Synthesis and characterization of nanosized ZnS confined in ordered mesoporous silica

Nanosized ZnS has been prepared inside MCM-41 hosts by two related schemes, both of which are derived from surface modification methods. The ZnS-containing MCM-41 samples with and without the functional groups (ethylenediamine groups in this case) were designated as ZnS-ED-MCM-41 and ZnS-MCM-41(cal), respectively. The ZnS-MCM-41 composites were characterized by powder X-ray diffraction patterns, transmission electron microscopy, energy disperse spectra, N₂ adsorption-desorption isotherms, UV-vis diffuse reflectance spectra, and photoluminescence (PL) spectra. The ZnS was mainly formed and retained in the channels of the MCM-41 host, and its growth was controlled by the channels. In contrast, the amount of ZnS on the external surface is much smaller. The existence of ZnS inside the MCM-41 hosts resulted in a considerable decrease in surface area, pore diameter, and pore volume, and a massive blue shift in the UV-vis spectra was observed. In comparison with the ZnS-MCM-41(cal) sample, a dramatic increase in PL emission for the ZnS-ED-MCM-41 sample was observed, which was suggested to arise from a strong interaction between the ZnS clusters and the organic component. The nature of the PL spectra has been tentatively attributed to the sulfur vacancies in the present experiment. Finally, the synthesis of other sulfides, such as CdS and CuS clusters, has also been explored inside the channels of the MCM-41 host.