Tunable emission property of biotin capped Gd:ZnS nanoparticles and their antibacterial activity

Gd doped ZnS nanoparticles have been successfully fabricated by a microwave irradiation method whose surface was passivated with biotin at different concentration. The structural property was investigated by characterizing the samples with the help of X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM). Energy dispersive spectroscopy (EDS) measurement showed the existence of Gd ion in the Gd-doped ZnS nanoparticles. Optical confirmation was done with the help of UV-visible and photoluminescence spectroscopy. Diffraction data confirmed the zinc blend structure for all the samples with grain size of 5.8 nm for uncapped and 3-4 nm for capped nanoparticles with varying concentration of biotin. Spherical shape with 7 nm (uncapped) and 4 nm (capped) were definite from TEM images. HRTEM images and SAED patterns with bright circular rings designated the cubical environment of these nanoparticles. Emission bands in the blue, green and red regions were observed for both the samples, which was blue shifted in case of capped nanoparticles with increased intensity. Enhanced luminescence property was observed in the case of capped Gd:ZnS nanoparticles when compared to uncapped and thus can be of biomedical uses. Notably these biotin capped Gd:ZnS nanoparticles proved to be a potential antibacterial agent against different pathogenic bacterial strains, which showed maximum zone of inhibition at concentration of 10 µg/ml. The bioactivity sums up that this surface passivated nanoparticle emerges as a new class of antibacterial agent.