Yangyang Zhan,Zhibin Shao,Tianhao Jiang,Jing Ye,Xiaofeng Wu,Bingchang Zhang,Ke Ding,Di Wu,Jiansheng Jie
Two-dimensional (2D) vertical heterojunctions possess peculiar electronic and optoelectronic properties according to their complementary composition, ultrathin thickness, and unique geometry. However, it is still a challenge to synthesize 2D vertical heterojunctions based on non-layered materials due to strong covalent bonds and abundant surface dangling bonds. Here we developed a partial cation exchange method for the synthesis of 2D vertical Cu2S/CdS heterojunctions. Large-size and single-crystalline CdS nanosheets prepared by a van der Waals epitaxy method served as host lattices for cation exchange reactions. The evolution of the nanosheets in terms of their morphology, composition and crystal structure was elaborately characterized. The as-prepared 2D vertical heterojunctions have two-layer ultra-thin structures and form large-area junctions at their interfaces. Under light irradiation, the photogenerated electron–hole pairs can be quickly separated under the electric field in the junction region, minimizing the possibility of charge recombination. As a result, the device based on 2D vertical Cu2S/CdS heterojunctions exhibits a higher photoelectric conversion capability compared with the device based on single-component 2D CdS or Cu2S Schottky junctions. Our work opens up opportunities to explore 2D vertical heterojunctions based on non-layered materials for high-performance optoelectronic devices.
The strong acidic cationic exchange fiber (SACEF) was used to adsorb yohimbine from alcoholic solution. Batch experiments were performed to examine the effects of adsorbent dosage, solution pH and temperature in the adsorption process. The thermodynamics and kinetics of adsorption were also analyzed. The optimum yohimbine adsorption onto the SACEF was found at pH = 5 of solution and equilibrium could be attained within 20 min. The equilibrium adsorption data were preferably modeled with the Freundlich isotherm model and the thermodynamic parameters were calculated to be: 11.99 kJ/mol < Δ H < 13.72 kJ/mol, −21.17 kJ/mol < Δ G < −17.87 kJ/mol and 63.18 J/mol K < Δ S < 65.60 J/mol K. The results demonstrated that the adsorption was an endothermic, spontaneous and feasible process of physisorption . Meanwhile, yohimbine adsorption on SACEF fitted well to the pseudo-second-order kinetic model and the adsorption rate was limited by film diffusion. The activation energy Ea was calculated to be 14.39 kJ/mol. Furthermore, the surface morphologies of the SACEF before and after yohimbine adsorption were analyzed by SEM and the adsorption mechanism was discussed by FTIR analysis. SACEF could effectively adsorb yohimbine from alcoholic solution and could be used repeatedly for more than five cycles.
危险品化学品经营许可证（带存储）