Abstract

Cadmium is a highly toxic heavy metal, and exposure to cadmium ions (Cd²⁺) can pose serious health risks to humans and the environment. Recent advancements in digital imaging have made high-resolution photo production from digital cameras more cost-effective, opening opportunities for rapid and affordable colorimetric methods in quantitative chemical analysis. The method employs the prime color space RGB (Red-Green-Blue) with individual values varying from 0 to 255. RGB data were extracted from square-homogenous cropped digital images using ImageJ software to construct a calibration curve in quantitative determination. TEM analysis confirmed the synthesis of mostly spherical AuNPs. FTIR data showed peaks at 3,442, 1,579, and 1,347 cm^-1 corresponding to the O-H, C=O, and C-O symmetric stretching vibrations of the -COOH groups on the surface of the synthesized AuNPs. XRD analysis revealed peaks at 38.3, 43.5, 64.6, 77.7, and 81.7º, confirming the crystalline nature of the AuNPs. The presence of cadmium causes the nanoparticles to aggregate, resulting in a color change from red (520 nm) to blue (650 nm), which can be analyzed using digital image methods. The method has good selectivity and sensitivity, with a detection limit of 0.050 ppm and a linear range from 0 to 10 ppm (R² = 0.9952). Therefore, this method can be successfully employed for detecting and quantifying unknown concentrations of cadmium.