The ZnCr2O4 nanoparticles were synthesized and characterized by different techniques such as; XRD, SEM, EDS, VSM, TEM and IR. In order to modify the morphology of structures, various alkaline and capping agents were used. For this work TETA, en and NH3 as alkaline agents and salicylaldehyde, N,N'-(bis (salicylidene)-ethylene-1,2-diamine) and SDS as capping agents were employed. The cubic morphology for the ZnCr2O4 nanoparticles were obtained by using TETA and N,N'-(bis(salicylidene)-ethylene-1,2-dia mine). When SDS and TETA were used, very uniform spherical zinc chromite nanoparticles with fine grain size were produced. Then on the surface of these nanoparticles, Ag nanoparticles were covered by photodeposition method. For investigation photocatalytic activity of the nanoparticles, several factors such as various azo dyes, temperature, grain size and morphology were investigated. Also by using of ZnCr2O4/Ag nanoparticles prepared polymer based nanocomposite. Results indicate that, nanoparticles can enhance the thermal stability of the PVA matrix. (C) 2017 Elsevier Inc. All rights reserved.