Precisely Engineered Photoreactive Titanium Nanoarray Coating to Mitigate Biofouling in Ultrafiltration

Abstract

To combat biofouling on membranes, diverse nanostructures of titanium dioxide (TiO 2 ) have emerged as effective antimicrobial coatings due to TiO 2 's abilities to transport charge and photoinduce oxidation. However, TiO 2 composite polymeric membranes synthesized using traditional methods of growing crystals have proven chemically unstable, with loss of coating and diminishing antimicrobial performance. Thus, new fabrication methods to enhance durability and efficacy should be considered. In this work, we propose a stepwise approach to construct a stable, uniform TiO 2 nanoarray of regularly spaced, aligned crystals on the surface of a polytetrafluoroethylene ultrafiltration membrane using precisely controlled atomic layer deposition (ALD) followed by solvothermal deposition. We demonstrate that ALD can uniformly seed TiO 2 nanoparticles on the membrane surface with atomic-scale precision. Subsequently, solvothermal deposition assembles and aligns a uniform TiO 2 nanoarray forest. In the presence of sunlight, this TiO 2 nanoarray effectively inactivates any deposited bacteria, increasing flux recovery after membrane cleaning. By systematically investigating this antimicrobial activity, we found that TiO 2 both physically damages cell membranes as well as produces reactive oxygen species in the presence of sunlight that inactivate bacteria. Our study provides an effective bottom-up synthesis scheme to optimize and tailor antifouling TiO 2 coatings for ultrafiltration and other surfaces for a wide range of applications.

Nanostructured Geometries Strongly Affect Fouling of Carbon Electrodes

“…The moderately hydrophilic planar PyC surface contained a high carbon content with negligible functionalities and a high I d / I g ratio, indicating the presence of the sp 3 -bonded carbon and highly reactive sp-type carbon. The modulation of free surface energies could play an important role in controlling the fouling of the electrodes. − However, due to the non-uniformity of MWCNT/ta-C and CNF/ta-C, we could not get reliable contact angle measurements for several liquids, thus limiting the possibility to study the surface energies.…”

Atomic Layer Deposition of Antibacterial Nanocoatings: A Review

“…The disruption of cell wall integrity due to ROS action can be observed via scanning electron microscopy. For example, Zhang et al observed a significant bactericidal effect due to cell membrane damage of E. coli on the surface of TiO 2 nanoarrays after sunlight irradiation (Figure 2b-e) [39]. In fact, according to a number of studies [29,30,39,54], significant antibacterial and antifungal activity is only shown when TiO 2 is irradiated in the ultraviolet range.…”

“…Despite the low growth rate, nanocoatings of inorganic bactericidal materials obtained via ALD can find wide applications in a variety of products such as dental and orthopedic implants [25][26][27][28], contact lenses [29], touch screens [30][31][32], antibacterial textiles [33][34][35][36], and water purification systems [37][38][39].…”

The Role of Inorganic and Carbon Nanomaterials in Surface Modification to Attain Antibiofouling Polymeric Membranes for Water Treatment─A Review

“…176 In situ polymerization of PES and TiO 2 that had been previously factionalized via biphasic solvothermal reaction led to realization of an antibacterial membrane which reduced E. coli from 12.2 log 10 (CFU/mL) for TFC membrane to 10.7 log 10 (CFU/mL). 79 Zhang et al 177 demonstrated that atomic layer deposition (ALD) can uniformly seed TiO 2 NPs on the polytetrafluoroethylene (PTFE) membrane surface with precision. The TiO 2 −PTFE composite membrane inactivated 97.7% E. coli through the physical piercing of cells by sharp crystalline vertices and by oxidative stress from the production of hydroxyl radicals.…”