Transient absorption spectroscopy slow measurement

The kinetics of the oxidation of iodide by the oxidized state of c -[Ru (dcbpy)2-(NCS)2] sensitizer adsorbed on nanocrystalline Ti02 films was measured by transient laser spectroscopy [92]. Figure 16 shows the transient absorption kinetics recorded in propylene carbonate with various electrolytes added. In all cases, the recovery of the ground-state absorption of the dye, after the fast electron injection into the solid, does not follow a simple kinetic law. In the absence of any electrolyte (trace a), the time needed to reach half of the initial absorbance (/1/2) through back electron transfer is 2 ps. Total recovery of the initial absorption, however, requires several hundreds of microseconds to milliseconds. Traces b, c, and d were recorded after addition of a common concentration of 0.1 m of iodide in the form of tetra-butylammonium (TBA+), Li+, and Mg + salts, respectively. Addition of the electrolyte in all three cases led to a considerable acceleration of the dye regeneration with ti/2 < 200 ns and complete suppression of the slow kinetic tail. 

Silylenes are short-lived intermediates, and their detection requires fast methods such as ultraviolet (UV)24 or laser-induced fluorescence spectroscopy.25 The characteristic absorption maxima in the UV-visible spectra of these species, which are assigned to n - p transitions of electrons at the silicon atom, were used as a fingerprint to prove the occurrence of silylenes in matrices or solution. In addition, these transient species, which under normal conditions are too short lived to be observed by a slow detection method such as infrared (IR) spectroscopy, can be isolated in inert hydrocarbon or noble gas matrices, thus allowing the accurate measurement of their IR spectra. 

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