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https://www.readbyqxmd.com/read/29782672/high-yield-production-of-monolayer-feps-3-quantum-sheets-via-chemical-exfoliation-for-efficient-photocatalytic-hydrogen-evolution
#1
Zhongzhou Cheng, Tofik Ahmed Shifa, Fengmei Wang, Yi Gao, Peng He, Kai Zhang, Chao Jiang, Quanlin Liu, Jun He
2D layered transition metal phosphorus trichalcogenides (MPX3 ) possess higher in-plane stiffness and lower cleavage energies than graphite. This allows them to be exfoliated down to the atomic thickness. However, a rational exfoliation route has to be sought to achieve surface-active and uniform individual layers. Herein, monolayered FePS3 quantum sheets (QSs) are systematically obtained, whose diameters range from 4-8 nm, through exfoliation of the bulk in hydrazine solution. These QSs exhibit a widened bandgap of 2...
May 21, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29782667/synergies-of-electrochemical-metallization-and-valance-change-in-all-inorganic-perovskite-quantum-dots-for-resistive-switching
#2
Yan Wang, Ziyu Lv, Qiufan Liao, Haiquan Shan, Jinrui Chen, Ye Zhou, Li Zhou, Xiaoli Chen, Vellaisamy A L Roy, Zhanpeng Wang, Zongxiang Xu, Yu-Jia Zeng, Su-Ting Han
The in-depth understanding of ions' generation and movement inside all-inorganic perovskite quantum dots (CsPbBr3 QDs), which may lead to a paradigm to break through the conventional von Neumann bottleneck, is strictly limited. Here, it is shown that formation and annihilation of metal conductive filaments and Br- ion vacancy filaments driven by an external electric field and light irradiation can lead to pronounced resistive-switching effects. Verified by field-emission scanning electron microscopy as well as energy-dispersive X-ray spectroscopy analysis, the resistive switching behavior of CsPbBr3 QD-based photonic resistive random-access memory (RRAM) is initiated by the electrochemical metallization and valance change...
May 21, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29782165/linked-cluster-formulation-of-electron-hole-interaction-kernel-in-real-space-representation-without-using-unoccupied-states
#3
Michael G Bayne, Jeremy A Scher, Benjamin H Ellis, Arindam Chakraborty
Electron-hole or quasiparticle representation plays a central role in describing electronic excitations in many-electron systems. For charge-neutral excitation, the electron-hole interaction kernel is the quantity of interest for calculating important excitation properties such as optical gap, optical spectra, electron-hole recombination and electron-hole binding energies. The electron-hole interaction kernel can be formally derived from the density-density correlation function using both Green's function and TDDFT formalism...
May 21, 2018: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/29782145/stackable-lab-on-paper-device-with-all-in-one-au-electrode-for-high-efficiency-photoelectrochemical-cyto-sensing
#4
Hongmei Yang, Yan Zhang, Lina Zhang, Kang Cui, Shenguang Ge, Jiadong Huang, Jinghua Yu
Highly conductive, robust, and multifunctional integrated paper-supported electrodes are requisite to fulfill the promise of paper-based analytical application. Herein, an all-in-one Au electrode comprising of detection zone, waterproof electronic bridge, and signal output contactor was engineered via combining the double-sided growth method with the secondary wax-printing. Benefiting from the strongly omnidirectional conductivity and desirably mechanical robustness of the as-prepared electrode, a stackable lab-on-paper cyto-device integrated with high-efficiency photoelectrochemical strategy was developed for the MCF-7 cells assay...
May 21, 2018: Analytical Chemistry
https://www.readbyqxmd.com/read/29782026/experimental-and-quantum-chemical-studies-of-anionic-analogues-of-n-heterocyclic-carbenes
#5
Haoyu Niu, Robert J Mangan, Andrey V Protchenko, Nicholas Phillips, Wiebke Unkrig, Christian Friedmann, Eugene L Kolychev, Rémi Tirfoin, Jamie Hicks, Simon Aldridge
A combination of quantum chemical and synthetic/crystallographic methods have been employed to probe electronic structure in two series of anionic ligands related to the well known N-heterocyclic carbene (NHC) class of donor. Analyses of (i) the respective frontier orbital energies/compositions for the 'free' ligands and the results of ETS-NOCV studies of the bonding in model group 11 complexes; and (ii) the structural metrics for (new) linear gold(i) compounds, have been used to probe the bonding in complexes of NHC ligands which incorporate a backbone-appended weakly-coordinating anion component (WCA-NHCs) and in systems featuring the isoelectronic (formally anionic) diazaborolyl ligand family...
May 21, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29781625/vertically-emitting-indium-phosphide-nanowire-lasers
#6
Wei-Zong Xu, Fang-Fang Ren, Dimitars Jevtics, Antonio Hurtado, Li Li, Qian Gao, Jiandong Ye, Fan Wang, Benoit Guilhabert, Lan Fu, Hai Lu, Rong Zhang, Hark Hoe Tan, Martin Dawson, Chennupati Jagadish
Semiconductor nanowire (NW) lasers have attracted considerable research effort given their excellent promise for nanoscale photonic sources. However, NW lasers currently exhibit poor directionality and high threshold gain, issues critically limiting their prospects for on-chip light sources with extremely reduced footprint and efficient power consumption. Here, we propose a new design and experimentally demonstrate a vertically emitting indium phosphide (InP) NW laser structure showing high emission directionality and reduced energy requirements for operation...
May 21, 2018: Nano Letters
https://www.readbyqxmd.com/read/29781624/helium-ion-microscopy-as-a-high-resolution-probe-for-complex-quantum-heterostructures-in-core-shell-nanowires
#7
Christian Pöpsel, Jonathan Becker, Nari Jeon, Markus Döblinger, Thomas Stettner, Yeanitza Trujillo Gottschalk, Bernhard Loitsch, Sonja Matich, Marcus Altzschner, Alexander W Holleitner, Jonathan Finley, Lincoln J Lauhon, Gregor Koblmueller
Core-shell semiconductor nanowires (NW) with internal quantum heterostructures are among the most complex nanostructured materials to be explored for assessing the ultimate capabilities of diverse ultrahigh-resolution imaging techniques. To probe the structure and composition of these materials in their native environment with minimal damage and sample preparation calls for high-resolution electron or ion microscopy methods, which have not yet been tested on such classes of ultra-small quantum nanostructures...
May 21, 2018: Nano Letters
https://www.readbyqxmd.com/read/29781621/enhanced-single-photon-emission-from-carbon-nanotube-dopant-states-coupled-to-silicon-microcavities
#8
Akihiro Ishii, Xiaowei He, Nicolai F Hartmann, Hidenori Machiya, Han Htoon, Stephen K Doorn, Yuichiro K Kato
Single-walled carbon nanotubes are a promising material as quantum light sources at room temperature and as nanoscale light sources for integrated photonic circuits on silicon. Here we show that integration of dopant states in carbon nanotubes and silicon microcavities can provide bright and high-purity single photon emitters on silicon photonics platform at room temperature. We perform photoluminescence spectroscopy and observe enhancement of emission from the dopant states by a factor of ∼50, and cavity-enhanced radiative decay is confirmed using time-resolved measurements, where ∼30% decrease of emission lifetime is observed...
May 21, 2018: Nano Letters
https://www.readbyqxmd.com/read/29781620/nonadiabatic-quantum-dynamics-with-frozen-width-gaussians
#9
Loic Joubert-Doriol, Artur F Izmaylov
We review techniques for simulating fully quantum nonadiabatic dynamics using the frozen-width moving Gaussian basis functions to represent the nuclear wavefunction. A choice of these basis functions is primarily motivated by the idea of the on-the-fly dynamics that will involve electronic structure calculations done locally in the vicinity of each Gaussian center and thus avoiding "curse of dimensionality'' appearing in large systems. For quantum dynamics involving multiple electronic states there are several aspects that need to be addressed...
May 21, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29781617/unexpected-optical-blue-shift-in-large-colloidal-quantum-dots-by-anionic-migration-and-exchange
#10
Maria Acebron, Juan F Galisteo-López, Cefe Lopez, Facundo C Herrera, Martin D Mizrahi, Felix G Requejo, Francisco Javier Palomares, Beatriz H Juarez
Compositional changes taking place during the synthesis of alloyed CdSeZnS nanocrystals (NCs) allow shifting the optical features to higher energy as the NCs grow. Under certain synthetic conditions, the effect of those changes on the surface/interface chemistry competes with and dominates over the conventional quantum confinement effect in growing NCs. These changes, identified by means of complementary advanced spectroscopic techniques such as XPS (X-ray Photoelectron Spectroscopy) and XAS (X-ray absorption Spectroscopy), are understood in the frame of an ion migration and exchange mechanism taking place during the synthesis...
May 21, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29781601/artificial-plasmonic-molecules-and-their-interaction-with-real-molecules
#11
Gilad Haran, Lev Chuntonov
Plasmonic molecules are small assemblies of nanosized metal particles. Interactions between the particles modify their optical properties and make them attractive for multiple applications in spectroscopy and sensing. In this review, we focus on basic properties rather than on applications. Plasmonic molecules can be created using either nanofabrication methods or self-assembly techniques in solution. The interaction of plasmonic molecules with light leads to excitations that are classified using the concept of normal modes...
May 21, 2018: Chemical Reviews
https://www.readbyqxmd.com/read/29781492/single-electron-transport-through-stabilised-silicon-nanocrystals
#12
Tuhin Shuvra Basu, Simon Diesch, Elke Scheer
We have fabricated organically capped stable luminescent silicon nanocrystals with narrow size distribution by a novel, high yield and easy to implement technique. We demonstrate transport measurements of individual silicon nanocrystals by scanning tunnelling microscopy at a low temperature in a double-barrier tunnel junction arrangement in which we observed pronounced single electron tunnelling effects. The tunnelling spectroscopy of these nanocrystals with different diameters reveals quantum confinement induced bandgap modifications...
May 21, 2018: Nanoscale
https://www.readbyqxmd.com/read/29781484/microsolvated-complexes-of-ibuprofen-as-revealed-by-high-resolution-rotational-spectroscopy
#13
P Pinacho, A Krin, C Pérez, S Zinn, J C López, S Blanco, M Schnell
Hydrogen-bonded complexes between ibuprofen and water generated in a supersonic expansion were characterized using chirped-pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency range. Four spectra were observed allowing the determination of their rotational parameters. Comparison with quantum-chemical calculations led to their identification as the lowest energy 1 : 1 ibuprofen-water complexes. These correspond to the complexes between water and the four different conformers of ibuprofen previously detected in the gas phase, owing to their similar stabilization energies and abundances...
May 21, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29781477/methyl-rotation-dynamics-in-metal-organic-frameworks-probed-with-terahertz-spectroscopy
#14
Qi Li, Adam J Zaczek, Timothy M Korter, J Axel Zeitler, Michael T Ruggiero
In ZIF-8 and its cobalt analogue ZIF-67, the imidazolate methyl-groups, which point directly into the void space, have been shown to freely rotate - even down to cryogenic temperatures. Using a combination of experimental terahertz time-domain spectroscopy, low-frequency Raman spectroscopy, and state-of-the-art ab initio simulations, the methyl-rotor dynamics in ZIF-8 and ZIF-67 are fully characterized within the context of a quantum-mechanical hindered-rotor model. The results lend insight into the fundamental origins of the experimentally observed methyl-rotor dynamics, and provide valuable insight into the nature of the weak interactions present within this important class of materials...
May 21, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29781281/comparison-of-phonon-damping-behavior-in-quantum-dots-capped-with-organic-and-inorganic-ligands
#15
Kyle J Schnitzenbaumer, Gordana Dukovic
Surface ligand modification of colloidal semiconductor nanocrystals has been widely used as a means of controlling photoexcited state generation, relaxation, and coupling to the environment. While progress has been made in understanding how surface ligand modification affects the behavior of excitonic states, less is known about the influence of surface ligand modification on phonon behavior, which impacts relaxation dynamics and transport phenomena. In this work we compare the dynamics of optical and acoustic phonons in CdTe quantum dots (QDs), CdTe/CdSe core/shell QDs capped with octadecylphosphonic acid ligands, and CdTe QDs capped with Se2- to ascertain how ligand exchange from native aliphatic ligands to single-atom Se2- ligands affects phonon behavior...
May 21, 2018: Nano Letters
https://www.readbyqxmd.com/read/29781029/infrared-spectrum-and-intermolecular-potential-energy-surface-of-the-co-o-2-dimer
#16
A J Barclay, A R W McKellar, N Moazzen-Ahmadi, Richard Dawes, Xiao-Gang Wang, Tucker Carrington
Only a few weakly-bound complexes containing the O2 molecule have been characterized by high resolution spectroscopy, no doubt due to the complications added by the oxygen molecule's unpaired electron spin. Here we report an extensive infrared spectrum of CO-O2, observed in the CO fundamental band region using a tunable quantum cascade laser to probe a pulsed supersonic jet expansion. The rotational energy level pattern derived from the spectrum consists of stacks of levels characterized by the total angular momentum, J, and its projection on the intermolecular axis, K...
May 21, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29780995/magnetic-conjugated-polymer-nanoparticles-doped-with-a-europium-complex-for-biomedical-imaging
#17
E Kemal, R Peters, S Bourke, S Fairclough, P Bergstrom-Mann, D M Owen, L Sandiford, L A Dailey, M Green
Self-assembling conjugated polymer nanoparticles containing PVK and PLGA-PEG as a matrix polymer were doped with both a luminescent rare-earth complex and magnetic nanoparticles (SPIONs), giving rise to materials that are both luminescent and magnetic. Nanoparticle sizes ranged from 80-110 nm without SPIONs and showed an increase in size (200-1000 nm) with additional SPION content (11-54%). Quantum yields (QYs) of 24% and 18% were measured for systems without and with 11% SPIONs, respectively. Optical properties were stable and suitable for biological imaging applications...
May 21, 2018: Photochemical & Photobiological Sciences
https://www.readbyqxmd.com/read/29780991/plasmonically-enhanced-electromotive-force-of-narrow-bandgap-pbs-qd-based-photovoltaics
#18
Xiaowei Li, Paul D McNaughter, Paul O'Brien, Hiro Minamimoto, Kei Murakoshi
Electromotive force of photovoltaics is a key to define the output power density of photovoltaics. Multiple exciton generation (MEG) exhibited by semiconductor quantum dots (QDs) has great potential to enhance photovoltaic performance owing to the ability to generate more than one electron-hole pairs when absorbing a single photon. However, even in MEG-based photovoltaics, limitation of modifying the electromotive force exists due to the intrinsic electrochemical potential of the conduction band-edges of QDs...
May 21, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29780556/integration-of-isothermal-amplification-with-quantum-dot-based-fluorescence-resonance-energy-transfer-for-simultaneous-detection-of-multiple-micrornas
#19
Juan Hu, Ming-Hao Liu, Chun-Yang Zhang
MicroRNAs (miRNAs) are small non-coding RNAs that regulate important physiological processes, and their dysregulation is associated with various human diseases. Simultaneous sensitive detection of multiple miRNAs may facilitate early clinical diagnosis. In this research, we demonstrate for the first time the integration of hyperbranched rolling circle amplification (HRCA) with quantum dot (QD)-based fluorescence resonance energy transfer (FRET) for the simultaneous detection of multiple microRNAs with a single-color QD as the donor and two fluorescent dyes as the acceptors...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780542/unusual-mechanisms-in-claisen-rearrangements-an-ionic-fragmentation-leading-to-a-meta-selective-rearrangement
#20
Boris Maryasin, Dainis Kaldre, Renan Galaverna, Immo Klose, Stefan Ruider, Martina Drescher, Hanspeter Kählig, Leticia González, Marcos N Eberlin, Igor D Jurberg, Nuno Maulide
A mechanistic investigation of the acid-catalysed redox-neutral oxoarylation reaction of ynamides using electrospray ionisation mass-spectrometry (ESI-MS) and quantum chemical calculations (DFT and MP2) is presented. This study reveals the diversity of pathways and products available from an otherwise deceptively simple-looking, classical transformation: fragmentation, an unusual meta -arylation and competing α-carbonyl cation pathways are some of the alternatives unveiled by ESI-MS and mechanistic experiments...
May 7, 2018: Chemical Science
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