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Photocatalytic mechanism of action of apatite-coated Ag=AgBr=TiO 2 on phenol and Escherichia coli and Bacillus subtilis bacteria under various conditions

Elahifard, M. R ; Sharif University of Technology | 2011

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  1. Type of Document: Article
  2. DOI: 10.3184/146867810X12925913885187
  3. Publisher: 2011
  4. Abstract:
  5. Multi-component photocatalysts based on apatite-coated Ag=AgBr=TiO 2 were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-static. The mechanism for deactivation of bacteria in the dark can be related to the linkage between the phosphate group of the composite and the outer membrane of the cell. The photocatalytic destruction of bacteria under visible light indicates that attachment of the catalysts to the outer wall of the cell causes them to destroy effectively the cell wall and inner membrane by various reactive species such as ·OH, ·O2 · - and 1O2. Thus this effect increases the photoactivity more than two-fold. Oxidation of phenol was also achieved under visible light- and UVAirradiation using apatite-coated Ag=AgBr=TiO2 powders. UnderUVAillumination, the · OH produced from the hole of the TiO 2 valence band is responsible for the photodegradation of phenol, while under visible light, AgBr acts as the phot oactive component of the catalyst, that can not produce · OH and oxidize the phenol
  6. Keywords:
  7. Bacteria-static ; Bacillus subtilis ; Cell walls ; Deposition methods ; Different mechanisms ; Growth of bacteria ; Inner membranes ; Mechanism of action ; Multicomponents ; Nano-size ; Outer membrane ; Oxidation of phenol ; Phosphate group ; Photo-catalytic ; Photoactivity ; Photocatalytic activities ; Reactive species ; TEM images ; TiO ; Visible light ; Apatite ; Bacilli ; Escherichia coli ; Phenols ; Phosphate minerals ; Photocatalysis ; Photocatalysts ; Silver ; Silver alloys ; Silver halides ; Bacteriology
  8. Source: Progress in Reaction Kinetics and Mechanism ; Volume 36, Issue 1 , February , 2011 , Pages 38-52 ; 14686783 (ISSN)
  9. URL: http://www.ingentaconnect.com/content/stl/prk/2011/00000036/00000001/art00004?token=004410607e442f20672136762a704523566c247363687627504541676249266d656c