Precisely Engineered Photoreactive Titanium Nanoarray Coating to Mitigate Biofouling in Ultrafiltration.

To combat biofouling on membranes, diverse nanostructures of titanium dioxide (TiO) have emerged as effective antimicrobial coatings due to TiO's abilities to transport charge and photoinduce oxidation. However, TiO 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 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 nanoparticles on the membrane surface with atomic-scale precision. Subsequently, solvothermal deposition assembles and aligns a uniform TiO nanoarray forest. In the presence of sunlight, this TiO nanoarray effectively inactivates any deposited bacteria, increasing flux recovery after membrane cleaning. By systematically investigating this antimicrobial activity, we found that TiO 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 coatings for ultrafiltration and other surfaces for a wide range of applications.