Green Synthesis of AuNPs Using Ocimum Basilicum Extract and Study of Its Potential as Microplastic Detection

Abstract

Nanoparticles have emerged as promising materials for real-time environmental monitoring due to their unique optical and physicochemical properties. Among them, gold nanoparticles (AuNPs) have gained considerable attention for sensing applications, including the detection of emerging pollutants such as microplastics. However, conventional AuNP synthesis commonly relies on hazardous chemicals and energy-intensive processes, creating environmental and sustainability concerns. Therefore, the development of green synthesis methods using plant-based bioreductors offers a more sustainable alternative. This study aims to determine the optimal conditions for the green synthesis of AuNPs using Ocimum basilicum extract, characterize the synthesized nanoparticles, and evaluate their potential application for microplastic detection. The research involved the extraction of Ocimum basilicum, optimization of synthesis parameters, nanoparticle characterization, and assessment of microplastic monitoring capability. The results showed that stable AuNPs were successfully synthesized under optimum conditions at pH 6 with a precursor-to-bioreductor ratio of 6:3 (mL). The synthesized AuNPs-OB exhibited an average particle size of 3.52 nm, indicating the formation of small and highly reactive nanoparticles. Fourier Transform Infrared (FTIR) analysis revealed the presence of hydroxyl (O–H) and alkene (C=C) functional groups originating from Ocimum basilicum phytochemicals, which contributed to both the reduction and stabilization of the nanoparticles. Furthermore, AuNPs-OB demonstrated promising potential for microplastic detection through direct and indirect approaches. The direct method involved surface modification with non-polar compounds to enhance interactions with microplastics, while the indirect method employed acetone as an aggregating agent to induce detectable optical changes. These findings demonstrate that green-synthesized AuNPs-OB are environmentally friendly nanomaterials with strong potential for sustainable microplastic monitoring applications.