Preparation of polypyrrole/TiO2 nanocomposites with enhanced photocatalytic performance

A simple in situ method was developed to synthesize polypyrrole （PPy）/TiO2 nanocomposites hav- ing high photocatalytic activity under simulated solar light. The structure and morphology of the PPy/TiO2 nanocomposites were characterized by X-ray powder diffraction （XRD）, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy. The visible light photocatalytic properties of the nanocomposites were demonstrated by Rhodamine B degra- dation and by the production of methanol from CO2. The XRD analysis showed that the coating of PPy did not change the crystallinity of the TiO2. The UV-vis diffuse reflectance spectra indicated that the light adsorption range of the TiO2 was enlarged after modification. Energy-dispersive X-ray spectroscopy anal- ysis confirmed the presence of PPy and TiO2 in the nanocomposite catalyst. The RhB degradation using the nanocomposites was increased by 41% and the methanol yield was enhanced by 34 wt% in comparison with those obtained with pure TiO2. The improvements were considered to originate from the increased separation efficiency of hole-electron pairs from TiO2 and the enhancement of the light adsorption range by the introduced PPy.

Tuning the Electrically Conductive Network of Grafted Nanoparticles in Polymer Nanocomposites by the Shear Field

Contolling the formation of the conductive network in the polymer nanocomposites(PNCs)is very meaningful to enhance their electrical property.In this work,we investigated the effect of grafted nanoparticles(NPs)on the conductive probability of PNCs in the quiescent state as well as under the shear field via a coarse grained molecular dynamics simulation.It is found that the smallest percolation threshold is realized at the moderate grafting density,the moderate length of grafted chains or the moderate interaction between grafted chains and free chains.Corresponding to it,the dispersion state of NPs varies from the contact aggregation to the uniform dispersion.By analyzing the connection mode among NPs,the probabilty of NPs which connect three other ones reaches the maximum value at their moderate dispersion state which is responsible for the optimal conductive probability.In addition,the main cluster size is characterized to better understand the conductive network which is consistent with the percolation threshold.It is interesting to find that the percolation threshold is smaller under the shear field than under the quiescent state.The shear field induces more NPs which connect three other ones.This benefits the formation of the new conductive network.Meanwhile,the anisotropy of the conductive probability is reduced with increasing the grafting density.In summary,this work provides a clear picture on how the conductive network of grafted NPs evolves under the shear field.

Green Chemical Engineering

1. Introduction Green chemical engineering is regarded as one of the most effi- cient means of achieving sustainable development in chemical in- dustrial processes. It can be divided into two main categories： Green product engineering. Examples include the develop- ment of new catalysts and the development and use of renewa- ble resources （e.g., solar energy and biomass）.

Understanding the interactions between tris(pentafluoroethyl)-trifluorophosphate-based ionic liquid and small molecules from molecular dynamics simulation

Tris(pentafluoroethyl)trifluorophosphate ([FEP])-based ionic liquids have been widely applied in many fields. For better understanding the properties of [FEP]-based ionic liquids, the interactions between 1-hexyl-3-methylimidazolium ([hmim])[FEP] and small molecules were investigated by molecular dynamics simulations in this work. The small molecules are water, methanol and dimethyl ether. The united-atom (UA) force fields were proposed for methanol and dimethyl ether based on AMBER force field. The densities, enthalpies of vaporization, excess molar properties, and diffusion coefficients of the mixtures were calculated, as well as the microscopic structures characterized by radial distribution functions. Both of the results of the excess energies and microscopic properties show that the strongest interaction is between [hmim][FEP] and dimethyl ether, whereas the interaction between [hmim][FEP] and water is the weakest. Moreover, [hmim][FEP] is more hydrophobic than [hmim] hexafluorophosphate ([PF6]), and the three solutes are mainly distributed around [FEP] anion.

Controllable precipitation of naproxen micro-particles with different morphologies

A simple precipitation method was proposed to prepare naproxen micro-particles with different controllable morphologies, using capillary video microscopy to study the precipitation process. Different particle shapes were obtained including spherical, platelet-like, stick-like, needle-like, and butterfly-like, all in the micro-size range. It was found that the sizes and morphologies of the formed naproxen particles were sensitive to the nature and concentration of the added surfactant, and depended significantly on processing conditions such as temperature, stirring speed, and initial drug concentration. In addition, pre- cipitation with different surfactant types and concentrations would not affect the crystal microstructure of the formed nanroxen oarticles.