Visible Light Harnessing Transition Metal Oxide Cages and Low Dimensional Structures

二氧化钛能够吸收光线，并利用储存的能量驱动各种有趣的、可能非常有用的化学过程，如破坏环境污染物或从水中生产氢气。后者特别有吸引力，因为它提供了从阳光产生完全无碳能源的前景。然而，二氧化钛本身只有在紫外线照射下才能发挥这些功能，紫外光相当于到达地球表面的太阳光的4%左右。因此，基于二氧化钛的太阳能应用效率太低，无法实际使用。如果我们能够对二氧化钛进行改性，以获得来自太阳的可见光，那么效率将大大提高，从而使实际应用成为可能。实现可见光光活性的一个好方法是在二氧化钛中掺杂少量的外来原子，如硼、碳、氮或硫。但要使这种方法有用，掺杂方法必须是(一)可控的(二)可重复性的(三)能够放大以生产千克量的(四)低成本。到目前为止，没有一种方法满足所有这些标准/大多数方法至少在两个方面失败。最近，我们表明，直接应用廉价的湿化学可以生产出满足所有上述标准的高效N掺杂二氧化钛光催化剂。本项目旨在通过向前迈出一大步，在这一成就的基础上再接再厉。我们计划制作一系列由钛和氧原子组成的新型笼子，它们的外围带有各种有机官能团。通过改变笼子的大小并在它们中掺杂外来原子，我们将能够以系统和可重复的方式改变它们的性质。此外，我们将(I)将笼子系在固体表面上(Ii)将它们交联，以制成各种形状和大小的笼形聚合物(Iii)将它们转化为表面支撑的掺杂纳米颗粒和薄膜。这一战略将使人们能够接触到各种各样的结构和成分，这应该使我们能够找到表现出比以前取得的任何成果都更好的可见光活性的系统。此外，我们应该能够以一定程度的重复性和规模来实现这一点，使实际应用成为可能。

Titanium dioxide is capable of absorbing light and using the stored energy to drive a variety of interesting and potentially very useful chemical processes such as the destruction of environmental pollutants or the production of hydrogen from water. The latter is especially attractive as it offers the prospect of entirely carbon-free energy generation from sunlight. However, titanium dioxide itself can perform these functions only when irradiated with ultra violet light, which corresponds to just ~4% of the sunlight reaching the earth's surface. As a result, solar powered applications based on titanium dioxide are too inefficient to be of practical use. If we could modify titanium dioxide so as to harvest the visible light from the sun, huge gains in efficiency would result, enabling practical applications.A good way of achieving visible light photoactivity is to dope the titanium dioxide with small amounts of foreign atoms such as boron, carbon, nitrogen or sulphur. But for this approach to be useful, the method of doping must be (i) controllable (ii) reproducible (iii) capable of being scaled up for the production of kilogram quantities (iv) low cost. None of the methods that have been devised thus far meets all these criteria/most fail on at least two counts.Recently, we showed that straightforward application of inexpensive wet chemistry could produce highly effective N-doped titanium dioxide photocatalysts that meet all the above criteria. The present project is aimed at building on this achievement by taking a big step forward. We propose to make a series of novel cages consisting of titanium and oxygen atoms with a variety of organic functional groups at their peripheries. By varying the cage size and by doping them with foreign atoms we shall be able to vary their properties in a systematic and reproducible way. In addition, we shall (i) tether the cages to solid surfaces (ii) cross-link them to make cage polymers of a variety of shapes and sizes (iii) convert them to surface-supported doped nanoparticles and thin films. The wide variety of structures and compositions that this strategy will make accessible should allow us to find systems that exhibit visible light photoactivity superior to anything previously achieved. Moreover, we should be able to do this with a degree of reproducibly and on a scale that make practical applications a real possibility.