chloride trihydrate (HAuCl4·3H2O, 99%),
cetyltrimethylammonium bromide (CTAB),
2-methylimidazole (2-MIM, 99%), zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 99%), polyvinylpyrrolidone
(PVP, K30), and methanol (AR grade, 99.9%) were purchased from Shanghai
Macklin Biochemical Co., Ltd. Silver nitrate, ascorbic acid, and sodium
borohydride were bought from Sinopharm Chemical Reagent Co., Ltd.
5-Bromosalicylic acid was supplied by Shanghai Aladdin Biochemical
Technology Co., Ltd. All the chemicals were used as received without
further purification. Ultrapure water (Millipore Milli-Q grade) with
a resistivity of 18.2 MΩ was used in all the experiments.