### Inhibiting recombination of electron and hole  
The photocatalytic mechanism is demonstrated below with S\({}_{\text{Ag}}\) as an example. The S\({}_{\text{Au}}\) has photoresponse in the visible light region due to the LSPR effect of Au NPs. Analyzing by EIS, the Au NP-doped TiO\({}_{2}\) membrane represented lower resistances than the pure TiO\({}_{2}\) membrane, which could make the charge transfer at the interface more rapid and effective. The charges on the surface of Au NPs are subjected to collective shock under irradiation of visible light and become free elections, which results in a strengthened local electric field. Under the local electric field, free electrons then rapidly jump to the conduction band (CB) of TiO\({}_{2}\) and overcome the Schottky junction, which results in the separation of photogenerated electrons and holes and thus improves quantum efficiency. Generally, pure TiO\({}_{2}\) has a wide band gap. Under light irradiation, the excitation of an electron would take place if the light energy is greater than the band gap of the catalysts. The wide band gap of pure TiO\({}_{2}\) is known to be 3.2 eV. By using Mott\(-\)Schottky plots and XPS spectra, the band gap from the valence band to the conduction band for Ag-decorated TiO\({}_{2}\) deceased to 2.6 eV. Therefore, the material showed photocatalytic activity under visible light irradiation. The photogenerated electrons can react with the O\({}_{2}\) on the surface of catalyst to form -O\({}_{2}\)\({}^{-}\), and the holes of Au can combine with H\({}_{2}\)O on the catalyst surface to form -OH, both of which are strongly oxidative. These oxidative species can then oxidize the RhB molecule on the surface of Au NPs. The photocatalysis degradation is divided into three stages. They are the formation of both the hole and electron under light excitation, the production of radical species and the reaction of the  
Figure 3: Scheme of the mechanism of inhibiting the recombination of electrons and holes by TiO\({}_{2}\) membranes and enhancing the separation of electrons and holes. radical species with the targets (pollutants, bacteria, etc.). Electron paramagnetic resonance (EPR) has confirmed the separation of the hole and electron [40]. The production of radical species along time was also proven by the different adduct species detected with EPR [41]. The degradation product of the targets was detected by some groups [42]. The silver content is closely related to the separation of the hole and electron and the production of radical species, as described above. As a result, silver will affect photocatalysis and degradation efficiency significantly. Au or Ag NPs experience an evolution during the photocatalytic process. A moderate growth of particle size was observed. From the statistics of the TEM images, the particle size of Ag and Au NPs increased from 2.3 \(\pm\) 0.1 nm-13 \(\pm\) 0.3 nm and from 2.4 \(\pm\) 0.1 nm-17 \(\pm\) 0.4 nm after photocatalysis, respectively. On the other hand, the photocatalytic activity did not change in the catalyst recyclability test (Supplementary Material S3), showing that Au or Ag NPs maintain a dominant metallic state. The surface morphology of the _E. coli_ cells was examined by SEM. Figure 4A shows that the native _E. coli_ cells had a rod-like structure with regular wrinkles, which was changed after the photocatalytic degradation. Figure 4B shows that some depressions appeared on the surface of cells treated with P25 TiO\({}_{2}\), and irregular wrinkles appeared on the cells treated with S\({}_{\text{Au}}\). The results suggested that the cell surface was damaged and the cell membrane structure was altered. The outer membrane of Gram-negative bacteria is composed of lipopolysaccharide-acrylamide (LPS), peptidoglycan and phospholipid layers. The mechanical strength of the cell membrane depends on peptidoglycan, and LPS is responsible for the surface structure and morphology [43; 44; 45]. The beta 1,4-link between the two amino sugars of \(N\)-acetyl glucose amine and \(N\)-acetyl acid forms the LPS.