Reagents for ZnS Hierarchical and Non-Hierarchical Porous Self-Assembly

Monodispersed highly ordered and homogeneous ZnS microsphere with precisely controlled hierarchical and non-hierarchical surface structure was successfully fabricated in water-ethanol mixed solvent and in water without using any catalysts or templates in a hydrothermal process. The microsphere formation has been facilitated by self-assembly followed by Ostwald ripening process. The products were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDX). The XRD results indicated that the cubic phase ZnS formed in hydrothermal process at various reaction times. Introducing ethanol as a co-solvent with water facilitated hierarchical porous surface structure. The influences of various zinc and sulfur precursors, various alcohols as co-solvent, and solvent ratio on the formation of specific surface structured microsphere was investigated. The water-ethanol (1:1) solvent ratio is the minimum required to facilitate hierarchical porous surface structure. The by-products formed during the hydrothermal process are induced specific surface structure in ZnS microsphere. This is the first report on in situ generated by-products being used as a reagent to facilitate surface structured material fabrication. The formed by-products could be used as recyclable reagents to fabricate hierarchical porous ZnS in three consecutive cycles. A plausible growth mechanism of by-product-induced surface structure in different solvent was discussed. The research results may lay down new vistas for the in situ generated by-product-assisted specific surface structured ZnS fabrication.