CdS nanoparticles were synthesized by the microwave assisted chemical precipitation method and solvothermal method. X-ray power diffraction, scanning electron microscopy, and transmission electron microscopy were employed to characterize the crystalline structure, morphology, and size of the synthesized samples. X-ray diffraction studies reveal that the synthesized samples are of two different forms, cubic and hexagonal. The DC electrical resistance of the two samples was measured in the temperature range 300–500 K. Near room temperature cubic nanoparticles behave as a semiconductor, and hexagonal nanoparticles show the behavior of an insulator. The temperature resistance curves of the cubic sample show a transition from the cubic to hexagonal phase above 340 K. The temperature resistance curve of the hexagonal sample also shows a discontinuity at 463 K due to the transition from the hexagonal to cubic phase. The thermogravimetric analysis of the two samples also confirms the two transitions. UV, PL, and Raman spectra of the two forms are compared.

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Zinc Sulphide nanoparticles (ZnS-NPs) are synthesized by microwave assisted chemical precipitation method. The as-synthesized nanoparticles are identified by X ray diffraction and electrical studies to examine the structural transition. The HT-XRD at 1000 C (373 K) and 2000 C (473 K) of ZnS-NPs also confirms structural transition of cubic to hexagonal phase. Thermal properties of the ZnS sample is also studied using thermo gravimetricdifferential thermal analysis (TG-DTA). From D.C. electrical resistance, a discontinuity occurs in the temperature resistance curve of the ZnS-NPs due to phase transition around 450 K. The energy dispersed x-ray analysis and Raman spectra of the ZnS-NPs confirm the presence of zinc and sulphur. The optical studies of the prepared ZnS-NPs are confirmed by its UV-vis and PL spectra. The TEM image of cubic ZnS-NPs reveals the well distribution of spherical shaped particles with mean size of 12.52 nm with standard deviation of 9.326 nm. According to the photocatalytic results of ZnS-NPs for the degradation of methylene blue (MB) have the highest degradation efficiency of 93.24% under UV irradiation within 80 min. Antibacterial effects of ZnS-NPs nanoparticles against some pathogens, like gram-negative, gram-positive, E. coli (Escherichia coli), S. aureus (Staphylococcus aureus) bacteria.

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