Bio-synthesised Silver Nanoparticle-Conjugated l-Cysteine Ceiled Mn:ZnS Quantum Dots for Eco-friendly Biosensor and Antimicrobial Applications

The present work deals with the green synthesis of silver nanoparticles (Ag NPs) from bio-reduction of Ag nitrate using different concentrations of medicinal plant extracts, namely, Mentha arvensis, Bryophyllum pinnatum and Dalbergia sissoo. The bio-synthesis route with a non-toxic approach is an attractive research topic in the area of nano-biomedicine and material science. Eco-friendly Ag NPs have been confirmed from the brown color of the solutions, and via UV–Vis spectroscopy. Further, Ag NP-conjugated l-cysteine capped ZnS:Mn quantum dots have been developed successfully. This prepared conjugation aims at antimicrobial activity using antibiotic-resistant gram-positive and gram-negative bacteria, namely, Staphylococcus aureus and Escherichia coli, respectively. In anti-microbial studies, a zone of inhibition (antibiotic sensitivity) was found to vary significantly with the varied concentration of Ag NPs that also depends on the specific type of plant extract. These studies may open the door for non-toxic material to synthesize plasmonic NPs for biosensors and detectors.