Scalable Hybrid Antibacterial Surfaces: TiO2 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 TiO2-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 TiO2 nanoparticles. Unlike ALD, spray- and spin-coated TiO2 nanoparticles do not reduce the roughness of a structured surface, which improves antibacterial performance by 23%. Integration of nanostructures with spray-coated TiO2 is potentially a low-cost and scalable technology for large-area antibacterial surfaces.

Ambient Light-Activated Antibacterial Material: Manganese Vanadium Oxide (Mn2V2O7).

Antimicrobial surfaces can reduce the spread of bacteria from high-touch surfaces, saving millions of lives worldwide. Antibacterial photocatalytic films, like TiO2, are widely reported but limited in practice because they need high-intensity UV light. More practical but less reported are photocatalysts that work under low-intensity visible light from an indoor lamp. Here, we demonstrate that manganese vanadium oxide (MVO) is an antibacterial photocatalyst that works under light-emitting diode (LED) lights at ∼3000 lux. MVO is an earth-abundant semiconductor with a band gap of 1.7 eV that absorbs visible light to create reactive oxygen species (ROS) in water. ROS reduces bacteria counts by 4 orders of magnitude in 8 h under 9000 lux LED light. The antibacterial effect is significant even in MVO powder and films, which are amenable to large-area fabrication. MVO is a promising candidate for next-generation antimicrobial coatings that are stable, cheap, effective, earth-abundant, and activated by indoor lights.