Enhanced antimicrobial activity of ZnO nanofluids in sonophotocatalysis and its mechanism

Abstract

This study investigated the inactivation efficiency of ZnO nanofluids against E. coli in sonophotocatalysis with the aeration of nitrogen, oxygen, argon and their mixtures. The results showed that inactivation efficiency was increased when aeration was combined with sonophotocatalysis. Addition of different types of gases could lead to the different inactivation efficiency. The inactivation efficiencies were shown in the following order: no aeration < nitrogen < argon < oxygen < Ar/O(3:7) < Ar/O(7:3) < Ar/O(5:5). The production of hydroxyl radicals was explored to understand the inactivation mechanism. Compared with sonophotocatalysis without aeration, more hydroxyl radicals were produced in sonophotocatalysis with aeration, which could lead to changes of cellular substances. Furthermore, characterization of E. coli cells using Raman spectroscopy and FTIR illustrated that sonophotocalysis could affect the cellular substances containing carbohydrates, proteins and P containing molecules. Results suggested that the enhanced antimicrobial activity with aeration was originated from stronger cavitational activity, together with the formation of hydroxyl radicals. Compared to sonophotocatalysis without aeration, more dissolved oxygen was existed in sonophotocatalysis with aeration, which could enhance the formation of hydroxyl radicals.

When sonochemistry meets heterogeneous photocatalysis: designing a sonophotoreactor towards sustainable selective oxidation

“…However, the majority of the successful applications of sonophotocatalysis have been focused on environmental remediation applications, especially for waste-water treatment against toxic organic compounds, through uncontrollable advanced oxidation processes (AOPs). [36][37][38][39][40] The reported cases of successful combination of photo-and sonochemistry as a Hybrid Advanced Oxidation Process (HAOP) toward specific selective catalytic reactions and valorization of biomass are limited due to the complexity of manipulating the formed active oxygen species, developing an appropriate sonophotoreactor and of course an appropriate sonophotocatalyst. 11 Regarding the latter issue, the ultimate goal is to avoid the usage of precious noble and/or rare-earth metal-based catalysts, addition of hazardous and non-reusable chemicals, and the need for harsh experimental conditions.…”

Recent Progress and Prospects in Catalytic Water Treatment

“…Experiments carried out in sonophotocatalytic degradation of E. coli in different environments showed that the inactivation efficiency of ZnO nanofluids under purging with nitrogen, oxygen, argon, and their mixtures led to different inactivation efficiency being correlated to the production of hydroxyl radicals and the inactivation mechanism. 1017 It varied in the following order: no aeration < nitrogen < argon < oxygen < Ar/O 2 (3:7) < Ar/ O 2 (7:3) < Ar/O 2 (5:5). The deposition of ZnO nanoparticles onto multiwalled carbon nanotubes afforded an increased absorbance of photocatalyst in the visible-light region that correlates with an enhanced degradation of Rhodamine B dye.…”

“…The atmosphere in which the sono­photodegradation is carried out exerts an important effect as well. Experiments carried out in sono­photocatalytic degradation of E. coli in different environments showed that the inactivation efficiency of ZnO nanofluids under purging with nitrogen, oxygen, argon, and their mixtures led to different inactivation efficiency being correlated to the production of hydroxyl radicals and the inactivation mechanism . It varied in the following order: no aeration < nitrogen < argon < oxygen < Ar/O 2 (3:7) < Ar/O 2 (7:3) < Ar/O 2 (5:5).…”

Practical photocatalytic and sonophotocatalytic reduction of nitroarenes in water under blue LED irradiation using β-CD modified TiO2 as a green nest photocatalyst

“…However, sonophotocatalysis, through advanced oxidation processes (AOPs), has been most widely used in environmental remediation, especially waste-water treatment. 17–22…”