Green-Synthesized Silver Nanoparticles from Ocimum sanctum Leaf Extract for a Chitosan–Starch Colorimetric Hg2+ Sensor

Yussi Pratiwi, Fuad Alfan Asyifa, Agus Darmawan, Harfi Amania Khansa, Elsa Vera Nanda, Baiq Amelia Riyandari, Aneesha Sheik Musthafa Ajeetha

Abstract

The presence of Hg2+ ions in soil and water poses a potential risk to living organisms, including humans, necessitating simple and accessible detection methods. This study evaluated Ocimum sanctum (Tulsi) leaf extract as a reducing and stabilizing agent for the green synthesis of silver nanoparticles (AgNPs) and subsequently developed a chitosan-starch nanocomposite film for the colorimetric detection of Hg2+. AgNPs produced using various extract preparation methods were comparatively evaluated based on their physicochemical characteristics and colloidal stability. AgNPs with the most suitable properties were selected for incorporation into the nanocomposite film. The selected AgNPs exhibited a particle size of 66.8 nm, a polydispersity index of 0.295, and a zeta potential of −26.9 mV, indicating a relatively uniform particle distribution and moderate colloidal stability. The AgNPs-loaded chitosan-starch nanocomposite film demonstrated a selective colorimetric response to Hg2+ under the tested conditions, with a linear response across the Hg2+ concentration range of 0–10 ppm. The sensor exhibited a limit of detection of 0.68 ppm and a limit of quantification of 2.07 ppm, while maintaining its detection performance for up to four weeks. These findings highlight the potential of plant-synthesized AgNPs incorporated into a chitosan-starch matrix as a simple colorimetric platform for Hg2+ detection.

Keywords

Colorimetric sensor, Hg²⁺ detection, Silver nanoparticles, Tulsi leaf extract

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References

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DOI: https://doi.org/10.20961/jkpk.v11i2.119903

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