Photocatalytic antibacterial performance of TiO2 and Ag-doped TiO2 against S. aureus. P. aeruginosa and E. coli

Kiran Gupta,Ashutosh Pandey,Anjana Pandey,R P Singh

doi:10.3762/bjnano.4.40

Abstract

This paper reports the structural and optical properties and comparative photocatalytic activity of TiO2 and Ag-doped TiO2 nanoparticles against different bacterial strains under visible-light irradiation. The TiO2 and Ag-doped TiO2 photocatalysts were synthesized by acid catalyzed sol–gel technique and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis spectroscopy and photoluminescence (PL). The XRD pattern revealed that the annealed sample of TiO2 has both anatase and rutile phases while only an anatase phase was found in Ag-doped TiO2 nanoparticles. The decreased band-gap energy of Ag-doped TiO2 nanoparticles in comparison to TiO2 nanoparticles was investigated by UV–vis spectroscopy. The rate of recombination and transfer behaviour of the photoexcited electron–hole pairs in the semiconductors was recorded by photoluminescence. The antimicrobial activity of TiO2 and Ag-doped TiO2 nanoparticles (3% and 7%) was investigated against both gram positive (Staphylococcus aureus) and gram negative (Pseudomonas aeruginosa, Escherichia coli) bacteria. As a result, the viability of all three microorganisms was reduced to zero at 60 mg/30 mL culture in the case of both (3% and 7% doping) concentrations of Ag-doped TiO2 nanoparticles. Annealed TiO2 showed zero viability at 80 mg/30 mL whereas doped Ag-TiO2 7% showed zero viability at 40 mg/30 mL culture in the case of P. aeruginosa only.

Highlights

The photocatalytic agent TiO2, known for its chemical stability and optical competency, has been used extensively for killing different groups of microorganisms including bacteria, fungi and viruses, because it has high photoreactivity, broad-spectrum antibiosis and chemical stability [1,2,3,4,5,6]
In this paper we have reported the structural, optical and photocatalytic properties of TiO2 and Ag-doped TiO2 synthesized by an acid-catalyzed sol–gel technique
The X-ray diffraction (XRD) pattern showed the coexistence of silver and anatase TiO2 phases

Summary

Introduction

The photocatalytic agent TiO2, known for its chemical stability and optical competency, has been used extensively for killing different groups of microorganisms including bacteria, fungi and viruses, because it has high photoreactivity, broad-spectrum antibiosis and chemical stability [1,2,3,4,5,6]. The simplest photocatalytic mechanism of silver ions is that it may take part in catalytic oxidation reactions between oxygen molecules in the cell and hydrogen atoms of thiol groups, i.e., two thiol groups become covalently bonded to one another through disulfide bonds (R–S–S–R), which leads to blocking of respiration and cell death of the bacteria [10]. Another remarkable mechanism of the antimicrobial activity of Ag nanoparticles is related to the formation of free radicals and consequent free-radical-induced oxidative damage of the cell membranes of bacteria [11,12]. The same result was not found with gold nanoparticles [12]

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