No abstract

Under basic condition, SiTPyP(O−)2 exerts two-electron oxidation of water to form hydrogen peroxide as the primary product in aqueous acetonitrile, which is initiated through one-electron oxidized process on the electrode with faradaic yield of 84–92%.

Fluorescence enhancement in DNA and on nanosheets.

The molecular catalyst sensitized system (MCSS), where an excited molecular catalyst adsorbed on a semiconductor such as TiO 2 injects electrons to the conduction band of the semiconductor leading to hydrogen evolution/ CO 2 reduction coupled with an oxidation of water on the molecular catalyst, has been one of the most probable candidates in the approach to artificial photosynthesis. For a full utilization of visible light, however, a serious light scattering of the aqueous suspension of TiO 2 in the visible region, which is generally experienced, should be avoided. Here, we report a preparation of optically transparent colloidal dispersion of TiO 2 by the sol/gel reaction of TiCl 4 through progressive hydrolysis/condensation under the basic condition without any calcination processes. The TiO 2 nanoparticles (TiO 2 (NPs)) obtained were characterized as an amorphous particle (∼10−15 nm) having a microcrystal domain of anatase within several nm by XRD, Raman spectroscopies, XRF, XAFS, TG/DTA, and HRTEM, respectively. The energy-resolved distribution of carrier electron traps in TiO 2 (NPs) as a fingerprint of TiO 2 was characterized through reversed double-beam photo-acoustic spectroscopy to have a close similarity to that of TiO 2 (ST-01) as well as the observation of carrier traps by transient absorption spectroscopy. Though the powder TiO 2 (NP) itself was not dispersed well in aqueous solution, the wet TiO 2 (NPs) as prepared before being dried up provided a completely transparent aqueous dispersion under the acidic condition (1 M HCl). Addition of methanol enabled the colloidal dispersion (TiO 2 (NPs, MeOH/H 2 O, 0.1 M HCl)) to keep the optical transparency for longer than 1 year (550 days), which is the first example of TiO 2 dispersion storable for such a long period. TiO 2 (NPs, MeOH/H 2 O) exhibited a moderate photocatalytic reactivity of H 2 evolution with a quantum yield of ∼2.6% upon 365 nm light irradiation. An optically transparent thin film of TiO 2 (NPs, MeOH/H 2 O) was also successfully prepared on a glass plate to exhibit an enhanced hydrophilicity upon UV light irradiation.