Deciphering Camellia sinensis Leaf Extract-Mediated Silver Nanoparticles as a Colorimetric Sensor for Mercury...

The current study explores the biosynthesis of silver nanoparticles (AgNPs) using green tea (GT) extract (Camellia sinensis) and its application in detecting mercury ions in potable water samples. The biologically synthesized GT-AgNPs were characterized through a series of spectral analyses. The UV-visible spectroscopy of the GT-AgNPs exhibited a λ max at 417 nm. Fourier Transform-Infrared spectroscopy indicated the presence of functional groups (hydroxyl, amines, alkynes, esters, ethers, and thiols) involved in the capping and stabilization of AgNPs. X-ray Diffraction analysis validated the crystalline structure. Electron microscopic studies revealed that synthesized GT-AgNPs are spherical-shaped. Dynamic light scattering indicated an average particle size of 86.3 nm. The zeta potential value > -30 mV suggested that GT-AgNPs are more stable. The detection of Hg²⁺ through colorimetric analysis demonstrated that the introduction of GT-AgNPs into varying concentrations of Hg²⁺ ions resulted in a significant color change from brownish yellow to a colorless solution, thereby recording the Limit of Detection to be 0.6 μM and the Limit of Quantification as 1.82 μM. Results of the recovery study using various micromolar (0.25-0.75 μM) concentrations of Hg²⁺ ions spiked with drinking and tap water showed a relative standard deviation of less than 5% and a recovery rate > 91%. Considering the sensitivity and selectivity of GT-AgNPs, this calorimetric assay clearly emphasized its potential in detecting Hg²⁺ ions in contaminated aquatic ecosystems. Furthermore, the green tea extracts used to fabricate AgNPs presented several advantages: simple, low-cost, and one-step, with no harmful organic solvents.