Figure 20.

Using KPFM, Jian et al. [217] are able to study the modulation of the surface potential as a function of the light of power. (a–c) It is observed that with increasing light power toward the LSPR wavelength, more electrons are excited and flow to the Au nanoparticles resulting in a decrease in the surface potential of the Au nanoparticle. This switches upon the start of LSPR absorption resulting in a potential rise from −36 mV to 30 mV and gradual saturation at longer wavelengths. (d) Narrow band-pass filters of visible light for six central wavelengths: 405 nm, 430 nm, 470 nm, 520 nm, 590 nm, and 780 nm corresponding to characteristics of the absorption spectrum of Au nanoparticles (the dip, the low absorption peak, LSPR absorption, LSPR peak, end of LSPR absorption, and the long wavelength side). Reprinted with permission from Ref. [217] Copyright Elsevier (2019).