Fabrication and luminescence switching of Pt-loaded macro-porous Y2WO6:Eu3+ phosphor thin films for hydrogen-gas detection

A luminescence-switching phenomenon of Pt/Y2WO6:Eu3+ phosphor thin films was examined under redox conditions using hydrogen gas and air as a reductant and an oxidant, respectively. Macro-porous Y2WO6:Eu3+ thin films were initially synthesized by a Pechini-type sol–gel dip-coating method on silica glass substrates. Attempts were then made to load Pt nanoparticles (NPs) on the surface of the Y2WO6:Eu3+ thin films immersed in aqueous K2PtCl4 solutions through a method of self-regulated reduction of surfactants using a nonionic triblock copolymer (P-123). The amount of P-123, the concentration of the K2PtCl4 solutions, and the immersion duration were set as three parameters influencing the deposition of the Pt NPs. The number and size of the Pt NPs were found to be dependent on all the three parameters and their excessive deposition led to inevitable quenching of the Eu3+ emission from thin films. In contrast, the lightly loaded Pt NPs were effective to induce turn-off luminescence upon exposure of the thin films to hydrogen gas at a low temperature of 150 °C probably through their catalytic action. The recovery of luminescence was also possible simply by treating the reduced thin films at 200 °C in air. Thus the Pt/Y2WO6:Eu3+ phosphor thin films are promising as a facile hydrogen-gas detector.