Red luminescence of spherical CuxZn1−xS semiconductor nanoparticles using 2-mercaptoethanol as capping agent

Cu2+-doped (0–2 at%) ZnS nanoparticles stabilized by 2-mercaptoethanol (2-ME) were successfully prepared using wet precipitation route in aqueous solution. The structural and optical characteristics were studied by various techniques. XRD pattern showed zinc blende cubic structure of Cu2+-doped ZnS with grain size of 4±0.5 nm. Spherical shape and well distribution of particles is confirmed by TEM, SEM and STM microscopy. Copper doping were identified by elemental dispersive (EDS) spectrometry. UV–vis spectroscopy revealed strong confinement effect due to blue shift in absorption shoulder peak as compared to bulk ZnS. Red luminescence band at∼657 nm on Cu2+ doping may be arising from recombination of electrons at sulfur vacancies (Vs) and Cu(t2) states formed at ZnS band gap. Optimum concentration of 0.25 at% (red band) of Cu2+ doping was selected by the observed enhanced PL emission.