Iridium optical properties

Iridium as an electrode material has received considerable attention in the last decade not only because of its excellent catalytic properties but also in relation to the electrochromic effect observed for anodic iridium oxide films (AIROF). Electrochromism of iridium was thought to be of technical relevance for display applications and triggered several studies of the electrochemical and optical properties of AlROFs [67, 85-88],... 

In order to explain the changing optical properties of AIROFs several models were proposed. The UPS investigations of the valence band of the emersed film support band theory models by Gottesfeld [94] and by Mozota and Conway [79, 88]. The assumption of nonstoichiometry and electron hopping in the model proposed by Burke et al. [87] is not necessary. Recent electroreflectance measurements on anodic iridium oxide films performed by Gutierrez et al. [95] showed a shift of optical absorption bands to lower photon energies with increasing anodic electrode potentials, which is probably due to a shift of the Fermi level with respect to the t2g band [67]. 

The choice of a suitable counter-electrode for a successful EW is not easy since only a few compounds fulfil the desired operational requirements which call for an uncommon combination of electrochemical and optical properties. The most promising, and, thus far, the mostly used materials are indium tin oxide, nickel oxide, iridium oxide and cobalt oxide among the inorganic ECMs, and polyaniline (PANI) among the organic ECMs. The electrochromic properties of indium tin oxide and PANI have been described in Chapter 7. Therefore, here attention will be mainly focused on transition metal oxide counter-electrodes. 

Anodic Electrochromic Materials. The most commonly used anodic electrochromic materials are nickel oxide (Svensson and Granqvist [1986]) and iridium oxide (Gottesfeld et al. [1978]). They switch from a transparent state to a colored one upon extraction of protons. Charge-balancing electrons are simultaneously extracted from the valence band. The films are probably a mixture of oxide and hydroxide components in the bleached state, since there needs to exist a reservoir of protons in the films. Due to the high cost of iridium, the use of nickel oxide is favored for large scale appfications. Recently, a class of mixed nickel oxides with enhanced modulation between the transparent and the colored state have been discovered (Avendano et al. [2003]). Intercalation of Li into ifickel oxide films has been attempted, but the optical properties are not modulated very much (Decker et al. [1992]). The mechanism of optical absorption is not known in detail. However, in... 

While in the previous two examples we have discussed the initial stages of oxidation, we now shall focus our attention on the optical properties of thicker oxide layers. Anodically formed iridium oxide films have attracted particular attention because of their pronounced electrochromic effect. When an Ir electrode is scanned anodically in 0.5 M H2SO4, oxidation starts at +0.6 V versus SCE. On the cathodic scan, however, the oxide layer is not reduced to the metallic state but to a low-conductivity hydroxide film facilitating further oxide formation with each anodic potential cycle. Continuous cycling of the iridium electrode between -0.25 and +1.3 V (SCE), at a frequency of 1 cps, therefore has been used as a standard treatment for the formation of thick anodic iridium oxide films. ... 

Abstract Pressure-sensitive paint (PSP) is applied to the areodynamics measurement. PSP is optical sensor based on the luminescence of dye probe molecules quenching by oxygen gas. Many PSPs are composed of probe dye molecules, such as polycyclic aromatic hydrocarbons (pyrene, pyrene derivative etc.), transition metal complexes (ruthenium(II), osumium(II), iridium(III) etc.), and metalloporphyrins (platinum (II), palladium(II), etc.) immobilized in oxygen permeable polymer (silicone, polystyrene, fluorinated polymer, cellulose derivative, etc.) film. Dye probe molecules adsorbed layer based PSPs such as pyrene derivative and porphyrins directly adsorbed onto anodic oxidised aluminium plat substrate also developed. In this section the properties of various oxygen permeable polymer for matrix and various dye probes for PSP are described. 

Research in the chemistry of rhodium and iridium Af-heterocyclic carbene (NHC) complexes has extraordinarily evolved since 2000. A quick search for rhodiimi-NHC and iridiimi-NHC complexes in the SCl-expanded database, with a 2005-2013 timespan, results in more than 360 hits for rhodium, and more than 340 for iridiiun, which gives a good idea on the interest that rhodium and iridium NHC-based chemistry have achieved in the last few years. It is important to note that a nimiber of reviews and book chapters specifically concerning the chemistry of NHC-based compounds of rhodium and iridiiun have recently appeared [1]. This chapter will deal with all new aspects of the NHC-M (M = Rh, Ir) chemistry not reviewed before, and therefore is mainly restricted to the last 4-5 years. The chapter is classified into two main sections, the first of which deals with relevant structural and electronic features of Rh-NHC and Ir-NHC complexes, and the second with the catalytic applications of these compounds. While not pretending to be completely comprehensive, we have tried to describe the most relevant examples assigned to each section. Some other relevant applications of these complexes have not been considered, such as the emerging biochemical applications, mostly referred to Rh-NHC complexes [2], and the luminescent properties of some Ir-NHC complexes, mostly used for the fabrication of electro-optical devices [3]. 

Johnson J.A., Lisoni J.G., Wonters D.J. Iridium based electrodes for ferroelectric capacitor fabrication. Mater. Res. Soc. Symp. Proc. 2002 688 59-64 Kang J., Yoko T., Kozuka H., Sakka S. Preparation of Pb-based complex perovskite coating films by sol-gel method. In Sol-Gel Optics, vol. II, J.D. Mackenzie, ed. Pfoc. SPIE 1992 1758 249-259 Kim Dong-Joo, Maria Jon-Paul, Kingon A.I. Compositional effect on the piezoelectric and ferroelectric properties of chemical deposited PZT thin films. Mater. Res. Soc. Symp. Proc. 2002 688 351-356... 

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