The authors have demonstrated an approach to sensitized-type solar cells, based on TiO2 inverse opal and the use of CdSe quantum dots (QDs) as sensitizers. CdSe QDs were grown in situ on TiO2 inverse opal electrodes, utilizing a chemical bath deposition method. All of the photovoltaic performances, including short circuit photocurrent density, open circuit voltage, fill factor, and efficiency, were significantly improved by surface modification with ZnS and fluoride ions. A power conversion efficiency of about 2.7% has been attained, under solar illumination of 100mW∕cm2. This value is relatively high for metal oxide solar cells, sensitized with semiconductor QDs.

CdSe quantum dots (QDs) were adsorbed onto nanostructured TiO2 films for different times by using a chemical bath deposition method in order to produce QD-sensitized solar cells (QDSSCs). Surface modification was done by coating ZnS onto the CdSe QDs. The optical absorption and current-voltage characteristics of these devices were studied. The size of the CdSe QDs increased with increasing adsorption time, and there was an optimum CdSe adsorption time for achieving the best photovoltaic conversion efficiency. The photovoltaic properties of short-circuit current density, open-circuit voltage, and photovoltaic conversion efficiency were significantly improved after modifying the surface with ZnS. Under a solar illumination of 100 mW/cm2, an efficiency as high as 2.02% was achieved for the CdSe QDSSCs that were made by using this method.

[Ir(cod)Cl](2)/DPPF or BINAP efficiently catalyzed the cycloaddition of α,ω-diynes with nitriles to give pyridines. The reaction can accommodate a very wide range of nitriles. Both aliphatic and aromatic nitriles smoothly reacted with α,ω-diynes to give pyridines. Ten equivalents of unactivated aliphatic nitrile were enough to give the product in high yield. Aliphatic nitriles bearing an acetal or amino moiety could be used for the reaction. The highly regioselective cycloaddition of unsymmetrical diyne bearing two different internal alkyne moieties was achieved. The observed regioselectivity could be reasonably explained by considering the different reactivities of the α-position in iridacyclopentadiene. Regioselective cycloaddition was successfully applied to the synthesis of terpyridine and quinquepyridine. This chemistry was extended to a new and efficient synthesis of oligoheteroarenes. Five aromatic or heteroaromatic rings were connected in a single operation. [Ir(cod)Cl](2)/chiral diphosphine catalyst can be applied to enantioselective synthesis. Kinetic resolution of the racemic secondary benzyl nitrile catalyzed by [Ir(cod)Cl](2)/SEGPHOS gave a central carbon chiral pyridine in 80% ee. The mechanism was analyzed on the basis of the B3LYP level of density functional calculations.

The rate of hydrogen generation from water with an alumina-supported mixed semiconductor catalyst (ZnS-CdS/Al,O,) has been found to be much higher than those from water with singly supported catalysts (ZnS/Al,O, and CdS/Al,O,) under irradiation by both U.V. and visible light. The activity is not improved by the physical mixture of these singly supported catalysts even when the amounts of ZnS and CdS are the same as those present in the ZnS-CdS/Al,O,. The significant improvement in the rate of hydrogen production over ZnS-CdS/Al,O, catalyst is attributed to the intimate contact between ZnS and CdS particles that results from the deposition of fine ZnS particles over the CdS surface. Sites for hydrogen production seem to be newly generated on these contacting regions.

No abstract