Green synthesized plasmonic nano-silver: A prominent colorimetric sensing probe for the selective detection of mercury (II) ions in cosmetics samples

This study presents an environmentally friendly and scalable method for synthesizing biogenic silver nanoparticles (AgNPs), demonstrating their great functionality in mercury (Hg²⁺) sensing. The formation of AgNPs was initially confirmed by a distinct color change in the reaction solution, which was subsequently validated by a characteristic surface plasmon resonance (SPR) band at 444 nm in UV-Vis spectroscopy. Comprehensive physicochemical characterization provided further insights into the properties of the synthesized nanoparticles. Fourier-transform infrared (FTIR) spectroscopy, alongside energy-dispersive X-ray (EDX) spectroscopy and thermogravimetric analysis (TGA), collectively confirmed that various phytochemicals from the plant extract acted as capping and reducing agents, ensuring nanoparticle stability. X-ray diffraction (XRD) analysis revealed a crystalline, face-centered cubic (FCC) structure for the AgNPs, with an average crystallite size calculated to be 17 nm. Morphological examination via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) further corroborated these findings, showing the nanoparticles to be predominantly spherical and monodispersed, with an average particle size of approximately 20 nm, which aligns closely with the XRD data. The synthesized AgNPs exhibited exceptional sensitivity for the detection of Hg²⁺. This was achieved through a visual colorimetric method and a corresponding shift in the SPR band, allowing for the determination of low concentrations of mercury ions. The detection limit (LOD) and quantification limit (LOQ) were determined to be 14 ppm and 41 ppm, respectively, highlighting the nanoparticles' potential for practical sensing applications. This "green" synthesis approach offers a sustainable and cost-effective alternative to conventional methods, paving the way for large-scale production of AgNPs. The successful application of these biogenic nanoparticles for selective Hg²⁺ detection in wastewater underscores their environmental relevance. Furthermore, their potential for use in cosmetic samples could help raise awareness of health impacts and provide crucial guidance for regulatory bodies.

• Research Project