SYNTHESIS AND STABILIZATION OF GOLD NANOPARTICLES FROM CHLORIDE AND CYANIDE SYSTEMS

Generating gold nanoparticles (AuNPs) from gold chloride solution by precipitating with compounds can be difficult due to the potentially required high temperatures. Tin chloride can be used to overcome this dilemma. The process that is known to make Purple of Cassius is a method where gold chloride and tin chloride solutions are mixed to form AuNPs and tin oxide precipitate. However, it is modified by adding hydrazine to resolubilize the tin oxide and provide a more stable solution for the AuNPs. A three-factor central composite experimentally designed model was created using Design Expert incorporating pH, temperature, and gold concentration as the variables. The response of AuNP size was obtained using a Malvern Zetasizer which measures the size of the AuNP agglomerates using dynamic light scattering. Field emission scanning electron microscopy (FESEM) confirmed the size and showed that the shape of the AuNPs tended to be spherical. Resulting statistical models yielded response surfaces with temperature and gold concentration having significant effects on the size of the AuNPs, whereas, pH did not have a significant effect. From these initial results, a secondary gold chloride system was created. A three-factor central composite model was utilized with the factors being gold concentration, temperature, and thiol concentration. The thiol factor was added to test how a thiol stabilizer affected the size and shape of the produced AuNPs. The Malvern Zetasizer and the FESEM were used to determine the shape and size of the AuNPs. Two models were created for both the size and zeta potential of the data. A similar statistical designed model was created for the gold cyanide with oxalic acid system to determine its response to pH, temperature, gold concentration, and thiol concentration. The Malvern Zetasizer and SEM were the methods to determine the size and shape of the AuNPs. The experiments produced a size model and a zeta potential model. Testing using three different froth flotation chemicals was done on the gold cyanide system to determine if they are candidates for being stabilizers