Development of nano-porous photo-catalysis with opal and inverse opal structure

近年来，由晶格参数与可见光波长相当的空间有序介质组成的光子晶体因其在控制光传播方面的独特性质而受到人们的广泛关注。即使那些没有表现出完全光子带隙的晶体，仍然可以显示出有趣的光学性质，例如也可以作为结构颜色观察到的光学阻带。在许多实际应用中，能够通过外界激励来控制光子能带结构是非常重要的。沿着这条线，我们通过将光响应液晶渗透到反蛋白石结构的薄膜中来制备可调光子带隙晶体。它们的光学性质可以通过液晶的光诱导相变来实现。可以通过测量它们在光照射下的光学性质的变化来评价其光诱导相变行为，并且清楚地观察到这种行为随温度和光强的变化而变化。这种材料可以存储和显示通过光掩模用LTV光照射产生的图像。这种技术的一个很大的优点是，薄膜本身可以在不使用偏振器或其他辅助材料的情况下显示图像，并且它们还可以呈现可以通过改变反蛋白石结构的晶格距离来选择的彩色显示。此外，我们还通过外加电场实现了对其光学性质的控制。由于电场诱导的状态与光致相变产生的状态不同，现在可以通过这两种技术的组合在三种状态之间切换。我们开发的材料有可能在光学器件中得到实际应用。

Recently, photonic crystals (PCs) composed of spatially ordered dielectrics with lattice parameters comparable to the wavelength of visible light have received much attention due to their unique properties in controlling the propagation of light. Even those crystals that do not exhibit a complete photonic band gap can still show interesting optical properties, such as an optical stop band that can also be observed as a structural color. It is important to be able to control the photonic band structure through external stimuli for many practical applications. Along this line we prepared tunable photonic band gap crystals by infiltrating photoresponsive liquid crystals into inverse opal structure films. The tuning of their optical properties could be realized by means of photoinduced phase transition of liquid crystals. The photoinduced phase transition behavior could be evaluated by measuring the change in their optical properties under light irradiation, and it was clearly observed that the behavior varied with temperature and light intensity. The materials could store and display images that were created by the irradiation with LTV light through a photomask. A great advantage of this technique is that the films themselves can display an image without the use of polarizers or other assistant materials, and they can also render a color display that can be selected by varying the lattice distance of the inverse opal structure. In addition, we achieved the control of their optical properties by the application of an electric field. Because the state induced by the electric field is different from that engendered by a photoinduced phase transition, it is now possible to switch among three states by a combination of these two techniques. The materials that we have developed have possibilities for practical applications in optical devices.