Synthesis And Characterization Of Zinc Sulfide In The Mesoporous Of MCM-41 Silicates

As a wide-band gap semiconductor, ZnS particles have been found applications in thin-film electroluminescent devices, light-emitting diode, IR windows materials and photocatalysis. Nanosized materials are of importance due to its novel properties which differ from its bulk. It is well accepted that the stability of nanoscale materials is a key factor which determines their applications. Nanoscale materials often exhibit high chemical reactivity. The high chemical reactivity often results in dramatic changes in their structures and properties, which limits their applications. In order to lower the chemical reactivity of ZnS, some researchers prepared the nanomaterials in porous materials or the other inert film. With the protection of porous materials or the inert film, the nanocrystals were not easy to aggregation. In recent years, many studies indicate that the mesoporous MCM-41 is one of the best host materials, due to its regular hexagonal arrays of uniform pore opening.In order to enhance the stability of the nano-sized materials, the present work describes the preparation of binary semiconductor ZnS nanocrystals in the channels of mesoporous MCM-41 using solvothermal method, microwave method and pore value impregnation. The nano-sized materials prepared by the three methods were characterized by XRD, UV-Vis, N₂ adsorption-desorption isotherms and TEM et al. It is shown that the nano zinc sulfide crystals are about 1.6-2.0 nm. The existence of ZnS inside the host results in the decrease of surface area, pore diameter and pore volume. And a blue shift(28⁴5nm) in UV-Vis absorption spectra is observed. It shows that the solvothermal method is an effective route to assemble zinc sulfide into the mesoporous channels of MCM-41. The diameter of zinc sulfide synthesized by solvothermal method is smaller and the hexagonal order of the host material is maintained during the assembly process. In addition, the synthesis conditions of the solvothermal method are investigated. The results show that the ZnS/MCM-41 materials assembled by solvothermal method can be achieved in a wide range of conditions. And the best conditions are as follows:(1) Sulfidation conditions: H2S flow rate 80 ml/min, temperature 120℃, time 2h.(2) The conditions of synthesizing ZnO/MCM-41: Zn(CH₃COO)₂ concentration 0.03M, crystalization temperature 70℃, crytalization time 2 h, ethanol as the solvent.