Electron shifts upon charge-transfer

Fig. 2 Electronic spectra of the carbon tetrachloride solutions of diiodine attendant upon addition of excess amounts of benzene (Act = 285 nm), mesitylene (Act = 327 nm) and hexamethylbenzene (Act = 369 nm) with the charge-transfer band showing significant red-shifts with increasing strength of the aromatic donors...

SAMFETs have also been used in chemical sensing. The a-substituted quincpiethiophene SAMFETs were covered with a 10-nm pinhole-riddled iron tetraphenylporphyrin chloride layer, that acts as a receptor to nitric oxide (NO), an important biomarker [74]. The threshold voltage, measured by the FET transfer characteristics with the porphyrin receptor shifts upon increased exposure to NO. Annealing the monolayer FET in vacuum restores the initial FET behavior. Also, in the single monolayer HBC assembled FETs between metallic SWCNT source and drain electrodes increased current levels were measured in /d-Fds and Aj-Fg characteristics (Fig. 9) upon exposure to solutions of the electron acceptor TCNQ [68]. While the mechanism of response is not known, TCNQ has an affinity for coronene, and likely gives rise to charge transfer between electron-deficient TCNQ... 

In order to obtain high conversion efficiencies, optimization of the short-circuit photocurrent (z sc) and open-circuit potential (Voc) of the solar cell is essential. The conduction band of the TiO is known to have a Nernstian dependence on pH [13,18], The fully protonated sensitizer (22), upon adsorption, transfers most of its protons to the TiO surface, charging it positively. The electric field associated with the surface dipole generated in this fashion enhances the adsorption of the anionic ruthenium complex and assists electron injection from the excited state of the sensitizer in the titania conduction band, favoring high photocurrents (18-19 inA/cm ). However, the open-circuit potential (0.65 V) is lower due to the positive shift of the conduction-band edge induced by the surface protonation. 

In our liquid ammonia experiments the amide concentration (1.5 — 8 X 10 6 M) is in a range in which appreciable ionic dissociation occurs. Negative ions in aqueous solution are well known to yield solvated electrons upon excitation in their charge-transfer bands (7, 15, 19, 22), and one may expect the same process to operate also for NH2 - in ammonia. The large blue shift of the amide peak with decreasing temperature (3) supports the view that the absorption is a charge-transfer band (27). We therefore write for potassium amide in liquid ammonia (e signifies the solvated electron) ... 

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