Synthesis and optical properties of ZnS nanoparticles decorated on SiO2 nanospheres

Abstract

Introduction: In this study, ZnS nanoparticles were decorated on SiO2 nanospheres via coprecipitation and the StÓ§ber method.

Methods: The materials were studied by X-ray diffraction (XRD), nano scanning electron microscopy (SEM), and photoluminescence spectra (PL).

Results: ZnS nanoparticles exhibit a sphalerite structure with an average particle size of 2.8 nm and SiO2 in the form of 115 nm nanospheres. The absorption spectrum of these nanoparticles displays a prominent band peaking at 320 nm. Additionally, at 300 K, the PL spectrum of ZnS reveals a broad band, comprising two component bands with peaks at 470 nm and 491 nm, attributed to lattice defects such as zinc and sulfur vacancies, interstitials, and surface states. Upon decorating ZnS nanoparticles on the surface of SiO2 nanospheres, the UV‒Vis absorption and PL spectra of ZnS shift toward longer wavelengths. The maximum peak of the UV‒vis spectrum shifted from 322 to 328 nm, and two bands in the PL spectrum slightly changed to 472 and 494 nm.

Conclusion: The shifts in the UV‒vis and PL spectra are due to alterations in the surface states of the ZnS nanoparticles induced by the presence of SiO2. From the dependence of the PL spectra of ZnS nanopartcles and SiO2-decorated ZnS on the measured temperature from 10 to 300 K, the activation energies of ZnS and SiO2-decorated SiO2 were estimated to be 38 and 40 meV, respectively.