Fig. 6. Photocatalytic activity, regenerability, and photocatalytic mechanism of the samples.

a UV–Vis absorption spectra of MG solutions upon degradation by AC–Ag3 NCs. b Time-dependent photodegradation efficiency of MG in the presence of Cu₂O nanocrystals, Au@Cu₂O, and AC–Ag3 NCs. c Schematic illustration of the mechanisms of photodegradation driven by Au@Cu₂O–Ag under visible-light irradiation. d SERS spectra of MG before and after the self-cleaning measurement carried out by the AC–Ag3 substrates and (e) the corresponding SERS intensities at 1613 cm⁻¹ of the six recycling tests.