Visible light photochromism of polyoxometalates-based composite film with deposition of ZnFe2O4 nanoparticles

• Novel phosphomolybdic acid-based composite film was synthesized by entrapping PMoA particles into a silica sol–gel matrix and introducing ZnFe2O4 nanoparticles as visible light sensitizers.
• Resulted composite film exhibited high visible light photochromic responsiveness as well as reversible photochromism.
• Photo-generated electron transfer mechanism was identified due to the appearance of Mo5+ species during the photochromic process.

By introducing ZnFe2O4 nanoparticles as light sensitizer into the silica sol–gel matrix, a novel phosphomolybdic acid (PMoA)-based composite film with high visible light photochromism was successfully prepared. The resulted thin film was denoted as PMoA/SiO2/ZnFe2O4. The microstructure, visible-light photochromic behaviors and mechanism were fully investigated. Characterizations revealed that the Keggin geometry of PMoA particles and structure of tetrahedral zinc ions were well retained in the film. With visible light irradiation, the colorless transparent PMoA/SiO2/ZnFe2O4 composite film turned to blue and exhibited high photochromic responsiveness as well as reversible photochromism. According to the XPS analysis, the appearance of Mo5+ species indicated the photo-reduction reaction occurred between PMoA naoparticles and ZnFe2O4 sensitizers suggesting the photo-generated electron transfer mechanism during the photochromic process.

Novel phosphomolybdic acid-based composite film (denoted as PMoA/SiO2/ZnFe2O4) was successfully synthesized by entrapping PMoA particles into a silica sol–gel matrix and introducing ZnFe2O4 nanoparticles as visible light sensitizers. Remarkably, the resulted composite film exhibited high visible light photochromic responsiveness as well as reversible photochromism. Meanwhile, the photo-generated electron transfer was identified due to the appearance of Mo5+ species during the photochromic process.Figure optionsDownload as PowerPoint slide