Cerium doped strontium sulfide nanostructures were synthesized by the solid state diffusion method in the presence of sodium thiosulfate. XRD confirmed the single phase rocksalt structure of the synthesized samples and the average grain size using the Debye–Scherrer relation is calculated to be 55 nm. TEM micrographs reveal the agglomerated whisker-like morphology with a diametre of 55–60 nm and length of several nanometres, which is in close agreement with XRD results. The effect of dopant concentration on photoluminescence (PL) intensity has been studied. PL emission for SrS : Ce (0.5 mol%) is at 481 nm with a shoulder at 530 nm at an excitation wavelength of 430 nm, which is attributed to the transitions from the 5d state to the 4f (2f7/2, 2f5/2) states of Ce3+. Ultraviolet and visible (UV–VIS) spectroscopy shows band-to-band absorption at 273 nm (4.54 eV), which is blue shifted in comparison to the band gap of bulk SrS (4.2 eV), which may be due to quantum confinement. The effect of high energy ball milling on the grain size and PL intensity has also been investigated for the first time in the doped SrS system. The PL emission wavelength is blue shifted by 3 nm but the emission intensity decreases unexpectedly as the milling time increases, although there is a reduction in size which is evident from XRD peak broadening of the milled samples. This may be ascribed to surface defects generated by ball milling which act as killing centres, quenching the PL.

Nanosized bismuth doped calcium sulfide (CaS:Bi) particles have been synthesized by a wet chemical co-precipitation method. The average size of the nanoparticles was found to be about 30 nm. The particles were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy and fluorescence spectroscopy. The effect of particle size on the photoluminescence (PL) of CaS:Bi has been studied. The optimum dopant concentration was found to be 0.025 mol% of bismuth for maximum PL emission intensity. A comparative study between bulk CaS:Bi prepared by a reduction method and nanosized CaS:Bi made by the wet co-precipitation method has been carried out. Increase in band gap with decrease in particle size has been explained on the basis of the quantum size effect. The PL intensity of the nanoparticles was found to increase to almost twice that of the bulk particles. The effect of different dopant concentrations on emission intensity has also been studied.

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The thermoluminescence (TL) studies of CaS : Bi nanocrystalline phosphors prepared by the wet chemical co-precipitation method and exposed to γ-rays have been discussed. The average grain size of the samples was estimated as 35 nm using Scherrer's equation. The samples exhibit a complex TL glow curve with multiple peaks. Sample exposed to γ-rays showed that the TL intensity increases linearly as the radiation doses increased in the 1.012–40.48 mGy range. The trap parameters namely, activation energy (E), order of kinetics (b) and frequency factor (s) of the main peaks of the CaS : Bi(0.08 mole%) sample have been determined using Chen's method. The effect of different dopant concentrations and different heating rates has also been discussed.

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