First-principles calculations of high-pressure physical properties anisotropy for magnesite.

The first-principles calculations based on density functional theory with projector-augmented wave are used to study the anisotropy of elastic modulus, mechanical hardness, minimum thermal conductivity, acoustic velocity and thermal expansion of magnesite (MgCO3) under deep mantle pressure. The calculation results of the phase transition pressure, equation of state, elastic constants, elastic moduli, elastic wave velocities and thermal expansion coefficient are consistent with those determined experimentally. The research results show that the elastic moduli have strong anisotropy, the mechanical hardness gradually softens with increasing pressure, the conduction velocity of heat in the [100] direction is faster than that in the [001] direction, the plane wave velocity anisotropy first increases and then gradually decreases with increasing pressure, and the shear wave velocity anisotropy increases with the increase of pressure, the thermal expansion in the [100] direction is greater than that in the [001] direction. The research results are of great significance to people's understanding of the high-pressure physical properties of carbonates in the deep mantle.

Two novel self-assemblies of supramolecular solar cells using N-heterocyclic-anchoring porphyrins.

Two novel N-substituted anchoring porphyrins (ZnPAtz and ZnPAim) have been devised and synthesized. Moreover, these two anchoring porphyrins were linked to the TiO2 semiconductor through carboxyl groups and then a zinc porphyrin ZnP was bound to the anchoring porphyrin using a zinc-to-ligand axial coordination approach. The different performances of these assemblies were compared with single anchoring porphyrin devices ZnPAtz and ZnPAim. The photoelectric conversion efficiency of the new supramolecular solar cells sensitized by ZnP-ZnPAx (x=tz, im) has been improved. The ZnP-ZnPAtz-based DSSCs provided the highest photovoltaic efficiency (1.86%). Fundamental studies showed that incorporation of these assemblies promote light-harvesting efficiency.

The electronic structure engineering of organic dye sensitizers for solar cells: The case of JK derivatives.

The design and development of novel dye sensitizers are effective method to improve the performance of dye-sensitized solar cells (DSSCs) because dye sensitizers have significant influence on photo-to-current conversion efficiency. In the procedure of dye sensitizer design, it is very important to understand how to tune their electronic structures and related properties through the substitution of electronic donors, acceptors, and conjugated bridges in dye sensitizers. Here, the electronic structures and excited-state properties of organic JK dye sensitizers are calculated by using density functional theory (DFT) and time dependent DFT methods. Based upon the calculated results, we investigated the role of different electronic donors, acceptors, and π-conjugated bridges in the modification of electronic structures, absorption properties, as well as the free energy variations for electron injection and dye regeneration. In terms of the analysis of transition configurations and molecular orbitals, the effective chromophores which are favorable for electron injection in DSSCs are addressed. Meanwhile, considering the absorption spectra and free energy variation, the promising electronic donors, π-conjugated bridges, and acceptors are presented to design dye sensitizers.

[Evolutionary analysis of neuraminidase gene of A/H7N9 influenza virus].

In 2013, the World Health Organization reported the first case of human infection with a new influenza A (H7N9) virus in China. This has caused damage and panic within certain areas in China. Therefore, analysis of this virus with bioinformatics technology is very necessary. Neuraminidase (NA) is one of the most important antigens of the influenza virus and an important target for anti-flu drugs. In this study, the nucleotide and protein sequences of NA gene of A/H7N9 influenza viruses were retrieved from the NCBI database, and MEGA 5.0 software was employed to construct a phylogenetic tree based on the nucleotide coding sequence; BioEdit software was used to align the nucleotide and protein sequences of NA and calculate the homologies of nucleotides and amino acids and then to analyze the important mutation sites of NA gene. The results demonstrated that the spread of influenza virus H7N9 showed certain geographical and temporal relations. The H7N9 virus isolated from China in 2013 belonged to Euroasiatic serotype, and its NA stalk region hadobvious variation, which may be one of the reasons that this virus infects human. These analyses may be very helpful for understanding the evolutionary relationship and mutation trend of A/H7N9 influenza viruses.

Design and fabrication of a series of metal-mediated assemblies with tetrapyridylporphyrins for supramolecular solar cells.

In this work, a metal-mediated assembling strategy has been used to organize a series of new assemblies based on tetrapyridylporphyrin () on nanostructured TiO2 electrode surfaces, wherein the metal ions (, = Zn(2+), Cd(2+), Hg(2+) and Mn(2+)) bridge the pyridyl units of and (E)-4-[(pyridin-4-ylmethylene)-amino]benzoic acid (), resulting in a assembled mode. The assembled structures were characterized by transmission electron microscopy (TEM), computational calculations, energy-dispersive X-ray spectroscopy (EDX), IR, UV-vis absorption and fluorescence spectra. The performances of the assembly-sensitized solar cells were also measured under an irradiance of 100 mW cm(-2) AM 1.5G sunlight. Photoelectrochemical results reveal a relatively large photocurrent of the device. Simultaneously, a large open-circuit photovoltage and a significantly improved conversion efficiency of the device are also observed. These findings may serve as another good testing ground for the fabrication of supramolecular solar cells in future.

Understanding the electronic structures and absorption properties of porphyrin sensitizers YD2 and YD2-o-C8 for dye-sensitized solar cells.

The electronic structures and excitation properties of dye sensitizers determine the photon-to-current conversion efficiency of dye sensitized solar cells (DSSCs). In order to understand the different performance of porphyrin dye sensitizers YD2 and YD2-o-C8 in DSSC, their geometries and electronic structures have been studied using density functional theory (DFT), and the electronic absorption properties have been investigated via time-dependent DFT (TDDFT) with polarizable continuum model for solvent effects. The geometrical parameters indicate that YD2 and YD2-o-C8 have similar conjugate length and charge transfer (CT) distance. According to the experimental spectra, the HSE06 functional in TDDFT is the most suitable functional for describing the Q and B absorption bands of porphyrins. The transition configurations and molecular orbital analysis suggest that the diarylamino groups are major chromophores for effective CT excitations (ECTE), and therefore act as electron donor in photon-induced electron injection in DSSCs. The analysis of excited states properties and the free energy changes for electron injection support that the better performance of YD2-o-C8 in DSSCs result from the more excited states with ECTE character and the larger absolute value of free energy change for electron injection.

The role of the conjugate bridge in electronic structures and related properties of tetrahydroquinoline for dye sensitized solar cells.

To understand the role of the conjugate bridge in modifying the properties of organic dye sensitizers in solar cells, the computations of the geometries and electronic structures for 10 kinds of tetrahydroquinoline dyes were performed using density functional theory (DFT), and the electronic absorption and fluorescence properties were investigated via time dependent DFT. The population analysis, molecular orbital energies, radiative lifetimes, exciton binding energies (EBE), and light harvesting efficiencies (LHE), as well as the free energy changes of electron injection ( ) and dye regeneration ( ) were also addressed. The correlation of charge populations and experimental open-circuit voltage (Voc) indicates that more charges populated in acceptor groups correspond to larger Voc. The elongating of conjugate bridge by thiophene units generates the larger oscillator strength, higher LHE, larger absolute value of , and longer relative radiative lifetime, but it induces the decreasing of EBE and . So the extending of conjugate bridge with thiopene units in organic dye is an effective way to increase the harvest of solar light, and it is also favorable for electron injection due to their larger . While the inversely correlated relationship between EBE and LHE implies that the dyes with lower EBE produce more efficient light harvesting.

Comparative study on electronic structures and optical properties of indoline and triphenylamine dye sensitizers for solar cells.

The computations of the geometries, electronic structures, dipole moments and polarizabilities for indoline and triphenylamine (TPA) based dye sensitizers, including D102, D131, D149, D205, TPAR1, TPAR2, TPAR4, and TPAR5, were performed using density functional theory, and the electronic absorption properties were investigated via time-dependent density functional theory with polarizable continuum model for solvent effects. The population analysis indicates that the donating electron capability of TPA is better than that of indoline group. The reduction driving forces for the oxidized D131 and TPAR1 are slightly larger than that of other dyes because of their lower highest occupied molecular orbital level. The absorption properties and molecular orbital analysis suggest that the TPA and 4-(2,2diphenylethenyl)phenyl substituent indoline groups are effective chromophores in intramolecular charge transfer (IMCT), and they play an important role in sensitization of dye-sensitized solar cells (DSCs). The better performance of D205 in DSCs results from more IMCT excited states with larger oscillator strength and higher light harvesting efficiency. While for TPA dyes, the longer conjugate bridges generate the larger oscillator strength and light harvesting efficiency, and the TPAR1 and TPAR4 have larger free energy change for electron injection and dye regeneration.

Quantification of hyperconjugative effect on the proton donor X-H bond length changes in the red- and blueshifted hydrogen-bonded complexes.

A whole dataset containing 55 hydrogen bonds were studied at the MP2/aug-cc-pVTZ level of theory. The changes of geometries and stretching vibrational frequencies show that there are 31 redshifted and 24 blueshifted hydrogen-bonded complexes. Natural bond orbital analysis was carried out at the B3LYP/aug-cc-pVTZ level of theory to obtain the electron densities in the bonding and antibonding orbitals of the proton donor X-H bond, which are closely associated with its bond length. Based on their relationship, a generally applicable method considering both the electron densities in the bonding and antibonding orbitals of the proton donor X-H bond has been developed to quantitatively describe the hyperconjugative effect on the X-H bond length changes in these hydrogen-bonded complexes.

Halogen as halogen-bonding donor and hydrogen-bonding acceptor simultaneously in ring-shaped H3N·X(Y)·HF (X = Cl, Br and Y = F, Cl, Br) complexes.

A series of ring-shaped molecular complexes formed by H(3)N, HF and XY (X = Cl, Br and Y = F, Cl, Br) have been investigated at the MP2/aug-cc-pVTZ level of theory. Their optimized geometry, stretching mode, and interaction energy have been obtained. We found that each complex possesses two red-shifted hydrogen bonds and one red-shifted halogen bond, and the two hydrogen bonds exhibit strong cooperative effects on the halogen bond. The cooperativity among the NH(3)···FH, FH···XY and H(3)N···XY interactions leads to the formations of these complexes. The AIM analysis has been performed at the CCSD(T)/aug-cc-pVQZ level of theory to examine the topological characteristics at the bond critical point and at the ring critical point, confirming the coexistence of the two hydrogen bonds and one halogen bond for each complex. The NBO analysis carried out at the B3LYP/aug-cc-pVTZ level of theory demonstrates the effects of hyperconjugation, hybridization, and polarization coming into play during the hydrogen and halogen bonding formations processes, based on which a clockwise loop of charge transfer was discovered. The molecular electrostatic potential has been employed to explore the formation mechanisms of these molecular complexes.