Green synthesis of zinc oxysulfide quantum dots using aegle marmelos fruit extract and their cytotoxicity in HeLa cells

Zinc oxysulfide quantum dots have been attracting increasing research interest due to their tunable electronic, optical and magnetic properties. In this paper we report the green synthesis of zinc oxysulfide quantum dots in the range of a few nanometers using aegle marmelos fruit extract through a facile precipitation route. The zinc oxysulfide quantum dots (ZOS QDs) were characterized by X-ray diffraction, ultra violet-visible absorbance spectroscopy, photoluminescence spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. Energy dispersive X-ray spectroscopy of the synthesized samples indicates that 16% oxygen is incorporated into the zinc sulfide crystal lattice that results in an optical band-gap transformation from direct type for the zinc sulfide cubic phase to a decreased bandgap of 3.46 eV. The vibrating sample magnetometer analysis results showed the existence of room temperature ferromagnetism (RTF) in zinc oxysulfide quantum dots. The bandgap engineering approach adopted in this work to tailor the optical and electronic properties of zinc sulfide with the RTF magnetic properties of zinc oxide will have a significant impact on the development of ternary chalcogenides for magnetic and photonic applications. The prepared ZOS QDs exhibit good cell viability with HeLa cells and the toxicity results obtained from this research work provide a new direction for the development of nontoxic bandgap engineered ZOS based QDs for biological applications. To the best of our knowledge, this is the first report on the biocompatibility of novel ZOS QDs in HeLa cells.