The incorporation of small guest molecules or ions by bottom-up hydrothermal synthesis has recently emerged as a promising new way to engineer 1T-phase MoS2 with high hydrogen evolution reaction （HER） activity. Howe...The incorporation of small guest molecules or ions by bottom-up hydrothermal synthesis has recently emerged as a promising new way to engineer 1T-phase MoS2 with high hydrogen evolution reaction （HER） activity. However, the mechanism of the associated structural evolution remains elusive and controversial, leading to a lack of effective routes to prepare 1T-phase MoS2 with controlled structure and morphology, along with high purity and stability. Herein, urea is chosen as precursor of small molecules or ions to simultaneously engineer the phase （16.4%, - 69.4%, and -90.2% of 1T phase） and size （98.8, - 151.6, and - 251.8 nm for the 90.2% 1T phase） of MoS2 nanosheets, which represent an ideal model system for investigating the structural evolution in these materials, as well as developing a new type of 1T-phase MoS2 arrays. Using reaction intermediate monitoring and theoretical calculations, we show that the oriented growth of 1T-phase MoS2 is controlled by ammonia-assisted assembly recrystallization, and stabilization processes. A superior HER performance in acidic media is obtained, with an overpotential of only 76 mV required to achieve a stable current density of 10 mA.cm-2 for 15 h. This excellent performance is attributed to the unique array structure, involving well-dispersed, edge-terminated, and high-purity 1T-phase MoS2 nanosheets.展开更多
Poly（D,L-lactide-co-glycolide）（PLGA） microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres ...Poly（D,L-lactide-co-glycolide）（PLGA） microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell（denoted by hollow in brief） and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin（BSA） was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior.展开更多
文摘The incorporation of small guest molecules or ions by bottom-up hydrothermal synthesis has recently emerged as a promising new way to engineer 1T-phase MoS2 with high hydrogen evolution reaction （HER） activity. However, the mechanism of the associated structural evolution remains elusive and controversial, leading to a lack of effective routes to prepare 1T-phase MoS2 with controlled structure and morphology, along with high purity and stability. Herein, urea is chosen as precursor of small molecules or ions to simultaneously engineer the phase （16.4%, - 69.4%, and -90.2% of 1T phase） and size （98.8, - 151.6, and - 251.8 nm for the 90.2% 1T phase） of MoS2 nanosheets, which represent an ideal model system for investigating the structural evolution in these materials, as well as developing a new type of 1T-phase MoS2 arrays. Using reaction intermediate monitoring and theoretical calculations, we show that the oriented growth of 1T-phase MoS2 is controlled by ammonia-assisted assembly recrystallization, and stabilization processes. A superior HER performance in acidic media is obtained, with an overpotential of only 76 mV required to achieve a stable current density of 10 mA.cm-2 for 15 h. This excellent performance is attributed to the unique array structure, involving well-dispersed, edge-terminated, and high-purity 1T-phase MoS2 nanosheets.
基金financially supported by the National Natural Science Foundation of China(Nos.51003109,51125007 and 51025314)
文摘Poly（D,L-lactide-co-glycolide）（PLGA） microspheres were prepared by emulsion solvent evaporation method. The influences of inner aqueous phase, organic solvent, PLGA concentration on the morphology of microspheres were studied. The results showed that addition of porogen or surfactants to the inner aqueous phase, types of organic solvents and polymer concentration affected greatly the microsphere morphology. When dichloromethane was adopted as organic solvent, microspheres with porous structure were produced. When ethyl acetate served as organic solvent, two different morphologies were obtained. One was hollow microspheres with thin porous shell under a lower PLGA concentration, another was erythrocyte-like microspheres under a higher PLGA concentration. Three types of microspheres including porous, hollow core with thin porous shell（denoted by hollow in brief） and solid structures were finally selected for in vitro drug release tests. Bovine serum albumin（BSA） was chosen as model drug and encapsulated within the microspheres. The BSA encapsulation efficiency of porous, hollow and solid microspheres was respectively 90.4%, 79.8% and 0. And the ultimate accumulative release was respectively 74.5%, 58.9% and 0. The release rate of porous microspheres was much slower than that of hollow microspheres. The experiment results indicated that microspheres with different porous structures showed great potentials in controlling drug release behavior.
