Energy transfer and luminescence enhancement of Cu²⁺ ions in polyvinyl pyrrolidone caped ZnS:Cu nanoparticles

Abstract

Cu doped ZnS nanoparticles (ZnS:Cu) were synthesized by the co-precipitation method from Zn(CH3COO)2 0,1 M, Cu(CH3COO)2 0,1 M and Na2S 0,1 M solutions. Then they were coated by polyvinyl pyrrolidone (PVP) with different masses from 0.1 to 0.8 g. The photoluminescence excitation (PLE) spectra of 525 nm green photoluminescence (PL) band using xenon lamp shows the 330 nm peak and prominent peaks at 450, 470, 480 nm. The 330 nm peak is attributed by characterizes of nearshore absorption displacement of the ZnS crystal and the 450, 470, 480 nm peaks are involved in the adsorption displacement of Cu2+ (3d9) ions in the ZnS:Cu nanoparticles. The PVP coating hardly changes the crystal structure, the average crystal size, the morphology, the position of PL and PLE peaks that only increase their intensity. This enhancement is due to the transfer of excitation energy from PVP to Cu2+ ions (3d9) through the –C=O–M2+ (M2+: Zn2+, Cu2+) coordination bonds between the O atoms of the C=O group and ions Zn2+, Cu2+ on the surface of the nanoparticles.