Substituent effect on the π linkers in triphenylamine dyes for sensitized solar cells: a DFT/TDDFT study.

A series of metal-free organic donor-π bridge-acceptor dyes are studied computationally using density functional theory (DFT) and time-dependent DFT (TDDFT) approaches to explore their potential performances in dye-sensitized solar cells (DSSCs). Taking triphenylamine (TPA) and cyanoacrylic acid moieties as donor and acceptor units, respectively, the effects of different substituents of the π linkers in the TPA-based dyes on the energy conversion efficiency of the DSSCs are theoretically evaluated through optimized geometries, charge distributions, electronic structures, simulated absorption spectra, and free energies of injection. The results show that the molecular orbital energy levels and electron-injection driving forces of the TPA dyes can be tuned by the introduction of substituents with different electron-withdrawing or -donating abilities. The electron-withdrawing substituent always lowers the energies of both frontier orbitals, while the electron-donating one heightens them simultaneously. The efficiency trend of these TPA derivatives as sensitizers in DSSCs is also predicted by analyzing the light-harvesting efficiencies and the free energies of injection. The following substituents are shown to increase the efficiency of the dye: OMe, OEt, OHe, and OH.

QSPR studies of impact sensitivity of nitro energetic compounds using three-dimensional descriptors.

The quantitative structure-property relationship (QSPR) studies were performed between molecular structures and impact sensitivity for a diverse set of nitro energetic compounds based on three-dimensional (3D) descriptors. The entire set of 156 compounds was divided into a training set of 127 compounds and a test set of 29 compounds according to Kennard and Stones algorithm. Multiple linear regression (MLR) analysis was employed to select the best subset of descriptors and to build linear models; while nonlinear models were developed by means of artificial neural network (ANN). The obtained models with ten descriptors involved show good predictive power for the test set: a squared correlation coefficient (R²) of 0.7222 and a standard error of estimation (s) of 0.177 were achieved by the MLR model; while by the ANN model, R² and s were 0.8658 and 0.130, respectively. Therefore, the proposed models can be used to predict the impact sensitivity of new nitro compounds for engineering.

The effect of anchoring group number on molecular structures and absorption spectra of triphenylamine sensitizers: a computational study.

The molecular structures and absorption spectra of triphenylamine dyes containing different numbers of anchoring groups (S1-S3) were investigated by density functional theory (DFT) and time-dependent DFT. The calculated geometries indicate that strong conjugation is formed in the dyes. The interfacial charge transfer between the TiO(2) electrode and S1-S3 are electron injection processes from the excited dyes to the semiconductor conduction band. The simulated absorption bands are assigned to π → π* transitions according to the qualitative agreement between the experimental and calculated results. The effect of anchoring group number on the molecular structures, absorption spectra and photovoltaic performance were comparatively discussed.

The biodegradation of zein in vitro and in vivo and its application in implants.

A unique polymer-based sustained-release implant drug delivery system was prepared by using biocompatible and biodegradable Zein as the skeleton material. After preparing Zein colloids, the Zein-loaded implant rods were formulated by injection molding followed by evaporating the solvent, and being coated with poly(lactic-co-glycolic) acid (PLGA) solution. Drug release kinetics was examined by using Fluorouracil (5-FU) as model drug. Nearly zero-order release was achieved for the model drugs for a period of 0-25 days when the implants were incubated in distilled water at 37 °C. And then the degradation kinetics of the rods in vivo and in vitro were evaluated, which indicated that Zein could be absorbed by body and has good degradation property. The effects of different ratios of Zein/5-FU and the rods' diameter on drug release were studied, respectively. The plasma concentration of 5-FU in the implants were determined by HPLC after implanting a single dose of the implants in rats. All data were subsequently processed by using the computer program 3P97, and the values were showed as follows: the area under the plasma concentration-time curve (AUC) value was 321.88 (µg/ml) × day, and the mean residence time (MRT) value was 23.05 days. The sustained-release implants of Zein/5-FU were successfully formulated. The uniqueness of the article is that Zein has been used as a skeleton material in implant delivery system for the first time and zero-order release kinetics has been obtained successfully.