The seed solution of the GNRs was prepared according to the technique reported previously [27].
The CTAB solution (1.5 mL, 0.1 M) was mixed with 100 L of 0.02 M HAuCl4,
and 100 L of icecold 0.01 M NaBH4 was added to the solution to form a brownish yellow solution.
Vigorous stirring was continued for 2 min and then the seed solution was kept at room temperature (25 ◦C) and used at least 2 h after preparation.