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Journal of Physical Chemistry Letters

Alex P Gaiduk, Giulia Galli
Determining how the structure of water is modified by the presence of salts is instrumental to understanding the solvation of biomolecules and, in general, the role played by salts in biochemical processes. However, the extent of hydrogen bonding disruption induced by salts remains controversial. We performed extensive first-principles simulations of solutions of a simple salt (NaCl) and found that, while the cation does not significantly change the structure of water beyond the first solvation shell, the anion has a further reaching effect, modifying the hydrogen-bond network even outside its second solvation shell...
March 21, 2017: Journal of Physical Chemistry Letters
Torben Jasper-Toennies, Manuel Gruber, Sujoy Karan, Hanne Jacob, Felix Tuczek, Richard Berndt
Spin-crossover molecules on metallic substrates have recently attracted considerable interest for their potential applications in molecular spintronics. Using scanning tunneling microscopy, we evidence the first successful deposition of a charged FeIII spin-crossover complex, [Fe(pap)2 ]+ (pap=N-2-pyridylmethylidene-2- hydroxyphenylaminato), on Au(111). Furthermore, the bulk form of the molecules is stabilized by a perchlorate counter ion, which depending on the deposition technique, may affect the quality of the deposition and the measurements...
March 20, 2017: Journal of Physical Chemistry Letters
Shinichi Enami, Agustin J Colussi
In the troposphere, the fate of gas-phase Criegee intermediates (CIs) is deemed to be determined by their reactions with water molecules. Here it is shown that CIs produced in situ on the surface of water/acetonitrile (W/AN) solutions react competitively with millimolar carboxylic acids. Present experiments probe, via online electrospray mass spectrometry, CIs chemistry on the surface of alpha-humulene and beta-caryophyllene in W/AN microjets exposed to O3(g) for < 10 micro sec. Mass-specific identification lets us establish the progeny of products and intermediates generated in the early stages of CIs reactions with H2O, D2O, H2O(18), and n-alkyl-COOH (n = 1-7)...
March 20, 2017: Journal of Physical Chemistry Letters
Shuang Li, Zhimin Ao, Jiaji Zhu, Jichang Ren, Jiabao Yi, Guoxiu Wang, Wei Liu
A reliable control of magnetic states is central to the use of magnetic nanostructures. Here, by using state-of-the-art density-functional theory calculations, we find that Mn atoms decorated silicene has an anomalously fixed magnetic moment and a high Curie temperature. In addition, a tunable magnetic exchange coupling is achieved for Mn-silicene system with the application of biaxial strain, which induces a transformation from the ferromagnetic (FM) to the antiferromagnetic (AFM) state. As such, an atomic "bit" could be obtained by superimposing strain field once the FM and AFM states are referred to as "1" and "0"...
March 20, 2017: Journal of Physical Chemistry Letters
Fabien Lacombat, Pascal Plaza, Marie-Aude Plamont, Agathe Espagne
Because of growing applications in advanced fluorescence imaging, the mechanisms and dynamics of photoinduced reactions in reversibly photoswitchable fluorescent proteins are currently attracting much interest. We report the first time-resolved study of the photoswitching of Dreiklang, so far the only fluorescent protein to undergo reversible photoinduced chromophore hydration. Using broadband femtosecond transient absorption spectroscopy, we show that the reaction is triggered by an ultrafast deprotonation of the chromophore phenol group in the excited state in 100 fs...
March 20, 2017: Journal of Physical Chemistry Letters
Falk Schneider, Daja Ruhlandt, Ingo Gregor, Jörg Enderlein, Alexey I Chizhik
Precise knowledge of the quantum yield is important for many fluorescence-spectroscopic techniques, for example, for Förster resonance energy transfer. However, to measure it for emitters in a complex environment and at low concentrations is far from being trivial. Using a plasmonic nanocavity, we measure the absolute quantum yield value of lipid-conjugated dyes incorporated into a supported lipid bilayer. We show that for both hydrophobic and hydrophilic molecules the quantum yield of dyes inside the lipid bilayer strongly differs from its value in aqueous solution...
March 20, 2017: Journal of Physical Chemistry Letters
Vanessa Quaranta, Matti Hellström, Jörg Behler
The dissociation of water is an important step in many chemical processes at solid surfaces. In particular, water often spontaneously dissociates near metal oxide surfaces, resulting in a mixture of H2O, H(+), and OH(-) at the interface. Ubiquitous proton-transfer (PT) reactions cause these species to dynamically interconvert, but the underlying mechanisms are poorly understood. Here, we develop and use a reactive high-dimensional neural-network potential based on density functional theory data to elucidate the structural and dynamical properties of the interfacial species at the liquid-water-metal-oxide interface, using the nonpolar ZnO(101̅0) surface as a prototypical case...
March 20, 2017: Journal of Physical Chemistry Letters
Wahib Aggoune, Caterina Cocchi, Dmitrii Nabok, Karim Rezouali, Mohamed Akli Belkhir, Claudia Draxl
By investigating the optoelectronic properties of prototypical graphene/hexagonal boron nitride (h-BN) heterostructures, we demonstrate how a nanostructured combination of these materials can lead to a dramatic enhancement of light-matter interaction and give rise to unique excitations. In the framework of ab initio many-body perturbation theory, we show that such heterostructures absorb light over a broad frequency range, from the near-infrared to the ultraviolet (UV), and that each spectral region is characterized by a specific type of excitations...
March 20, 2017: Journal of Physical Chemistry Letters
Sandra Wiedbrauk, Benjamin Maerz, Elena Samoylova, Peter Mayer, Wolfgang Zinth, Henry Dube
TICT formation in hemithioindigo photoswitches has recently been reported and constitutes a second deexcitation pathway complementary to photoisomerization. Typically this behavior is not found for this type of photoswitches and it takes special geometric and electronic conditions to realize it. Here we present a systematic study that identifies the molecular preconditions leading to TICT formation in donor substituted hemithioindigo, which can thus serve as a frame of reference for other photoswitching systems...
March 17, 2017: Journal of Physical Chemistry Letters
Zachary Patrick Degregorio, Youngdong Yoo, James E Johns
Controlling the growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs) is an important step to utilizing these materials for either electronics or catalysis. Here, we report a new surface-templated growth mechanism that enables the fabrication of MoO2/MoS2 and MoO2/MoTe2 core/shell nanoplates epitaxially aligned on (0001)-oriented 4H-silicon carbide and sapphire substrates. These heterostructures are characterized by a variety of techniques to identify the chemical and structural nature of the interface...
March 17, 2017: Journal of Physical Chemistry Letters
Adrian F Morrison, John M Herbert
Singlet fission proceeds rapidly and with high quantum efficiency in both crystalline tetracene and pentacene, which poses a conundrum given that the process in tetracene is disfavored by the electronic energetics. Here, we use an ab initio exciton model to compute nonadiabatic couplings in the unit cell of tetracene in order to identify the modes that promote this process. Four intramolecular modes in the range of 1400-1600 cm(-1), which are nearly resonant with the single-exciton/multiexciton energy gap, appear to play a key role...
March 17, 2017: Journal of Physical Chemistry Letters
Ranjana Gupta, Xiao-Xi Li, Kyung-Bin Cho, Mian Guo, Yong-Min Lee, Yong Wang, Shunichi Fukuzumi, Wonwoo Nam
The rate constants of the C=C epoxidation and the C-H hydroxylation (i.e., allylic C-H bond activation) in the oxidation of cyclohexene by a high-valent iron(IV)-oxo porphyrin π-cation radical complex, [(TMP(•+))Fe(IV)(O)(Cl)] (1, TMP = meso-tetramesitylporphyrin dianion), were determined at various temperatures by analyzing the overall rate constants and the products obtained in the cyclohexene oxidation by 1, leading us to conclude that the reaction pathway changes from the C=C epoxidation to the C-H hydroxylation by decreasing reaction temperature...
March 16, 2017: Journal of Physical Chemistry Letters
Raffaele Pastore, Giuseppe Pesce, Antonio Sasso, Massimo Pica Ciamarra
Glassy dynamics is intermittent, as particles suddenly jump out of the cage formed by their neighbours, and heterogeneous, as these jumps are not uniformly distributed across the system. Relating these features of the dynamics to the diverse local environments explored by the particles is essential to rationalize the relaxation process. Here we investigate this issue characterizing the local environment of a particle with the amplitude of its short time vibrational motion, as determined by segmenting in cages and jumps the particle trajectories...
March 16, 2017: Journal of Physical Chemistry Letters
Denis Jacquemin, Ivan Duchemin, Xavier Blase
Developing ab initio approaches able to provide accurate excited-state energies at a reasonable computational cost is one of the biggest challenges in theoretical chemistry. In that framework the Bethe-Salpeter equation approach, combined with the GW exchange-correlation self-energy, that maintains the same scaling with system size as TD-DFT, has recently been the focus of a rapidly increasing number of applications in molecular chemistry. Using a recently-proposed set encompassing excitation energies of many kinds [J...
March 16, 2017: Journal of Physical Chemistry Letters
Ines M Hauner, Antoine Deblais, James K Beattie, Hamid Kellay, Daniel Bonn
The surface tension of water is an important parameter for many biological or industrial processes, and roughly a factor of three higher than that of non-polar liquids such as oils, which is usually attributed to hydrogen bonding and dipolar interactions. Here we show by studying the formation of water drops that the surface tension of a freshly created water surface is even higher (~ 90 mNm(-1)) than under equilibrium conditions (~ 72 mNm(-1)) with a relaxation process occurring on a long timescale (~ 1 ms)...
March 16, 2017: Journal of Physical Chemistry Letters
Lei Zhang, WanZhen Liang
This work aims at exploring the intrinsic properties of 2D-layered perovskites, (PEA)2 PbI4(N) and Cs2PbI4(N), and demonstrating how their structures and properties vary with N. The results reveal that both (PEA)2PbI4(N) and Cs2PbI4(N) are direct bandgap semiconductors, their band/optical gaps and exciton-binding energies vary linearly with 1/N at N ≥3, and the effective masses slowly varies with N. Compared to the bulk phases, the structures of ultrathin (PEA)2PbI4(N) are more flexible and deformable than Cs2PbI4(N)...
March 16, 2017: Journal of Physical Chemistry Letters
Sofia Garakyaraghi, Cedric Mongin, Devin B Granger, John E Anthony, Felix N Castellano
The generation and transfer of triplet excitons across the molecular-semiconductor interface represents an important technological breakthrough featuring numerous fundamental scientific questions. This contribution demonstrates unprecedented delayed formation of TIPS-pentacene molecular triplet excitons bound on the surface of PbS nanocrystals mediated through the initial production of a proposed charge transfer intermediate following selective excitation of the PbS quantum dots. Ultrafast UV-Vis and near-IR transient absorption spectroscopy was used to track the dynamics of the initial PbS exciton quenching as well as time scale of the formation of molecular triplet excited states that persisted for 10 μs on the PbS surface, enabling subsequent energy and electron transfer reactivity...
March 16, 2017: Journal of Physical Chemistry Letters
Sanjib Das, John A Peters, Wenwen Lin, Svetlana S Kostina, Pice Chen, Joon-Il Kim, Mercouri G Kanatzidis, Bruce W Wessels
The chalcohalide compound Tl6SeI4 is a promising wide bandgap semiconductor for efficient hard radiation detection at room temperature due to its high density, average atomic number and mobility-lifetime product. However, the nature of its charge transport kinetics, especially the role of defects in recombination, has not been examined in detail. To determine the charge transport kinetics in Tl6SeI4 single crystals, electrical conductivity and photoinduced current transient spectroscopy were measured over the temperature range of 105-330 K...
March 16, 2017: Journal of Physical Chemistry Letters
Chuang Zhang, Dali Sun, Xiaojie Liu, Chuanxiang Sheng, Zeev Valy Vardeny
Organo-lead halide perovskites show excellent optoelectronic properties; however, the unexpected inconsistency in forward/backward I-V characteristics remains a problem for fabricating solar panels. Here we have investigated the reasons behind this "hysteresis" by following the changes in photocurrent/photoluminescence under electric field poling in transverse CH3NH3PbI3-based devices from 300 K to 10 K. We found that the hysteresis disappears at cryogenic temperatures, indicating the "freeze-out" of ionic diffusion contribution...
March 16, 2017: Journal of Physical Chemistry Letters
Krista G Steenbergen, Elke Pahl, Peter Schwerdtfeger
Using first-principles calculations and the "interface pinning" method in large-scale density functional molecular dynamics simulations of bulk melting, we prove that mercury is a liquid at room temperature due to relativistic effects. The relativistic model gives a melting temperature of 241 K, in excellent agreement with the experimental temperature of 234 K. The nonrelativistic melting temperature is remarkably high at 402 K.
March 16, 2017: Journal of Physical Chemistry Letters
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