Ruthenium dyes

Wolfbeis / Leiner 1986 ruthenium dyes in fiber optic oxygen sensors... 

Demas / Bacon 1987 ruthenium dyes in oxygen sensors... 

Eqs. (19) and (20) were derived applying the steady-state approximation to the oxidized Fe-TAML species and using the mass balance equation [Fe-TAML] = 1 + [oxidized Fe-TAML] ([Fe-TAML] is the total concentration of all iron species, which is significantly lower than the concentrations of H2O2 and ED). The oxidation of ruthenium dye 8 is a zeroth-order reaction in 8. This implies that n[ED] i+ [H202]( i+ m). Eq. (19) becomes very simple, i.e.,... 

Figure 3.31. Organic solar cell with the molecular glass Spiro-MeOTAD as the solid-state electrolyte. The photosensitive ruthenium dye is attached as a monolayer to Ti02 nanoparticles, thus forming a large active area for photoinduced electron transfer.

Figure 3.32. Energy level scheme of the device in Figure 3.31. Photoinduced electron transfer takes place from the photoexcited ruthenium dye into the Ti02 conduction band. The recombination directly back to the dye has to be suppressed. Instead, the current is directed through the circuit to the counterelectrode and the hole conductor that brings the electrons back via hopping transport. HTM hole transport material.

Similar behavior is observed in the potential-dependent luminescence of a ruthenium dye adsorbed to 2 [52]. Although the flat-band potential of 2 is known to shift positive in the presence of the potential-determining Li+ ion, relative to the TBA+ ion [5,68], this effect cannot explain the observed behavior. For example, in our experiments, the dye injects in both cases, but it takes a much smaller negative potential excursion to turn off the injection process in the presence of Li+ than with TBA+ [52]. This is the opposite of what would be expected if only equilibrium (i.e., dark) band edge motion were responsible for the effect. 

Ruthenium dye photosensitizers attached on the 2 surface absorb incident photon flux. 

A solid-state solar cell was assembled with an ionic liquid—l-ethyl-3-methylimidazolium bis(trifluoromethanesulfone)amide (EMITFSA) containing 0.2 M lithium bis(trifluoromethanesulfone)amide and 0.2 M 4-tert-butylpyridine—as the electrolyte and Au or Pt sputtered film as the cathode.51,52 The in situ PEP of polypyrrole and PEDOT allows efficient hole transport between the ruthenium dye and the hole conducting polymer, which was facilitated by the improved electronic interaction of the HOMO of the ruthenium dye and the conduction band of the hole transport material. The best photovoltaic result ( 7p=0.62 %, 7SC=104 pA/cm2, FOC=0.716 V, and FF=0.78) was obtained from the ruthenium dye 5 with polypyrrole as the hole transport layer and the carbon-based counterelectrode under 10 mW/cm2 illumination. The use of carbon-based materials has improved the electric connectivity between the hole transport layer and the electrode.51... 

The same approach was adapted in a later study. An efficient solid-state DSSC was fabricated using hybridized ruthenium dye 8. The hole conducting PEDOT was formed in situ via PEP. The thickness of the mesoporous Ti02 layer of the solar cell was varied. The highest efficiency (2.6% under 100 mW/ cm2 illumination) was achieved by using a 5.8- pm-thick Ti02 layer.52... 

This is considerably different from the recombination reaction with, for example, typical ruthenium dyes. This slow re-reduction of the dyad is explained by the low redox potential of the osmium center, the value of 0.66 V (vs. SCE) observed, points to a small driving force for the redox process. This observation is important for the design of dyes for solar cell applications. Osmium compounds have very attractive absorption features, which cover a large part of the solar spectrum. However, their much less positive metal-based oxidation potentials will result in a less effective re-reduction of the dyes based on that metal and this will seriously affect the efficiency of solar cells. In addition, for many ruthenium-based dyes, the presence of low energy absorptions, desirable for spectral coverage, is often connected with low metal-based redox potentials. This intrinsically hinders the search for dyes which have a more complete coverage of the solar spectrum. Since electronic and electrochemical properties are very much related, a lowering of the LUMO-HOMO distance also leads to a less positive oxidation potential. 

The photocurrents generated from PSII coated Ti02 electrodes were of low magnitude, 5-15uA. But PSII coated on a ruthenium dye-derivatised Ti02 electrode generated photocurrents of the order of 700 uA however this electrode was not stable at pH 6 and the material leaked out into the electrolyte within a few seconds. 

The physical and optical properties of the NPs used in this investigation are described in Table 6.1. The optical absorption properties of the ruthenium dye complex are also detailed in the table. It can be seen that there is good overlap between 7 of the pure silver and alloy NPs and the absorption band of the complex, while the gold NPs lie outside the absorption peak and are used as a negative control. The dependence of the excitation spectra of the dye complex on NP-dye distance is shown in Figure 6.14 for the case of the pure silver NPs. Also included in the figure is the excitation spectrum for the complex coated on the PEL layer in the absence of NPs. From Table 6.1, it can be seen that there is very good overlap between 7 of the silver NPs and the dye absorption band which constitutes the optimum plasmonic enhancement condition for the case of excitation enhancement. 

Size Spherical gold/silver alloy nanoparticles, surrounded by a silica spacer shell, to which is attached a fluorescent ruthenium dye, have been studied. The... 

Similar optical biosensors have been prepared for many other analytes. For example, a cholesterol optical biosensor has been devised based on fluorescence quenching of an oxygen-sensitive dye that is coupled to consumption of oxygen resulting from the enzyme-catalyzed oxidation of cholesterol by the enzyme cholesterol oxidase. Serum bilirubin has been detected using bilirubin oxidase, coimmobilized with a ruthenium dye, on an optical fiber.The bilirubin sensor was reported to exhibit a lower detection limit of iO Xmol/L, a linear range up to 30mmol/L, and a typical reproducibihty of 3% (CV), certainly adequate for clinical application. 

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