SYNTHESIS OF GOLD NANOPARTICLES AND INTERACTION WITH AN ORGANIC DYE UNDER VARYING PH CONDITIONS: A UV–VISIBLE SPECTROSCOPIC STUDY

Abstract

Gold nanoparticles or shortened as AuNPs possess unique optical and physicochemical properties, enabling them to be used in various applications such as in sensing, catalysis, photonics, and biomedical systems. In this study, gold nanoparticles were synthesized by the Turkevich citrate reduction method and their interaction with sodium fluorescein (NaFl) was investigated by UV–Visible spectroscopy under varying pH conditions. Spherical AuNPs have been seen to exhibit a surface plasmon resonance (SPR) peak in the 530–543nm region. Interaction studies revealed that sodium fluorescein demonstrated pH-dependent interaction, with clear evidence of dimer formation and enhanced adsorption onto the AuNP surface at alkaline pH (pH 9.2). This result highlights the interaction behaviour of structurally and functionally different organic dyes with gold nanoparticles, emphasizing the critical role of dye charge, structures of the molecules, and the pH of the solutions in governing nanoparticle–dye interactions.