TiO₂ Nanofilms on Polymeric Substrates for the Photocatalytic Degradation of Methylene Blue

A low-temperature process to synthesize and print photoactive TiO₂ nanofilms onto polymeric substrates using a modified desktop inkjet printer is presented. The coated substrates were assembled in a microfluidic device for photocatalytic studies fabricated by selective transmission laser welding. The synthesized TiO₂ showed a competitive activity compared with commercial TiO₂ nanopowders. Furthermore, the coated catalyst remained active and intact even after a long-term reaction run. The inkjet printing method can be utilized for the efficient immobilization of catalytic films onto reactor walls in the design of continuous flow reactors. A dispersed TiO₂ sol was prepared by the thermohydrolysis of TiCl₄ below 100 °C. The resulting sol was stabilized by using ethylene glycol and directly printed onto the substrate without further heat processing. The printability and colloidal stability of the inks were assessed by measuring their rheological and interfacial properties. X-ray powder diffraction (XRD) analysis identified the synthesized TiO₂ as pure anatase nanosized particles (∼4.5 nm) verified by transmission electron microscopy (TEM). The photocatalytic activity of the printed layers was studied in the microreactor based on the degradation of methylene blue. Inkjet printing proved to be a customizable technique for coating active nanocatalysts. The overall process presented here is cost-effective and efficient in manufacturing flexible lightweight microreactors coated with highly tunable TiO₂ catalytic films.