Development of photofunctional nanohybrids by using soft matrices provided by colloidally dispersed niobate nanosheets

我们研究了一种胶体体系的光化学行为，该体系由剥离层状己酸盐K_4Nb_6O_<17>制备的铌酸盐纳米片（被称为光催化剂）、光化学非活性纳米片的硅石粘土和作为电子受体的甲基紫素（MV^<2+>）组成。多组分胶体表现出稳定的光诱导电荷分离。这种行为归因于胶体分散的光催化活性铌酸盐纳米片的独特上层结构。这种结构原理可用于设计新型的光能转换系统。结果总结如下：1。铌酸盐和粘土纳米片的共存是稳定电荷分离的前提。它们引起微相分离，在胶体中形成微畴，MV2+分子被选择性地吸附在粘土纳米片上。这种结构导致铌酸盐纳米片作为电子供体和MV^<2+>分子的空间分离，更重要的是作为电子受体来稳定电荷分离状态。胶体的光照射诱导电子从铌酸盐纳米片转移到MV^<2+>分子。在适当的条件下，还原物的寿命超过10小时，比在固体体系中观察到的MV^<2+>分子掺入铌酸盐的寿命更长。这种稳定性是不寻常的，因为胶体系统的流动性允许反向电子转移。电荷分离的稳定性在很大程度上取决于胶体中共存粘土的浓度。随着粘土含量的增加，电荷分离状态趋于稳定。然而，当粘土含量很高时，不会发生电子转移以使胶体凝胶化。这些结果表明，当纳米片的扩散速度减慢而不是完全抑制时，就会发生稳定的电荷分离。稳定的电荷分离是通过同时利用系统的各种特性来实现的，例如畴结构，流动性，以及按组分划分供体和受体功能。少

We investigated photochemical behavior of a colloidal system composed of niobate nanosheets prepared by exfoliating layered hexaniobate K_4Nb_6O_<17> known as a photocatalyst, photochemically inactive nanosheets of hectroite clay, and methylviologen (MV^<2+>) that can work as an electron acceptor. The multi-component colloid exhibited stable photoinduced charge-separation. This behavior was ascribed to a unique superstructure of the colloidally dispersed photocatalytically active niobate nanosheets. Such a structural principle can be utilized to design novel photoenergy conversion systems. The results are summarized as follows.1. Coexistence of the niobate and clay nanosheets is prerequisite for the stable charge-separation. They cause microphase separation to form microdomains in the colloid, and the MV2+ molecules are selectively adsorbed on the clay nanosheets. This structure results in spatial separation of the niobate nanosheets working as an electron donor and MV^<2+> molecules b … More ehaving as an electron acceptor to stabilize the charge-separated state.2. Photoirradiation of the colloid induced electron transfer from the niobate nanosheets to the MV^<2+> molecules. The lifetime of reduced viologen species exceeds 10 h under appropriate conditions, the lifetime which is longer than that observed for the solid system where MV^<2+> molecules are incorporated into the niobate. Such stability is unusual because fluidity of the colloidal system allows backward electron transfer.3. The stability of charge-separation greatly depends on the concentration of clay coexisting in the colloid. The charge-separated state becomes stable as increasing the clay content. However, electron transfer does not occur when the clay content is very high to gel the colloid. These results suggest that the stable charge-separation takes place when the diffusion of the nanosheets is decelerated but not completely suppressed.4. The stable charge-separation is achieved by simultaneously utilizing various characteristics of the system, such as domain structure, fluidity, and dividing the donor and acceptor functions by constituents. Less