“…The systematic procedure followed the literature with minor modifications. 25 First, 100 μL of HAuCl 4 (24.28 mM) was mixed with 7.5 mL of CTAB (0.1 M) solution; then, 1.8 mL of DI water was added to the mixture. Second, 0.6 mL of cold NaBH 4 (0.01 M) was added to the above solution under the condition of quick stirring to obtain a Au seed suspension.…”