Zn0.97-xCuxCr0.03S (x=0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) nanoparticles were synthesized by chemical co-precipitation method for the first time. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive analysis of X-rays (EDAX). Diffuse reflectance spectra (DRS) and photoluminescence spectra (PL). EDAX spectra confirmed the presence of Cr and Cu in the samples with expected stoichiometry. XRD patterns showed that dopant atoms of Cr and Cu were incorporated at the Zn sites in the cubic structure without disturbing the original ZnS cubic structure. However, at a concentration of 5 at.% the planes corresponding to Cu were observed. This shows the immiscibility of Cu in ZnS for a concentration of 5 at.%. Reflectance of Cu co-doped samples decreased with increase in Cu concentration. Photoluminescence for pure ZnS was observed in the blue region. 1 at.% Cu doping in ZnS:Cr resulted in a significant enhancement of PL intensity. Higher dopant concentrations resulted in a strong quenching of PL intensity. PL emission peak showed a red shift with increase in Cu content. FTIR studies revealed that the nanoparticles were sterically stabilized by EDTA. Magnetization studies indicated that Cu co-doping enhanced significantly the room temperature ferromagnetism of the samples. (c) 2012 Elsevier B.V. All rights reserved.