Synthesis and luminescence studies of CdSrS nanostructures

Cadmium strontium sulfide nanostructures were synthesized by solid state diffusion method in the presence of sodium thiosulfate. XRD confirmed the presence of CdS and SrS structures in the synthesized samples. TEM micrographs revealed the formation of nearly spherical nanoparticles with grain size in the range 30–40 nm. The PL emission was centred around 532 nm with a shoulder at 468 nm. The PL emission of CdSrS shows a blue shift in comparison to that of CdS. Substantially enhanced photoluminescence emission was observed with the addition of Bi3+ as a dopant. The effects of different excitation wavelengths on the PL spectra have also been investigated. It is suggested that the emission processes are linked to divalent Cd ions with broadening resulting due to these ions in being differing ion environments.

Research highlights▶ More recent researches in the field of CdS and ZnS have revealed that major luminescence effects are associated with the incorporation of activators or alloying. For example, doping with foreign atoms can introduce characteristic luminescence peaks in photoluminescence spectra of nanocrystals and reduce lasing threshold of semiconductor nanocrystals. Particular interest has been invoked in alloyed systems such as Ca1−xCdxS where Lehmann [18], Ray et al. [19] and Barrett et al. [20] have observed immensely enhanced luminescence emission both in terms of intensity and spectral distribution. ▶ Recently, we have reported the luminescence of undoped and Bi doped CdS [21] and SrS:Bi [22] and [23] nanostructures. The SrS compounds crystallize only in the rock salt structure which is incompatible with the zincblende or wurtzite structure in which IIB–VIB compounds crystallize [24]. The resulting IIB–IIA–VIB compound is generally thought to form an immiscible system, hence the investigation for these compounds is very limited and therefore many fundamental aspects in optoelectronic properties of these compounds are not yet unveiled. Systematic luminescence studies of CdSrS (group IIB–IIA–VIB) nanostructures have been reported in this paper. The solid state diffusion method has been used for the synthesis of CdSrS nanostructures in the presence of sodium thiosulfate. The advantage of this method is that synthesis can be done on a large scale with a little chance of undesired impurities. The effect of excitation wavelengths and Bi doping on PL intensity has also been investigated. To the best of our knowledge, the effect of Bi doping on PL intensity has been investigated for the first time in CdSrS nanophosphors. These products have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy.