Mussel adhesive protein-coated titanium oxide nanoparticles for effective NO removal from versatile substrates

Titanium dioxide (TiO2)-based photocatalysis has been adopted to decrease nitrogenous oxides levels in air. However, the low binding abilities of polymeric binders used to bind TiO2 particles to various substrates in wet conditions, and the formation of large agglomerates of TiO2 particles due to poor the adhesion between polymeric binders and TiO2 particles have obstructed various indoor and outdoor applications of TiO2. In this study, we demonstrated an effective method of dispersing TiO2 particles in an aqueous solution with the help of mussel adhesive protein (MAP). The MAP was homogeneously coated on the surfaces of TiO2 particles with a thickness of 3–4 nm. The MAP acted as a dispersing agent for the TiO2 particles and enabled strong and stable adhesion between TiO2 and the substrates. Moreover, the homogeneously coated MAP layer did not affect the intrinsic photocatalytic activity of the TiO2 particles. Notably, the MAP/TiO2 nanoparticle-coated stainless steel sample exhibited a superior NO removal rate to mortar, glass, and wood-containing samples because of the enhanced efficiency of the photocatalytic redox process. The developed protein-based suspension could be successfully applied to various construction materials including cement, glass, wood, and stainless steel because of the strong binding ability of MAP, especially in wet conditions.