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Zhihua Fu, Gang Xu
The thin film of metal-organic frameworks (MOFs) is a rapidly developing research area which has tremendous potential applications in many fields. One of the major challenges in this area is to fabricate MOF thin film with good crystallinity, high orientation and well-controlled thickness. In order to address this challenge, different appealing approaches have been studied intensively. Among various oriented MOF films, many efforts have also been devoted to developing novel properties and broad applications, such as in gas separator, thermoelectric, storage medium and photovoltaics...
October 24, 2016: Chemical Record: An Official Publication of the Chemical Society of Japan ... [et Al.]
Pablo Alonso-González, Alexey Y Nikitin, Yuanda Gao, Achim Woessner, Mark B Lundeberg, Alessandro Principi, Nicolò Forcellini, Wenjing Yan, Saül Vélez, Andreas J Huber, Kenji Watanabe, Takashi Taniguchi, Félix Casanova, Luis E Hueso, Marco Polini, James Hone, Frank H L Koppens, Rainer Hillenbrand
Terahertz (THz) fields are widely used for sensing, communication and quality control. In future applications, they could be efficiently confined, enhanced and manipulated well below the classical diffraction limit through the excitation of graphene plasmons (GPs). These possibilities emerge from the strongly reduced GP wavelength, λp, compared with the photon wavelength, λ0, which can be controlled by modulating the carrier density of graphene via electrical gating. Recently, GPs in a graphene/insulator/metal configuration have been predicted to exhibit a linear dispersion (thus called acoustic plasmons) and a further reduced wavelength, implying an improved field confinement, analogous to plasmons in two-dimensional electron gases (2DEGs) near conductive substrates...
October 24, 2016: Nature Nanotechnology
Hyunwoo Bark, Jeongmin Lee, Ho Sun Lim, Hye Young Koo, Wonmok Lee, Hyunjung Lee
We report a simple method for preparing highly efficient thermoelectric materials through the fabrication of nitrogen-doped reduced graphene oxide(GO) with a porous structure. The samples were produced by thermal annealing of GO/ nitrogen-rich polystyrene (N-PS) particle composite films using a colloidal templating method. N-PS particles were served as a nitrogen dopant source for the nitrogen-doped thermally reduced graphene oxide (TrGO) as well as sacrificial particles for the porous structure. The S values of the porous TrGO films were negative, indicating that the samples were transformed into n-type materials...
October 24, 2016: ACS Applied Materials & Interfaces
Gabin Guélou, Paz Vaqueiro, Jesús Prado-Gonjal, Tristan Barbier, Sylvie Hébert, Emmanuel Guilmeau, Winfried Kockelmann, Anthony V Powell
A family of phases, Co x TiS2 (0 ≤ x ≤ 0.75) has been prepared and characterised by powder X-ray and neutron diffraction, electrical and thermal transport property measurements, thermal analysis and SQUID magnetometry. With increasing cobalt content, the structure evolves from a disordered arrangement of cobalt ions in octahedral sites located in the van der Waals' gap (x ≤ 0.2), through three different ordered vacancy phases, to a second disordered phase at x ≥ 0.67. Powder neutron diffraction reveals that both octahedral and tetrahedral inter-layer sites are occupied in Co0...
March 7, 2016: Journal of Materials Chemistry. C, Materials for Optical and Electronic Devices
Miles A White, Gordon J Miller, Javier Vela
The first example of polytypism in the I-II-V semiconductors has been demonstrated with the synthesis of cubic LiZnSb by low temperature solution phase methods. This phase exhibits a unique coloring pattern that is novel for this class of compounds. The choice of site configuration has considerable impact on the band structure of these materials which, in turn, effects the transport properties. While the hexagonal polytype has been suggested as a promising n-type and extremely poor p-type thermoelectric material, the cubic analogue is calculated to have high efficiencies at 600K for both n- and p-type derivatives of 1...
October 21, 2016: Journal of the American Chemical Society
Kunsu Park, Kyunghan Ahn, Joonil Cha, Sanghwa Lee, Sue In Chae, Sung-Pyo Cho, Siheon Ryee, Jino Im, Jaeki Lee, Su-Dong Park, Myung Joon Han, In Chung, Taeghwan Hyeon
Thermoelectrics directly converts waste heat into electricity and is considered a promising means of sustainable energy generation. While most of the recent advances in the enhancement of the thermoelectric figure of merit (ZT) resulted from a decrease in lattice thermal conductivity by nanostructuring, there have been very few attempts to enhance electrical transport properties, i.e., the power factor. Here we use nanochemistry to stabilize bulk bismuth telluride (Bi2Te3) that violates phase equilibrium, namely, phase-pure n-type K0...
October 20, 2016: Journal of the American Chemical Society
Andreas Brenneis, Felix Schade, Simon Drieschner, Florian Heimbach, Helmut Karl, Jose A Garrido, Alexander W Holleitner
For future on-chip communication schemes, it is essential to integrate nanoscale materials with an ultrafast optoelectronic functionality into high-frequency circuits. The atomically thin graphene has been widely demonstrated to be suitable for photovoltaic and optoelectronic devices because of its broadband optical absorption and its high electron mobility. Moreover, the ultrafast relaxation of photogenerated charge carriers has been verified in graphene. Here, we show that dual-gated graphene junctions can be functional parts of THz-circuits...
October 20, 2016: Scientific Reports
Yaakov Kleeorin, Yigal Meir, Francesco Giazotto, Yonatan Dubi
In spite of extended efforts, detecting thermoelectric effects in superconductors has proven to be a challenging task, due to the inherent superconducting particle-hole symmetry. Here we present a theoretical study of an experimentally attainable Superconductor - Quantum Dot - Superconductor (SC-QD-SC) Josephson Junction. Using Keldysh Green's functions we derive the exact thermo-phase and thermal response of the junction, and demonstrate that such a junction has highly tunable thermoelectric properties and a significant thermal response...
October 13, 2016: Scientific Reports
Sunbin Hwang, William J Potscavage, Yu Seok Yang, In Seob Park, Toshinori Matsushima, Chihaya Adachi
Recent progress in conducting polymer-based organic thermoelectric generators (OTEGs) has resulted in high performance due to high Seebeck coefficient, high electrical conductivity (σ), and low thermal conductivity obtained by chemically controlling the materials's redox levels. In addition to improving the properties of individual OTEGs to obtain high performance, the development of solution processes for the fabrication of OTEG modules is necessary to realize large thermoelectric voltage and low-cost mass production...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Bolin Liao, A A Maznev, Keith A Nelson, Gang Chen
There is a growing interest in the mode-by-mode understanding of electron and phonon transport for improving energy conversion technologies, such as thermoelectrics and photovoltaics. Whereas remarkable progress has been made in probing phonon-phonon interactions, it has been a challenge to directly measure electron-phonon interactions at the single-mode level, especially their effect on phonon transport above cryogenic temperatures. Here we use three-pulse photoacoustic spectroscopy to investigate the damping of a single sub-terahertz coherent phonon mode by free charge carriers in silicon at room temperature...
October 12, 2016: Nature Communications
Zhaoyang Lin, Anxiang Yin, Jun Mao, Yi Xia, Nicholas Kempf, Qiyuan He, Yiliu Wang, Chih-Yen Chen, Yanliang Zhang, Vidvuds Ozolins, Zhifeng Ren, Yu Huang, Xiangfeng Duan
Epitaxial heterostructures with precisely controlled composition and electronic modulation are of central importance for electronics, optoelectronics, thermoelectrics, and catalysis. In general, epitaxial material growth requires identical or nearly identical crystal structures with small misfit in lattice symmetry and parameters and is typically achieved by vapor-phase depositions in vacuum. We report a scalable solution-phase growth of symmetry-mismatched PbSe/Bi2Se3 epitaxial heterostructures by using two-dimensional (2D) Bi2Se3 nanoplates as soft templates...
October 2016: Science Advances
Wenyu Zhao, Zhiyuan Liu, Ping Wei, Qingjie Zhang, Wanting Zhu, Xianli Su, Xinfeng Tang, Jihui Yang, Yong Liu, Jing Shi, Yimin Chao, Siqi Lin, Yanzhong Pei
How to suppress the performance deterioration of thermoelectric materials in the intrinsic excitation region remains a key challenge. The magnetic transition of permanent magnet nanoparticles from ferromagnetism to paramagnetism provides an effective approach to finding the solution to this challenge. Here, we have designed and prepared magnetic nanocomposite thermoelectric materials consisting of BaFe12O19 nanoparticles and Ba0.3In0.3Co4Sb12 matrix. It was found that the electrical transport behaviours of the nanocomposites are controlled by the magnetic transition of BaFe12O19 nanoparticles from ferromagnetism to paramagnetism...
October 10, 2016: Nature Nanotechnology
Sobhit Singh, Wilfredo Ibarra-Hernández, Irais Valencia-Jaime, Guillermo Avendaño-Franco, Aldo H Romero
Semi-conducting alloys BixSb1-x have emerged as a potential candidate for topological insulators and are well known for their novel thermoelectric properties. In this work, we present a systematic study of the low-energy phases of 35 different compositions of BixSb1-x (0 < x < 1) at zero temperature and zero pressure. We explore the potential energy surface of BixSb1-x as a function of Sb concentration by using the ab initio minima hopping structural search method. Even though Bi and Sb crystallize in the same R3[combining macron]m space group, our calculations indicate that BixSb1-x alloys can have several other thermodynamically stable crystal structures...
September 30, 2016: Physical Chemistry Chemical Physics: PCCP
Miquel Royo, Riccardo Rurali
We study thermal transport in isotopically disordered Si nanowires, discussing the feasibility of phonon engineering for thermoelectric applications within these systems. To this purpose, we carry out atomistic molecular dynamics and nonequilibrium Green's function calculations to characterize the dependence of the thermal conductance as a function of the isotope concentration, isotope radial distribution and temperature. We show that a reduction of the conductivity of up to 20% can be achieved with suitable isotope blends at room temperature and approximately 50% at low temperature...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Mette Andersen Borup, Anders Bank Blichfeld, Solveig Røgild Madsen, Bo Brummerstedt Iversen
The structures of thermoelectric ZnSb and Zn4Sb3 have been studied extensively as a function of temperature but not in detail as a function of pressure. High pressure single crystal X-ray diffraction data allow structure refinements of ZnSb and Zn4Sb3 up to 12.8(2) GPa and 10.6(2) GPa, respectively, and in contrast to previous reports without any signs of phase transitions. At high pressure a redistribution of Zn in Zn4Sb3 is present, which is distinctly different from the thermal response of the structure...
September 27, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Zhenzhao Jia, Caizhen Li, Xinqi Li, Junren Shi, Zhimin Liao, Dapeng Yu, Xiaosong Wu
Discovery of Weyl semimetals has revived interest in Weyl fermions which has not been observed in high energy experiments. It now becomes possible to study, in solids, their exotic properties. Extensive photoemission spectroscopy and electrical resistivity experiments have been carried out. However, many other properties remain unexplored. Here we show the thermoelectric signature of the chiral anomaly of Weyl fermions in Cd3As2 under a magnetic field. We observe a strong quadratic suppression of the thermopower when the magnetic field is parallel to the temperature gradient...
October 10, 2016: Nature Communications
Simone Schuler, Daniel Schall, Daniel Neumaier, Lukas Dobusch, Ole Bethge, Benedikt Schwarz, Michael Krall, Thomas Mueller
With its electrically tunable light absorption and ultrafast photoresponse, graphene is a promising candidate for high-speed chip-integrated photonics. The generation mechanisms of photosignals in graphene photodetectors have been studied extensively in the past years. However, the knowledge about efficient light conversion at graphene pn-junctions has not yet been translated into high-performance devices. Here, we present a graphene photodetector integrated on a silicon slot-waveguide, acting as a dual-gate to create a pn-junction in the optical absorption region of the device...
October 7, 2016: Nano Letters
Ting-Yu Ko, Muthaiah Shellaiah, Kien Wen Sun
In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb2Se3 nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10(-4) S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined...
October 7, 2016: Scientific Reports
P C Sreeparvathy, V Kanchana, G Vaitheeswaran, N E Christensen
First principles calculations predict the promising thermoelectric material ZnGeSb2 with a huge power factor (S(2)σ/τ) on the order of 3 × 10(17) W m(-1) K(-2) s(-1), due to the ultra-high electrical conductivity scaled by a relaxation time of around 8.5 × 10(25) Ω(-1) m(-1) s(-1), observed in its massive Dirac state. The observed electrical conductivity is higher than the well-established Dirac materials, and is almost carrier concentration independent with similar behaviour of both n and p type carriers, which may certainly attract device applications...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Deepanshu Srivastava, Colin Norman, Feridoon Azough, Marion C Schäfer, Emmanuel Guilmeau, Demie Kepaptsoglou, Quentin M Ramasse, Giuseppe Nicotra, Robert Freer
Ceramics based on Sr0.8La0.067Ti0.8Nb0.2O3-δ have been prepared by the mixed oxide route. The La1/3NbO3 component generates ∼13.4% A-site vacancies; this was fixed for all samples. Powders were sintered under air and reducing conditions at 1450 to 1700 K; products were of high density (>90% theoretical). Processing under reducing conditions led to the formation of a Ti1-xNbxO2-y second phase, core-shell structures and oxygen deficiency. X-ray diffraction (XRD) confirmed a simple cubic structure with space group Pm3[combining macron]m...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
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