Hydroxyl radical (OH ·) was produced under visible light as an oxidized product and superoxide anion (O
2 ·) as a reduced product from silver-loaded hydrogen zirconium phosphate [Ag
1-xH
xZr
2 (PO
4)
3] suspension in air. These radicals showed the electron spin resonance (ESR) spectra of 5, 5-dimethyl-1- pyrroline-
N-oxide (DMPO) adducts, and usually only DMPO-OH can be obtained because of the rates of reaction between DMPO and OH · and O2 · The ESR spectrum of DMPO-O
2- emanated in the presence of I
- because I
- is a trapping reagent of OH ·.I
- acted first as an inhibitor and finally as did the bactericidal species in the bactericidal activity against
Escherichia coli. I
2 formed from the reaction between OH · and I
-.This indicated that OH · was a bactericidal species. OH · produces (CH
3)
2 C · OH and CH
3C · H OH from ethyl alcohol and isopropyl alcohol because the redox potential of OH · is much more positive than those of the alcohols. Those radicals showed stronger bactericidal activities than OH ·. We propose that the strong reducing species has higher bactericidal activity against
E. coil than the strong oxidizing species.
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