selection of the R groups of the LaH(O3PR)2 host matrices and of the Eu3+ and Tb3+ contents. Effects of host matrices, lanthanide doping rates and excitation wavelengths upon Tb3+ cross relaxation and concentration quenching phenomenon in La1-xLnxH(O3PR)2 materials will be presented in details and linked with the evolution of decay times and photoluminescence intensities.
1 Rosa, I. L. V et al. J. of Alloys and Compounds, 275-277, 315-317, (1998)
2 Rosa, I. L. V. et al. J. Fluoresc. 16, 455–459 (2006).
3 Mutelet, B. et al. Dalton Trans 44, 1186–1192 (2015).
4 S.Y. Song et al. Inorg. Chem. 45, 1201-1207, (2006)
5 W. Di et al. J. Phys. Chem. C, 114, 6290-6297, (2010)
6 W. Di et al. CrystEngComm, 13, 5226-5233, (2011)
10:30 AM - MD7.1.04
Resolving the Ambiguity in the Relation between Stokes Shift and Huang–Rhys Parameter
Mathijs de Jong 1,Luis Seijo 3,Andries Meijerink 1,Freddy Rabouw 1
1 Chemistry Utrecht University Utrecht Netherlands,2 Departamento de Química Universidad Autonoma de Madrid Madrid Spain,3 Instituto Universitario de Ciencia de Materiales Universidad Autonoma de Madrid Madrid Spain
Show AbstractThe shapes of absorption and emission spectra that are observed in luminescence spectroscopy give essential information about the type of electronic transition that is studied. Electronic transitions in luminescent molecules or luminescent centers in crystals couple to vibrations. This results in broadening of absorption and emission bands, as well as in the occurence of a Stokes shift. In principle, one can derive from the Stokes shift the Huang-Rhys parameter S, which describes the microscopic details of the vibrational coupling and can be related to the equilibrium position offset between the ground state and excited state potential energy surfaces of the transitions. A relation between EStokes and S allows for a direct link between the Stokes shift and the molecular properties of the system which can also be addressed through quantum mechanical calculations.
Suprisingly, the two commonly found textbook relations EStokes=(2S-1)hω/2π and EStokes=2Shω/2π are contradictory. We have attempted to resolve this ambiguity. We investigate how EStokes is related to S by modelling the emission spectra as a function of the Huang-Rhys parameter. To this end we use the simple Franck-Condon overlap integrals and take into account the effects of a finite temperature through line broadening and thermal occupation of excited vibrational states. We show that in different ranges of temperature, different approximate relations between EStokes and S are appropriate. The two textbook relation are valid in limiting situations and set boundaries to the values that the Stokes shift can take.
Moreover, we demonstrate a new method for relating the absorption and emission spectra to the microscopic properties of the system: instead of using the maxima of the bands, the difference between the barycenters of absorption and emission bands can be used to determine S in an unambiguous way. The position of the barycenter is, contrary to the Stokes shift, unaffected by temperature.
This work settles the debate about the validity of the two relations that are commonly used to relate the Stokes shift to the Huang-Rhys parameter in the field of luminescence spectroscopy. It finds immediate application in all the fields in which this technique is used to determine the Huang-Rhys parameter from experimentally observed spectra.
11:15 AM - *MD7.1.05
Multi-Functional Lanthanide Systems for Biological Applications: Imaging and Inhibition of Tumor
Rick W.K. Wong 1,Hongshan He 2
1 Hong Kong Baptist Univ Kowloon China,2 Chemistry Eastern Illinois University Charleston United States
Show AbstractNear-infrared (NIR) luminescent materials containing lanthanide(III) ions are used increasingly in telecommunications engineering, laser technology and biomedical science due to their extraordinary optical properties. However, lanthanides are constrained intrinsically by the Laporte-forbidden 4f – 4f transitions that render direct excitation of them rather inefficient; their extreme susceptibility towards non-radiative quenching by water’s vibrational O-H harmonic oscillations cannot be overstated. These constraints make lanthanide luminescence studies challenging. To sensitize and protect the lanthanide ion, porphyrin-based macrocycles, in this regard, are one of the promising organic antenna ligands to be utilized. With high absorption cross sections for intense UV absorption and low energy triplet states well matched to the lanthanides’ NIR emitting states, porphyrins can absorb the excitation light effectively, transfer the energy to the lanthanide ion efficiently, and coordinate with them to form robust complexes. In the 1st part of lecture, we will highlight some recent advances in the development of NIR emissive porphyrin-based lanthanide complexes, porphyrin-coated lanthanide nanoparticles, and their potential bio-applications in terms of being NIR probes and antitumor agents.
In the second half, a new gadolinium complex (Gd-N) as a tumor-specific photodynamic therapy (PDT) agent will be discussed. Gd-N has great potential of serving as an anti-cancer torpedo boat which is equipped with visible-to-NIR emission for tumor imaging, discriminating radar for tumor targeting, and powerful 1O2 torpedo generation for tumor killing. This new gadolinium complex here can be promising and applicable for the development of long-term live cancer cell tracking and imaging, as well as modern practical PDT.
References:
1. D. Qi, Q. Wang, H. Li, T. Zhang, R. Lan, W.-K. Wong, K.-L. Wong, S. Li, F. Lu, Molecular Biosystems, (2015) In Press. DOI: 10.1039/C5MB00497G.
2. T. Zhang, R. Lan, L. Gong, B. Wu, Y. Wang, D. W. J. Kwong, W.-K. Wong, K.-L. Wong, D. Xing, ChemBioChem, (2015) In Press 10.1002/cbic.201500349.
3. T. Zhang, R. Lan, C.-F. Chan, G.-L. Law, W.-K. Wong, K.-L. Wong, Proceedings of National Academy of Science USA, 111 (2014) E5492-E5497.
4. T. Zhang, C.-F. Chan, R. Lan, W.-K. Wong, K.-L. Wong, Chemistry-A European Journal, (2014), 971-973.
5. T. Zhang, C.-F. Chan, J. Hao, G.-L. Law, W.-K. Wong, K.-L. Wong, RSC Advances, 3 (2013) 382-385.
6. T. Zhang, C.-F. Chan, R. Lan, H. Li, N.-K. Mak, W.-K. Wong, K.-L. Wong, Chemical Communications, 49 (2013) 7258-7260.
7. J. Zhang, H. Li, C.-F. Chan, R. Lan, W.-L. Chan, G.-L. Law, W.-K. Wong, K.-L. Wong, Chemical Communications, 48 (2012) 9646-9648.
8. T. Zhang, X. Zhu, W.-M. Kwok, C. T.-L. Chan, H.-L. Tam, W.-K. Wong, K.-L. Wong, Journal of the American Chemistry Society, 50, (2011) 20120-20122.
11:45 AM - MD7.1.06
Cathodoluminescence-Activated Imaging by Resonance Energy Transfer (CLAIRE): Using Ultra-Thin Films of Cerium-Doped Yttrium Aluminum Perovskite for Nanoscale Imaging
Connor Bischak 1,Craig Hetherington 1,Claire Stachelrodt 1,Clarice Aiello 1,Zhe Wang 2,Hao Wu 1,Darrell Schlom 2,Naomi Ginsberg 1
1 Department of Chemistry University of California, Berkeley Berkeley United States,2 Department of Materials Science and Engineering Cornell University Ithaca United States
Show AbstractTo generate a nanoscale optical probe for interrogating dynamics in biological systems, we have developed a new approach called cathodoluminescence-activated imaging by resonance energy transfer (CLAIRE) that combines the nanoscale focusing of scanning electron microscopy and the chemical specificity and non-invasiveness of fluorescence microscopy. Our super-resolution optical imaging platform consists of a high-brightness, rapidly scannable, 20-nm optical spot in a cathodoluminescent cerium-doped yttrium aluminum perovskite (YAlO3:Ce, YAP:Ce) thin film. The nanoscale excitation volume is generated by a low energy, focused electron beam from a scanning electron microscope. Optical excitations in the ultrathin (10-20 nm) YAP:Ce thin film, activated by the electron beam, interact in the near-field with the sample. Interactions between the excited cerium dopants in the YAP:Ce film and the sample can provide contrast by quenching or enhancing the emission of the YAP:Ce film. Additionally, excitations in the film can be non-radiatively transferred to adjacent luminescent samples via Förster resonance energy transfer (FRET). By correlating the position of the electron beam with the cathodoluminescence intensity of the film or with fluorescence from the sample, we generate images with nanoscale resolution and high optical contrast. Thus far, we have imaged metal nanostructures based on cathodoluminescence-activated enhancement of the YAP:Ce film emission. We have also used FRET to image soft samples, such as organic light-emitting polymer blends, which would otherwise be damaged by direct electron excitation. Recently, we have begun imaging dried biological samples and tracking the movement of samples in fluid environments. By encapsulating aqueous biological samples adjacent to the YAP:Ce film, we anticipate imaging biological dynamics, such as diffusion on lipid membranes, on the nanoscale.
12:00 PM - MD7.1.07
Exfoliation of Lanthanum Hexaboride Using Solution-Based Methods
Roshini Ramachandran 1,Tina Salguero 1
1 University of Georgia Athens United States,
Show AbstractMetal boride ceramics are of great interest as high performance materials due to their high melting points, thermal stability, chemical inertness and extreme hardness. In particular, lanthanum hexaboride also possesses other useful properties such as a very low work function and one of the highest electron emissivities known. However, even with these exceptional properties, its industrial use is limited due to its difficulty in being processed into thin films.
To that end, we have developed a technique that utilizes a lithium ion incorporation-exfoliation reaction to convert lathanum hexaboride into its constituent nanosheets, making it solution-processable. Using this synthetic methodology, we obtained LaB6 nanosheets with lateral dimensions on the micron scale and thickness less than 5 nm. The effect of using different starting material morphologies, lithium ion sources and reaction conditions on the size, shape and morphology of the nanosheets were also studied. We are currently investigating the Li ion incorporation into the lanthanum hexaboride lattice and further evaluating the near infra-red absorption properties of LaB6 nanosheets.
12:15 PM - *MD7.1.08
On the Optical and Magnetic Properties of Ln3+ Based Nanoparticles
Frank Van Veggel 1
1 Univ of Victoria Victoria Canada,
Show AbstractOne of our main research thrusts in the field of colloidal nanomaterials and their applications is based on the trivalent lanthanide ions, which have unique optical and magnetic properties. We cover the range from synthesis and characterisation to (in vivo) applications, with a recent focus on MRI (Magnetic resonance Imaging) for cancer diagnostics. The colloidal stability is typically obtained by a “soft” layer of organic molecules. To this purpose, we have developed synthesis techniques to make core-shell architectures which allows the optical and magnetic properties to be optimized separately. Additionally, we do surface modifications by organic chemistry to impart compatibility with biological media and to impart binding specificity (e.g. through antibodies).
The synthesis and basic characterisation of the nanoparticles will only briefly be discussed, but the core-shell synthesis will be discussed in some detail. Some emphasis will be on the challenges to prove the actual formation of core-shell structures and the Ln3+ dopant distribution. The main focus of the talk is on their surface modification and use as optical and magnetic probes for bioimaging. Soem recent in vivo MRI studies will be included showing their potential as MRI contrast agent at high magnetic fields in brain, breast and prostate cancer.
MD7.2: Synthesis, Sensing and Imaging II
Session Chairs
Hongshan He
Zhiping Zheng
Wednesday PM, March 30, 2016
PCC West, 100 Level, Room 106 A
2:30 PM - *MD7.2.01
Counterintuitive Design of Lanthanide-Doped Upconverting Nanocrystals for Single Particle Imaging
Bruce Cohen 1,Emory Chan 1,P. James Schuck 1,Daniel Gargas 1,Alexis Ostrowski 1
1 Lawrence Berkeley National Lab Berkeley United States,
Show AbstractImaging complex materials at the single-molecule level reveals spatial and temporal heterogeneities that are lost in ensemble imaging experiments. An ongoing challenge is the development of probes with the photostability, brightness, and continuous emission necessary at higher single-molecule excitation intensities. We have found that lanthanide-doped upconverting nanoparticles (UCNPs), which absorb multiple photons in the NIR and emit at higher energies in the NIR or visible, have unusual properties that make them valuable luminescent reporters, including: no measurable photobleaching, even under prolonged single-particle excitation; no overlap with autofluorescence in biological systems; an absence of on-off blinking; and efficiencies 5-6 orders of magnitude higher than the most efficient 2-photon fluorescence processes. But the brightness of UCNPs has been limited by a poor understanding energy transfer and relaxation within individual nanocrystals and unavoidable trade-offs between brightness and size. We have recently engineered UCNPs under 10 nm in diameter that are over an order of magnitude brighter under single-particle imaging conditions than the brightest ensemble compositions, allowing us to visualize single upconverting nanoparticles as small as fluorescent proteins. We have used a combination of advanced characterization (single-nanocrystal lifetimes and full emission spectra) and theoretical modeling to find that surface effects become critical at diameters under 20 nm, and that the higher fluences used in single-molecule imaging fundamentally change the factors that determine nanocrystal brightness. We find that factors known to increase brightness in bulk experiments are unimportant at higher excitation powers, and that, paradoxically, the brightest probes under single-molecule excitation are barely luminescent at the ensemble level. We have also applied this modeling strategy to develop efficient hybrid UCNP-dye biosensors that may be deployed as local sensors of cell signaling.
3:00 PM - MD7.2.02
Potential for Lanthanide-Based Tetrakis Smart Sensor Materials
William Hollerman 1,Ross Fontenot 1,Stephen Williams 1,Sara White 1,Clint Crail 1
1 Univ of Louisiana-Lafayette Lafayette United States,2 Naval Surface Warfare Center West Bethesda United States,1 Univ of Louisiana-Lafayette Lafayette United States
Show AbstractFor more than a decade, we have been pushing the boundaries of special material class that emits light when it is stressed, strained, and/or fractured. These materials have been proposed for the active element of impact sensors, earthquake detectors, and stress sensors in a variety of applications. While there are a number of techniques currently being used for damage detection and monitoring of civil, aerospace, and military structures and aircraft, they do not provide in-situ and distributed sensing. Wiedemann and Schmidt defined triboluminescence (TL) as the emission of light produced by the fracturing of materials. In recent years, triboluminescent materials have been proposed for use as the active element in smart vehicular or static structural sensors. To sense damage, these materials would be embedded into the object. If damage occurs, the embedded triboluminescent material would give off visible light. This light could be transmitted by lightweight fiber optics or wireless detector to a computer-based detection system to warn occupants in real time that a significant impact event has occurred. In addition, the triboluminescent-based sensor could allow for real-time monitoring of both the magnitude and location of damage with influence to the host object. For this type of sensor to be adopted, it must operate in the harshest of environments, like space. However, in order for this concept to go from the laboratory to use in real world applications, the light emission from these functional materials must be quite bright so that inexpensive light detectors can be used. One of the brightest materials found thus far is europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA). This material has a luminescent emission yield that is so bright that it can be observed in daylight. Other lanthanides can be used to synthesize tetrakis compounds, each with different light emission characteristics. Tetrakis compounds can also be doped with other compounds to make them brighter. This talk will provide an overview into our research to synthesize and characterize tetrakis-based luminescent materials
3:30 PM - MD7.2.04
Carbon Monoxide Gas Sensing Performance of Monodisperse CeO2 Microspheres
Carlos Michel 1,Edgar Lopez-Mena 2,Alma Martinez-Preciado 1,Alex Elias-Zuniga 2
1 Universidad de Guadalajara Guadalajara Jalisco Mexico,2 Escuela de Ingenieria y Ciencias Tecnologico de Monterrey Monterrey Mexico
Show AbstractCeO2 has been intensively studied due to their notable physical and chemical properties. Applications in fields like catalysis, membranes, photocatalysis, fuel cells, gas sensors and medicine have been reported for this material. In catalysis, the ability of cerium ions to change their oxidation state, from Ce+3 to Ce+4, explained its efficiency to store and transport oxygen. In this work, monodisperse CeO2 microspheres were prepared by a microwave-assisted coprecipitation method, using ceric nitrate and formic acid. The reaction between the latter produced the precipitation of a white powder, with simultaneous emission of NO2. X-ray diffraction results revealed the formation of cerium formate, at room temperature. Calcination of the precipiate from 300oC produced single-phase CeO2, which has cubic crystal structure. The morphology of the samples corresponds to monodisperse microspheres, with a size of approximately 1 μm. Observation by transmission electron microscopy of samples calcined at 500oC show the formation of nanograins and abundant nanoporosity. In order to evaluate the synthesis parameters, the effect of the calcination temperature and the concentration of ceric nitrate were investigated. The results show that the increase on the calcination temperature caused the thermal decomposition of organic matter, which produced nanoporosity and microspheres with rough surface. On the other hand, the increase on the amount of ceric nitrate in solution, yielded larger particles with uneven size. Measurements of the gas sesning properties were performed on thick films made by depositing a suspension of the CeO2 powder, on alumina substrates. Alternating current (AC) and direct current (DC) were used in this characterization. The films exhibited a reliable and quantitative detection of carbon monoxide from 250oC. According to its electrical response, CeO2 has the n-type semiconductor behavior; which is described by a decrease of the impedance in CO flows. Moreover, the increase on the applied frequency produced reproducible and more stable gas response partterns. The operating temperature played also a key role in the sensor performace, by decreasing the response time to about 10 s, at 300oC. A comparison of these results with those previously reported for this material was done.
4:15 PM - *MD7.2.05
Thermochromism, the Alexandrite Effect and Other Fascinating Properties of 4f/3d Materials
Thomas Albrecht-Schmitt 1
1 Florida State University Tallahassee United States,
Show AbstractWe have prepared many large families of 4f/3d materials in the search for compounds with unusual optical and magnetic properties. While long-range magnetic coupling has remained elusive, a number of unexpected structures and structure-property relationships have been observed. In particular, this talk will focus on origin of atypical optical properties such as thermochromism and the Alexandrite Effect in these families of compounds.
4:45 PM - MD7.2.06
Rare-Earth Oxysulfate Hollow Nanospheres for Upconversion
Gen Chen 1,Hongmei Luo 1
1 Chemical and Materials Engineering New Mexico State Univ Las Cruces United States,
Show AbstractBulk glass and crystalline materials are usually used for upconversion, but bulk materials are often not suitable for certain applications such as biological imaging or biolabelling. Upconversion materials on nanometer scales are desirable. However, synthesis of small nanocrystals that exhibit high monodispersibility and excellent upconversion properties remains a challenge.
In this work, nanoscale monodisperse rare-earth-metal-doped oxysulfate RE2O2SO4 (RE = Y, Gd) hollow spheres were prepared for upconversion via a biomolecule-assisted hydrothermal method followed by calcination. The size and crystallinity of nanospheres, as well as the upconversion properties could be tuned by changing the experimental conditions such as surfactants, hydrothermal/annealing temperature, and chemical compositions. Upconversion properties revealed that the energy transfer between the sensitizer and the activator was strongly depended on the concentration of activator, the ratio of sensitizer to activator, chemical compositions and crystallinity of the hollow spheres.
5:00 PM - MD7.2.07
Analytical Study of the Thermal Activation of Tb3+ Doped Amorphous SiC:H Thin Films
Jorge Guerra 2,Roland Weingaertner 1,Albrecht Winnacker 2
1 Pontificia Universidad Catolica del Peru Lima Peru,2 WW7 University of Erlangen-Nürnberg Erlangen Germany,1 Pontificia Universidad Catolica del Peru Lima Peru2 WW7 University of Erlangen-Nürnberg Erlangen Germany
Show AbstractRare earth (RE) doped semiconductors have found applications as efficient luminescent materials, optical amplifiers, lasers, photon down- and up-conversion coatings among others. The interest on RE-doped materials is attributed to the narrow light emission spectral lines and long fluorescence lifetimes they present at wavelengths that are practically unaffected by the host environment. This is owing to the fact that the RE luminescence arises from the partially filled intra-4f shell electronic transitions. The 4f electrons are shielded from the 6s bonding electrons by the 5s and 5p shells. Consequently, the mixing with the 4f electrons is very low, and thus the effect on the 4f energy levels due to the RE bonding with the host matrix atoms is weak. However, the excitation mechanisms and subsequent recombination in RE ions are highly susceptible to host matrix electronic properties, such as defect states and the optical bandgap.
It is well established that the light emission intensity of RE doped materials can be enhanced after annealing treatments [1]. The study of the annealing behavior can help elucidate the underlying mechanism for producing optically active RE centers in a host [2,3]. However, the variation of the light emission intensity with thermal annealing treatments not only obeys the increase of luminesce centers. The annealing treatments also induce the variation of non-radiative recombination paths, thus modifying the light emission intensity by energy migration between luminescence centers and the host matrix. In the present work, Tb ions were incorporated into a-SiC:H thin films by RF-sputtering. After deposition, we performed thermal annealing treatments to induce the RE activation. We assessed the latter activation by the systematical analysis of the Urbach energy and by recording sub-bandgap excitation photoluminescence spectra for different Tb concentrations and annealing temperatures. Finally, in order to discriminate the effect on the luminescence of the Tb3+ activation from the variation of host-related recombination paths, we report the variation of the light emission intensity versus de Tb3+ concentration at different annealing temperatures. We describe the dependence of the intensity with the RE concentration by a rate equation model [4]. Three fitting parameters were extracted for each annealing temperature from our comprehensive dataset. These parameters are related to the RE activation degree, the interaction probability between RE ions, and the probability of energy loss through a host-related non-radiative recombination channel, respectively. Surprisingly, the results show a suppression of the self quenching by a thermally-induced reduction of the RE interaction probability.
References
[1] A. R. Zanatta, J. Phys. D: Appl. Phys. 42 (2009) 025109.
[2] A. Janotta et al, Phys. Rev. B 68 (2003) 165207.
[3] S. Abedrabbo et al, J. of Phys. D: Appl. Phys. 44 (2011) 315401.
[4] F. Benz et al, J. Lumin 137 (2013) 73.
5:15 PM - *MD7.2.08
Luminescent Nanothermometry: Nanothermometers and Nanoheaters Get Closer
Luis Carlos 1
1 Physics Department and CICECO - Aveiro Institute of Materials Universidade de Aveiro Aveiro Portugal,
Show AbstractNanothermometry has indeed experienced an unprecedented growth over the past five years following, in most examples, the technological trends of sub-micron miniaturization, namely in the temperature mapping of microcircuits and microfluidic devices.1 There is also a high demand of nanothermometry for biomedical uses, like the development of intracellular thermometers capable of accurate temperature determination in living cells.2
Despite promising progresses on the temperature mapping of microfluidic devices and living cells, precision control of fluid temperature by accounting for local temperature gradients, heat propagation and accurate temperature distributions have not yet been satisfactorily addressed. The major obstacle for this has been the unavailability of a thermometer with the following requirements: i) high temperature resolution (ca. 0.1 degree); ii) ratiometric temperature output; iii) high spatial resolution (
5:45 PM - MD7.2.09
Explaining the Nanoscale Effect in the Upconversion Dynamics of β-NaYF4:Yb3+,Er3+ Core and Core/Shell Nanomaterials
Mary Berry 1,Amy Hor 2,QuocAnh Luu 2,Md Yeathad Hossan 1,Steve Smith 2,P. Stanley May 1
1 Univ of South Dakota Vermillion United States,2 South Dakota School of Mines and Technology Rapid City United States
Show AbstractNanocrystals of NaYF4:Yb3+,Er3+ are known to have much lower upconversion (UC) quantum efficiencies than large high-quality crystals, and exhibit more rapid UC dynamics when excited with a pulsed source near 980 nm. Here we show that a recently developed model for UC in powders of micron-sized b-NaYF4:18%Yb3+,2%Er3+ crystals correctly predicts the time-resolved luminescence curve shapes and the relative intensities of the various emission lines for core and core/shell nanoparticles, along with the observed drop in quantum efficiency. The model clearly shows that the nanoscale effect on upconversion in these materials is almost entirely explained by rapid energy migration at the 1 µm energy level for both Yb3+(2F5/2) and Er3+(4I11/2), such that an equilibrium is achieved between interior and rapidly relaxing surface sites at that energy level. Thus, the only significant difference in the UC dynamics for the micron–sized crystals and nanocrystals arises from the rate constants for multiphonon relaxation from Yb3+(2F5/2) and Er3+(4I11/2).
MD7.3: Poster Session: Synthesis, Sensing and Imaging
Session Chairs
Thursday AM, March 31, 2016
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - MD7.3.01
Lanthanide Selective Adsorption by Nd-Imprinted Polymer with Chelidonic Acid Monoamide Groups
Tomohito Ide 1,Akiko Suzuki 1,Toshihiro Imada 1
1 Corporate Research amp; Development Center, Toshiba Corporation Kawasaki-shi Japan,
Show AbstractLanthanides (rare earth elements) separation by solid-phase extraction remains challenging, but is a safe and economical method. The ion-imprinted adsorbent (or sorbent) is promising for lanthanide selective solid-phase extraction. In the ion-imprinted materials, the ligands are ordered like a complex and exhibit the selectivity for the target ion. In this work, chelidonic acid was focused on as the ligand. Electron-withdrawing carbonyl group in chelidonic acid improves the acidity of carboxylic acid group and enhances adsorption capability in the acidic range. Herein we report synthesis of Nd-imprinted polymer with chelidonic acid monoamide group and their adsorption properties.
A polymerizable ligand with chelidonic acid group was obtained by condensation of chelidonic acid and 4-aminostyrene. A Nd-complex monomer was synthesized from the obtained ligand and Nd(NO3)3. Copolymerization of the Nd-complex monomer, styrene and divinylbenzene afforded Nd-containing polymer. Nd ion in the polymer was removed by 6 M HCl three times to afford Nd-imprinted polymer. A non-imprinted polymer composed by the ligand, styrene and divinylbenzene was also synthesized. Elemental analysis revealed that the content of chelidonic acid monoamide ligand determined from the amount of nitrogen in the non-imprinted and Nd-imprinted polymer is 1.70 and 1.56 μmol/g, respectively. BET method indicated that non-imprinted and Nd-imprinted polymer has specific surface area of 14.7 m2/g and 1.51 m2/g respectively.
Selectivity of the obtained polymers was revealed by competitive adsorption. Aqueous solution of 0.2 M ammonium acetate containing lanthanide (Nd3+, Dy3+) and selected transition metal (Cu2+, Zn2+, Co2+) ions with concentration of 0.1 M was used as solution to be treated. A pH range of solution was from 3.0 to 7.0. Non-imprinted polymer shows maximum adsorption amount of lanthanides at pH 5.0 (33.8 μmol-Dy/g, 36.8 μmol-Nd/g). Selectivity of Dy is slightly higher than that of Nd below pH 4.0. Molar percentage of lanthanides is from 51% (pH 7.0) to 63% (pH 3.75). Nd-imprinted polymer has adsorption maximum of lanthanides at pH 3.75 (77.9 μmol-Dy/g, 81.3 μmol-Nd/g) with lanthanides selectivity 73% in spite of the same ligands. Moreover, Nd-imprinted polymer exhibits slightly larger adsorption amount of Nd than that of Dy over a range of pH 3.0–7.0. Lanthanide selectivity is up to 82% at pH 3.0 with adsorption amount of Dy was 68.4 μmol/g and Nd was 72.7 μmol/g. Total amount of adsorbed metals of Nd-imprinted polymer is surprisingly superior to that of non-imprinted polymer in spite of low content of ligands and small surface area. These results were explained by the ion-imprint effect. Namely, two or more chelidonic acid monoamide ligands are ordered in the suitable direction and distance for adsorption of Nd ion and ordered ligands enhanced lanthanide selectivity.
9:00 PM - MD7.3.02
Recyclable Photoluminescence Switcher Property of Eu(III) Doped CeO2 Nanorods Regulated by l(+)-Ascorbic Acid and Hydrogen Peroxides
Wei Gao 2,Yongquan Qu 2,Johnny Ho 2
1 City Univ of Hong Kong Hong Kong Hong Kong,2 Xi’an Jiaotong University Xian China,2 Xi’an Jiaotong University Xian China
Show AbstractRare earth elements are broadly researched in imaging and sensing because of their special optical property. Series of Eu3+-doped CeO2 nanorods with rod-like morphologies were synthesized by a hydrothermal method followed by high temperature calcinations. Phosphors with different Eu3+ contents can be effectively excited at 340 nm due to the charge transfer from O2- to Ce4+, and display orange and red emission. Treating by L (+)-ascorbic acid (AA), the photoluminescence intensity of Eu3+-doped CeO2 nanorods was exponentially decreased with the increasing concentration of AA, resulting from the chemical reduction of Ce4+ into Ce3+ and subsequent excitation cutoff of O2- to Ce4+. The photoluminescence intensity of reduced phosphor was restored to the original intensity reversibly by adding hydrogen peroxide, which oxidized Ce3+ into Ce4+. The evolution in photoluminescence intensity was consistent with surface Ce3+ fractions of Eu3+-doped CeO2nanorods, which were 22.0% for as-synthesized phosphors, 34.6% for reduced phosphors and 23.2% for restorative phosphors oxidized by H2O2, respectively. The quantitative and repetitive photoluminescence switching of Eu3+-doped CeO2nanorods by adding AA and hydrogen peroxide alternatively indicates their potential applications as photoluminescence switching devices and chemical or biological sensors for detection and monitoring.
Reference:
W. Gao, J. Li, X, Zhou, Z. Zhang, Y. Ma and Y. Qu, J. Mater. Chem. C, 2014, 2, 8729.
Z. Tian, J. Li, Z. Zhang, W. Gao, X. Zhou and Y. Qu, Biomaterials, 2015, 59, 116.
9:00 PM - MD7.3.03
Ab Initio Study of the Lattice Dynamical, Electronic and Optical Properties of Double Perovskite La2HoErO6 Compound
Gokhan Surucu 2,Aytac Erkisi 3,Nurettin Korozlu 4,Yasemin Ciftci 2,Engin Deligoz 5
1 Ahi Evran University Kirsehir Turkey,2 Gazi University Ankara Turkey,3 Hacettepe University Ankara Turkey4 Erzincan University Erzincan Turkey2 Gazi University Ankara Turkey5 Aksaray University Aksaray Turkey
Show AbstractPerovskite like structures have drawn a considerable amount of research interest because of their importance in technological applications[1-2]. A common formula of the perovskite structure can be generalised as ABX
3 where A and B atoms are cations with a remarkable size difference (A>B), while X atom is anion which is known to be oxygen in naturally occurring perovskites and halogens in synthetic compounds[3]. Oxides of perovskites are ideally formed in cubic structure with A atoms on the corners, B atoms in the body centre and C atoms on the face centres. In most cases, due to the mismatch in the cations’ sizes, a structural distortion occurs leading to a transformation from cubic phase to a low-symmetry orthorhombic or tetragonal phase[1,2,4]. These phase transformations result in significant effects on the electrical properties, thus perovskite-type oxides have been in the focus of ferro/anti-ferroelectric and high-K dielectric applications[4-7]. Also, these oxides are key elements of colossal magnetoresistance, PTC thermistor, battery material industry as well as smart and superconducting devices[2,8]. Interlanthanide perovskites, where A is the larger element from the left side of lanthanide series while B is the smaller one from the opposite side constitute an important sub-group of perovskite oxides due to their applications in the protonic conductor and scintillator studies [9].
In this work, the class of A
2BB’O
6 type double perovskite oxides, La
2HoErO
6 compound was investigated in varied phases by using generalized gradient approximation in the density functional theory. On-site Coulomb interaction is also included in calculations (GGA+U). The structural, mechanical, vibrational properties were studied. Especially the electronic band structure, density of states, optical properties and their related quantities such as dielectric constants, refraction index and energy-loss function were calculated.
References:
[1] Rhodes, C.J., Science Progress 97(2014) 279-287.
[2] Lufaso, M.W., Woodward, P.M., Acta Cryst. B 57
(2001) 725–738.
[3] Jones, A.P., et al., Rare Earth Minerals: Chemistry, Origin and Ore Deposits, Springer, 1996
[4] Coh, S., et al., Phys. Rev. B 82
(2010) 064101.
[5] Saha, S., et al., Phys. Rev. B 62
(2000) 8828-8834.
[6] Auciello, O., et al., Phys. Today 51 (1998) 22-27.
[7] Hill, N.A., J. Phys. Chem. B 104
(2000) 6694-6709.
[8] LI, C., et al., J. Alloys Compd. 372 (2004) 40–48.
[9] Artini, C., et al., J. Alloys Compd. 494
(2010) 336-339.
9:00 PM - MD7.3.04
Infrared-to-Visible Light Upconversion in Er:Yb:SrFBr
K. Tauni Dissanayake 1,Federico Rabuffetti 1
1 Wayne State University Detroit United States,
Show AbstractSrFBr nanocrystals codoped with ~1 mol. % of Er and Yb and an average size of 64 nm were synthesized using metal trifluoroacetates and tribromoacetic acid as fluoride and bromide sources, respectively. The average and local crystal structures conformed to those expected on the basis of the P4/nmm tetragonal space-group. Excitation of Yb3+ at 980 nm resulted in two-photon upconversion and green-yellow emission from Er3+. The intensity of the emission was comparable to that of Er:Yb:SrF2 nanocrystals featuring doping levels an order of magnitude higher. This finding highlights the potential of alkaline-earth fluorohalides as hosts for Yb3+-Er3+ sensitizer-activator upconverting pairs.
9:00 PM - MD7.3.05
Non-Linear Density Dependent Upconversion Luminescence Enhancement of β-NaYF4: Yb3+: Er3+ Nanoparticles on Random Ag Nanowire Aggregates
Amy Hor 1,QuocAnh Luu 1,P. Stanley May 2,Mary Berry 2,Steve Smith 1
1 Nanoscience and Nanoengineering South Dakota School of Mines and Technology Rapid City United States,2 Chemistry Department University of South Dakota Vermillion United States
Show AbstractSpectroscopic imaging and statistical analysis of NIR-to-visible upconversion luminescence (UCL) from β-NaYF4:Yb3+:Er3+ upconverting nanoparticles (UCNPs) supported on a series of random Ag nanowire aggregates reveals a density dependent UCL enhancement. Statistical analysis of the spectrally resolved upconversion images shows a non-linear dependence of upconversion luminescence enhancement with Ag nanowire surface coverage. A maximum average enhancement of 5.8x was observed for 58% surface coverage. Based on the empirically determined trend with density, it is estimated that up to 20x upconversion luminescence enhancement can be achieved at 100% surface coverage, even at high excitation intensity. This projection is commensurate with the 20x enhancement ratio observed for select locations within the imaged micro-ensemble. Time-resolved emission of the UC luminescence from UCNPs on the Ag nanowire aggregates confirms the surface plasmon effects on the UCNPs kinetics. Such Ag nanowire aggregates show potential as a scalable and relatively simple metal-enhanced upconversion substrate.
9:00 PM - MD7.3.06
White Light Emission through Partial Energy Transfer from Organic Molecules to Lanthanide Complexes in Gel
Prashant Kumar 1
1 Chemistry Indian Institute of Technology Madras Chennai India,
Show AbstractLanthanide based inorganic-organic hybrid materials have gained much attention in recent years due to their widespread application in different fields like optoelectronics1 and cellular imaging.2 Herein, we have developed lanthanide based white light emitting hybrid hydrogel, where the hydrogel was formed by a dendron derivative {glucose cored poly (aryl ether)}.3 The donor {phenanthrene, naphthalene and pyrene} and acceptor {europium(+3) and terbium(+3)} molecules have been incorporated in the gel matrix. Phenanthrene- Eu+3-Tb+3 (I), naphthalene –Eu+3-Tb+3 (III), and pyrene- Eu+3-Tb+3 (III) form triad systems, which undergo resonance energy transfer. Upon excitation of the organic fluorophores, partial energy transfer leads to the tri-colour emission from organic and inorganic components in the system, leading to the formation of white light. White light emission was verified by CIE (Commission Internationale d’Eclairage) coordinates. In case of I, the CIE values were {0.33, 0.32}, while in case of II and III, the CIE values were {0.35, 0.37}, {0.35, 0.33} respectively. The CIE values were very close to ideal white light CIE values {0.33, 0.33}. We have also measured colour temperature of the light source using McCamy’s formula4 for the above mentioned white light emitting gel. The colour temperature value were 5520 K, 4886 K, and 4548 K for I, II and III, respectively. The values indicate that cool white light is generated, which have a potential application to develop various lightening devices.
References
1.Binnemans, K., Chem. Rev. 2009, 109, 4283-4374.
2.Deiters, E.; Song, B.; Chauvin, A.-S.; Vandevyver, C. D. B.; Gumy, F.; Bünzli, J.-C. G., Chem.- Eur. J. 2009, 15, 885-900.
3.Rajamalli, P.; Sheet, P. S.; Prasad, E., Chem. Commun. 2013, 49, 6758-6760.
4. McCamy, C. S., Color Res Appl. 1992, 17, 142-144.
Symposium Organizers
Hongshan He, Eastern Illinois University
Paola Deplano, University of Cagliari
Nobuhiko Iki, Tohoku University
Xingqiang Lv, Northwest University
MD7.4: Synthesis, Sensing and Imaging III
Session Chairs
P. Stanley May
Frank Van Veggel
Thursday AM, March 31, 2016
PCC West, 100 Level, Room 106 A
9:30 AM - *MD7.4.01
Lanthanide Luminescent Helicates for Detecting Biomarkers
Jean-Claude Bunzli 1
1 EPFL Lausanne Switzerland,
Show AbstractUnderstanding the structure and functional properties of cells, organs, and living organisms is a key challenge in present-day biology and medicine, which stimulates the development of imaging techniques with high resolution and sensitivity. Luminescence imaging possesses these attributes in addition to featuring high penetration depth. The drawback of organic chromophores is their sensitivity to photobleaching, their small Stokes’ shifts, and their short excited state lifetimes, which renders difficult separating the probe signal from the autofluorescence background. Since the mid 1980’s, lanthanide chelates have successfully replaced organic chromophores in luminescence immunoassays since they are not much sensitive to photobleaching, lend themselves to time-resolved detection, and have easily recognizable sharp emission lines; therefore both wavelength and time discrimination concur to isolate the probe signal from the background noise [1-3].
After a general introduction to the field, we focus on ditopic hexadentate ligands with benzimidazole core which self-assemble in water at physiological pH to yield robust and highly luminescent dinuclear helicates [Ln2(LCX)3]. These entities are thermodynamically stable, kinetically inert and non-cytotoxic (IC50>500 µM). They enter into live cells by endocytosis and stain the endoplasmic reticulum as shown by time-resolved luminescence microscopy. The probes are also amenable to NIR excitation by multiphoton processes and can be inserted into nanoparticles [4]. Further derivatization affords helicates which can be bioconjugated to avidin and various monoclonal antibodies. When combined with a microfluidic device, the dinuclear bioconjugates are highly efficient in multiplex detection of biomarkers expressed by cancerous cells and tissues. The efficiency of the technique is exemplified with the simultaneous detection of the estrogen and Human epidermal growth factor receptors in cancerous tissue sections from real patients [5].
[1] Jean-Claude G. Bünzli, Lanthanide light for biology and medical diagnosis, J. Lumin. 2015, doi:10.1016/j.jlumin.2015.07.033
[2] Jean-Claude G. Bünzli, Luminescence Bioimaging with Lanthanide Complexes, in “Luminescence in Lanthanide Coordination Compounds and Nanomaterials”, Ed. A. de Bettencourt-Dias, Wiley-Blackwell, Oxford, 2014, Ch. 4, pp. 125-197.
[3] Jean-Claude G. Bünzli, Lanthanide Luminescence for Biomedical Analyses and Imaging, Chem. Rev.110, 2729-2755 (2010).
[4] Jean-Claude G. Bünzli, Lighting up cells with lanthanide self-assembled helicates, Interface Focus, 3, Art. Nr. 20130032, (2013), pp 1-17.
[5] Vanesa Fernandez-Moreira, Bo Song, Venkat Sivagnanam, Anne-Sophie Chauvin, Caroline D. B. Vandevyver, Martinus A. M. Gijs, Hans-Anton Lehr, Jean-Claude G. Bünzli, Bioconjugated Lanthanide Luminescent Helicates as Multilabels for Lab-on-a-Chip Detection of Cancer Biomarkers, The Analyst, 135, 42-52 (2010).
10:00 AM - MD7.4.02
Lanthanides-TTF Complexes: Single Molecule Magnet Behaviour and Luminescence
Lahcene Ouahab 1,Fabrice Pointillart 1,Olivier Cador 1,Stephane Golhen 1
1 CNRS-Univ of Rennes1 Rennes France,
Show AbstractLanthanide-based complexes have greatly contributed to the development of molecular magnetism in the last decade and more particularly in the branch of single molecule magnets (SMMs)1. The main reasons are their large magnetic moments associated to their intrinsic large magnetic anisotropy. The splitting of the multiplet ground state of a single-ion in a given environment is responsible of the trapping of the magnetic moment in one direction in SMMs. However, the analyses of the crystal field effects on the magnetic anisotropy are not so common2. A better understanding of the magneto-structural correlations in lanthanide-based complexes should provide tools to improve their potentialities.
In this presentation we will focus on the specific magnetic properties of TTF-based lanthanide mononuclear and polynuclear complexes. We will show how optimize the SMM behavior playing on i) the modulation of the supramolecular effects via chemical modifications of the TTF ligand3, ii) simple molecular engineering modifying the electronic distribution and symmetry of the coordination polyhedron, iii) magnetic dilutions (solution and doping) and iv) isotopic enrichment of the dysprosium4.
References
1 R. Sessoli and A. K. Powell, Coord. Chem. Rev., 2009, 253, 2328-2341.
2 J. D. Rinehart and J. R. Long, Chem. Sci., 2011, 2, 2078-2085.
3 T. T. da Cunha, J. Jung, M.-E. Boulon, G. Campo, F. Pointillart, C. L. M. Pereira, B. Le Guennic, O. Cador, Kevin Bernot, F. Pineider, S. Golhen, L. Ouahab, J. Am. Chem. Soc. 2013, 135, 16332.
4 F. Pointillart, K. Bernot, B. Le Guennic, S. Golhen, O. Cador, L. Ouahab, Angew. Chem. Int. Ed. 2015, 54, 1504-1507.
Acknowledgements
This work was supported by the CNRS, Rennes Métropole, Université de Rennes 1, Région Bretagne, FEDER and Agence Nationale de la Recherche (N° ANR-13-BS07-0022-01).
10:15 AM - MD7.4.03
Thermochemistry of Rare Earth Perovskites
Dawei Feng 1,Alexandra Navrotsky 1
1 Peter A Rock Thermo Lab amp; NEAT Univ of California-Davis Davis United States,
Show AbstractThe mineral loparite with the composition (Ln, Na, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3 is the principal ore of the light rare-earth elements (LREE) and niobium and tantalum. In order to understand its thermodynamics high temperature oxide melt solution calorimetry using sodium molybdate (3Na2O[center dot]MoO3) solvent at 973 K was performed for perovskite solid solutions, RE0.67-xNa3xTiO3 (RE = La, Ce) and Ca1-2xNaxLaxTiO3 .The enthalpies of formation from oxides and elements of lanthanum and cerium perovskites and its solid solutions have been obtained. RE0.67-xNa3xTiO3 (RE = La, Ce) perovskites become more stable relative to oxide components as sodium content increases. Na0.5Ce0.5TiO3 and Na0.5La0.5TiO3 can be considered stable endmembers in natural loparite minerals. For perovskite solid solutions Ca1-2xNaxLaxTiO3, the enthalpies of formation from the constituent oxides become more exothermic with increasing Na+La content, suggesting a stabilizing effect of the substitution Na+ + La3+ → 2Ca2+ on the perovskite structure. The trend of increasing thermodynamic stability with decreasing structural distortion is similar to that seen in many other ABO3 perovskites. The thermodynamic stability of rare earth perovskite provides insights into the natural occurrence of loparite mineral (La, Na, Sr, Ca)(Ti, Nb, Ta, Fe3+)O3.
10:30 AM - MD7.4.04
Ternary Rare Earth GdxLa2-xO3:Eu3+0.01 Pigments for Phosphor-Based Thermometric Systems
Salek Guillaume 1
1 ICMCB Bordeaux France,
Show AbstractOver the past few decades, research on phosphors based thermometry systems are becoming increasingly important in different fields: engineering 1, nanosciences etc….. The temperature dependence characteristics of the thermographic phosphors can be evaluated by a spectral 2, 3 and/or a temporal modification of the radiative emission. Within the different thermometric phosphors, the rare earth sesquioxides which possess a high melting point, could be used as thermographic phosphors to mark high temperatures. They crystallize in three main allotropic forms, depending on the size of the cation and the temperature. The GdxLa2-xO3 system provides access to a transition from cubic (C) phase to high-temperature monoclinic phase (B) and allows the modulation of the phase transition temperature by varying the La/Gd ratio. By doping this GdxLa2-xO3 white matrix with a luminescent Eu3+ ions, a modification of this local probe emission during the Cà B phase transition is expected as observed Gd2O3 . The antisymmetric character of the cationic sites present in the B-form is more pronounced than those in the C-form. Indeed, the cationic sites are 6/7-fold coordinated non-centrosymmetric sites in the B-form while 6-fold centrosymmetric and non-centrosymmetric sites are present in the C-form. Among the different radiative transitions of the Eu3+ ions, the 5D0 → 7F2 transitions present a hypersensitivity to the local Eu3+ environment (symmetry and coordination number). By considering spectroscopy characterizations (luminescence spectral repartition and decay times ), a fine determination of the exposure temperature can be given over a large scale range (800°C-1300°C).
The relationship between the annealing temperature and the luminescence due to a modification of the antisymmetric sites occupied by the Eu3+ions in the matrix was established combining X-ray diffraction and luminescence spectroscopy (spectral repartition and lifetimes decay). We report the study of the structural and luminescence properties of a La2O3-Gd2O3 solid solution with La<20%mol doped by of Eu3+. To begin, a theoretical approach has been realized to find a structural filiation between the two allotropic forms of this component. Then, an experimental study has been performed on the undoped matrix to evaluate the Gd/La ratio optimum to obtain the Cà B phase transition at low temperature (700°C). Thereafter complementary structural (riedvelt) refinement and photoluminescence (spectral and temporal) characterizations have been conducted on the Eu3+-doped matrix to finely characterize the transition phase.
Keywords: Thermal sensors, Luminescence, rare earth, lifetime
1 M. Aldén, A. Omrane, M. Richter and G. Särner, Prog. Energy Combust. Sci., 2011, 37, 422–461.
2 G. Salek, a. Demourgues, V. Jubera, a. Garcia and M. Gaudon, Opt. Mater. (Amst)., 2015, 47, 323–327.
3 L. Cornu, M. Gaudon and V. Jubera, J. Mater. Chem. C, 2013, 1, 5419.
11:15 AM - *MD7.4.05
Magnetoluminescent Nanoparticles – Combining the Dual Power of Time-Resolved Luminescence and MRI Contrast Agents of Lanthanide Complexes
Valerie Pierre 1
1 University of Minnesota Minneapolis United States,
Show AbstractMultimodal nanocomposite probes - nanoparticle assemblies that enable imaging by two or more techniques have become increasingly prevalent over the past decade. Of these, magnetoluminescent agents are receiving the much attention due to their ability to combine two widespread techniques, magnetic resonance imaging (MRI) and fluorescence microscopy, which are complementary in terms of three-dimensional imaging capability and spatial resolution, respectively. We will describe two approaches to designing magnetoluminescent nanoparticles for dual magnetic resonance imaging and time-gated fluorescence spectroscopy and microscopy. The first includes functionalizing iron oxide nanoparticles with responsive luminescent terbium complexes. The second, involves novel microporous silica nanoshells selectively functionalized with gadolinium contrast agents and bright luminescent europium complexes. The synthesis and contrasting properties of these two sets of multimodal nanoparticles will be discussed.
11:45 AM - MD7.4.06
Electrochemical Recycling of Erbium Using Ionic Liquids
Leo Small 1,Timothy Lambert 1,Julian Vigil 1,Maria Kelly 1,Timothy Boyle 1,Jeremiah Sears 1,Ryan Hess 1
1 Sandia National Laboratories Albuquerque United States,
Show AbstractRecovery of rare earth (RE) metals from industrial and commercial waste streams has the potential to reduce the need to mine this ‘nationally critical’ material. In this work, an electrochemical scheme is presented for the recovery of RE metals based on their selective electrochemical oxidation and subsequent reduction in a convenient room temperature ionic liquid electrolyte. The efficacy of this process is explored for a variety of quarternary ammonium ionic liquids containing SO3CF3-, N(SO2CF3)2-, or N(CN)2- anions. In many cases, formation of a complex, amorphous interfacial layer hinders both oxidation of Er0 into solution, and reduction of Er3+ onto clean platinum surfaces. Characterization of these surfaces by cyclic voltammetry, infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy provides insight into the electrochemical processes underway and elucidated paths forward for the recycling of RE metals.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
12:00 PM - MD7.4.07
Multi-NIR-Emissive Materials Based on Heterolanthanide Molecular Assemblies
Flavia Artizzu 1,Francesco Quochi 1,Luciano Marchio 2,Michele Saba 1,Angela Serpe 1,Andrea Mura 1,Maria Laura Mercuri 1,Giovanni Bongiovanni 1,Paola Deplano 1
1 University of Cagliari Cagliari Italy,2 University of Parma Parma Italy
Show AbstractHeterometallic assemblies containing two or more different lanthanide (Ln) ions as carriers of distinctive functionalities are particularly attractive as they can open unprecedented possibilities toward multifunctional materials and enhanced properties may be achieved through intermetallic communication. In particular, heterometallic luminescent materials where Ln ions can “talk” to each other, hold potential for the development of highly performing emitters for optical applications (optical fibers and amplifiers, lasers) as they allow more advanced and convenient ways of optical pumping. However, controlled codoping of inorganic glassy or polymeric matrices so far studied for these purposes is often an intrinsically difficult task. A strategy to achieve composition control relies on the encapsulation of selected Ln ions into the same molecule to afford intermetallic communication (energy transfer, ET) between optically active metal centers sitting at fixed positions and short distance (within few Å, as required for efficient ET) in a predesigned architecture.
The Ln3Q9 (Q=8-quinolinolate) molecular framework has shown to be particularly suitable for preparing heterolanthanide multi-emissive assemblies, providing: i) high coordinating ability; ii) excellent “antenna” properties of the Q ligand; iii) short intermetallic distances (Heterolanthanide complexes of the NIR-emissive Nd, Er, Yb ions, ErxYb(3-x)Q9 (1, x = 1, 2), NdYb2Q9 (2), NdErYbQ9 (3), have been obtained through a simple molecular strategy, by controlling reactant stoichiometry. Combined chemical/photophysical studies on 1 and 2 have shown that the Yb→Er1,2 and Nd→Yb3 ET processes reach unitary efficiency, thanks to short intermetallic distances and enhanced spectral overlap between the donor emission and the acceptor absorption bands, broadened by crystal field effects in the molecular assembly. Remarkably, 3 represents the first example of a discrete molecular entity containing three different Ln ions simultaneously emitting in three different spectral regions in the NIR, upon single visible wavelength excitation.4 The templating effect of the molecular framework allows to control the metal distribution across the coordination sites where the central position is occupied by the larger Nd ion and the terminal ones by the almost vicariants Yb3+ and Er3+, drastically reducing molecular speciation. Highly transparent and homogeneous silica thin films have been prepared, which show the same optical properties of the incorporated complex in solution.2
This strategy seems thus promising for the development of highly performing codoped Er/Yb/Nd materials for optical applications.
[1] J.Phys. Chem. Lett., 2013, 4, 3062; [2] Chem. Mater., 2015, 27, 4082; [3] J. Mater. Chem. C, 2015, DOI: 10.1039/C5TC02985F; [4] Chem. – A Eur. J., 2015, 21, 3882
12:15 PM - *MD7.4.08
Nanoparticles as Sensitizers of Lanthanide Ion Emission
Ana de Bettencourt-Dias 1,Rodney Tigaa 1,Samuel Silva-Hernandez 1,Gary Lucas 1
1 Univ of Nevada Reno United States,
Show AbstractWe have explored semi-conducting nanoparticles with and without shell and with size-tunable bandgaps, as well as carbon dots, as sensitizers of lanthanide ion luminescence. To that effect, we synthesized new capping ligands, capable of chelating lanthanide ions, appended those ligands to quantum dots of varying types and sizes and then added the metal ions. We will discuss the synthesis and characterization by TEM, EDX and SAXS of the systems isolated. Their ability to transfer energy to the lanthanide ions with and without participation in the energy transfer process by the capping ligand and as a function of quantum dot type and size was assessed through absorption, excitation and emission spectroscopy and will be presented.
MD7.5: Synthesis, Sensing and Imaging IV
Session Chairs
Thursday PM, March 31, 2016
PCC West, 100 Level, Room 106 A
2:30 PM - *MD7.5.01
Lanthanide Time Resolved Luminescence: From Basics to Business
Kenneth Raymond 2,David Tatum 2
1 Department of Chemistry University of California Berkeley United States,2 Lumiphore, Inc. Berkeley United States,
Show AbstractThe long luminescent lifetimes of the visibly emitting lanthanides EuIII and TbIII facilitate temporal discrimination of the emission signal. Temporal discrimination offers large signal-to-noise gains when probing biological samples, whether the emission is used directly in applications like time-resolved luminescence microscopy (TRLM) or indirectly by pumping an organic dye in homogenous time-resolved fluorescence (HTRF) assays. As a result of these exciting biological applications, much research has been focused on generating brighter luminescent lanthanide complexes, but practical applications also require that the luminescent materials persist within biological media. We have developed many siderophore-inspired ligands that form bright and stable lanthanide complexes, including isophthalamide (IAM) derivatives suitable for TbIII luminescence (1-3) and 1,2-hydroxypyridinone (1,2-HOPO) derivatives suitable for EuIII luminescence (4-6). We have found that ligand geometry significantly affects the brightness of the EuIII complexes, which may have to do with the sensitization mechanism for these systems. Our primary focus continues to be the development of bifunctional, macrocyclic ligands for coordinating and attaching lanthanides to biological targets of interest. The IAM-based TbIII macrocycle is used in commercial products by three different companies for high throughput screening, drugs of abuse assays, and human diagnostics. (7)
(1) S. Petoud, S.M. Cohen, J.-C.G. Bünzli, K.N. Raymond, J. Am. Chem. Soc., 2003, 125, 13324-13325.
(2) A.P.S. Samuel, E.G. Moore, M. Melchior, J. Xu, K.N. Raymond, Inorg. Chem., 2008, 47, 7535-7544.
(3) J. Xu, T.M. Corneillie, E.G. Moore, G.-L. Law, N.G. Butlin, K.N. Raymond, J. Am. Chem. Soc. 2011, 133, 19900–19910.
(4) J.I. Pacold, D.S.Tatum, G.T. Seidler, K.N. Raymond, X. Zhang, A.B. Stickrath, A.B. Mortensen, J. Am. Chem. Soc., 2014, 136, 4186-4191.
(5) L.J. Daumann, D.S. Tatum, B.E.R. Snyder, C. Ni, G. Law, E.I. Solomon, K.N. Raymond, J. Am. Chem. Soc., 2015, 137, 2816-2819.
(6) A. D’Aleo, E.G. Moore, J. Xu, L.J. Daumann, K.N. Raymond, Inorg. Chem. 2015. 54, 6807-6820.
(7) www.lumiphore.com
3:00 PM - MD7.5.02
Design Rules for Multiple d-f Emission Bands in Lanthanides
Mathijs de Jong 1,Zoila Barandiaran 3,Luis Seijo 3,Karl Kraemer 4,Daniel Biner 4,Andries Meijerink 1
1 Chemistry Utrecht University Utrecht Netherlands,2 Departamento de Química Universidad Autónoma de Madrid Madrid Spain,3 Instituto Universitario de Ciencia de Materiales Nicolás Cabrera Universidad Autónoma de Madrid Madrid Spain4 Department of Chemistry amp; Biochemistry University of Bern Bern Switzerland
Show AbstractThe lanthanide ions constitute the most important class of activators in inorganic luminescent materials, both from a scientific as well as a technological point of view. There have been extensive studies on the parity-forbidden 4fn→4fn transitions, resulting in a good understanding of these transitions. However, much remains to be understood about the parity-allowed 4fn→4fn-15d1 transitions. In most luminescent materials, excitation of a high excited state results in rapid non-radiative relaxation to the lowest excited state, from which radiative decay can take place. This is known as Kasha's rule. The same is true for the manifold of 4fn-15d1 excited states in the lanthanides. However, it is known that Tm2+ violates this rule and shows emission from multiple 4f125d1 excited states giving rise to two-photon emission. In addition, the emission from higher energy excited f-d states can also be used for efficient upconversion following broad band excitation in the lower excited f-d state.
In this work we use various methods to understand the behavior of the luminescence in Tm2+-doped CsCaBr3 and CsCaCl3. We have performed a two-color two-photon upconversion experiment, in which Tm2+ is brought with a first photon in the lowest 4f125d1 excited state, from which higher excited states can be probed with a second photon of varying energy. Also, we present cutting-edge ab initio wavefunction-based embedded-cluster calculations. Both approaches confirm the presence of an energy gap within a group of 4f125d1 excited states that only differ in the state of their 4f12 core. Since the 4f-shell is well shielded from the environment, this results in the presence of parallel potential energy surfaces, in which non-radiative relaxation is very inefficient. Slow non-radiative relaxation allows for radiative transitions to take place from multiple 4f125d1 excited states.
The increased understanding of relaxation processes between excited f-d states does not only give new insights in Tm2+ luminescence, but also in non-radiative relaxation in lanthanides and other luminescent centers in general. We investigated whether other divalent lanthanides fulfill the requirements for multiple d-f emission bands. We found that, of the chemically stable divalent lanthanides, also for Yb2+ there can be a significant energy gap within a manifold of excited states with parallel potential energy surfaces. We are currently extending the study to Yb2+, which in some host lattices can fulfill these requirements too.
3:15 PM - MD7.5.03
Functionalized BODIPY Dyes for Near-Infrared Emission of Lanthanide Ions
Adedayo Eukoyi 1,Rukshani Arachchi 1,Priyangika Senevirathne 1,Hongshan He 1
1 Department of Chemistry Eastern Illinois Univ Charleston United States,
Show AbstractNear-infrared (NIR) emission from lanthanide ions has great potential for high sensitivity detection of biological substrates. The emission is often achieved through energy transfer from an organic chromophore to the lanthanide ion in their complexes. BODIPY dyes are promising sensitizers for NIR emitting lanthanide ions due to their easy preparation and several unique characteristics favorable to the sensitization of lanthanide emission, including (i) tunable spectral coverage from ~500 up to 780 nm; (ii) high absorption capability with molar absorption coefficients as high as 110,000 M-1cm-1; (iii) exceptional chemical and photo-resistance in solution and in solid state; (iv) very good solubility in organic solvents, and (v) easy structural modification for further functionalization. To this end, we found a series of phenanthroline-based BODIPY dyes that can sensitize lanthanide ions efficiently. The isolated compounds with a general formula [Yb(HFA)3(BODIPY)] exhibited distinctive emission centered at 980 nm with a quite long decay lifetime. The synthesis, structures and photophysical properties of prepared complexes will be presented.
3:30 PM - MD7.5.04
Kinetics and Mechanisms of Synthesis and Shell-Growth for Upconversion Nanomaterials
P. Stanley May 1,John Suter 2,Paul May 3,Samantha Wang 4,Molly Cleland 5,Md Yeathad Hossan 1,Mary Berry 1,David Tatum 6
1 Univ of South Dakota Vermillion United States,1 Univ of South Dakota Vermillion United States,2 PPG Aerospace Irvine United States3 South Dakota State University Brookings United States4 Washington University St Louis United States5 Chadron State College Chadron United States6 Lumiphore, Inc. Richmond United States
Show AbstractWe have shown that monitoring the NIR-to-visible upconversion emission from the reaction mixture in real-time during β-NaYF4:Yb, Er nanocrystal synthesis and shell addition is a very valuable technique for studying the kinetics and mechanism of the reaction. The method provides insight into the intricacies of the reaction and into the processes responsible for the observed variations in reaction time. Using the spectroscopic signatures, the various stages of the reaction can be followed without the need for aliquot extraction and work up. The influence of changing reaction parameters on the reaction mechanism will be discussed, as will the use of the technique to monitor shell addition. A mathematical model will also be presented describing the timeline for crystal growth and phase transition during the synthesis. The theoretical model for the reaction is expressed in terms of straightforward physical constants (e.g., rate constants, diffusion constants), the values of which can be optimized to experimental observation using non-linear fitting routines. The model is suitable for nanoparticle growth in any phase. The reaction system is described at all time points as a discrete distribution of a finite number of nanocrystals. It will be demonstrated that the model accurately describes the time-evolution of the nanocrystal synthesis and shell addition.