Laser—synthesised Ag₂S nanoparticles in liquid: effect of laser fluence on structural and optical properties

In this study, we report for the first time the preparation and characterization of silver sulfide nanoparticles (NPs) by one-step laser ablation of the silver target in thiourea aqueous solution without using a catalyst. The effect of laser fluence on the crystal structure, morphology, size and elemental composition of Ag₂S NPs was investigated. X-ray diffraction (XRD) results show Ag₂S NPs are polycrystalline with monoclinic phase and the variation in laser fluence affects the crystallinity of the synthesized NPs. The optical energy gap decreases from 2.2 eV to 1.6 eV as the laser fluence increases from 2.38 Jcm⁻² to 6.77 Jcm⁻². Transmission electron microscope (TEM) investigation confirms the formation of spherical Ag₂S NPs and nanosheets morphologies and the particle size is found increases from 30 nm to 65 nm when the laser fluence increases from 2.38 Jcm⁻² to 6.77 Jcm⁻². The Raman spectra of Ag₂S NPs show the presence of six active Raman peaks and their intensity increased with laser fluence. (paper)