Synthesis and Photo-chemical Properites of Semiconductors Incorporated in the Interlayer

制备了层状化合物/半导体非复合材料，并对其光化学性能进行了研究。半导体如CdS， Fe_2O_3。CuO、NiO、MnO、TiO_2等依次嵌入到H_2Ti_4O_9、H_4Nb_6O_<17>、HCaNb_3O_<10>、HNbWO_6、HTaWO_6等层状化合物中。掺入的半导体颗粒厚度小于1 nm，带隙能量略大于正常的无支撑半导体晶体。含小带隙半导体的CdS、Fe_2O_3、CuO、NiO和MnO等非复合材料在可见光（波长>400 am）照射下表现出高效的析氢活性。另一方面，结合TiO_2和/或TiO_2和Pt的纳米复合材料能够在不牺牲空穴受体的情况下通过带隙辐照将水劈裂成氢和氧。半导体颗粒具有优异的光催化活性，主要归因于客体电子向主电子转移的电荷分离。通过分析掺入H_2T_<14 bb_0 O_9和H4Nb_6O_<17 bb_1的CdS和TiO_2的荧光寿命，证实了CdS和/或中间层TiO_2中的光致电子迅速转移到宿主层。测定了CdS到H2Ti4O9和/或H_4Nb_6O_<17>的电子转移速率常数约为10^6 sec-1，而从TiO_2到H_2T_<14>O_9和H_4Nb_6O_<17>的电子转移速率常数为l08 sec^<-1>。

Layered compound/semiconductor nonocomposites incorporating semiconductor nanoparticles in the interlayer of layered compounds were fabricated and their photo-chemical properties were investigate. Semiconductors such as CdS, Fe_2O_3. CuO, NiO, MnO, TiO_2, etc. were successively intercalated in various layered compounds such as H_2Ti_4O_9, H_4Nb_6O_<17>, HCaNb_3O_<10>, HNbWO_6, HTaWO_6, etc. The thickness of semiconductor particles incorporated was less than 1 nm and the band gap energy was slightly larger than that of normal unsupported semiconductor crystals. Nonocomposites incorporating small band gap semiconductor such as CdS, Fe_2O_3, CuO, NiO and MnO showed efficient hydrogen evolution activity under visible light irradiation (wave length>400 am). On the other hand, nanocomposites incorporating TiO_2 and/or TiO_2 and Pt were capable to clevage water into hydrogen and oxygen without sacrificial hole acceptor by band gap irradiation. The excellent photocatalytic activity of semiconductor particles incorporated wad attributed to the charge separation by guest to host electron transfer. By analyzing the fluorescence life times of CdS and TiO_2 incorporated in H_2T_<14>O_9 and H4Nb_6O_<17>, it was confirmed that photoinduced electron in CdS and/or TiO_2 in the interlayer quickly transfer to the host layers. The electron transfer rate constant from CdS to H2Ti4O9 and/or H_4Nb_6O_<17> were determined as ca. 10^6 sec-1 and those from TiO_2 to H_2T_<14>O_9 and H_4Nb_6O_<17> were l08 sec^<-1>.