Evidence for the Mechanism of Photocatalytic Degradation of the Bacterial Wall Membrane at the TiO₂ Interface by ATR-FTIR and Laser Kinetic Spectroscopy

Abstract

The photocatalytic peroxidation of E. coli cell, lipo-polysaccharide (LPS), phosphatidyl-ethanolcholine (PE), and peptidoglycan (PGN) of the E. coli membrane wall has been investigated on TiO2 porous films by ATR-FTIR spectroscopy. The fast reactions of the photogenerated charge carriers in TiO2 with E. coli, LPS, and PE were monitored by laser kinetic spectroscopy. ATR-FTIR spectroscopy allowed the identification of E. coli, LPS, PE, and PGN as photocatalytic peroxidation products. The PGN was observed to be the most resistant membrane wall component. Shorter peroxidation times were observed for LPS and PE. Laser photolysis shows that E. coli, LPS, and PE compete in the scavenging of a surface trapped holes (h+) with the recombination reaction of h+ with the generated electrons (e-) within times > 50 ns. This scavenging leads to the formation of organic radicals initiating the radical chain peroxidation of E. coli, LPS, PE, and PE.

ZrNO–Ag co-sputtered surfaces leading to E. coli inactivation under actinic light: Evidence for the oligodynamic effect

“…Recently, we have reported the mechanism of the damage induced by TiO 2 photocatalysis on the bilayer cell-envelope of Escherichia coli in several studies [20][21][22][23]. Other groups working in the disinfection field have also addressed the mechanism of disinfection [24][25][26][27].…”

Differences in photoelectrocatalytic inactivation processes between E. coli and its isogenic single gene knockoff mutants: Destruction of membrane framework or associated proteins?

“…Lipid peroxidation is widely accepted as the damage pathway caused by RSs attack. MDA, a product of lipid peroxidation, was used to indicate this oxidative process [13,16,32,33]. Fig.…”

Photoelectrocatalytic Inactivation of E. coli by ZnSe/CdS Co-sensitized TiO2 Nanotube Array

“…31 The nucleic acid bands were observed near 1240 cm -1 , overlapping with the asymmetric stretching mode νas(PO 2-) of the phospholipid phospho-diester. 32 Moreover, the peak of 1088 cm -1 was assigned to the vibrations of the sugar rings of lipopolysaccharides. With the irradiation time increasing, all of these characteristic peaks significantly decayed in intensity or even disappeared, which indicated that the reactive species sterilize bacteria and lead to leakages of the carboxylic acid during the photoelectrocatalysis process.…”

“…[3][4][5][6] TiO2-based photocatalysts have been used to inactivate bacteria, viruses, and cancer cells. [7][8][9][10][11][12] However, the wide band gap (3.2 eV) of TiO2 means it can only absorb spectrum in the near-UV region, which limits its, practical applications for photocatalytic inactivation of bacteria. There is thus a need to enhance the absorption capability of bactericidal materials in the visible region.…”

“…On the other hand, because of the proper matching of the energy levels, ZnSe and CdS are applied to construct an appropriate step-wise structure in the CdS/ZnSe/TiO2 NTs photoelectrode. 32 Such a structure is advantageous not only for transport of the photogenerated electron but also for the separation of the excited electron-hole pairs. Based on the above reasons, a significant enhancement of photocurrent is displayed in the CdS/ZnSe/TiO2 NTs electrode.…”