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2. In-situ resonant band engineering of solution-processed semiconductors generates high performance n-type thermoelectric nano-inks

Author

Ayaskanta Sahu, Boris Russ, Miao Liu, Fan Yang, Edmond W. Zaia, Madeleine P. Gordon, Jason D. Forster, Ya-Qian Zhang, Mary C. Scott, Kristin A. Persson, Nelson E. Coates, Rachel A. Segalman, and Jeffrey J. Urban

Subjects
Science
Abstract

The design of solution-processed thermoelectric nanomaterials with efficient, stable performance remains a challenge. Here, the authors report an in-situ doping method based on nanoscale interface engineering to realize n-type thermoelectric nanowires with high performance and stability.

Published
2020
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3. Colloidal quantum dots for thermal infrared sensing and imaging

Author

Shihab Bin Hafiz, Michael Scimeca, Ayaskanta Sahu, and Dong-Kyun Ko

Subjects
Colloidal quantum dots, Optoelectronics, Thermal infrared, Photodetectors, Technology, Chemical technology, TP1-1185, Biotechnology, TP248.13-248.65, Science, Physics, QC1-999
Abstract

Abstract Colloidal quantum dots provide a powerful materials platform to engineer optoelectronics devices, opening up new opportunities in the thermal infrared spectral regions where no other solution-processed material options exist. This mini-review collates recent research reports that push the technological envelope of colloidal quantum dot-based photodetectors toward mid- and long-wavelength infrared. We survey the synthesis and characterization of various thermal infrared colloidal quantum dots reported to date, discuss the basic theory of device operation, review the fabrication and measurement of photodetectors, and conclude with the future prospect of this emerging technology.

Published
2019
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5. Solution-Processed Cu2Se Nanocrystal Films with Bulk-Like Thermoelectric Performance

Author

Jason D. Forster, Jared J. Lynch, Nelson E. Coates, Jun Liu, Hyejin Jang, Edmond Zaia, Madeleine P. Gordon, Maxime Szybowski, Ayaskanta Sahu, David G. Cahill, and Jeffrey J. Urban

Subjects
Medicine, Science
Abstract

Abstract Thermoelectric power generation can play a key role in a sustainable energy future by converting waste heat from power plants and other industrial processes into usable electrical power. Current thermoelectric devices, however, require energy intensive manufacturing processes such as alloying and spark plasma sintering. Here, we describe the fabrication of a p-type thermoelectric material, copper selenide (Cu2Se), utilizing solution-processing and thermal annealing to produce a thin film that achieves a figure of merit, ZT, which is as high as its traditionally processed counterpart, a value of 0.14 at room temperature. This is the first report of a fully solution-processed nanomaterial achieving performance equivalent to its bulk form and represents a general strategy to reduce the energy required to manufacture advanced energy conversion and harvesting materials.

Published
2017
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6. The Vanishing Confinement Regime in THz HgTe Nanocrystals Studied Under Extreme Conditions of Temperature and Pressure

Author

Stefano Pierini, Francesco Capitani, Michael Scimeca, Sergei Kozlov, Debora Pierucci, Rodolphe Alchaar, Claire Abadie, Adrien Khalili, Mariarosa Cavallo, Tung Huu Dang, Huichen Zhang, Erwan Bossavit, Charlie Gréboval, José Avila, Benoit Baptiste, Stefan Klotz, Ayaskanta Sahu, Cheryl Feuillet-Palma, Xiang Zhen Xu, Abdelkarim Ouerghi, Sandrine Ithurria, James K. Utterback, Sebastien Sauvage, Emmanuel Lhuillier, Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), New York University [New York] (NYU), NYU System (NYU), Laboratoire de Physique et d'Etude des Matériaux (UMR 8213) (LPEM), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Physique des systèmes simples en conditions extrêmes [IMPMC] (IMPMC_PHYSIX), Institut de minéralogie, de physique des matériaux et de cosmochimie (IMPMC), Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de recherche pour le développement [IRD] : UR206-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-19-CE24-0022,COPIN,Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge(2019), ANR-19-CE09-0026,GRaSkop,Tuning Giant Rashba Spin-Orbit Coupling in Polar Single Layer Transition Metal Dichalcogenides(2019), ANR-21-CE24-0012,BRIGHT,Diode électroluminescente infrarouge brillante par exaltation du couplage lumière-matière(2021), ANR-21-CE09-0029,MixDFerro,Heterostructures à dimensions mixtes sous contrôle ferroélectrique 2D(2021), ANR-20-ASTR-0008,NITquantum,Design et fabrication d'un plan focal dans le proche infrarouge à base de nanocrisrtaux(2020), ANR-19-CE09-0017,FRONTAL,Nanocristaux Colloïdaux Dopés Infrarouges(2019), and European Project: 756225,blackQD

Subjects
terahertz, pressure, nanocrystals, phase transition, General Materials Science, [CHIM.MATE]Chemical Sciences/Material chemistry, Physical and Theoretical Chemistry, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], electronic structure, HgTe
Abstract

While HgTe nanocrystals (NCs) in the mid-infrared region have reached a high level of maturity, their far-infrared counterparts remain far less studied, raising the need for an in-depth investigation of the material before efficient device integration can be considered. Here, we explore the effect of temperature and pressure on the structural, spectroscopic, and transport properties of HgTe NCs displaying an intraband absorption at 10 THz. The temperature leads to a very weak modulation of the spectrum as opposed to what was observed for strongly confined HgTe NCs. HgTe NC films present ambipolar conduction with a clear prevalence of electron conduction as confirmed by transistor and thermoelectric measurements. Under the application of pressure, the material undergoes phase transitions from the zinc blende to cinnabar phase and later to the rock salt phase which we reveal using joint X-ray diffraction and infrared spectroscopy measurements. We discuss how the pressure existence domain of each phase is affected by the particle size.

Published
2022
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7. Anisotropic Magnetic Resonance in Random Nanocrystal Quantum Dot Ensembles

Author

David J. Norris, Ayaskanta Sahu, Martin Stutzmann, Martin S. Brandt, Gleb N. Kakazei, Rui N. Pereira, Haripriya Kannan, A. J. Almeida, Nano Electronics, and MESA+ Institute

Subjects
Materials science, medicine.diagnostic_test, Condensed matter physics, General Chemical Engineering, Magnetic resonance imaging, General Chemistry, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Article, Condensed Matter::Materials Science, Magnetic anisotropy, Chemistry, Nanocrystal, Quantum dot, medicine, Anisotropy, QD1-999, Electron magnetic resonance
Abstract

Magnetic anisotropy critically determines the utility of magnetic nanocrystals (NCs) in new nanomagnetism technologies. Using angular-dependent electron magnetic resonance (EMR), we observe magnetic anisotropy in isotropically arranged NCs of a nonmagnetic material. We show that the shape of the EMR angular variation can be well described by a simple model that considers magnetic dipole–dipole interactions between dipoles randomly located in the NCs, most likely due to surface dangling bonds. The magnetic anisotropy results from the fact that the energy term arising from the magnetic dipole–dipole interactions between all magnetic moments in the system is dominated by only a few dipole pairs, which always have an anisotropic geometric arrangement. Our work shows that magnetic anisotropy may be a general feature of NC systems containing randomly distributed magnetic dipoles., ACS Omega, 5 (20), ISSN:2470-1343

Published
2020

8. Evolution of the Nanostructure and Viscoelastic Properties of Nitrile Rubber upon Mechanical Rejuvenation and Physical Aging

Author

Gabriel E. Sanoja, Valérie Briand, Ingrid J. Paredes, Annie Brûlet, Bruno Bresson, Ayaskanta Sahu, Costantino Creton, Valentine Hervio, Sciences et Ingénierie de la Matière Molle (UMR 7615) (SIMM), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), LLB - Matière molle et biophysique (MMB), Laboratoire Léon Brillouin (LLB - UMR 12), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay, New York University [New York] (NYU), NYU System (NYU), Safran Aerosystems, and Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)

Subjects
chemistry.chemical_classification, Nanostructure, Materials science, Polymers and Plastics, Organic Chemistry, 02 engineering and technology, Polymer, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, Synthetic rubber, Viscoelasticity, 0104 chemical sciences, Inorganic Chemistry, Rheology, chemistry, Materials Chemistry, Copolymer, Stress relaxation, Composite material, 0210 nano-technology, Nitrile rubber, [PHYS.COND.CM-SCM]Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft]
Abstract

International audience; Extending the mechanical lifetime of NBR (i.e., poly(acrylonitrile-co-butadiene)), a large-volume synthetic rubber, requires a better understanding of its structure–property relationships. We demonstrate that industrial-grade and uncross-linked NBR can be mechanically rejuvenated and physically aged due to an inhomogeneous distribution of monomers along the polymer chains. As opposed to its nonpolar SBR counterpart (i.e., poly(styrene-co-butadiene)), NBR experiences thermodynamic driving forces for microphase separation and kinetic barriers for processing like those of block copolymers. Extruding NBR at high temperature and shear results in a weakly microphase-separated nanostructure of low relaxation time and resistance to flow, whereas physically aging NBR leads to lamellar nanodomains, a more solid-like material, and delayed stress relaxation. This effect of rejuvenation and aging on the nanostructure and rheological properties of NBR has important consequences on processing and storage conditions, such as the formation of defect-free interfaces in multilayered parts by polymer interdiffusion.

Published
2021
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10. Localization of Ag dopant atoms in CdSe nanocrystals by reverse Monte Carlo analysis of EXAFS spectra

Author

Alexander Kompch, Markus Winterer, Florian Ott, David J. Norris, Christian Notthoff, and Ayaskanta Sahu

Subjects
Materials science, Absorption spectroscopy, Extended X-ray absorption fine structure, Ab initio, Reverse Monte Carlo, XANES, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Crystallography, General Energy, Nanocrystal, Maschinenbau, Interstitial defect, Physical and Theoretical Chemistry, Wurtzite crystal structure
Abstract

The structure of CdSe nanocrystals doped with 0.2%–2.5% Ag corresponding to 1.1–13.6 Ag atoms per nanocrystal is studied in detail by a combination of X-ray diffraction (XRD) and X-ray absorption spectroscopy at the Ag–K, Cd–K, and Se–K edges. X-ray absorption near-edge structure (XANES) data are compared with ab initio multiple scattering simulations. Extended X-ray absorption fine structure (EXAFS) spectra are analyzed by reverse Monte Carlo (RMC) simulations. The XANES data provide evidence that Ag is located inside the CdSe nanocrystals, and the EXAFS spectra show that the local structure of Ag can be described by tetrahedral interstitial sites in either wurtzite or zinc blende lattices similar to the coordination of Ag in Ag2Se.

Published
2015

11. Size- and Temperature-Dependent Charge Transport in PbSe Nanocrystal Thin Films.

Author

Moon Sung Kang, Ayaskanta Sahu, David J. Norris, and C. Daniel Frisbie

Subjects
*CHARGE transfer, *TEMPERATURE effect, *LEAD selenide crystals, *THIN films, *NANOCRYSTALS, *PHASE transitions, *COULOMB potential, *PARTICLE size distribution
Abstract

We report the size- and temperature-dependence of electron transport in thin films of PbSe nanocrystals. Upon increasing temperature over the range 28–200 K, the electron transport underwent a transition in mechanism from Efros-Shklovskii-variable-range-hopping (ES-VRH) to nearest-neighbor-hopping (NNH). The transition occurred at higher temperatures for films with smaller particles. The electron localization length, estimated from the ES-VRH model, was comparable to the nanocrystal size and scaled systematically with nanocrystal diameter. The activation energy from the NNH regime was also size-dependent, which is attributed both to size-dependent Coulomb effects and the size-distribution of nanocrystals. [ABSTRACT FROM AUTHOR]

Published
2011
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12. Size-Dependent Electrical Transport in CdSe Nanocrystal Thin Films.

Author

Moon Sung Kang, Ayaskanta Sahu, David J. Norris, and C. Daniel Frisbie

Subjects
*THIN films, *NANOCRYSTALS, *CADMIUM selenide, *ELECTRON distribution, *ELECTRIC charge, *ELECTRON mobility
Abstract

Electrical transport in films of CdSe nanocrystals with diameters varying from 2.9 to 5.1 nm was examined over 233−300 K by employing electrolyte gating to control the electron density. The transport parameters varied strongly and systematically with nanocrystal diameter. First, a strong correlation was observed between the device turn-on voltage and the size-dependent position of the lowest unoccupied electronic states of the nanocrystals. Second, the electron mobility increased with increasing particle diameter and reached a high value of 0.6 cm2/(V s) for films with 5.1 nm nanocrystals. Third, the charge transport could be described in terms of the nearest-neighbor-hopping mechanism with a size-dependent activation energy and a pre-exponential factor for mobility. The activation energy can be viewed as a size-dependent charging energy of an individual nanocrystal. Collectively, the combination of size- and temperature-dependent measurements provides a powerful approach to understanding electrical transport in nanocrystal films. [ABSTRACT FROM AUTHOR]

Published
2010
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