Molecular interaction study of hydroquinone adsorption on functionalized gold nanoparticles by inelastic neutron scattering - MAPS

The global demand for cosmetic products, especially skin whitening creams, has risen sharply in recent years. Hydroquinone (HQ), a common depigmenting agent, is widely used but poses serious health risks when overused, such as skin hyperpigmentation and potential carcinogenic effects. Regulatory authorities like the European Economic Community have restricted HQ concentrations in cosmetics to 2% (w/w), prompting the need for accurate detection methods. In this study, gold nanoparticles (AuNPs) were synthesized via a green method using Aquilaria malaccensis L. (AML) leaf extract, which acted as both a reducing and functionalising agent—a novel approach. The synthesized AuNPs were analyzed using FTIR and Raman spectroscopy, confirming functional group presence from AML and interaction with HQ. Surface-enhanced Raman scattering (SERS) revealed key peaks, indicating HQ adsorption onto AuNPs. To further explore HQ-AuNP interactions at the molecular level, inelastic neutron scattering (INS) is proposed as an advanced and complementary tool. Initial results show shifts in vibrational modes, particularly in OH bands, upon HQ binding, suggesting molecular interaction. Further INS analysis is planned to gain deeper insight. Understanding these interactions is critical for optimizing AuNP functionalisation in HQ detection.