Figure 1.

Optical photos of the obtained gold colloids, the diluted samples and their corresponding UV-vis spectra. (A) Photos of gold colloids prepared from a solution of 0.25 mM to 2.0 mM HAuCl₄ 3H₂O (corresponding to 0.1 mg/ml to 0.8 mg/ml, respectively) and their diluted samples at a content of 0.25 mM Au. (B) The corresponding UV-vis spectra of the diluted samples. (Baseline was adjusted artificially).