Silver nanoparticles decorated two dimensional MoS2 nanosheets for enhanced photocatalytic activity

Abstract

Hybrid nano-structure consisting of silver nanoparticles (Ag NPs) on two dimensional (2D) MoS2 nanosheets (NS), prepared by liquid exfoliation method and ultrasonic mixing, showed solar energy driven enhanced photocatalytic capability on a model organic dye methylene blue (MB), having possible consequence in water purification. The Schottky junction between the Ag NP and MoS2 NS interface induces shift of Fermi level to more negative potential, thereby increasing the life time of the charge carriers even more which leads to formation of sink for photo-excited electrons, and the Ag NPs and ultra-small (US) Ag NPs based Ag-MoS2 samples show quick photocatalytic degradation of MB dye within 30 min (87%) and 8 min (93%), monitored by UV-Vis spectroscopy, with rate constants 64.1 × 10−3 min−1 and 88.6 × 10−3 min−1 respectively. With decreasing size of Ag NPs a wide surface area was covered and quantum confinement occurred which enhanced the electron transfer at the interface. These electrons are relocated to the constitutively existing molecular oxygen to produce numbers of influential oxidative radicals which results in effective degradation of MB. The corresponding photoluminescence spectra show blue shift and quenching with decreasing Ag NP size and lower MoS2 number of layers, determined by Raman spectroscopy with respect to that of original MoS2 nanosheet structures. The corresponding microstructures were determined by transmission electron microscopy (TEM), while the chemical composition was found using X-ray photoelectron spectroscopy (XPS).