Figure 1.

UV–vis and PL spectra. UV–vis (a and b) and PL spectra (c and d) of Au NCs before etching (a and d) and after etching (b and c). The photographs of Au NCs after etching are shown as an inset. The clear solution is under visible light, and the red emission is under a UV lamp. The fluorescence emission spectra were measured at the excitation wavelength of 470 nm.