Enhanced luminescence of triethanolamine capped calcium sulfide nanoparticles synthesized using wet chemical method

Semiconductor nanophosphors have smart technological applications in optoelectronic devices and in nanomedicine. Here we report the synthesis of Calcium sulfide nanophosphors by wet chemical method using Triethanolamine (TEOA) as capping agent. The structural characterization of the prepared nanoparticles was done using X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The XRD pattern confirmed the cubic CaS phase with an average grain size of 21 nm of the formed samples. From TEM images, the TEOA capped nanoparticles were found to have a spherical morphology with diameter in the range 5-15 nm. The optical studies of the capped nanoparticles were carried out using Photoluminescence spectroscopy and UV-vis absorption spectroscopy. We obtained a highly intense blue emission on exciting the TEOA capped nanoparticles at 318 nm which was found to be greater than the luminescence intensity of uncapped CaS nanoparticles. The optical band gap of the capped nanoparticles was estimated from the Diffuse Reflectance Spectra and an increase in bandgap was observed which can be explained on the basis of quantum size effect. Thermogravimetric analysis and Fourier Transform Infrared Spectra analysis confirmed the presence of capping agent in the synthesized CaS nanoparticles.