Room temperature synthesis of NIR emitting Ag₂S nanoparticles through aqueous route and its influence on structural...

Near infra-red (NIR) light emitting nanomaterials had shown great promise in clinical imaging in view of negligible absorption by skin or tissue of mammalian. Thus, it demands for synthesizing stable NIR emitting nanomaterials in water environment. The present work presents synthesis of biologically acceptable luminescent near-IR emitting silver sulfide nanoparticles through an aqueous route using 2-mercaptoethanol. The prepared as-synthesized Ag₂S nanoparticles exhibited bright photoluminescence with quantum yield of ca. 4%. X-ray diffraction (XRD) analysis indicated that the products were monoclinic α-Ag₂S. Fourier transform infrared spectral analysis revealed that the stretching vibration at 2560 cm^-1 responsible for S-H bond of thiol group disappeared suggesting the conjugation of 2-mercaptoethanol with Ag₂S nanoparticles. In view of investigating any possible effect on genetic materials, interactions of the synthesized particles with calf thymus DNA was investigated employing Ethidium bromide (EB) as structural probe. To understand the binding mechanism, the UV-vis absorption, fluorescence and circular dichroism (CD) spectroscopic, as well as DNA melting studies measurements were carried out. The observed results confirm that nanoparticles interact with DNA through groove binding.