Angular selective transmittance through electrochromic tungsten oxide films made by oblique angle sputtering

Bellac, D. Le; Azens, A.; Granqvist, C.G.

doi:10.1063/1.113343

Cited by 54 publications

(37 citation statements)

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“…[10] Because of the distinctive and promising properties of WO 3 , as-synthesized nanorods may also serve as functional building blocks in the fabrication of 3D nanostructures or multifunctional heteronanostructures. Recently Zhou et al demonstrated the 3D growth of WO 3 nanowire networks using a thermal evaporation method.…”

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confidence: 99%

A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO₃ Nanowhiskers

2006

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The assembly of 1D nanostructures in the fabrication of nanoelectronic and nanophotonic devices is currently attracting significant attention. In particular, semiconductor and metal nanowires or nanorods are considered to be important building blocks in the fabrication of future nanodevices. Various types of nanowire heterostructures have been reported, including core/shell [1] and core/multishell nanocable structures, [2] coaxial nanowire heterojunctions, [3] epitaxial nanorod heterostructures, [4] and hierarchical heterostructures.[ [5g]Nanorods of transition metal oxides, such as WO 3, which have large surface areas and a high-aspect-ratio structure, are promising candidates for a vast range of applications including gas sensors, [6] photocatalysts, [7] electrochromic devices, [8] field-emission devices, [9] and solar-energy devices.[10] Because of the distinctive and promising properties of WO 3 , as-synthesized nanorods may also serve as functional building blocks in the fabrication of 3D nanostructures or multifunctional heteronanostructures. Recently Zhou et al. demonstrated the 3D growth of WO 3 nanowire networks using a thermal evaporation method.[11]W is a metal with a fairly low resistivity and a near-ideal midgap work function, and can be produced with a high refractivity through high-temperature processes. W can be used in metal gates in applications of complementary metal oxide semiconductor (CMOS) technology in nanodevices smaller than 100 nm.[12] W materials can be produced with various dimensions; 1D W nanowires have been found in particular to have useful electrical properties, such as efficient field-electron emission in a moderate electric field.[13] Although 1Dnanostructures of W and WO 3 have been studied extensively, few studies of W/WO 3 heteronanostructures have been reported.In this communication, we report the fabrication of a novel hierarchical heteronanostructure: single-crystal W nanothorns grown on WO 3 nanowhiskers (hereafter these heteronanostructures will be referred to as WWOs). In this WWO nanostructure, the WO 3 nanowhiskers were coated with thin W layers and W nanothorns grew on them. We used a two-step evaporation process to fabricate the hierarchical WWOs.In the first step, WO 3 nanowhiskers were deposited on a W plate by heating WO 3 powder at 1100°C on the substrate. Then, a mixture of WO 3 and graphite powder was used as the source material for the growth of the W nanothorns on the asprepared WO 3 nanowhiskers. Si powder was also heated with the substrate at 1100°C. We used the carbothermal reduction of WO 3 (WO 3 + C → WO x + CO 3-x ; x = 1-2) [14] and were able to expedite the further reduction of WO x species by using Si (WO x + Si → W + SiO x ) to produce W vapor. It is well known that W can be grown by Si reduction of W compounds.[15] The resulting W vapor was deposited on the WO 3 nanowhiskers to produce the WWO heteronanostructure. Our method for growing W nanomaterials is different to that used in previous studies: the thermal-heating of W films was the previ...

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A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO₃ Nanowhiskers

2006

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“…: 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.…”

Section: Introductionmentioning

confidence: 99%

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

Zanoni¹

2011

J. Braz. Chem. Soc.

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Eletrodo nanoporoso auto-organizado de W/WO 3 pode ser obtido através da anodização eletroquímica de placas de W em solução de NaF 0,15 mol L -1 como eletrólito suporte, aplicando uma rampa de potencial de 0,2 V s -1 , até alcançar 60 V, mantendo por 2 h. A forma monoclínica altamente ordenada do WO 3 é majoritária quando calcinado a 450 0 C durante 30 min, obtendo uma maior fotoatividade quando irradiada na luz visível em relação a luz UV. O eletrodo promove a descoloração total do vermelho básico 51, utilizado em tinturas de cabelo, após 60 min de oxidação fotoeletrocatalítica, em densidade de corrente de 1,25 mA cm -2 e irradiação em comprimento de onda 420-630 nm. Nessa condição foi obtido 63% de mineralização. Uma menor eficiência é obtida para o sistema irradiado por comprimento de onda (280-400 nm), quando apenas 40% de remoção de carbono orgânico total é obtida, necessitando de 120 min de tratamento para a descoloração total da solução do vermelho básico 51.Self-organized W/WO 3 nanoporous electrodes can be obtained by simple electrochemical anodization of W foil in 0.15 mol L -1 NaF solution as the supporting electrolyte, applying a ramp potential of 0.2 V s -1 until it reached 60 V, which was maintained for 2 h. The monoclinic form is majority in the highly ordered WO 3 annealed at 450 °C , obtaining a higher photoactivity when irradiated by visible light than by UV light. The electrode promotes complete discoloration of the investigated basic red 51 dye after 60 min of photoelectrocatalytic oxidation, on current density of 1.25 mA cm -2 and irradiation on wavelength of 420-630 nm. In this condition it was obtained 63% of mineralization. Lower efficiency is obtained for the system irradiated by wavelength (280-400 nm) when only 40% of total organic carbon removal is obtained and 120 min is required for complete discoloration.Keywords: W/WO 3 electrodes, electrochemical anodization, photoelectrocatalysis, basic red 51, hair dye IntroductionThe use of TiO 2 as photoanode in photoelectrocatalytic degradation of pollutants is well known in literature. [1][2][3][4][5][6][7][8][9][10] Nevertheless, this material presents band gap energy around 3.2 eV, which is photoexcited only in the ultraviolet region (l ≤ 380 nm).11-14 Tungsten trioxide has been an excellent alternative material, since it presents smaller band gap energy (2.4-2.8 eV) and can be photoexcited in the visible region close to the UV region. [15][16][17][18] 28-34 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. The electrodeposited Pt/WO 3 catalysts have improved the oxidation of methanol and formic acid. [35][36][37][38] The WO x films with Pt, Sn, and Ru dopands were used for electrooxidation of acetaldehyde. Some authors have de...

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“…[6][7][8] Tungsten trioxide (WO 3 ) is a promising electrochromic material candidate for these devices, available at low-cost, with a simple procedure for film preparation. [9,10] Although WO 3 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.…”

Section: Introductionmentioning

confidence: 99%

“…Fast responses, of within a few seconds, to these potential switches were exhibited by the electrochromic hybrid film. Keywords: electrochemistry · electrochromic material · hybrid film · ruthenium · tungsten trioxide be prepared by several techniques, for example, vacuum evaporation, [11] chemical vapor deposition, [12] sol-gel precipitation, [13] spin-coating, [14] sputtering, [9] and electrodeposition, [15] simple and low-cost procedures should be selected for emerging applications.…”

Section: Introductionmentioning

confidence: 99%

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

Yagi

Sone

Yamada

et al. 2004

Chemistry A European J

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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.

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Angular selective transmittance through electrochromic tungsten oxide films made by oblique angle sputtering

Cited by 54 publications

References 1 publication

A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO₃ Nanowhiskers

A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO₃ Nanowhiskers

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

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

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Angular selective transmittance through electrochromic tungsten oxide films made by oblique angle sputtering

Cited by 54 publications

References 1 publication

A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO3 Nanowhiskers

A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO3 Nanowhiskers

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

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

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A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO₃ Nanowhiskers

A Novel Heteronanostructure System: Hierarchical W Nanothorn Arrays on WO₃ Nanowhiskers

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