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

Surface Conditioning Effects on Submerged Optical Sensors: A Comparative Study of Fused Silica, Titanium Dioxide, Aluminum Oxide, and Parylene C

Optical sensors excel in performance but face efficacy challenges when submerged due to potential surface colonization, leading to signal deviation. This necessitates robust solutions for sustained accuracy. Protein and microorganism adsorption on solid surfaces is crucial in antibiofilm studies, contributing to conditioning film and biofilm formation. Most studies focus on surface characteristics (hydrophilicity, roughness, charge, and composition) individually for their adhesion impact. In this work, we tested four materials: silica, titanium dioxide, aluminum oxide, and parylene C. Bovine Serum Albumin (BSA) served as the biofouling conditioning model, assessed with X-ray photoelectron spectroscopy (XPS). Its effect on microorganism adhesion (modeled with functionalized microbeads) was quantified using a shear stress flow chamber. Surface features and adhesion properties were correlated via Principal Component Analysis (PCA). Protein adsorption is influenced by nanoscale roughness, hydrophilicity, and likely correlated with superficial electron distribution and bond nature. Conditioning films alter the surface interaction with microbeads, affecting hydrophilicity and local charge distribution. Silica shows a significant increase in microbead adhesion, while parylene C exhibits a moderate increase, and titanium dioxide shows reduced adhesion. Alumina demonstrates notable stability, with the conditioning film minimally impacting adhesion, which remains low.

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

Titanium dioxide (TiO2) is a well-known photocatalytic compound that can be used to effectively reduce the presence of pathogens in human and animal hospitals via ROS release. The aim of this study was to investigate the efficacy of a polymer-based composite layer containing TiO2 and zinc oxide (ZnO) against Escherichia coli (E. coli) of animal origin. We showed that the photocatalyst coating caused a significant (p < 0.001) reduction in pathogen numbers compared to the control with an average reduction of 94% over 30 min. We used six light sources of different wattages (4 W, 7 W, 9 W, 12 W, 18 W, 36 W) at six distances (35 cm, 100 cm, 150 cm, 200 cm, 250 cm, 300 cm). Samples (n = 2160) were taken in the 36 settings and showed no significant difference in efficacy between light intensity and distance. We also investigated the influence of organic contaminant that resulted in lower activity as well as the effect of a water jet and a high-pressure device on the antibacterial activity. We found that the latter completely removed the coating from the surface, which significantly (p < 0.0001) reduced its antibacterial potential. As a conclusion, light intensity and distance does not reduce the efficacy of the polymer, but the presence of organic contaminants does.

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

Photocatalytic degradation of organic pollutants in water is a highly efficient and green approach. However, the low quantum efficiency is an intractable obstacle to lower the photocatalytic efficiency of photocatalysts. Herein, the TiO₂/ZnO heterojunction thin films combined with surface oxygen vacancies (OVs) were prepared through magnetron sputtering, which was designed to drive rapid bulk and surface separation of charge carriers. The morphology and structural and compositional properties of films were investigated via different techniques such as SEM, XRD, Raman, AFM, and XPS. It has been found that by controlling the O₂/Ar ratio, the surface morphology, thickness, chemical composition, and crystal structure can be regulated, ultimately enhancing the photocatalytic performance of the TiO₂/ZnO heterostructures. In addition, the heterojunction thin film showed improved photocatalytic properties compared with the other nano-films when the outer TiO₂ layer was prepared at an O₂/Ar ratio of 10:35. It degraded 88.0% of Rhodamine B (RhB) in 90 min and 90.8% of RhB in 120 min. This was attributed to the heterojunction interface and surface OVs, which accelerated the separation of electron–hole (e–h) pairs.

Efficient photocatalytic inactivation of E. coli by Mn-CdS/ZnCuInSe/CuInS2 quantum dots-sensitized TiO2 nanowires

A novel visible light-driven photocatalyst (represented as Mn-CdS/ZCISe/CIS/TiO₂) for the passivation of E. coli was prepared with TiO₂ nanowires as support and using CuInS₂ (CIS) and ZnCuInSe (ZCISe) quantum dots (QDs), as well as Mn-doped CdS (Mn-CdS) nanoparticles (NPs) as sensitizers. The use of CIS and ZCISe QDs and Mn-CdS NPs extends the light harvest region to visible light. The photoelectric conversion efficiency was consequently improved, with a photocurrent density of 12.5 mA cm^-2, about 60 times that of pure TiO₂ nanowires. The germicidal efficiency of the photocatalyst was assessed by passivation of E. coli, 96% bacteria in 50 ml 10⁵ colony forming units (CFU) ml^-1 solution were killed within 50 min. Besides the high efficiency, the composite has good stability and satisfactory recycling performance. The antibiotic mechanism was also performed by using photoluminescence and a scavenging agent of different active matter, revealing that the photo-generated holes play a major role in the sterilization process.