Block copolymer-templated gasochromic WO3 thin films with uniform mesopores for fast optical hydrogen sensing

A method to prepare mesoporous WO 3 thin films (represented by MP-WO 3 ) with a uniform pore size of ∼18 nm is developed successfully by utilizing poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as the structure-directing agent (SDA). The properties of the gasochromic MP-WO 3 thin film are studied in detail and compared with the control groups prepared by using homopolymer PEO , PS, or their mixtures as SDA. Utilizing an optimized thermal treatment procedure, the gasochromic MP-WO 3 thin film of which the transmittance change Δ T is 59.1% exhibites the fastest coloration and bleaching speed with a coloration time of 27.3 s and a bleaching time of 19.7s as well as excellent reversibility within 90 cycles. This study offers a new strategy and insight into the development of mesoporous WO 3 hydrogen gasochromic films with excellent performances and paves its way toward the application of an optical hydrogen sensor.