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Journal of Physical Chemistry Letters

G Krishnamurthy Grandhi, Ranjani Viswanatha
The success of heterostructure quantum dots in optoelectronic and photovoltaic applications is based on our understanding of photo-generated charge carrier localization. However, often the actual location of charge carriers in heterostructure semiconductors is quite different from their predicted positions leading to sub-optimal results. In this work, photoluminescence of Cu doped heterostructures have been used to study the charge localization of alloys, inverse type I, type II and quasi type II core/shell structures and graded alloys...
April 21, 2017: Journal of Physical Chemistry Letters
Eva Pluharova, Damien Laage, Pavel Jungwirth
Long-range ordering of water around solutes has been invoked repeatedly in the literature as the key to understanding its biological function. Recently, it has been shown that in a dilute 8 mM aqueous NaCl solution the orientational correlation between water molecules extends beyond 8 nanometers. This was interpreted as arising from a long-range effect induced by the ions on the water collective hydrogen-bond interactions. Within this interpretation, each ion was supposed to affect tens of thousands or more water molecules in its surroundings, invoking a picture of ordered domains extending to several nanometers...
April 21, 2017: Journal of Physical Chemistry Letters
Andrea E Schlather, Alejandro Manjavacas, Adam Lauchner, Valeria Spolon Marangoni, Christopher J DeSantis, Peter Nordlander, Naomi J Halas
There is currently a worldwide need to develop efficient photocatalytic materials that can reduce the high energy cost of common industrial chemical processes. One possible solution focuses on metallic nanoparticles (NPs) that can act as efficient absorbers of light due to their surface plasmon resonance. Recent work indicates that small NPs, when photoexcited, may allow for efficient electron or hole transfer necessary for photocatalysis. Here we investigate the mechanisms behind hot hole carrier dynamics by studying the photo-driven oxidation of citrate ions on Au@SiO2@Au core-shell nanoparticles...
April 20, 2017: Journal of Physical Chemistry Letters
Lena Grimmelsmann, Alireza Marefat Khah, Christian Spies, Christof Hättig, Patrick Nuernberger
Many synthetic DNA minor groove binders exhibit a strong increase in fluorescence when bound to DNA. The pharmaceutical-relevant berenil (diminazene aceturate) is an exception with an extremely low fluorescence quantum yield (on the order of 10(-4)). We investigate the ultrafast excited-state dynamics of this triazene by femtosecond time-resolved fluorescence experiments in water, ethylene glycol, and buffer and bound to the enzyme β-trypsin, the minor groove of AT-rich DNA, and G-quadruplex DNA. Ab initio calculations provide additional mechanistic insight...
April 20, 2017: Journal of Physical Chemistry Letters
Patrick Bonnick, Xiaoqi Sun, Ka-Cheong Lau, Chen Liao, Linda F Nazar
Measurement of Li+ and Mg2+ diffusion in the same Ti2S4 thiospinel material in three electrode cells at elevated temperature negates factors of surface area and cell design, allowing the direct comparison of their diffusion coefficients (D). D values were measured using the Galvanic Intermittent Titration Technique (GITT) as a function of both ion concentration (x) and temperature. During discharge at 55 °C, DLi descends gradually from 2×10-8 cm2/s by an order of magnitude over the range 0 < xLi < 1...
April 20, 2017: Journal of Physical Chemistry Letters
Hirobumi Mineo, Yuichi Fujimura
Control of π-electrons in polycyclic aromatic hydrocarbons (PAHs) is one of the fundamental issues in optoelectronics for ultrafast optical switching devices. We have proposed an effective scenario for design of the generation of coherent ring currents in naphthalene (D2h), which is the smallest unit of planar PAHs. It has been demonstrated by using quantum chemical calculations and quantum optimal control (QOC) simulations that two types of ring currents, parallel and antiparallel ones, can be generated by resonance excitations by two linearly polarized lasers...
April 20, 2017: Journal of Physical Chemistry Letters
Cheng-Min Ji, Zhihua Sun, Aurang Zeb, Sijie Liu, Jing Zhang, Maochun Hong, Junhua Luo
Perovskite hybrids (e.g. CH3NH3PbI3) are holding great promise in photovoltaics and optoelectronics, due to their remarkable semiconducting property and potential ferroelectricity. However, up to date it still lacks conclusive evidence for the bulk ferroelectricity of CH3NH3PbI3. In this context, it is highly desirable to assemble concrete perovskite ferroelectric hybrids with the semiconducting feature. Here we report, for the first time, a class of lead-free perovskite halides, (N-methylpyrrolidinium)3Sb2Cl9-9xBr9x (x = 0-1), showing large ferroelectric polarization (5...
April 20, 2017: Journal of Physical Chemistry Letters
Carter W Abney, Changwoo Do, Huimin Luo, Joshua Wright, Lilin He, Sheng Dai
Recent research has revealed molecular structure beyond the inner coordination sphere is essential in defining the performance of separations processes, but nevertheless remains largely unexplored. Here we apply small angle neutron scattering (SANS) and x-ray absorption fine structure (XAFS) spectroscopy to investigate the structure of an ionic liquid system studied for f-block element separations. SANS data reveal dramatic changes in the ionic liquid microstructure (~150 Å) which we demonstrate can be controlled by judicious selection of counter ion...
April 19, 2017: Journal of Physical Chemistry Letters
Alessandra Magistrato, Jacopo Sgrignani, Rolf Krause, Andrea Cavalli
Cytochromes P450 (CYP450), in particular CYP19A1 and CYP17A1, are key clinical targets of breast and prostate anticancer therapies, critical players in drug metabolism and their overexpression in tumours is associated with drug resistance. In these enzymes ligands (substrates, drugs) metabolism occurs in deeply buried active sites accessible only via several gruelling channels, whose exact biological role remains unclear. Gaining direct insights on the mechanism by which ligands travel in and out, is becoming increasingly important given that channels are involved in the modulation of binding/dissociation kinetics and the specificity of ligands toward a CYP450...
April 19, 2017: Journal of Physical Chemistry Letters
Jin-Wook Lee, Yao-Tsung Hsieh, Nicholas De Marco, Sang-Hoon Bae, Qifeng Han, Yang Yang
Perovskite solar cells have become one of the strongest candidates for the next-generation solar energy technologies. A myriad of beneficial optoelectronic properties of the perovskite materials have enabled superb power conversion efficiencies (PCE) exceeding 22% for a single junction device. The high PCE achievable via low processing costs and relatively high variability in optical properties have opened new possibilities for perovskites in tandem solar cells. In this perspective, we will discuss current research trends in fabricating tandem perovskite-based solar cells in combination with a variety of mature photovoltaic devices such as organic, silicon, and Cu(In,Ga)(S,Se)2 (CIGS) solar cells...
April 19, 2017: Journal of Physical Chemistry Letters
Sharareh Izadnia, David Schönleber, Alexander Eisfeld, Alex Ruf, Aaron C LaForge, Frank Stienkemeier
The energy conversion in solar cells has conventionally been limited by the Shockley-Queisser limit. Singlet fission (SF), a decay mechanism where a single excited singlet state is converted into two triplet states, can drastically improve this efficiency. For the most part, observation of SF has been limited to crystalline structures in solids and films, where strong ordering was present. Here, we report on singlet fission in a disordered system where organic chromophores are distributed on the surface of a rare gas cluster...
April 19, 2017: Journal of Physical Chemistry Letters
Kurt R Brorsen, Yang Yang, Michael V Pak, Sharon Hammes-Schiffer
The development of approximate exchange-correlation functionals is critical for modern density functional theory. A recent analysis of atomic systems suggested that some modern functionals are straying from the path toward the exact functional because electron densities are becoming less accurate while energies are becoming more accurate since the year 2000. To investigate this trend for more chemically relevant systems, the electron densities in the bonding regions and the atomization energies are analyzed for a series of diatomic molecules with 90 different functionals...
April 19, 2017: Journal of Physical Chemistry Letters
Yinan Shu, Kelsey Anne Parker, Donald G Truhlar
Time-dependent Kohn-Sham density functional theory has been used successfully to compute vertical excitation energies, especially for large molecular systems. However, the lack of double excitation character in the excited amplitudes produced by linear response in the adiabatic approximation holds it back from broader applications in photochemistry; for example, it shows (3N-7)-dimensional conical intersection seams (where N is the number of atoms) between ground and excited states, although the correct dimensionality is 3N-8...
April 18, 2017: Journal of Physical Chemistry Letters
Bridget J Milorey, Dmitry Malyshka, Reinhard Schweitzer-Stenner
The conformational changes of ferricytochrome c upon binding to cardiolipin-containing small unilamellar vesicles were studied at slightly acidic pH using fluorescence, visible circular dichroism, UV/visible absorption, and resonance Raman spectroscopy. The obtained spectroscopic response data suggest a mode of interaction, which is clearly distinct from the binding process observed at neutral pH. Evidence for a reversible and electrostatic binding mechanism under these conditions is provided through binding inhibition in the presence of 150 mM NaCl...
April 18, 2017: Journal of Physical Chemistry Letters
Daniel S Levine, Martin Head-Gordon
This work reports an approach to variationally quantify orbital contraction in chemical bonds by an extension of an energy decomposition analysis (EDA). The orbital contraction energy is defined as the energy lowering due to optimization of the isolated fragments (that combine to form the bond) with a specially constructed virtual set of contraction/expansion functions. This set contains one function per occupied orbital, obtained as the linear response to scaling the nuclear charges. EDA results for a variety of single bonds show substantial changes in the importance of orbital contraction; it plays a critical role for bonds to H but only a very minor role in the bonds between heavier elements...
April 18, 2017: Journal of Physical Chemistry Letters
ByungDae Son, IlWon Seong, Jun Kyu Lee, Ju-Hyeon Shin, Heon Lee, Woo Young Yoon
A nanopillar-patterned Si substrate was fabricated by photolithography, and its potential as an anode material for Li ion secondary batteries was investigated. The Si nanopillar electrode showed a capacity of approximately 3000 mAh g-1 during 100 charging/discharging cycles, with 98.3% capacity retention. And it was revealed that the nanopillars underwent delithiation via a process similar to shape-memory behavior. Despite the tensile stress and structural fractures resulting from repeated lithiation, the nanoscale size and residual crystalline tip of the pillar (influenced by the bulk crystalline Si base) enabled recrystallization and transformation into a single crystalline phase...
April 17, 2017: Journal of Physical Chemistry Letters
Hyeon Jeong Lee, Delong Zhang, Ying Jiang, Xiangbing Wu, Pei-Yu Shih, Chien-Sheng Liao, Brittani Bungart, Xiao-Ming Xu, Ryan Drenan, Edward Bartlett, Ji-Xin Cheng
Detecting membrane potentials is critical for understanding how neuronal networks process information. We report a vibrational spectroscopic signature of neuronal membrane potentials identified through hyperspectral stimulated Raman scattering (SRS) imaging of patched primary neurons. High-speed SRS imaging allowed direct visualization of puff-induced depolarization of multiple neurons in mouse brain slices, confirmed by simultaneous calcium imaging. The observed signature, partially dependent on sodium ion influx, is interpreted as ion interactions on the CH3 Fermi resonance peak in proteins...
April 17, 2017: Journal of Physical Chemistry Letters
Haoxue Han, Samy Mérabia, Florian Müller-Plathe
The integration of three-dimensional microelectronics is hampered by overheating issues inherent to state-of-the-art integrated circuits. Fundamental understanding of heat transfer across soft-solid interfaces is important for developing efficient heat dissipation capabilities. At the microscopic scale, the formation of a dense liquid layer at the solid-liquid interface decreases the interfacial heat resistance. We show through molecular dynamics simulations of n-perfluorohexane on a generic wettable surface that enhancement of the liquid structure beyond a single adsorbed layer drastically enhances interfacial heat conductance...
April 17, 2017: Journal of Physical Chemistry Letters
Zhujie Li, Guillaume Jeanmairet, Trinidad Méndez-Morales, Mario Burbano, Matthieu Haefele, Mathieu Salanne
Nanoconfinement generally leads to a drastic effect on the physical and chemical properties of ionic liquids. Here we investigate how the electrochemical reactivity in such media may be impacted inside of nanoporous carbon electrodes. To this end, we study a simple electron transfer reaction using molecular dynamics simulations. The electrodes are held at constant electric potential by allowing the atomic charges on the carbon atoms to fluctuate. We show that the Fe(3+)/Fe(2+) couple dissolved in an ionic liquid exhibits a deviation with respect to Marcus theory...
April 17, 2017: Journal of Physical Chemistry Letters
James L McDonagh, Arnaldo F Silva, Mark A Vincent, Paul L A Popelier
The Interacting Quantum Atoms (IQA) method is used to analyze the correlated part of the Møller-Plesset (MP) perturbation theory two-particle density matrix. Such an analysis determines the effects of electron correlation within atoms and between atoms, which covers both bonds and nonbonded through-space atom-atom interactions within a molecule or molecular complex. Electron correlation lowers the energy of the atoms at either end of a bond, but for the bond itself, it can be stabilizing or destabilizing. Bonds are described in a two-dimensional world of exchange and charge transfer, where covalency is not the opposite of ionicity...
April 17, 2017: Journal of Physical Chemistry Letters
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