Tuning\nthe Crystallinity and Coverage of SiO₂–ZnIn₂S₄ Core–Shell Nanoparticles\nfor Efficient Hydrogen Generation

Abstract

The coverage, thickness, and crystallinity\nof ZnIn₂S₄ (ZIS) shells on SiO₂ core\nnanoparticles (SiO₂@ZIS) were systematically investigated\nusing microwave-assisted\nsolvothermal methods aided by the addition of acid in ethanolic medium.\nThe surface modification of the SiO₂ cores with (3-mercaptopropyl)­trimethoxysilane\nwas found to be critical to generate a homogeneous coverage of ZnIn₂S₄. The SiO₂@ZIS core–shell nanoparticles\nexhibited the best coverage but poor crystallinity when synthesized\nin pure ethanol, whereas best crystallinity but poor coverage was\nobserved when synthesized in an aqueous solution. The addition of\nselected amounts of acid (HCl) led to improved crystallinity in the\nethanolic medium. The thickness of the ZIS shell could be controlled\nin an ethanolic solution by judiciously varying the amounts of acid\nand the concentration of the ZIS precursor. Increasing the concentration\nof the ZIS precursor to twice the standard concentration in ethanolic\nsolution with the addition of 100 μL of HCl afforded better\ncrystallinity, homogeneous coverage, and optimal photocatalytic hydrogen\nproduction.