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Preparation and Multicolor Electrochromic Performance of a WO 3 /Tris(2,2′‐bipyridine)ruthenium( II )/Polymer Hybrid Film
Author(s) -
Yagi Masayuki,
Sone Koji,
Yamada Miki,
Umemiya Saori
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400323
Subject(s) - electrochromism , ruthenium , 2,2' bipyridine , bipyridine , materials science , inorganic chemistry , chemistry , polymer chemistry , crystallography , crystal structure , organic chemistry , catalysis , electrode
A tungsten trioxide (WO 3 )/tris(2,2′‐bipyridine)ruthenium( II ) ([Ru(bpy) 3 ] 2+ ; bp y =2,2′‐bipyridine)/poly(sodium 4‐styrenesulfonate) (PSS) hybrid film was prepared by electrodeposition from a colloidal triad solution containing peroxotungstic acid (PTA), [Ru(bpy) 3 ] 2+ , and PSS. A binary solution of [Ru(bpy) 3 ] 2+ and PTA (30 vol % ethanol in water) gradually gave an orange precipitate, possibly caused by the electrostatic interaction between the cationic [Ru(bpy) 3 ] 2+ and the anionic PTA. The addition of PSS to the binary PTA/[Ru(bpy) 3 ] 2+ solution remarkably suppressed this precipitation and caused a stable, colloidal triad solution to form. The spectrophotometric measurements and lifetime analyses of the photoluminescence from the excited [Ru(bpy) 3 ] 2+ ion in the colloidal triad solution suggested that the [Ru(bpy) 3 ] 2+ ion is partially shielded from electrostatic interaction with anionic PTA by the anionic PSS polymer chain. The formation of the colloidal triad made the ternary [Ru(bpy) 3 ] 2+ /PTA/PSS solution much more redox active. Consequently, the rate of electrodeposition of WO 3 from PTA increased appreciably by the formation of the colloidal triad, and fast electrodeposition is required for the unique preparation of this hybrid film. The absorption spectrum of the [Ru(bpy) 3 ] 2+ ion in the film was close to its spectrum in water, but the photoexcited state of the [Ru(bpy) 3 ] 2+ ion was found to be quenched completely by the presence of WO 3 in the hybrid film. The cyclic voltammogram (CV) of the hybrid film suggested that the [Ru(bpy) 3 ] 2+ ion performs as it is adsorbed onto WO 3 during the electrochemical oxidation. An ohmic contact between the [Ru(bpy) 3 ] 2+ ion and the WO 3 surface could allow the electrochemical reaction of adsorbed [Ru(bpy) 3 ] 2+ . The composition of the hybrid film, analyzed by electron probe microanalysis (EPMA), suggested that the positive charge of the [Ru(bpy) 3 ] 2+ ion could be neutralized by partially reduced WO 3 − ions, in addition to Cl − and PSS units, based on the charge balance in the film. The electrostatic interaction between the WO 3 − ion and the [Ru(bpy) 3 ] 2+ ion might be responsible for forming the electron transfer channel that causes the complete quenching of the photoexcited [Ru(bpy) 3 ] 2+ ion, as well as the formation of the ohmic contact between the [Ru(bpy) 3 ] 2+ ion and WO 3 . A multicolor electrochromic performance of the WO 3 /[Ru(bpy) 3 ] 2+ /PSS hybrid film was observed, in which transmittances at 459 and 800 nm could be changed, either individually or at once, by the selection of a potential switch. Fast responses, of within a few seconds, to these potential switches were exhibited by the electrochromic hybrid film.