Highly fluorescent CdTe quantum dots with reduced cytotoxicity-A Robust biomarker

l-Cysteine (Cys) capped CdTe quantum dots (CdTe@Cys QDs) were successfully synthesized in an aqueous medium. The synthesized CdTe@Cys samples were analyzed using Fourier transform infrared (FT-IR) spectroscopy, fluorescence (FL) spectroscopy, transmission electron microscopy (TEM), confocal microscopy and subsequently subjected to the antibacterial test. Systematic investigations were carried out for the determination of optimal conditions namely the ratios of Cd:Te, CdTe:Cys, pH value and the chemical stability of CdTe@Cys. Moreover, the reactivation of FL intensity in the CdTe@Cys sample was done easily by the addendum of Cys. The introduction of additional cysteine to the CdTe@Cys QDs sample showed an enhancement in terms of the FL intensity and stability along with the reduced antibacterial activity. This was further confirmed through Thiazolyl blue tetrazolium bromide (MTT) assays. Both the result of the bio-stability tests namely the antibacterial test and MTT assay displayed similarities between the externally added Cys and cytotoxicity of the bacteria and human HeLa cancer cell lines. Confocal microscopic images were captured for the CdTe@Cys conjugated Escherichia coli.