Transferability and Nonbond Functional Form of Coarse Grained Force Field – Tested on Linear Alkanes

Whether or not a coarse grained force field (CGFF) can be made to be transferrable is an important question to be addressed. By comparing potential energy with potential of mean force (PMF) of a molecular dimer, we proposed to use a free energy function (FE-12-6) with the parameters in entropic and energetic terms explicitly to represent the nonbond interactions in CGFF. Although the FE-12-6 function cannot accurately describe the PMF curves, a cancelation of short radii and strong repulsion makes the function a good approximation. For nonpolar molecules represented by linear alkanes, FE-12-6 is demonstrated to be highly effective in representing the nonbond interactions in CGFF. The force field parameters are well transferrable among different alkane molecules, in different thermodynamic states and for predicting various thermodynamic properties including heats of vaporization, vapor–liquid-equilibrium coexistence curves, surface tensions, and liquid densities

Plant Uptake-Assisted Round-the-Clock Photocatalysis for Complete Purification of Aquaculture Wastewater Using Sunlight

A novel reactor equipped with solar batteries, Bi₂O₃/TiO₂ film photocatalyst, and celery plant was designed and used for purification of aquaculture wastewater. The Bi₂O₃/TiO₂ film photocatalyst started photocatalytic degradation of organonitrogen compounds under irradiation of sunlight. Meanwhile, the solar batteries absorbed and converted excess sunlight into electric energy and then started UV lamps at night, leading to round-the-clock photocatalysis. Subsequently, the inorganic nitrogen species including NH₄⁺, NO₂^–, and NO₃^– resulting from photocatalytic degradation of the organonitrogen compounds could subsequently be uptaken by the celery plant as the fertilizer to reduce the secondary pollution. It was found that, after 24 h circulation, both organonitrogen compounds and NO₂^– species were completely removed, while NH₄⁺ and NO₃^– contents also decreased by 30% and 50%, respectively. The reactor could be used repetitively, showing a good potential in practical application

Surfactants with Aromatic-Group Tail and Single Quaternary Ammonium Head for Directing Single-Crystalline Mesostructured Zeolite Nanosheets

Single-crystalline mesostructured zeolite nanosheets (SCZN) are synthesized by using designed surfactants with an aromatic group and only single quaternary ammonium head. Both the number of benzene rings and the length of the carbon chain play important roles in the ordered self-assembly of these alternating MFI (mordenite framework inverted) nanosheets. The surfactants, only with two benzene rings and a carbon chain larger than 4, lead to the formation of SCZN because of their highly ordered orientation through π–π stacking; the interlamellar spacing of SCZN could be controlled in the range of 1.7–2.1 nm through variation of the carbon chain length from 6 to 10. A combination of X-ray diffraction patterns and electron microscopy provides visible evidence for the mesostructural transformation from two amorphous aluminosilicate layers to one MFI sheet. The highly ordered orientation of the aromatic groups through π–π stacking geometrically matches the MFI framework to form the crystallographically correlated mesostructure. The low binding energies for the self-assembly of this synthesis system, obtained by molecular mechanics calculations, provide theoretical evidence of the feasibility of our strategy. In addition, this strategy is successfully verified using bolaform cationic surfactants, which also result in the crystallographically ordered MFI nanosheets owning to the similar π–π stacking interactions