Effect of Titanium Dioxide Film Thickness on Photocatalytic and Bactericidal Activities Against Listeria monocytogenes

Abstract

Structural, microstructural and bactericidal surface properties of TiO 2 -coated glass substrates elaborated by reactive Radiofrequency sputtering are investigated. As pathogenic bacteria in biofilms are a major concern in food industries due to their growing resistance to cleaning and sanitizing procedures, the development of photoactive surfaces exhibiting bactericidal properties is acknowledged as an effective approach to tackle bacterial contaminations. Our principal aim concerns the study of the photoactive top-layer thickness impact (from 80 nm to~500 nm) on Listeria monocytogenes. Structural characterization of the TiO 2 layers demonstrates that anatase and rutile phases are both present, depending on the film thickness. Photocatalytic activity of the samples has been evaluated through the degradation of aqueous methylene blue (MB) solutions under UVA light illumination for various time periods. The results show an efficiency rating increase according to TiO 2 film thickness up to a threshold value close to 400 nm. Moreover, a significant decrease of the adherent bacteria number is observed after 20 min of UVA illumination. The quantitative study of the bactericidal activity associated with scanning electron microscopy observations of the postprocess bacteria damaged cells demonstrates the efficiency of the 240-nm-thick TiO 2 coating sample. The results are correlated with the production of hydroxyl radicals during the process of photocatalysis.

Antibacterial and Biofilm-Preventive Photocatalytic Activity and Mechanisms on P/F-Modified TiO2 Coatings

“…11 Applying TiO2-incorporated surfaces for self-disinfection enabled bacterial inactivation, even up to complete mineralization [12][13] on a wide range of Gram-negative and Gram-positive bacteria species. Aside from irradiation source power, 14 treatment time 15 and matrix (or substrate)-related factors, [16][17] the intrinsic physico-chemical properties of TiO2 greatly affect the photocatalytic oxidation performance of the coating by influencing the amount, recombination rate and diffusion length of the photogenerated charges. 18 The role of TiO2 itself was addressed in many studies by comparing the bactericidal performance of new TiO2 coatings 19 to that made of P25 TiO2, 20 the commercial photocatalyst largely admitted as a reference.…”

A High-Efficiency TiO2/ZnO Nano-Film with Surface Oxygen Vacancies for Dye Degradation

“…The annealing temperature for the anatase phase to change into the rutile phase is about 600 to 800 • C [27]. Furthermore, TiO 2 is liable to crystallize and transform to rutile with the increase of the thickness [28,29]. However, it is worth noting that ZT5 has similar thickness with ZT2, ZT3, and ZT4.…”

Photoreactive Coating Material as an Effective and Durable Antimicrobial Composite in Reducing Bacterial Load on Surfaces in Livestock

“…Bartomeuf et al examined a photoactive layer, which showed increased efficiency to 400 nm threshold against L. monocytogenes . In addition, the number of bacteria decreased significantly after 20 min UV-A lighting [ 68 ].…”