Efficient visible light sensitization of TiO₂by surface complexation with Fe(CN)₆^4–

Abstract

A coloured charge-transfer complex formed by adsorption of Fe(CN/& at the surface of Ti02 particles and electrodes upon photoexcitation injects electrons into the conduction band of this semiconductor with a quantum yield of at least 37%.

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2‐Based Nanomaterials

“…Drawing on the fundamental studies on dye sensitization of other wide bandgap semiconductors (ZnO, SnO 2 ) in the 1960s [55][56][57][58][59], attaching visiblelight-absorbing organic dyes to the surface of TiO 2 [60,61] has led to fabrication of regenerative dye-sensitized solar cells with the overall solar conversion efficiencies exceeding 10% [62][63][64]. Other sensitization approaches utilize chromophores like semiconductor quantum dots [65][66][67][68][69][70], plasmonic metal nanocrystals [71][72][73][74][75], simple coordination compounds like chloroplatinate (IV) complexes [29,32,76] or ferrocyanide ions [77][78][79], stable polymeric compounds [38,39,[80][81][82][83], or metal ions (Cu 2+ , Fe 3+ ) grafted onto the TiO 2 surface [84,85]. In contrast to these surfaceconfined sensitization protocols, bulk-doping of TiO 2 has also attracted significant interest.…”

Photosensitization and the Photocurrent Switching Effect in Nanocrystalline Titanium Dioxide Functionalized with Iron(II) Complexes: A Comparative Study

“…On the other hand the direct photoinduced electron transfer from the surface bound molecule described by the V RMS term (cf. Figure 1d) was reported only for cyanoferrate- [61][62][63][64][65][66][67][68][69][70][71][72] and catechol-modified [73] titanium dioxide. The above-mentioned theoretical background shows that irrespective of the chemical nature of the photosensitizer and its binding mode to the semiconductor surface, one should consider two main ways of populating the semiconductor CB: direct and indirect.…”

“…The broad band with maximum at 415 nm recorded for [Fe(CN) 6 , is attributed to the MMCT transition, namely Fe II !Ti IV . [61][62][63][64][65][66][67][68][69][70][71][72] The described spectral features of all three materials are parallel to the semiconductor/surface-complex interaction. The interaction between ferrocene and titanium dioxide is very weak-slight spectral changes reflect a simple physisorption of the iron complex at the surface of TiO 2 with a very weak electronic coupling.…”

“…The MMCT nature of this new absorption band has been described in detail elsewhere. [61][62][63][64][65][66][67][68][69][70][71][72] The strength of the electronic coupling can be also deduced from the shape of the photosensitizer absorption bands. No significant changes in the energy and shape of electronic transitions within the photosensitizer indicate a lack of electronic coupling ( Figure 3a).…”

Redox‐Controlled Photosensitization of Nanocrystalline Titanium Dioxide

“…[67][68][69] In most cases, these complexes undergo reversible electrode reactions. [69][70][71][72] Moreover, semiconducting materials with cyanoferrates chemisorbed on the surface show numerous interesting properties, for example, they photosensitize titanium dioxide towards visible light [61,62] and allow photocurrent switching. [34,35] Experimental Section ) was used to prepare porous electrodes.…”