Local Structures and Chemical Properties of Deprotonated Arginine

The potential energy surface of gaseous deprotonated arginine has been systematically in- vestigated by first principles calculations. At the B3LYP/6-31G（d） level, apart from the identification of several stable local structures, a new global minimum is located which is about 6.56 k J/tool more stable than what has been reported. The deprotonated arginine molecule has two distinct forms with the deprotonation at the carboxylate group （COO-）. These two forms are bridged by a very high energy barrier and possess very different IR spectral profiles. Our calculated proton dissociation energy and gas-phase acidity of argi- nine molecule are found to be in good agreement with the corresponding experimental results. The predicted geometries, dipole moments, rotational constants, vertical ionization energies and IR spectra of low energy conformers will be useful for future experimental measurements.

Tuning the O–O bond formation pathways of molecular water oxidation catalysts on electrode surfaces via second coordination sphere engineering

A molecular [Ru(bda)]-type(bda = 2,2’-bipyridine-6,6’-dicarboxylate) water oxidation catalyst with 4-vinylpyridine as the axial ligand(Complex 1) was immobilized or co-immobilized with 1-(trifluoromethyl)-4-vinylbenzene(3 F) or styrene(St) blocking units on the surface of glassy carbon(GC) electrodes by electrochemical polymerization, in order to prepare the corresponding poly-1@GC, poly-1+P3 F@GC, and poly-1+PSt@GC functional electrodes. Kinetic measurements of the electrode surface reaction revealed that [Ru(bda)] triggers the O–O bond formation via(1) the radical coupling interaction between the two metallo-oxyl radicals(I2 M) in the homo-coupling polymer(poly-1), and(2) the water nucleophilic attack(WNA) pathway in poly-1+P3 F and poly-1+PSt copolymers. The comparison of the three electrodes revealed that the second coordination sphere of the water oxidation catalysts plays vital roles in stabilizing their reaction intermediates, tuning the O–O bond formation pathways and improving the water oxidation reaction kinetics without changing the first coordination structures.

A novel water layer structure inside nanobubbles at room temperature

Molecularly thin water layer, with a hydrogen bonding network different from those in bulk water and ice, has unique properties and is generally involved in many important processes such as wetting, erosion, atmosphere chemical reaction, protein folding and biomolecular interaction. Here, we report a new water layer structure at room temperature, which is found inside nanobubbles by using synchrotron based scanning transmission soft X-ray microscopy(STXM). The three peaks 535.0, 536.8 and 540.9 e V at O K edge inside the nanobubbles show a novel characteristics of very thin water layers, which has never been observed before.

Isolation and Identification of Pseudo Seven-Coordinate Ru(Ⅲ)Intermediate Completing the Catalytic Cycle of Ru-bda Type of Water Oxidation Catalysts

Isolation of RuⅢ-bda(17-electron specie)complex with an aqua ligand(2-electron donor)is challenging due to violation of the 18-electron rule.Although considerable efforts have been dedicated to mechanistic studies of water oxidation by the Ru-bda family,the structure and initial formation of the Ru^(Ⅲ)-bda aqua complex are still controversial.Herein,we challenge this often overlooked step by designing a pocketshape Ru-based complex 1.The computational studies showed that 1 possesses the crucial hydrophobicity at the Ru^(V)(O)state as well as similar probability of access of terminal O to solvent water molecules when compared with classic Ru-bda catalysts.Through characterization of single-crystal structures at the Ru^(Ⅱ) and Ru^(Ⅲ) states,a pseudo seven-coordinate“ready-togo”aqua ligand with Ru^(Ⅲ)…O distance of 3.62A was observed.This aqua ligand was also found to be part of a formed hydrogen-bonding network,providing a good indication of how the Ru^(Ⅲ)-OH_(2)complex is formed.

Modulation of photovoltaic behavior of dye-sensitized solar cells by electron donors of porphyrin dyes and cosensitization

Porphyrin dyes have received great attention due to their excellent photovoltaic performance in dye- sensitized solar cells （DSSCs）. In this work, dyes XCI-XC3 were synthesized by introducing various numbers of bis（4-methoxyphenyl）amino and p-hexyloxyphenyl groups to porphyrin meso-positions. The XC1 molecule contains two p-hexyloxyphenyl groups, and its DSSCs showed the power conversion efficiency of 4.81%. For XC2 and XC3, the replacement of p-hexyloxyphenyl with diphenylamino groups can effectively enhance the light harvesting around 500 nm. However, the highest occupied molecular orbitals （HOMOs） were elevated too much, which suppressed the dye regeneration processes, leading to low cell efficiencies of 2.51% and 1.27% for XC2, and XC3, respectively. To further improve the cell performance, an anthracene derivative Cl was used as the cosensitizer for XCl, which increased both the Jsc and Voc values, with an improved efficiency of 5.75：g.

More Stable, More Estrogenic: The SERM-ERα LBD Complex

Many synthetic selective estrogen receptor modulators (SERMs) have been cocrystallized with the human estrogen receptor α ligand binding domain (ERα LBD). Despite stabilizing the same canonical inactive conformation of the LBD, most SERMs display different ligand-dependent pharmacological profiles. We show here that increased partial agonism of SERMs is associated with increased conformational stability of the SERM-LBD complexes, by investigation of dihydrobenzoxathiin-based SERMs using molecular modelling techniques. Analyses of tamoxifen (TAM) and 4-hydroxytamoxifen (OHT) in complex with the LBD furthermore indicates that the conversion of TAM to OHT increases both the affinity to ERα and the partial agonism of the anti-cancer drug, which provides a plausible explanation of the counterintuitive results of TAM therapy.

by a cascade optical field modulation strategy facilitating selective multispectral narrow-band near-infrared photodetection

Since selective detection of multiple narrow spectral bands in the near-infrared(NIR)region still poses a fundamental challenge,we have,in this work,developed NIR photodetectors(PDs)using photon upconversion nanocrystals(UCNCs)combined with perovskite films.To conquer the relatively high pumping threshold of UCNCs,we designed a novel cascade optical field modulation strategy to boost upconversion luminescence(UCL)by cascading the superlensing effect of dielectric microlens arrays and the plasmonic effect of gold nanorods,which readily leads to a UCL enhancement by more than four orders of magnitude under weak light irradiation.By accommodating multiple optically active lanthanide ions in a core-shell-shell hierarchical architecture,developed PDs on top of this structure can detect three well-separated narrow bands in the NIR region,i.e.,those centered at 808,980,and 1540 nm.Due to the large UCL enhancement,the obtained PDs demonstrate extremely high responsivities of 30.73,23.15,and 12.20 AW^(−1) and detectivities of 5.36,3.45,and 1.91×10^(11) Jones for 808,980,and 1540 nm light detection,respectively,together with short response times in the range of 80-120 ms.Moreover,we demonstrate for the first time that the response to the excitation modulation frequency of a PD can be employed to discriminate the incident light wavelength.We believe that our work provides novel insight for developing NIR PDs and that it can spur the development of other applications using upconversion nanotechnology.

Switching the O-O Bond Formation Pathways of Ru-pda Water Oxidation Catalyst by Third Coordination Sphere Engineering

Water oxidation is a vital anodic reaction for renewable fuel generation via electrochemical-and photoelectrochemical-driven water splitting or CO_(2)reduction.Ruthenium complexes,such as Ru-bda family,have been shown as highly efficient wateroxidation catalysts(WOCs),particularly when they undergo a bimolecular O-O bond formation pathway.In this study,a novel Ru(pda)-type(pda^(2–)=1,10-phenanthroline-2,9-dicarboxylate)molecular WOC with 4-vinylpyridine axial ligands was immobilized on the glassy carbon electrode surface by electrochemical polymerization.Electrochemical kinetic studies revealed that this homocoupling polymer catalyzes water oxidation through a bimolecular radical coupling pathway,where interaction between two Ru(pda)–oxyl moieties(I2M)forms the O-O bond.The calculated barrier of the I2M pathway by densityfunctional theory(DFT)is significantly lower than the barrier of a water nucleophilic attack(WNA)pathway.By using this polymerization strategy,the Ru centers are brought closer in the distance,and the O-O bond formation pathway by the Ru(pda)catalyst is switched from WNA in a homogeneous molecular catalytic system to I2M in the polymerized film,providing some deep insights into the importance of third coordination sphere engineering of the water oxidation catalyst.

软X射线光谱的第一性原理模拟(英文)

软X射线光谱是通过核激发或去激发以探测分子、表面及各种化合物的电子结构和化学结构的有效的测量技术。本文对基于密度泛函理论描述X射线吸收、发射的各种不同过程的计算方法进行了综述。重点讨论了各种方法的基本原理、实际操作和具体应用。提供了K边X射线光电子能谱、吸收和发射光谱详细的模拟细节以及一些代表性体系的算例(包括分子、富勒烯、碳纳米管、单层石墨和DNA链)。

Novel Organic Dyes Based on Bulky Tri（triphenylamine）-Substituted Styrene for Dye-Sensitized Solar Cells

Three novel donor-n-acceptor （D-π-A） metal-free organic dyes （TB, TS and TF） based on tri（triphenylamine）- substituted styrene as donor with various conjugated linkers （benzene, thiophene and furan） were synthesized, characterized and used for the application of dye-sensitized solar cells （DSSCs）. Under the same condition, The photo-to-electrical conversion efficiency of the DSSCs sensitized with TB, TS and TF reach 1.84%, 4.10% and 4.52%, respectively, which are lower than that sensitized with RI （5.02%） with one triphenylamine unit. The results suggest that these bulky donor-based sensitizers are unfavorable to DSSCs.