Activity

This work will inform the design of new generations of glycosidase inhibitors with restricted side chains that confer higher selectivity and/or affinity.Tackling membrane wetting is an ongoing challenge for large-scale applications of membrane distillation (MD). Herein, composite Janus MD membranes comprising an ultrathin dense hydrophilic layer are developed by layer-by-layer assembling cationic polyethyleneimine and anionic poly(sodium 4-styrenesulfonate) polyelectrolytes on a hydrophobic polyvinylidene fluoride substrate. Using surfactant-containing saline water as the feed with low surface tension, experiments reveal that the number of polyelectrolyte layers, rather than surface wettability or surface charge, determines the anti-wetting performance of the composite Janus membranes. More deposited layers yield higher wetting resistance. With the aid of positron annihilation spectroscopy, this study, for the first time, demonstrates the origin of the excellent wetting resistance of the composite Janus membranes. The effective pore size of the polyelectrolyte multilayer decreases with an increase in the number of the deposited layer. The membrane with an ultrathin hydrophilic multilayer of 48 nm has a sufficiently small pore size to sieve out surfactant molecules from the feed solution via a size exclusion mechanism, thus protecting the hydrophobic substrate from being wetted by the low-surface-tension feed water. This study may pave the way for developing next-generation anti-wetting Janus membranes for robust membrane distillation.The initial behavior of colloidal fouling is governed by foulant-clean-membrane interaction (F-M), and its long-term behavior is determined by foulant-fouled-membrane interaction (F-F). Nevertheless, the transitional fouling behavior from F-M to F-F has not been fully understood. This study reports a novel collision attachment (CA)-Monte Carlo (MC) approach, with the stochastic colloid-membrane collision events modeled by MC and the probability of colloidal attachment to the membrane determined by the interplay of flux and the energy barrier arising from colloid-membrane interaction (Em for F-M and Ef for F-F). The long-term membrane flux remains stable for large Ef, whereas severe fouling occurs when both Em and Ef are small. Our study reveals the existence of a metastable flux behavior for the combination of large Em but small Ef. The time evolution of flux behavior and colloidal deposition patterns shows a nearly constant flux for an extended period, with the high energy barrier Em retarding initial colloidal deposition. However, accidental random deposition of a colloidal particle could reduce the local energy barrier (toward the smaller Ef), seeding for further colloidal deposition in its vicinity. This initiates an uneven patch-wise fouling and eventually leads to a complete transition to F-F-dominated behavior. The metastable period can be effectively extended by increasing the energy barrier (Em or Ef) or lowering flux, which provides important implications to membrane design and operation.Developing an effective strategy to synthesize perfect titanosilicate TS-1 zeolite crystals with desirable morphologies, enriched isolated framework Ti species, and thus enhanced catalytic oxidation properties is a pervasive challenge in zeolite crystal engineering. We here used an amino acid l-carnitine as a crystal growth modifier and ethanol as a cosolvent to regulate the morphologies and the Ti coordination states of TS-1 zeolites. During the hydrothermal crystallization process, the introduced l-carnitine can not only tailor the anisotropic growth rates of zeolite crystals but also induce the formation of uniformly distributed framework Ti species through building a suitable chemical interaction with the Ti precursor species. Condition optimizations could afford the generation of perfect hexagonal plate TS-1 crystals and elongated platelet TS-1 crystals enriched in tetrahedral framework Ti sites (TiO4) or mononuclear octahedrally coordinated Ti species (TiO6). Both samples showed significant improvement in catalytic activity for the H2O2-mediated epoxidation of alkenes. In particular, the elongated platelet TS-1 enriched in “TiO6” species afforded the highest activity in 1-hexene epoxidation, with a turnover frequency (TOF) of up to 131 h-1, which is approximately twice as high as that of the conventional TS-1 zeolite (TOF 65 h-1) and even higher than those of the literature-reported TiO6-containting TS-1 catalysts derived from the hydrothermal post-treatment of TS-1 zeolites. This work demonstrates that the morphologies and the titanium coordination states of TS-1 zeolites can be effectively tuned by directly introducing suitable crystal growth modifiers, thus providing new opportunities for developing highly efficient titanosilicate zeolite catalysts for important catalytic applications.Sluggish conversion reactions severely impair the rate capability for lithium storage, which is the main disadvantage of the conversion-type anode materials. Here, the microplatform based on a single microelectrode is designed and utilized for the fundamental understanding of the conversion reaction. The kinetic-favorable layered structure of the anode material is on-site synthesized in the microplatform. The in situ characterization reveals that introducing an oxygen network distortion in the layered oxide anode effectively circumvents the severe passivation of the electrode material by lithium oxide, thus leading to highly reversible conversion reactions. As a result, the high-rate capability of the conversion-type anode materials is realized. GSK3235025 The on-site synthesis strategy is further applied in the large-scale synthesis of nanomaterials for lithium-ion batteries. As such, oxide nanorods with the layered structure are synthesized by a facile chemical strategy, showing high rate performance (574 mAh g-1 at 10 A g-1). This work unveils the beneficial effect of oxygen network distortion in the layered anode for conversion reactions over cycling, thus providing an alternative strategy to enhance the rate capability of conversion-type anodes for lithium storage.