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Journal of Physical Chemistry Letters

Robert C Dunbar, Jonathan Martens, Giel Berden, Jos Oomens
Ni(II) ions can be caged by surrounding peptide ligands in two basic binding patterns: the "iminol" (IM) binding pattern, where chelation occurs by deprotonated amide nitrogens, or the charge-solvated (CS) binding pattern, where chelation occurs by amide carbonyl oxygens. Gas-phase observation may clarify the factors affecting this choice in solution and in peptide and protein matrices. Infrared-spectroscopic determination of gas-phase structures shows here how microsolvation by just one water molecule switches the balance of this choice from IM to CS for the Ni2+Gly3 complex, in contrast to the always-CS structure of the Ni2+Gly4 complex...
May 24, 2017: Journal of Physical Chemistry Letters
Wen-Xiong Song, Zhi-Pan Liu, Limin Liu
Crystallization of solid is generally slow in kinetics for atom trapped in solid. Phase-change materials (PCMs) challenge current theory on its ultrafast reversible amorphous-to-crystal transition. Here by using stochastic surface walking global optimization method, we establish the first global potential energy surface (PES) for Ge2Sb2Te5. By analyzing all structures on global PES, we show that an inherent structural pattern of simple cubic lattice is present universally in low energy structures, either globally in a newly found metastable simple cubic crystal phase or locally in the amorphous structures...
May 23, 2017: Journal of Physical Chemistry Letters
Xuezheng Cao, Holger Merlitz, Chen-Xu Wu
Controlling the nanoparticle (NP) diffusion in polymers is a prerequisite to obtain polymer nanocomposites (PNCs) with desired dynamical and rheological properties, and to achieve targeted delivery of nanomedicine in biological systems. Here we determinate the suppression mechanism of direct NP-polymer attraction to hamper the NP mobility in adsorbing polymers, and then quantify the dependence of the effective viscosity \eta_{eff} felt by the NP on the adsorption duration \tau_{ads} of polymers on the NP, using scaling theory analysis and molecular dynamics (MD) simulations...
May 23, 2017: Journal of Physical Chemistry Letters
Marcello Sega, Balázs Fábián, Pal Jedlovszky
Surface tension, the tendency of fluid interfaces to behave elastically and minimize their surface, is routinely calculated as the difference between the lateral and normal components of the pressure or, invoking isotropy in momentum space, of the virial tensor. Here we show that the anisotropy of the kinetic energy tensor close to a liquid/vapour interface can be responsible for a large part of its surface tension (about 15 % for water, independently on temperature).
May 23, 2017: Journal of Physical Chemistry Letters
Suma S Thomas, Hao Tang, Adam Gaudes, Signe B Baggesen, Corinne L D Gibb, Bruce C Gibb, Cornelia Bohne
Hydrophobic or hydrophilic substituents have different effects on the binding dynamics of pyrene derivatives with a 2:1 capsule formed from two octaacid cavitands, showing a subtle interplay of different kinetic factors. Anchoring of the methyl group of 1-methylpyrene within one cavitand slowed the association and dissociation dynamics of the 1:1 complex by at least 1,000 times when compared to the 1:1 complex for pyrene. This slow down for the transient formation of the 1:1 complex is responsible for the overall increase in stability of the 2:1 complex without affecting the overall capsule dissociation...
May 23, 2017: Journal of Physical Chemistry Letters
Benjamin S Hoener, Hui Zhang, Thomas S Heiderscheit, Silke R Kirchner, Agampodi Swarnapali De Silva Indrasekara, Rashad Baiyasi, Yi-Yu Cai, Peter Nordlander, Stephan Link, Christy F Landes, Wei-Shun Chang
We report a study of the shape-dependent spectral response of the gold nanoparticle surface plasmon resonance at various electron densities to provide mechanistic insight into the role of capacitive charging, a topic of some debate. We demonstrate a morphology dependent spectral response for gold nanoparticles due to capacitive charging using single-particle spectroscopy in an inert electrochemical environment. A decrease in plasmon energy and increase in spectral width for gold nanospheres and nanorods was observed as the electron density was tuned through a potential window of -0...
May 23, 2017: Journal of Physical Chemistry Letters
Takuya Kurihara, Yasuto Noda, Kiyonori Takegoshi
Ligand-surface interaction of semiconductor nanoparticles (NPs) controls their optoelectronic properties, and thus examinations of the interaction are essential for the nanoelectronic applications of NPs. Herein, solid-state nuclear magnetic resonance (NMR) is performed to unravel the ligand-surface interaction in cysteine-capped CdSe magic-sized clusters. (15)N-(113)Cd through-bond J-filtered NMR directly shows the presence of the nitrogen-cadmium chemical bond for the first time and indicates that ~43% of the amines form the chemical bond...
May 23, 2017: Journal of Physical Chemistry Letters
Dejian Yu, Fei Cao, Yalong Shen, Xuhai Liu, Ying Zhu, Haibo Zeng
Two dimensional (2D) homologous halide perovskites (HPs) microcrystallines have emerged as promising alternative light-sensitive materials, however, the undesirable quantum confinement effect and severe interfacial charge carrier scattering still hamper their applications in photodetectors (PDs). Here we propose a novel post-synthetic treatment to simultaneously solve both problems. 2D (OA)2FAn-1PbnBr3n+1 (OA and FA represent octadecylamine and formamidine) microplatelets film was immersed into solution containing FA+, leading to improvements in two aspects...
May 23, 2017: Journal of Physical Chemistry Letters
Adam Faust, Yorai Amit, Uri Banin
Doping of semiconductor nanocrystals is an emerging tool to control their properties and has recently received increased interest as the means to characterize the impurities and their effect on the electronic characteristics of the nanocrystal evolve. We present a temperature-dependent Raman scattering study of Cu-doped InAs nanocrystals observing changes in the relative scattering intensities of the different modes upon increased dopant concentrations. First, the longitudinal optical (LO) phonon overtone mode is suppressed, indicating weakening of the coupling strength related to the effect of screening by the free electrons...
May 23, 2017: Journal of Physical Chemistry Letters
Sarina Sarina, Esa Jaatinen, Qi Xiao, Yi Ming Huang, Philip Christopher, Jin Cai Zhao, Huai Yong Zhu
By investigating the action spectra (the relationship between the irradiation wavelength and apparent quantum efficiency of reactions under constant irradiance) of a number of reactions catalyzed by nanoparticles including plasmonic metals, nonplasmonic metals, and their alloys at near-ambient temperatures, we found that a photon energy threshold exists in each photocatalytic reaction; only photons with sufficient energy (e.g., higher than the energy level of the lowest unoccupied molecular orbitals) can initiate the reactions...
May 23, 2017: Journal of Physical Chemistry Letters
David Mark Wilkins, David E Manolopoulos, Silvio Pipolo, Damien Laage, James T Hynes
We combine classical and ring polymer molecular dynamics simulations with the molecular jump model to provide a molecular description of the nuclear quantum effects (NQEs) on water reorientation and hydrogen-bond dynamics in liquid H2O and D2O. We show that while the net NQEs is negligible in D2O, it leads to a ∼13% acceleration in H2O dynamics compared to a classical description. Large angular jumps exchanging hydrogen-bond partners are the dominant reorientation pathway (just as in a classical description); the faster reorientation dynamics arise from the increased jump rate constant...
May 22, 2017: Journal of Physical Chemistry Letters
Kevin Whitham, Tobias Hanrath
The formation of epitaxially connected quantum dot solids involves a complex interplay of interfacial assembly, surface chemistry, and irreversible directed attachment. We describe the basic mechanism in context of a coherent phase transition with distinct nucleation and propagation steps. The proposed mechanism explains how defects in the pre-assembled structure influence nucleation and how basic geometric relationships govern the transformation from hexagonal assemblies of isolated dots to interconnected solids with square symmetry...
May 22, 2017: Journal of Physical Chemistry Letters
Rosana S Molina, Tam M Tran, Robert E Campbell, Gerard Glenn Lambert, Anya Salih, Nathan C Shaner, Thomas E Hughes, Mikhail Drobizhev
Fluorescent proteins (FPs) are indispensable markers for two-photon imaging of live tissue, especially in the brains of small model organisms. The quantity of physiologically relevant data collected, however, is limited by heat-induced damage of the tissue due to the high intensities of the excitation laser. We seek to minimize this damage by developing FPs with improved brightness. Among FPs with the same chromophore structure, the spectral properties can vary widely due to differences in the local protein environment...
May 22, 2017: Journal of Physical Chemistry Letters
Haruki Ishikawa, Itaru Kurusu, Reona Yagi, Ryota Kato, Yasutoshi Kasahara
To discuss the temperature effect on microscopic hydration structures in clusters, relative populations of the isomers having different hydration structures at well-defined temperatures are quite important. In the present study, we measured ultraviolet photodissociation spectra of the temperature-controlled hydrated phenol cation, [PhOH(H2O)5](+), trapped in the 22-pole ion trap. Two isomers having a distinct hydration motif with each other are identified in the spectra and a clear change in the relative populations is observed in temperature range from 30 K to 150 K...
May 22, 2017: Journal of Physical Chemistry Letters
Alberto Ceccon, Vitali Tugarinov, Andrew J Boughton, David Fushman, G Marius Clore
The interactions of two model multi-domain proteins - covalently linked di-ubiquitins, Ub2 - with lipid-based nanoparticles have been quantitatively probed by the measurements of NMR lifetime line broadening, ΔR2. By combined analysis of ΔR2 profiles arising from interactions with liposomes of varying sizes, an approach recently developed for the characterization of interactions of mono-ubiquitin with liposomes, we determine how the parameters of exchange (liposome binding) and dynamics of each individual domain of Ub2 on the surface of liposomes change when the domains are covalently attached to one another by a flexible linker...
May 22, 2017: Journal of Physical Chemistry Letters
Jan Philip Kraack, Angelo Frei, Roger Alberto, Peter Hamm
We investigate the ultrafast vibrational dynamics of monolayers from adsorbed rhenium-carbonyl CO2-reduction catalysts on a semiconductor surface (indium-tin-oxide (ITO)) with ultrafast two-dimensional attenuated total reflection infrared (2D ATR IR) spectroscopy. The complexes are partially equipped with isotope-labeled ((13)C) carbonyl ligands to generate two spectroscopically distinguishable forms of the molecules. Ultrafast vibrational energy transfer between the molecules is observed via the temporal evolution of cross-peaks between their symmetric carbonyl stretching vibrations...
May 22, 2017: Journal of Physical Chemistry Letters
Maria A Castellanos, Pengfei Huo
We apply a real-time path-integral approach to investigate the charge-transfer (CT)-mediated singlet fission quantum dynamics in a model pentacene dimer. Our path-integral method gives reliable fission dynamics across various reaction regimes as well as a broad range of reorganization energies and temperatures. With this method, we investigated the destructive interference between the two CT-mediated fission pathways and discovered two mechanisms that can suppress this deleterious effect. First, increasing the energy gap between the two CT states effectively shuts down the high-lying CT pathway, leaving a better functioning low-lying CT pathway with a minimum amount of destructive interference...
May 22, 2017: Journal of Physical Chemistry Letters
Haoyuan Li, Jean-Luc Brédas
Kinetic Monte Carlo (KMC) simulations have emerged as an important tool to help improve the efficiency of organic electronic devices by providing a better understanding of their device physics. In the KMC simulation of an organic device, the reliability of the results depends critically on the accuracy of the chosen charge-transfer rates, which are themselves strongly influenced by the site-energy differences. These site-energy differences include components coming from the electrostatic forces present in the system, which are often evaluated through electric potentials described by the Poisson equation...
May 22, 2017: Journal of Physical Chemistry Letters
Dingdi Wang, Haijing Zhang, William W Yu, Zikang Tang
In one-dimensional (1D) systems, the definition of three common states of matter (solid, liquid, and gas) becomes obscure because it has been theoretically predicted that a 1D system has no phase transition. Due to technical difficulty in tracking 1D thermal evolution, hardly any experimental evidence has demonstrated whether there exist these three states. Here we report Raman experimental observation that 1D iodine molecular chains formed inside the nanosized channel undergo continuous transformation from chain structure to single molecules with increasing temperature, without having a sudden change as commonly observed in phase transition...
May 22, 2017: Journal of Physical Chemistry Letters
Marek Szafrański, Andrzej Katrusiak
High-pressure studies on methylammonium trihaloplumbates, of general formula [CH3NH3](+)PbX3(-) (abbreviated MAPbX3, where X = Cl, Br, I), and its analogues shed new light on the materials for harvesting solar energy and open new perspectives for photovoltaic science and technology. However, there are considerable discrepancies between the reported structural, calorimetric, and spectroscopic results and even between the results obtained by the same technique, for example, of X-ray diffraction. The origins of these discrepancies and possible pitfalls in the diffraction and spectroscopic studies on MAPbX3 crystals have been investigated...
May 22, 2017: Journal of Physical Chemistry Letters
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