Titanium Dioxide-Carbon Nanotubes Composites Immobilized Ag Nanoparticles: Enhanced Photocatalytic Bacterial Inactivation and Mechanistic Study

Abstract

Ag nanoparticles modified TiO2-CNTs synthesized using polymeric template consisting of polyethylene glycol and polyvinyl alcohol (Tev) and loaded with different wt% of Ag (2%, 6%) were exploited to react hydrothermally (433 K for 48 h) with carboxylate functionalized SWCNT/MWCNT moieties. Several characterization techniques, including UVvisible diffuse reflectance spectroscopy, X-ray diffraction, HRTEM, and selected area electron diffraction (SAED), photoluminescence (PL), Raman, FTIR and N2 sorptiometry were used to obtain information about the morphology, crystalline phases, optical properties and surface texturing. The Antibacterial activity of synthesized photocatalysts towards Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) was tested by performing bacterial DNA and agar well diffusion method under visible irradiation (λ > 450 nm, an average light intensity of 60 mWcm -2 ). It has been shown that TevAg6-SWCNT verified the highest lethal action against bacterial growth compared to rest of samples due to delaying the recombination of electrons and holes, increasing the surface area value as well as decreasing the spherical nanoparticles of Ag o into 3 nm diameter. A clue about the attack mechanism of nanocomposites while disinfecting bacteria indicates the existence of ·OH and O2• − radicals those played important role in the inactivation process. The role of Ag + ions, leakage of K + ions, TEM images; taken while irradiating bacterial strains in presence of TevAg6-SWCNT, as well as protein damage were thoroughly studied and correlated to understanding the visible light induced disinfection mechanism. Catalyst recyclability for 6 consecutive times retains more than 96% activity highlighting the catalyst stability.