การประชุมวิชาการระดับชาติ ครั้งที่ 16
มหาวิทยาลัยราชภัฏนครปฐม

Arsenic contamination in the environment affects the body and causes disease, especially skin cancer. Arsenic contamination in surface water are mainly found in two forms: As(III) and As(V). To monitored for arsenic in water, we have developed a colorimetric method for arsenic measurement using modified silver nanoparticles (AgNPs). With synthesizing AgNPs by reduction reaction and optimization condition study for arsenic detection, AgNPs modified with L-Cysteine as ligand was found to be the most suitable as reaction time at 10 minutes. The color solution of AgNPs changed from yellow to purplish pink, this corresponds to the absorption peak intensity decrease to red shift from 402 to 522 nm. The interaction of Cysteine on As(III) on Ag₄ cluster was calculated with the M06-L density functional theory. The basis set was 6-311+G(2df,2p) / LANL2TZ. The As-Ag and S-As bonds was calculated, the adsorption energies were -16.1 and -23.7 kcal/mol, respectively. The NBO analysis found that the As-Ag and As-S bonds have energies of -0.50036 and -0.50281 eV, respectively. The excited states of complexes were calculated with TD-DFT. The wavelength for the first excited states were was calculated to be 723.6 nm. The results of this study indicate that the developed method can be used for measuring arsenic content in water samples.