Development of type-I/type-II hybrid dye sensitizer with both pyridyl group and catechol unit as anchoring group for type-I/type-II dye-sensitized solar cell.

A type-I/type-II hybrid dye sensitizer with a pyridyl group and a catechol unit as the anchoring group has been developed and its photovoltaic performance in dye-sensitized solar cells (DSSCs) is investigated. The sensitizer has the ability to adsorb on a TiO2 electrode through both the coordination bond at Lewis acid sites and the bidentate binuclear bridging linkage at Brønsted acid sites on the TiO2 surface, which makes it possible to inject an electron into the conduction band of the TiO2 electrode by the intramolecular charge-transfer (ICT) excitation (type-I pathway) and by the photoexcitation of the dye-to-TiO2 charge transfer (DTCT) band (type-II pathway). It was found that the type-I/type-II hybrid dye sensitizer adsorbed on TiO2 film exhibits a broad photoabsorption band originating from ICT and DTCT characteristics. Here we reveal the photophysical and electrochemical properties of the type-I/type-II hybrid dye sensitizer bearing a pyridyl group and a catechol unit, along with its adsorption modes onto TiO2 film, and its photovoltaic performance in type-I/type-II DSSC, based on optical (photoabsorption and fluorescence spectroscopy) and electrochemical measurements (cyclic voltammetry), density functional theory (DFT) calculation, FT-IR spectroscopy of the dyes adsorbed on TiO2 film, photocurrent-voltage (I-V) curves, incident photon-to-current conversion efficiency (IPCE) spectra, and electrochemical impedance spectroscopy (EIS) for DSSC.

Effect of Substituents in Catechol Dye Sensitizers on Photovoltaic Performance of Type II Dye-Sensitized Solar Cells.

In order to provide a direction in molecular design of catechol (Cat) dyes for type II dye-sensitized solar cells (DSSCs), the dye-to-TiO2 charge-transfer (DTCT) characteristics of Cat dyes with various substituents and their photovoltaic performance in DSSCs are investigated. The Cat dyes with electron-donating or moderately electron-withdrawing substituents exhibit a broad absorption band corresponding to DTCT upon binding to TiO2 films, whereas those with strongly electron-withdrawing substituents exhibit weak DTCT. This study indicates that the introduction of a moderately electron-withdrawing substituent on the Cat moiety leads to not only an increase in the DTCT efficiency, but also the retardation of back electron transfer. This results in favorable conditions for the type II electron-injection pathway from the ground state of the Cat dye to the conduction band of the TiO2 electrode by the photoexcitation of DTCT bands.

Molecular epidemiological analyses of Japanese encephalitis virus isolates from swine in Japan from 2002 to 2004.

To characterize Japanese encephalitis virus (JEV) strains recently prevalent in Japan, JEV surveillance was performed in pigs from 2002 to 2004. Eleven new JEV isolates were obtained and compared with previous isolates from Japan and other Asian countries. All of the isolates were classified into genotype 1 by nucleotide sequence analysis of the E gene. Two new isolates with different levels of neurovirulence and neuroinvasiveness, but with only one nucleotide difference in the E gene, Sw/Mie/34/2004 and Sw/Mie/40/2004, were isolated at the same farm on the same day. Sw/Mie/40/2004 displayed higher neurovirulence and neuroinvasiveness in mice than the other four new isolates. Another new isolate, Sw/Hiroshima/25/2002, was neutralized by antiserum to Beijing-1 at a level similar to the homologous Beijing-1 strain, whilst seven other new isolates were neutralized at 10-fold-lower titres. However, there were no amino acid differences in the E protein among these eight isolates. The present study indicated that the 11 new JEV isolates were genetically similar, but biologically and serologically heterogeneous.