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Journal of Physical Chemistry Letters

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https://www.readbyqxmd.com/read/29341623/is-subsurface-oxygen-necessary-for-the-electrochemical-reduction-of-co2-on-copper
#1
Alejandro Garza, Alexis T Bell, Martin Head-Gordon
It has recently been proposed that subsurface oxygen is crucial for the adsorption and subsequent electroreduction of CO2 on copper. Using density functional theory, we have studied the stability and diffusion of subsurface oxygen in single crystals of copper exposing (111) and (100) facets. Oxygen is at least 1.5 eV more stable on the surface than beneath it for both crystal orientations; interstitial sites are too small to accommodate oxygen. The rate of atomic oxygen diffusion from one layer below a Cu(111) surface to the surface is 5 × 103 s-1...
January 17, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29341616/stochasticity-of-pores-interconnectivity-in-li-o2-batteries-and-its-impact-on-the-variations-in-electrochemical-performance
#2
Amangeldi Torayev, José Alexis Rucci, Pieter M Magusin, Arnaud Demortiere, Vincent De Andrade, Clare P Grey, Céline Merlet, Alejandro A Franco
While large dispersions in electrochemical performance have been reported for lithium oxygen batteries in the literature, they have not been investigated in any depth. The variability in the results is often assumed to arise from differences in cell design, electrode structure, handling and cell preparation at different times. An accurate theoretical framework turns out to be needed to get a better insight into the mechanisms underneath and to interpreting experimental results. Here, we develop and use a pore network model to simulate the electrochemical performance of three-dimensionally resolved lithium-oxygen cathode mesostructures obtained from TXM nano-computed tomography images...
January 17, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29338269/the-reactivity-toward-ag-a-general-strategy-to-generate-a-new-emissive-center-from-the-nir-emitting-gold-nanoparticles
#3
Yaping Wang, Lulu Liu, Lingshan Gong, Ying Chen, Jinbin Liu
We report a facile strategy for the transformation of the single NIR-emitting AuNPs to dual-NIR-emitting bimetallic Ag@AuNPs based on the robust reactivity toward Ag(I) ions under mild conditions. The reactivities toward Ag(I) ions were discovered significantly different between the visible- and NIR-emitting glutathione(GSH)-coated AuNPs: the high GSH surface coverage on the 610 nm-emitting AuNPs resulted in an reversible interaction due to enough surface steric hindrance to resist Ag(I) ions from interaction with the Au(0) core, whereas the low GSH surface coverage on the 810 nm-emitting AuNPs led to both the anti-galvanic reaction and Ag(I)-carboxylate shell formation on surface of the AuNPs, which were responsible for the formation of a new emissive center at 705 nm...
January 17, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29338266/all-solid-state-batteries-with-thick-electrode-configurations
#4
Yuki Kato, Shinya Shiotani, Keisuke Morita, Kota Suzuki, Masaaki Hirayama, Ryoji Kanno
We report the preparation of thick electrode all-solid-state lithium-ion cells in which a large geometric capacity of 15.7 mAh cm-2 was achieved at room temperature using a 600 μm-thick cathode layer. The effect of ionic conductivity on the discharge performance was then examined using two different materials for the solid electrolyte. Furthermore, important morphological information regarding the tortuosity factor was electrochemically extracted from the capacity-current data. The effect of tortuosity on cell performance was also quantitatively discussed...
January 17, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29338246/non-transition-metal-catalytic-system-for-n2-reduction-to-nh3-a-dft-study-of-al-doped-graphene
#5
Yonghui Tian, Shuangli Hu, Xiao-Lan Sheng, Yixiang Duan, Jacek Jakowski, Bobby G Sumpter, Jingsong Huang
The prevalent catalysts for natural and artificial N2 fixation are known to hinge upon transition metal (TM) elements. Herein, we demonstrate by density functional theory that Al-doped graphene is a potential non-TM catalyst to convert N2 to NH3 in the presence of relatively mild proton/electron sources. In the integrated structure of catalyst, the Al atom serves as a binding site and catalytic center while the graphene framework severs as an electron buffer during the successive proton/electron additions to N2 and its various downstream NxHy intermediates...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337581/light-harvesting-by-equally-contributing-mechanisms-in-a-photosynthetic-antenna-protein
#6
Matthew J Guberman-Pfeffer, Jordan A Greco, Robert Richards Birge, Harry A Frank, José A Gascón
We report supramolecular quantum mechanics/molecular mechanics simulations on the peridinin-chlorophyll a protein (PCP) complex from the causative algal species of red tides. These calculations reproduce for the first time quantitatively the distinct peridinin absorptions, identify multichromophoric molecular excitations, and elucidate the mechanisms regulating the strongly-allowed S0 (11Ag-) → S2 (11Bu+) absorptions of the bound peridinins that span a 58 nm spectral range in the region of maximal solar irradiance...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337575/optical-signatures-of-impurity-impurity-interactions-in-copper-containing-ii-vi-alloy-nanocrystals
#7
Biswajit Bhattacharyya, Kushagra Gahlot, Ranjani Viswanatha, Anshu Pandey
We study the optical properties of copper containing II-VI alloy quantum dots (CuxZn¬yCd1-x-ySe). Copper mole fractions within the host are varied from 0.001 to 0.35. No impurity phases are observed over this composition range and the formation of secondary phases of copper selenide are observed only at xCu > 0.45. The optical absorption and emission spectra of these materials are observed to be a strong function of xCu, and provide information regarding composition induced impurity-impurity interactions...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337574/singlet-fission-mediated-photophysics-of-bodipy-dimers
#8
Raul Montero, Virginia Martinez-Martinez, Asier Longarte, Nerea Epelde-Elezcano, Eduardo Palao, Iker Lamas Frejo, Hegoi Manzano, Antonia R Agarrabeitia, Iñigo Lopez-Arbeloa, Maria José Ortiz, Inmaculada García-Moreno
The photodynamics of an orthogonal BODIPY dimer, particularly the formation of triplet states, has been explored by femtosecond and nanosecond transient absorption measurements. The short time-scale data show the appearance of transient features of triplet character that according to a quantitative analysis of their intensities, account for more than 100% percent of the initially excited molecules, which reveals the occurrence of a singlet fission process in the isolated dimers. The formation rate of the triplet correlated state 1(TT) is found to depend on the solvent polarity, pointing to the mediation of a charge transfer character state...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337573/cryoprotectants-severely-exacerbate-x-ray-induced-photoreduction
#9
Kurt H Nienaber, M Jake Pushie, Julien J H Cotelesage, Ingrid J Pickering, Graham N George
Approximately 11% of enzymes contain a transition metal ion that is essential for catalytic function. Such metalloenzymes catalyze much of the most chemically challenging and biologically essential chemistry carried out by life. X-ray based methods, predominantly macromolecular crystallography (MX) and also X-ray absorption spectroscopy (XAS), have proved essential for determining structures of transition metal ion-containing active sites in order to deduce enzyme catalytic mechanisms. However, X-ray irradiation can induce change in both oxidation state and structure of the metal, which is problematic in structure determination...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337571/direct-observation-of-a-transiently-formed-isomer-during-iodoform-photolysis-in-solution-by-time-resolved-x-ray-liquidography
#10
Chi Woo Ahn, Hosung Ki, Joonghan Kim, Jeongho Kim, Sungjun Park, Yunbeom Lee, Kyung Hwan Kim, Qingyu Kong, Jiwon Moon, Martin Nors Pedersen, Michael Wulff, Hyotcherl Ihee
Photolysis of iodoform (CHI3) in solution has been extensively studied but its reaction mechanism remains elusive. In particular, iso-iodoform (iso-CHI2-I) is formed as a product of the photolysis reaction, but its detailed structure is not known and whether it is a major intermediate species has been controversial. Here, by using time-resolved X-ray liquidography, we determined the reaction mechanism of CHI3 photodissociation in cyclohexane as well as the structure of iso-CHI2-I. Both iso-CHI2-I and CHI2 radical were found to be formed within 100 ps with a branching ratio of 40:60...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337570/self-organization-of-metal-nanoparticles-in-light-electrodynamics-molecular-dynamics-simulations-and-optical-binding-experiments
#11
Patrick McCormack, Fei Han, Zijie Yan
Light-driven self-organization of metal nanoparticles (NPs) can lead to unique optical matter systems, yet simulation of such self-organization (i.e., optical binding) is a complex computational problem that increases non-linearly with system size. Here we show that a combined electrodynamics-molecular dynamics simulation technique can simulate the trajectories and predict stable configurations of silver NPs in optical fields. The simulated dynamic equilibrium of a two-NP system matches the probability density of oscillations for two optically bound NPs obtained experimentally...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337568/rational-design-of-a-green-light-mediated-unimolecular-platform-for-fast-switchable-acidic-sensing
#12
Yunyun Zhou, Qi Zou, Jing Qiu, Linjun Wang, Liangliang Zhu
A controllable sensing ability strongly connects to complex and precise events in diagnosis and treatment. However, imposing visible light into the molecular-scale mediation of sensing process is restricted by the lack of structural relevance. To address this critical challenge, we present the rational design, synthesis, and in vitro studies of a novel cyanostyryl-modified azulene system for green light mediated fast switchable acidic sensing. The advantageous features of the design include a high- efficient green-light driven Z/E-isomerization (a quantum yield up to 61...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337564/vibrational-dynamics-and-couplings-of-the-hydrated-rna-backbone-a-2d-ir-study
#13
Eva M Bruening, Jakob Schauss, Torsten Uwe Siebert, Benjamin P Fingerhut, Thomas Elsaesser
The equilibrium structure of the RNA sugar-phosphate backbone and its hydration shell is distinctly different from hydrated DNA. Applying femtosecond two-dimensional infrared (2D-IR) spectroscopy in a range from 950 to 1300 cm-1, we elucidate the character, dynamics, and couplings of backbone modes of a double-stranded RNA A-helix geometry in its aqueous environment. The 2D-IR spectra display a larger number of backbone modes than for DNA, with distinctly different lineshapes of diagonal peaks. Phosphate-ribose interactions and local hydration structures are reflected in the complex coupling pattern of RNA modes...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29337563/magic-angle-stacking-and-strong-intermolecular-%C3%AF-%C3%AF-interaction-in-a-perylene-bisimide-crystal-an-approach-for-efficient-near-infrared-nir-emission-and-high-electron-mobility
#14
Jiadong Zhou, Wenqiang Zhang, Xiao-Fang Jiang, Cong Wang, Xuehong Zhou, Biao Xu, Linlin Liu, Zengqi Xie, Yuguang Ma
A single crystal of perylene bisimide possesses novel magic-angle stacking and strong intermolecular π-π interaction is achieved by physical vapor transport (PVT), which shows attractive optoelectronic functions such as efficient NIR emission and high electron mobility. In this special M-type staking, the elimination of long-distance Förster energy transfer enables the minimization of the possible fluorescence quenching, which ensures the highly efficient emission. Moreover, the strong π-π interaction elongates the "supramolecular conjugation" to reduce the energy gap and also benefit the electron mobility of the crystal...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29336156/infra-red-dielectric-screening-determines-the-low-exciton-binding-energy-of-metal-halide-perovskites
#15
Paolo Umari, Edoardo Mosconi, Filippo De Angelis
The performance of lead-halide perovskites in optoelectronic devices are due to a unique combina-tion of factors, including highly efficient generation, transport and collection of photogenerated charge carriers. The mechanism behind efficient charge generation in lead-halide perovskites is still largely unknown. Here, we investigate the factors which influence the exciton binding energy (Eb) in a series of metal-halide perovskites using accurate first-principles calculations based on solution of the Bethe-Salpeter equation, coupled to ab initio molecular dynamics simulations...
January 16, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29329502/energetic-costs-precision-and-transport-efficiency-of-molecular-motors
#16
Wonseok Hwang, Changbong Hyeon
An efficient molecular motor would deliver cargos to the target site at a high speed and in a punctual manner while consuming a minimal amount of energy. According to a recently formulated thermodynamic principle, referred to as the thermodynamic uncertainty relation, the travel distance of a motor and its variance are, however, constrained by the free energy being consumed. Here we use the principle underlying the uncertainty relation to quantify the transport efficiency of molecular motors for varying ATP concentration ([ATP]) and applied load (f)...
January 12, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29320636/how-do-london-dispersion-interactions-impact-the-photochemical-processes-of-molecular-switches
#17
Alberto Fabrizio, Clémence Corminboeuf
In the last two decades, linear-response time-dependent density functional theory (LR-TDDFT) has become one of the most widely used approaches for the computation of the excited-state properties of atoms and molecules. Despite its success in describing the photochemistry and the photophysics of a vast majority of molecular systems, its domain of applicability has been limited by several substantial drawbacks. Commonly identified problems of LR-TDDFT include the correct description of Rydberg states, charge-transfer excited states, doubly excited states, and nearly degenerate states...
January 12, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29325414/molecular-dynamics-of-photoinduced-reactions-of-acrylic-acid-products-mechanisms-and-comparison-with-experiment
#18
Dorit Shemesh, Robert Benny Gerber
The photochemistry of acrylic acid is of considerable atmospheric importance. However, the mechanisms and the timescales of the reactions involved are unknown. In this work, the products, yields and reaction pathways of acrylic acid photochemistry are investigated theoretically by molecular dynamics simulations on the ππ* excited state. Two methods were used to describe the excited state: the semi-empirical OM2/MRCI and the ab initio ADC(2). Over one hundred trajectories were computed with each method. A rich variety of reaction channels including mechanisms, timescales and yields, are predicted for the single potential energy surface used...
January 11, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29323911/capillary-condensation-in-8-nm-deep-channels
#19
Junjie Zhong, Jason Riordon, Seyed Hadi Zandavi, Yi Xu, Aaron Harrinarine Persad, Farshid Mostowfi, David Sinton
Condensation at the nanoscale is essential to understanding many natural and synthetic systems relevant to water, air and energy. Despite its importance, the underlying physics of condensation initiation and propagation remain largely unknown at sub-10 nm, mainly due to the challenges of controlling and probing such small systems. Here we study the condensation of n-propane down to 8-nm confinement in a nanofluidic system, distinct from previous studies at ~100 nm. The condensation initiates significantly earlier in the 8-nm channels and it initiates from the entrance, in contrast to channels just 10-times larger...
January 11, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29323907/ultrathin-semiconducting-bi2te2s-and-bi2te2se-with-high-electron-mobilities
#20
Bing Wang, Xianghong Niu, Yixin Ouyang, Qionghua Zhou, Jinlan Wang
High carrier mobility and moderate band gap are two key properties of electronic device applications. Two ultrathin two-dimensional (2D) semiconductors, namely Bi2Te2S and Bi2Te2Se nanosheets, with novel electronic and optical properties are predicted based on first-principles calculations. The Bi2Te2S and Bi2Te2Se monolayers own moderate band gaps (~ 0.7 eV) and high electronic mobilities (20000 cm2V-1s-1); and they can absorb sunlight efficiently through the whole incident solar spectrum. Meanwhile, layer-dependent exponential decay band gaps are also unveiled...
January 11, 2018: Journal of Physical Chemistry Letters
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