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Journal of Physical Chemistry Letters

Samantha N Hood, Ivan Kassal
Although organic heterojunctions can separate charges with near-unity efficiency and on a sub-picosecond timescale, the full details of the charge-separation process remain unclear. In typical models, the Coulomb binding between the electron and the hole can exceed the thermal energy kT by an order of magnitude, suggesting that it is impossible for the charges to separate before recombining. Here, we consider the entropic contribution to charge separation in the presence of disorder and find that even modest amounts of disorder have a decisive effect, reducing the charge-separation barrier to about kT or eliminating it altogether...
October 26, 2016: Journal of Physical Chemistry Letters
Anna L Gould, Kevin Rossi, C Richard A Catlow, Francesca Baletto, Andrew J Logsdail
We present a study of the transitional pathways between high-symmetry structural motifs for AgAu nanoparticles, with a specific focus on controlling the energetic barriers through chemical design. We show that the barriers can be altered by careful control of the elemental composition and chemical arrangement, with core@shell and vertex-decorated arrangements being specifically influential on the barrier heights. We also highlight the complexity of the potential and free energy landscapes for systems where there are low-symmetry geometric motifs that are energetically competitive to the high-symmetry arrangements...
October 26, 2016: Journal of Physical Chemistry Letters
Ryan Jacobs, Bing Zheng, Brian Puchala, Paul M Voyles, Andrew B Yankovich, Dane Morgan
Understanding the structure of ZnO surface reconstructions and their resultant properties is crucial to the rational design of ZnO-containing devices ranging from optoelectronics to catalysts. Here, we are motivated by recent experimental work which showed a new surface reconstruction containing Zn vacancies ordered in a Zn(3×3) pattern in the subsurface of (0001)-O terminated ZnO. A reconstruction with Zn vacancies on (0001)-O is surprising and counterintuitive because Zn vacancies enhance the surface dipole rather than reduce it...
October 25, 2016: Journal of Physical Chemistry Letters
Benjamin Paul Wiebenga-Sanford, Joseph A DiVerdi, Christopher D Rithner, Nancy E Levinger
Glucose nanoconfined by solubilization in water-containing AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles has been investigated using (1)H NMR. NMR spectra reveal well-defined signals for the glucose hydroxyl groups that suggest slow chemical exchange between them and the water hydroxyl group. Using the EXSY (ZZ-exchange) method, the chemical exchange rate from water to glucose hydroxyl groups was measured for glucose in reverse micelles with size parameter w0=5, 10 and 20, at 25˚ C. The chemical exchange rates observed in the nanoconfined interior are dramatically slower (5-20 times) than observed for glucose in bulk aqueous solution at the same concentration as the micelle interior...
October 25, 2016: Journal of Physical Chemistry Letters
Scott T Akin, Vicente Zamudio-Bayer, Kaining Duanmu, Georg Leistner, Konstantin Hirsch, Christine Buelow, Arkadiusz Lawicki, Akira Terasaki, Bernd von Issendorff, Donald G Truhlar, J Tobias Lau, Michael A Duncan
Cobalt-benzene cluster ions of the form Co3(bz)n+ (n = 0-3) were produced in the gas-phase, mass-selected, and cooled in a cryogenic ion trap held at 34 K. To explore ligand effects on cluster magnetic moments, these species were investigated with X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) spectroscopy. XMCD spectra yield both the spin and orbital angular momenta of these clusters. Co3+ has a spin magnetic moment of S = 6 µB and an orbital magnetic moment of L = 3 µB...
October 25, 2016: Journal of Physical Chemistry Letters
Qiangmin Yu, Chuxin Wu, Lunhui Guan
We report an efficient method for enriching high-purity metallic single-walled carbon nanotubes (m-SWCNTs) by using NO2 as oxidant to remove semiconducting components at 220°C. After etching, the m-SWCNTs with purity higher than 90% were obtained. The surviving m-SWCNTs remain intact structure, without any extra defects on their surface.
October 25, 2016: Journal of Physical Chemistry Letters
Thomas Schmidt, Alan J Situ, Tobias S Ulmer
The solvation of membrane proteins by both lipids and water makes their membrane immersion difficult to predict and the choice of a membrane mimic challenging. To characterize protein-lipid contacts and bicelle membrane mimics, we examined protein-lipid cross-relaxation of integrin αIIb and β3(A711P) transmembrane helices in isotropic phospholipid bicelles (q=0.5 and 0.7). Long-chain bicelle lipids dominated contacts with central helix segments, whereas both short- and long-chain lipids contacted the terminal turns of each helix in corroboration of the mixed bicelle model...
October 24, 2016: Journal of Physical Chemistry Letters
Feng Peng, Jorge Botana, Yanchao Wang, Yanming Ma, Mao-Sheng Miao
Xenon difluoride is the first and the most stable of hundreds of noble-gas (Ng) compounds. These compounds reveal the rich chemistry of Ngs. No stable compound that contains a Ng-Ng bond has been reported previously. Recent experiments have shown intriguing behaviors of this exemplar compound under high pressure, including increased coordination numbers and an insulator-to-metal transition. None of the be-haviors can be explained by electronic-structure calculations with fixed stoichiometry. We therefore con-ducted a structure search of xenon-fluorine compounds with various stoichiometries, and studied their stabili-ties under pressure using first principles calculations...
October 24, 2016: Journal of Physical Chemistry Letters
Adrian N Beyer, Jeremy O Richardson, Peter J Knowles, Judith Rommel, Stuart C Althorpe
The instanton method obtains approximate tunneling rates from the minimum-action path (known as the instanton) linking reactants to the products at a given temperature. An efficient way to find the instanton is to search for saddle-points on the ring-polymer potential surface, which is obtained by expressing the quantum Boltzmann operator as a discrete path-integral. Here we report a practical implementation of this ring-polymer form of instanton theory into the Molpro electronic-structure package, which allows the rates to be computed on-the-fly, without the need for a fitted analytic potential-energy surface...
October 24, 2016: Journal of Physical Chemistry Letters
Hyun Jin Yang, Michael Trenary, Maki Kawai, Yousoo Kim
In contrast to conventional spectroscopic studies of adsorbates at high coverage that provide only spatially averaged information, we have characterized the laterally confined shuttling dynamics of a single molecule under the influence of intermolecular interactions by vibrational spectroscopy using a scanning tunneling microscope. The bridge sites on Pt(111) are only occupied by a CO molecule that is surrounded by four other CO molecules at on-top sites. The bridge-site CO undergoes laterally confined shuttling toward an adjacent on-top site to transiently occupy a metastable site, which is slightly displaced from the center of an on-top site through repulsive interaction with adjacent on-top CO molecules...
October 24, 2016: Journal of Physical Chemistry Letters
Chao Wang, Chongyang Zhao, Lianrui Hu, Hui Chen
Cyanobacterial aldehyde-deformylating oxygenase (cADO) is a nonheme diiron enzyme that catalyzes the conversion of aldehyde to alk(a/e)ne, an important transformation in biofuel research. In this work, we report a highly desired computational study for probing the mechanism of cADO. By combining our QM/MM results with the available (57)Fe Mössbauer spectroscopic data, the gained detailed struc-tural information suggests construction of asymmetry from the symmetric diiron cofactor in aldehyde substrate and O2 activation...
October 24, 2016: Journal of Physical Chemistry Letters
Pan-Pan Zhang, Alexander Eisfeld
Two-dimensional electronic spectroscopy has become an important experimental technique to obtain information on, e.g., electronic coherences in large molecular complexes or vibronic couplings. For the correct interpretation of two-dimensional spectra, however, detailed theoretical calculations are required. Reliable theoretical calculations are impeded by large system sizes and number of vibrational degrees of freedom that need to be explicitly taken into account. Here we demonstrate that a numerical approach based on a stochastic hierarchy of pure states (HOPS) does allow to calculate two-dimensional spectra, notwithstanding the stochasticity of our method...
October 24, 2016: Journal of Physical Chemistry Letters
He Huang, Hong Lin, Stephen V Kershaw, Andrei S Susha, Wallace C H Choy, Andrey L Rogach
Beneficial role of an insulating material polyhedral oligomeric silsesquioxane (POSS) as a solution additive or an additional hole blocking layer to enhance the performance of electroluminescent green light emitting devices (LEDs) based on CsPbBr3 perovskite nanocrystals is demonstrated. POSS improves the surface coverage and the morphological features of the films deposited either from supernatant or suspension of perovskite nanocrystals. The external quantum efficiency and the luminance efficiency of LEDs with an additional POSS layer reach 0...
October 24, 2016: Journal of Physical Chemistry Letters
Hoon Taek Chung, Ulises Martinez, Ivana Matanovic, Yu Seung Kim
Rotating disk electrode voltammograms and infrared reflection absorption spectra indicate that the hydrogen oxidation reaction of platinum in 0.1 M tetramethylammonium hydroxide solution is adversely impacted by time-dependent and potential-driven cation-hydroxide-water co-adsorption. Impedance analysis suggests that the HOR inhibition is mainly caused by the hydrogen diffusion barrier of the co-adsorbed tri-layer rather than intuitive catalyst site blocking by the adsorbed cation species. These results give useful insights on how to design ionomeric binders and hydrogen oxidation electrocatalysts for advanced alkaline membrane fuel cells...
October 24, 2016: Journal of Physical Chemistry Letters
Jesús Ignacio Mendieta-Moreno, Daniel G Trabada, Jesus Mendieta, James P Lewis, Paulino Gómez-Puertas, Jose Ortega
The absorption of ultraviolet radiation by DNA may result in harmful genetic lesions that affect DNA replication and transcription, ultimately causing mutations, cancer and/or cell death. We analyze the most abundant photochemical reaction in DNA, the cyclobutane thymine dimer, using hybrid quantum mechanics / molecular mechanics (QM/MM) techniques and QM/MM nonadiabatic molecular dynamics. We find that, due to its double helix structure, DNA presents a free energy barrier between non-reactive and reactive conformations leading to the photolesion...
October 21, 2016: Journal of Physical Chemistry Letters
Koichiro Saito, Ichiro Tanabe, Tetsu Tatsuma
Plasmon-induced charge separation (PICS) at the interface between a plasmonic nanoparticle and semiconductor is now widely used for photovoltaics and photocatalysis. Here we take advantage of PICS for site-selective nanoetching of silver nanocubes on TiO2 beyond the diffraction limit. A silver nanocube exhibits two resonance modes localized at the top and bottom of the nanocube (distal and proximal modes, respectively) when it is placed on TiO2. We achieved selective etching at the top and the bottom of the nanocubes by PICS based on the distal and proximal modes, respectively...
October 21, 2016: Journal of Physical Chemistry Letters
Sarah I Allec, Bryan M Wong
Contrary to recent reports, we show that the electronic properties of phosphorene nanotubes are surprisingly rich and much more complex than previously assumed. We find that all phosphorene nanotubes exhibit an intricate direct-to-indirect band gap transition as the nanotube diameter decreases, a unique property not identified in any prior studies (which claimed either direct or indirect band gaps only) that we uncover with large-scale DFT calculations. We address these previous inconsistencies by detailed analyses of orbital interactions, which reveal that the strain associated with decreasing the nanotube diameter causes a transition from a direct to an indirect band gap for all of the phosphorene nanotubes...
October 21, 2016: Journal of Physical Chemistry Letters
Jingyi Zhu, Tilo Mathes, Yusaku Hontani, Maxime T A Alexandre, Kee Chua Toh, Peter Hegemann, John T M Kennis
The two Light, Oxygen, and Voltage domains of phototropin are blue-light photoreceptor domains which control various functions in plants and green algae. The key step of the light-driven reaction is the formation of a photoadduct between its FMN chromophore and a conserved cysteine, where the canonical reaction proceeds through the FMN triplet state. Here, complete photoreaction mapping of CrLOV2 from Chlamydomonas reinhardtii phototropin and AsLOV2 from Avena sativa phototropin-1 was realized by ultrafast broadband spectroscopy from femtoseconds to microseconds...
October 21, 2016: Journal of Physical Chemistry Letters
Aram Hong, Heeseon Jang, Changseop Jeong, Myoung Choul Choi, Jiyoung Heo, Nam Joon Kim
We obtained resonant two-photon ionization circular dichroism (R2PICD) spectra of jet-cooled phenylalanine (Phe) and its hydrated clusters (Phe(H2O)n, n=1-2) near the origin band of the S0-S1 transition. The R2PICD spectra of Phe exhibit well-resolved CD bands of six different conformers present in the jet, which vary in sign and magnitude depending on their conformations. We revised the previous structural assignments of the Phe conformers based on the comparison between the experimental and theoretical CD signs, infrared spectra, and rotational band contours...
October 21, 2016: Journal of Physical Chemistry Letters
Shaltiel Eloul, Richard G Compton
The diffusion of a particle from bulk solution is slowed as it moves close to an adsorbing surface. A general model is reported which is easily applied by theoreticians and experimentalists. Specifically, it is shown here that in general and regardless of the space size, the magnitude of the effect of hindered diffusion on the flux is a property of the diffusion layer thickness. We quantify and explain the effect. Predictions of concentration profiles show that a 'hindered diffusion layer' is formed near the adsorbing surface within the diffusion layer, observed even when the particle radius is just a 0...
October 19, 2016: Journal of Physical Chemistry Letters
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