OICC Press Journal of Nanostructure in Chemistry 2193-8865 3 1 (December 2013) 2013 04 15 Effect of 2-mercaptoethanol as capping agent on ZnS nanoparticles: structural and optical characterization 10.1186/2193-8865-3-10 EN Abbas Rahdar Department of Physics, Faculty of Science, University of Zabol, Zabol, 98615538, IR Journal Article 2013 04 15 Abstract In this work, we report the effect of a capping agent on the structural and optical properties of nanocrystalline ZnS particles, which have been synthesized by co-precipitation method. The structural properties of ZnS nanoparticles have been characterized by X-ray diffraction (XRD) analysis. The XRD patterns show a hexagonal structure in the nanoparticles. The mean crystallite size calculated from the XRD patterns has been found to be in the range of 1.80 to 2.45 nm with the increase in molar concentration of the capping agent. Absorption spectra have been obtained using a UV-vis spectrophotometer to find the optical direct band gap. We also found that optical band gap ( E g ) increases with the increase in molar concentration of the capping agent. This behavior is related to size quantization effect due to the small size of the particles.