Synthesis, feasibility study of production of singlet oxygen and hydroxyl radical and performance in antibacterial activity of ZnS:Eu QDs en en Eu doped zinc sulfide quantum dots (QDs) were prepared by the chemical Co-precipitation method. X-ray diffrac-tion analysis (XRD), scanning electron microscopy (SEM) and infrared Fourier transform (FT-IR) analysis were used to characterize the quantum dots. The size of nano-crystals was estimated using a Williamson Hall equation. Then, the synthesized nanoparticles were studied to investigate the antibacterial effect, containing different strains of pathogenic bacteria, and the lowest inhibitory concentration and halo diameter were calculated. Williamson Hall equation of about 6 nm with a strain of 0.7 nm, which is match with the reported size of the SEM image. The photoluminescence spectrum (PL) of ZnS:Eu QD in excitation wavelength of 280 nm shows two emission peaks at 384 and 715 nm. In order to use these QDs as photosensitizer in photodynamic therapy, anthracene and methylene blue chemical detectors were used for detection of singlet oxygen and hydroxyl radical, respectively. The significant point for these quantum dots is that, in addition to production of hydroxyl radical, they also have the ability to produce singlet oxygen with UVC radiation. The antimicrobial effect of ZnS:Eu QDs was also investigated using a disc diffusion method on 11 microbial strains. 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