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This research proposed the use of the serum from the skim natural rubber latex (SNRL), the waste from the concentrated latex production, as a source of reducing and stabilizing agents in a green synthesis of gold nanoparticles (AuNPs). The coagulants including H2SO4, CH3COOH, and cationic polyacrylamide (PAM) solutions were used to remove rubber particles and the serums with remaining coagulants were obtained. The serum was diluted with water for various dilution factors and then mixed with gold (III) chloride trihydrate (HAuCl4.3H2O). The results showed that the serum with remaining H2SO4 gave large particles, while the serums with both CH3COOH and PAM could stabilize and yield AuNPs, of which the characteristic absorbance peaks around 530 nm were observed. However, regarding the degree of colloidal stability when the reaction was prolonged, the serum with PAM was superior. Dilution of the serum was found necessary since the reaction could be controlled when the concentrations of both reducing and stabilizing agents were not too high. Figures from Transmission Electron Microscope (TEM) confirmed that using the serum with PAM, the AuNPs were synthesized and had the size ranged from 5-45 nm or the average diameter of 23±2 nm.
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