Preparation and Multicolor Electrochromic Performance of a WO₃/Tris(2,2′‐bipyridine)ruthenium(II)/Polymer Hybrid Film

Abstract

A tungsten trioxide (WO(3))/tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy)(3)](2+); bpy=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.

A single-molecule multicolor electrochromic device generated through medium engineering

“…Because the realization of a multicolor switch is preferred in the majority of their applications in displays, [4][5][6][7][8][9][10] various electrochromic materials including polymers, 11,12 small organic molecules 13,14 and metal-organic complexes, 15 and technologies aimed at multicolor switches have been intensively explored. Transition metals based on metal-organic complex multicolor electrochromic materials exhibit attractive properties, such as high stability and chemiluminescence.…”

Nanoporous of W/WO3 Thin Film Electrode Grown by Electrochemical Anodization Applied in the Photoelectrocatalytic Oxidation of the Basic Red 51 used in Hair Dye

“…: vacuum evaporation, 19 chemical vapor, 20,21 sol-gel precipitation, [22][23][24][25] spin coating, 26 sputtering, 27 and electrodeposition. [28][29][30][31][32][33][34] Although a sol-gel technique is one of the simplest and lowest-cost procedures selected for a wide range of applications, there have been only a few reports on photoelectrochemical characteristics of the WO 3 film prepared by a sol-gel technique. [5][6][7][8] Several techniques for improving photoresponse of thin film electrodes W/WO 3 have already been proposed.…”

Electrochromic Hysteresis Performance of a Prussian Blue Film Arising from Electron‐Transfer Control by a Tris(2,2′‐bipyridine)ruthenium(II)‐Doped WO3 Film as Studied by a Spectrocyclic Voltammetry Technique

“…These geared electrochemical reactions produced an electrochromic hysteresis performance of the PB film layered on the [Ru-A C H T U N G T R E N N U N G (bpy) 3 [RuA C H T U N G T R E N N U N G (bpy) 3 ] 2 + was doped in a WO 3 film by cathodic electrodeposition from an aqueous colloidal triad solution containing peroxotungstic acid (PTA), [RuA C H T U N G T R E N N U N G (bpy) 3 ] 2 + , and poly(sodium 4-styrenesulfonate) (PSS). [13,14] In the absence of PSS, precipitation is formed by electrostatic interaction between the cationic [RuA C H T U N G T R E N N U N G (bpy) 3 ] 2 + and anionic PTA. Remarkably, PSS suppresses the precipitation to provide a stable colloidal triad solution that is favorable for electrodeposition.…”

“…It allows the redox of Ru II /Ru III to occur at the potential (1.03 V vs saturated calomel electrode (SCE)) above the FB potential (0.26 V) of WO 3 . [13] We are interested in this unusual electrochemical feature because it could function as an electron-transfer channel passing through the Schottky barrier at the WO 3 heterojunction.…”

“…This is ascribed to the [RuA C H T U N G T R E N N U N G (bpy) 3 ] 2 + doping causing a decrease in FB potential of WO 3 to a potential (0.09 V) that is significantly lower than the redox potential (0.14 V) of PW/PB. [13] To reveal the electrochemical reactions for the [Ru-…”