Scalable Hybrid Antibacterial Surfaces: TiO 2 Nanoparticles with Black Silicon.

With the increase of drug resistance, there is a need for surface coatings that inhibit microbes without antibiotics. Nanostructured photocatalysts, like TiO 2 -coated nanotubes, are promising alternatives to antibiotics. Nanostructures rupture the cell wall by impaling the bacteria. Photocatalysts generate reactive oxygen species (ROS) in the presence of light, which oxidize organic matter. The combined effect of photocatalysts and nanostructures is better than the addition of individual components, as nanostructures also enhance the ROS production by trapping light. The synergetic effect is remarkably effective in reducing the growth of bacterial colonies, but scalability still remains a challenge. Conventional techniques like atomic layer deposition (ALD) are excellent for proof of concept but are not scalable to hundreds of square meters, as needed for practical applications. This report demonstrates two scalable and cost-effective techniques for synthesizing photocatalytic nanostructures: spray- and spin-coating TiO 2 nanoparticles. Unlike ALD, spray- and spin-coated TiO 2 nanoparticles do not reduce the roughness of a structured surface, which improves antibacterial performance by 23%. Integration of nanostructures with spray-coated TiO 2 is potentially a low-cost and scalable technology for large-area antibacterial surfaces.