New pyrazole based single precursor for the surfactantless synthesis of visible light responsive PbS nanocrystals: Synthesis, X-ray crystallography of ligand and photocatalytic activity

Abstract

A pyrazole based heterocyclic compound methyl 3, 5-dimethyl-3-(N′-methylsulfanylthio- carbonyl-hydrazino)-2,3-dihydro-pyrazole-1-carbodithioate (Hmdpc) and [Pb(mdpc)2] have been synthesized and characterized to obtain nanosized visible light responsive PbS nanocrystals (NCs). The presence of four-SCH3 groups in each Pb(II)-center in the SP controls the shape and size of the nanocrystals. A possible growth mechanism based on internal molecular transfer of thiol group for the preparation of spherical nanocrystals has been proposed. The synthesized PbS NCs were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution TEM (HRTEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The optical properties of the nanocrystals reveal the absorption in the entire visible region and can play significant role in showing photocatalytic activity. The PbS nanocrystals show prominent catalytic activity against degradation of Rose Bengal (RB) dyes in aqueous medium in presence of visible light.