Superhydrophobic and White Light-Activated Bactericidal Surface through a Simple Coating

Bacterial adhesion
and proliferation on surfaces are a challenge in medical and industrial
fields. Here, a simple one-step technique is reported to fabricate
self-cleaning and bactericidal surfaces. White, blue, and violet paints
were produced using titanium
dioxide nanoparticles, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, crystal
violet, toluidine Blue O, and ethanol solution. All of the painted
surfaces showed superhydrophobicity in air, and even after hexadecane
oil contamination, they retained water repellency and self-cleaning
properties. In an assay of bacterial adhesion, significant reductions
(>99.8%) in the number of adherent bacteria were observed for all
the painted surfaces. In bactericidal tests, the painted surfaces
not only demonstrated bactericidal activity against Staphylococcus
aureus and Escherichia coli in the dark
but also induced very potent photosensitization (>4.4 log reduction
in the number of viable bacteria on the violet painted surface) under
white light illumination. The technique that we developed here is
general and can be used on a wide range of substrates such as paper,
glass, polymers, and others.