<![CDATA[Therefore, this project was to prepare and characterize silver nanoparticles (AgNPs) and study their application for colorimetric detection of heavy metal ions. AgNPs are synthesized by a bottom-up method in which AgNO3 serves as the precursor, which is then reduced using trisodium citrate and stabilized by 1 vol.% polyacrylic acid (PAA). Trisodium citrate facilitates the reduction of Ag+ ions due to its negatively charged carboxylic groups, whereas PAA enhances stability and selectivity. Under the best reaction parameters condition, AgNPs produced brown-yellow colloids with a Surface Plasmon Resonance (SPR) peak of 403 nm. A particle size analysis showed an average particle diameter of 29.9 nm, with a standard deviation σ of 0.482. Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed that hydroxyl groups -OH and carbonyl groups C=O play a role in reducing Ag+ ions. Because they are highly active, AgNPs can respond to Hg2+ in tests, marking the color change from brown-yellow to transparent white within about one minute. Methods testing for validation of linearity revealed an R2 = 0.9985, and a LOD and LOQ are ca. 0.074 ppm and 0.224 ppm, respectively. At 700 ppm Hg2+, the selectivity was good. These results demonstrate that AgNPs are sensitive and efficient sensors of Hg2+ ions and indicate how to find promising new ways to detect heavy metals in environmental monitoring.]]>
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