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Journal of Physical Chemistry Letters

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https://www.readbyqxmd.com/read/28820945/a-chiral-gas-hydrate-structure-common-to-the-carbon-dioxide-water-and-hydrogen-water-systems
#1
Dan Amos, Mary-Ellen Donnelly, Pattanasak Teeratchanan, Craig L Bull, Andrzej Falenty, Werner F Kuhs, Andreas Hermann, John Loveday
We present diffraction studies and full in-situ structural solutions of carbon dioxide hydrate-II and hydrogen hydrate $C_0$ at elevated pressures. We find both hydrates adopt a common water network structure. The structure exhibits several features not previously found in hydrates, most notably it is chiral and has large open spiral channels along which the guest molecules are free to move. It has a network that is unrelated to any experimentally known ice, silica or zeolite network but is instead related to two Zintl compounds...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28820596/processing-solvent-dependent-electronic-and-structural-properties-of-cesium-lead-triiodide-thin-films
#2
Alexandra J Ramadan, Luke A Rochford, Sarah Fearn, Henry J Snaith
Cesium lead triiodide (CsPbI3) is an attractive material for photovoltaic applications due to its appropriate band gap, strong optical absorption and high thermal stability. However, the perovskite phase suffers from moisture induced structural instability. Previous studies have utilized a range of solvent systems to establish the role of solvent choice in structural instabilities. Despite this, effects of different solvents on the electronic structure of this material have not been compared. We report substantial chemical and compositional differences in thin films of CsPbI3 prepared from a range of solvent systems...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28820595/vibronic-origin-of-the-qy-absorption-tail-of-bacteriochlorophyll-a-verified-by-fluorescence-excitation-spectroscopy-and-quantum-chemical-simulations
#3
Kristjan Leiger, Juha Matti Linnanto, Arvi Freiberg
The long-wavelength tail of the lowest-energy Qy singlet absorption band of bacteriochlorophyll a in triethylamine peaking at 768.6 nm was examined by means of fluorescence excitation spectroscopy at ambient temperature of 22±1°C. The tail, usually considered a Gaussian, is in fact weakening quasi-exponentially, being clearly evident as far as 940 nm, nearly 2400 cm(-1) (~12 kBT) away from the absorption peak. Quantum chemical simulations identified vibronic transitions from the thermally populated normal modes and their overtones in the ground electronic state as the origin of this tail...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28820265/pressure-induced-polymerization-and-disproportionation-of-li2c2-accompanied-with-irreversible-conductivity-enhancement
#4
Lijuan Wang, Xiao Dong, Yajie Wang, Haiyan Zheng, Kuo Li, Xing Peng, Ho-Kwang Mao, Changqing Jin, Yufei Meng, Mingquan Huang, Zhisheng Zhao
Li2C2 has the highest theoretical capacity (1400mA•h•g-1) as the electrode material for Li-ion battery, but suffers from low conductivity. Here we found under external pressure its conductivity was irreversibly enhanced by 10^9-fold. To explain that, we performed X-ray diffraction, Raman, IR, Gas Chromatography-Mass Spectrometry and theoretical investigations under external pressure. We found the C22- anions approached to each other and polymerized upon compression, which is responsible for the irreversible enhancement of conductivity...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28819974/room-temperature-synthesis-of-mn-doped-cesium-lead-halide-quantum-dots-with-high-mn-substitution-ratio
#5
Jingrun Zhu, Xiaoling Yang, Yihua Zhu, Yuanwei Wang, Jin Cai, Jianhua Shen, Luyi Sun, Chunzhong Li
Here we report the room temperature, atmospheric synthesis of Mn-doped cesium lead halide (CsPbX3) perovskite QDs. The synthesis is performed without any sort of protection and the dual-color emission mechanism is revealed by density functional theory. The Mn concentration reaches a maximum atomic percentage of 37.73 at%, which is significantly higher in comparison to those achieved in earlier reports via high temperature hot injection method. The optical properties of as-prepared nanocrystals (NCs) remain consistent even after several months...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28812901/behavior-of-methylammonium-dipoles-in-mapbx3-x-br-and-i
#6
Sharada Govinda, Bhushan P Kore, Menno Bokdam, Pratibha Mahale, Abhinav Kumar, Somnath Pal, Biswajit Bhattacharyya, Jonathan Lahnsteiner, Georg Kresse, Cesare Franchini, Anshu Pandey, D D Sarma
Dielectric constants of MAPbX3 (X = Br, I) in the 1 kHz-1 MHz range show strong temperature dependence near room temperature, in contrast to the nearly temperature-independent dielectric constant of CsPbBr3. This strong temperature dependence for MAPbX3 in the tetragonal phase is attributed to the MA(+) dipoles rotating freely within the probing time scale. This interpretation is supported by ab initio molecular dynamics simulations on MAPbI3 that establish these dipoles as randomly oriented with a rotational relaxation time scale of ∼7 ps at 300 K...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28809496/time-resolved-coherent-anti-stokes-raman-scattering-of-graphene-dephasing-dynamics-of-optical-phonon
#7
Juha Koivistoinen, Pasi Myllyperkiö, Mika Pettersson
We report dynamics of the G-mode in graphene probed with time-resolved coherent anti-Stokes Raman scattering measurements. By applying BOXCARS excitation geometry with three different excitation wavelengths, various nonlinear processes can be selectively detected due to energy and momentum conservation and temporal sequence of the pulses. The Raman signal due to resonant coherent excitation of the G-mode shows exponential decay with lifetime of ∼325 ± 50 fs. This decay time is shorter than expected based on the line width of the G-mode in the Raman spectrum...
August 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28817773/surface-reaction-barriometry-methane-dissociation-on-flat-and-stepped-transition-metal-surfaces
#8
Davide Migliorini, Helen Jane Chadwick, Francesco Nattino, Ana Gutiérrez-Gonzáles, Eric Dombrowski, Eric A High, Han Guo, Arthur L Utz, Bret Earl Jackson, Rainer D Beck, Geert-Jan Kroes
Accurately simulating heterogeneously catalyzed reactions requires reliable barriers for molecules reacting at defects on metal surfaces, such as steps. However, first principles methods capable of computing these barriers to chemical accuracy have yet to be demonstrated. We show that state-resolved molecular beam experiments combined with ab initio molecular dynamics using specific reaction parameter density functional theory (SRP-DFT) can determine the molecule-metal surface interaction with the required reliability...
August 17, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28816458/pressure-induced-emission-enhancement-of-carbazole-the-restriction-of-intramolecular-vibration
#9
Yarong Gu, Kai Wang, Yu-Xiang Dai, Guanjun Xiao, Yuguo Ma, Yuancun Qiao, Bo Zou
Pressure-induced emission enhancement (PIEE), a novel phenomenon on the enhancement of the solid-state emission efficiency of fluorophores, has been arousing wide attention in recent years. However, researches on PIEE are still in the early stage. To further pursue more enhanced efficiency, discovering and designing more PIEE systems would be urgently desirable and of great importance. In this letter, we found carbazole presented a conspicuous emission enhancement under high pressure up to 1.0 GPa. In situ high-pressure infrared spectroscopy, angle-dispersive X-ray diffraction analysis combined with Hirshfeld surface theory calculation indicated that the PIEE of carbazole was attributed to the decrease of non-radiation vibration process...
August 17, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28816047/light-independent-ionic-transport-in-inorganic-perovskite-and-ultra-stable-cs-based-perovskite-solar-cells
#10
Wenke Zhou, Yicheng Zhao, Xu Zhou, Rui Fu, Qi Li, Yao Zhao, Kaihui Liu, Dapeng Yu, Qing Zhao
Due to light-induced effects in CH3NH3-based perovskites, such as ion migration, defects formation and halide segregation, the degradation of CH3NH3-based perovskite solar cells under maximum power point is generally concerned. Here we demonstrated that the effect of light-enhanced ion migration in CH3NH3PbI3 can be eliminated by inorganic Cs substitution, leading to an ultra-stable perovskite solar cell. Quantitatively, the ion migration barrier for CH3NH3PbI3 is 0.62 eV under dark, larger than CsPbI2Br (0...
August 17, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28816045/efficient-inorganic-perovskite-light-emitting-diodes-with-polyethylene-glycol-passivated-ultrathin-cspbbr3-films
#11
Li Song, Xiaoyang Guo, Yongsheng Hu, Ying Lv, Jie Lin, Zheqin Liu, Yi Fan, Xingyuan Liu
Efficient inorganic perovskite light-emitting diodes (PeLEDs) with an ultrathin perovskite emission layer (~30 nm) were realized by doping Lewis base Polyethylene Glycol (PEG) into CsPbBr3 films. PEG in the perovskite films not only physically fills the crystal boundaries, but also interacts with the perovskite crystals to passivate the crystal grains, reduce nonradiative recombination and ensure the efficient luminance and high efficiency. As a result, promoted brightness, current efficiency (CE) and external quantum efficiency (EQE) were achieved...
August 17, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28812351/structural-investigation-of-cesium-lead-halide-perovskites-for-high-efficiency-quantum-dot-light-emitting-diodes
#12
Quyet Van Le, Jong Beom Kim, Soo Young Kim, Byeongdu Lee, Dong Ryeol Lee
In this study, we have intensively investigated the effect of the reaction temperature of hot-injection method on the structural properties of CsPbX3 (X: Br, I, Cl) perovskite nanocrystals (NCs) using the small- and wide-angle X-ray scattering. Furthermore, light emitting diodes (LEDs) performance as well as photoluminescence characteristics for high-efficient LEDs is compared with reaction temperature. It is confirmed that the size of the NCs decreased as the reaction temperature decreased, resulting stronger quantum confinement...
August 16, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28799771/understanding-nonradiative-recombination-through-defect-induced-conical-intersections
#13
Yinan Shu, B Scott Fales, Wei-Tao Peng, Benjamin G Levine
Defects are known to introduce pathways for the nonradiative recombination of electronic excitations in semiconductors, but implicating a specific defect as a nonradiative center remains challenging for both experiment and theory. In this Perspective, we present recent progress toward this goal involving the identification and characterization of defect-induced conical intersections (DICIs), points of degeneracy between the ground and first excited electronic states of semiconductor materials that arise from the deformation of specific defects...
August 16, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28799764/ultrathin-one-and-two-dimensional-colloidal-semiconductor-nanocrystals-pushing-quantum-confinement-to-the-limit
#14
Anne C Berends, Celso de Mello Donega
Research on ultrathin nanomaterials is one of the fastest developing areas in contemporary nanoscience. The field of ultrathin one- (1D) and two-dimensional (2D) colloidal nanocrystals (NCs) is still in its infancy, but offers the prospect of production of ultrathin nanomaterials in liquid-phase at relatively low costs, with versatility in terms of composition, size, shape, and surface control. In this Perspective, the state of the art in the field is concisely outlined and critically discussed to highlight the essential concepts and challenges...
August 16, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28797162/nanoparticles-of-various-degrees-of-hydrophobicity-interacting-with-lipid-membranes
#15
Chan-Fei Su, Holger Merlitz, Hauke Rabbel, Jens-Uwe Sommer
Using coarse-grained molecular dynamics simulations, we study the passive translocation of nanoparticles with a size of about 1 nm and with tunable degrees of hydrophobicity through lipid bilayer membranes. We observe a window of translocation with a sharp maximum for nanoparticles having a hydrophobicity in between hydrophilic and hydrophobic. Passive translocation can be identified as diffusive motion of individual particles in a free energy landscape. By combining direct sampling with umbrella-sampling techniques we calculate the free energy landscape for nanoparticles covering a wide range of hydrophobicities...
August 16, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28777583/intercalated-vs-nonintercalated-morphologies-in-donor-acceptor-bulk-heterojunction-solar-cells-pbttt-fullerene-charge-generation-and-recombination-revisited
#16
Elisa Collado-Fregoso, Samantha N Hood, Safa Shoaee, Bob C Schroeder, Iain McCulloch, Ivan Kassal, Dieter Neher, James R Durrant
In this Letter, we study the role of the donor:acceptor interface nanostructure upon charge separation and recombination in organic photovoltaic devices and blend films, using mixtures of PBTTT and two different fullerene derivatives (PC70BM and ICTA) as models for intercalated and nonintercalated morphologies, respectively. Thermodynamic simulations show that while the completely intercalated system exhibits a large free-energy barrier for charge separation, this barrier is significantly lower in the nonintercalated system and almost vanishes when energetic disorder is included in the model...
August 16, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28809578/uv-vis-action-spectroscopy-reveals-a-conformational-collapse-in-hydrogen-rich-dinucleotide-cation-radicals
#17
Joseph A Korn, Jan Urban, Andy Dang, Huong T H Nguyen, Frantisek Turecek
We report the generation of deoxyriboadenosine dinucleotide cation radicals by gas-phase electron transfer to dinucleotide dications and their non-covalent complexes with crown ether ligands. Stable dinucleotide cation radicals of a novel hydrogen-rich type were generated and characterized by tandem mass spectrometry and UV-vis photodissociation (UVPD) action spectroscopy. Electron structure theory analysis indicated that upon electron attachment the dinucleotide dications underwent a conformational collapse followed by intramolecular proton migrations between the nucleobases to give species whose calculated UV-VIS absorption spectra matched the UVPD action spectra...
August 15, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28809493/macroscopic-structural-compositions-of-%C3%AF-conjugated-polymers-combined-insights-from-solid-state-nmr-and-molecular-dynamics-simulations
#18
Anton Melnyk, Matthias Junk, Michael D McGehee, Bradley F Chmelka, Michael Ryan Hansen, Denis Andrienko
Molecular dynamics simulations are combined with solid-state NMR measurements to gain insight into the macroscopic structural composition of the π-conjugated polymer poly(2,5-bis(3-tetradecyl-thiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT). The structural and dynamical properties, as established by the NMR analyses, were used to test the local structure of three constitutient mesophases with: (i) crystalline backbones and side chains, (ii) lamellar backbones and disordered side chains, or (iii) amorphous backbones and side chains...
August 15, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28809122/practical-li-ion-battery-assembly-with-one-dimensional-active-materials
#19
Vanchiappan Aravindan, Palanichamy Sennu, Yun-Sung Lee, Srinivasan Madhavi
Research activities on the development of one-dimensional (1D) nanostructures and their successful implementation in the fabrication of high-performance practical Li-ion batteries (LIBs) are described. Although numerous 1D-structured materials have been explored for use in LIBs as anodes, cathodes, and separator-cum-electrolytes, only a very limited number of studies report the practical assembly of LIBs using these components. As a result, the salient features of using 1D materials in charge-storage devices have not been realized from an application perspective...
August 15, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28792768/role-of-hydrogen-bonding-in-photoinduced-electron-proton-transfer-from-phenols-to-a-polypyridine-ru-complex-with-a-proton-accepting-ligand
#20
Sergei V Lymar, Mehmed Z Ertem, Anna Lewandowska-Andralojc, Dmitry E Polyansky
Electron-proton transfer (EPT) from phenols to a triplet metal-to-ligand charge transfer (MLCT)-excited Ru polypyridine complex containing an uncoordinated nitrogen site, 1(T), can be described by a kinetic model that accounts for the H-bonding of 1(T) to phenol, 1(T) to solvent, and phenol to solvent. The latter plays a major role in the kinetic solvent effect and commonly precludes simultaneous determination of the EPT rate constant and 1(T)-phenol H-bonding constant. A number of these quantities previously reported for similar systems are shown to be in error due to inconsistent data analysis...
August 15, 2017: Journal of Physical Chemistry Letters
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