Photochemical preparation, characterization and formation kinetics of riboflavin conjugated silver nanoparticles

Abstract

Riboflavin conjugated silver nanoparticles (RF–AgNPs) have been synthesized by photoreduction of Ag+ ions and characterized by UV–visible, X-ray diffraction (XRD), FTIR spectroscopy, spectrofluorimetry, dynamic light scattering (DLS) and atomic force microscopy (AFM). The RF–AgNPs exhibit a typical surface plasmon resonance (SPR) peak at 422 nm due to the interaction of RF and AgNPs. FTIR studies indicate the appearance of an intense absorption peak at 2920 cm–1 due to the interaction of RF and Ag. AFM studies indicate that the RF–AgNPs are spherical and polydisperse in nature (57–73 nm), which nicely complement the hydrodynamic radii (57.9–72.2 nm) measured by DLS. None of the tested concentrations (1-250 µg mL−1) of RF–conjugated AgNPs show any adverse effect on normal mouse fibroblast and cancerous non-small lung carcinoma cell lines. At acidic pH (2.0–6.2) aggregation of RF–AgNPs occurs due to an increase in the ionic strength of the medium. The rates of formation of RF–AgNPs on UV and visible light irradiation have been determined in the pH range of 8.0–10.5 and at different concentrations of Ag+ ions. The photochemical formation of RF–AgNPs follows a biphasic first–order reaction probably due to the formation of AgNPs in the first phase (fast) and the adsorption of RF on AgNPs to yield RF–AgNPs in the second phase (slow).