Visible Light Harnessing Transition Metal Oxide Cages and Low Dimensional Structures

二氧化钛能够吸收光，并利用储存的能量来驱动各种有趣的、潜在的非常有用的化学过程，如破坏环境污染物或从水中生产氢。后者尤其具有吸引力，因为它提供了完全无碳的太阳能发电的前景。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，而紫外线相当于到达地球表面的太阳光的4%。因此，以二氧化钛为基础的太阳能应用效率太低，无法实际应用。如果我们能对二氧化钛进行改造，使其能够从太阳中获取可见光，那么效率就会大大提高，从而实现实际应用。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。但为了使这种方法有用，掺杂方法必须(i)可控（ii）可复制（iii）能够按比例生产公斤数量（iv）低成本。迄今为止所设计的方法没有一个符合所有这些标准/大多数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高效的n掺杂二氧化钛光催化剂，满足上述所有标准。目前的项目旨在在这一成就的基础上向前迈出一大步。我们建议制作一系列由钛原子和氧原子组成的新型笼，并在其外围放置各种有机官能团。通过改变笼的尺寸，并在笼中掺杂外来原子，我们将能够系统地、可重复地改变笼的性质。此外，我们将(i)将笼系在固体表面上（ii）将它们交联以制成各种形状和尺寸的笼聚合物（iii）将它们转化为表面支撑的掺杂纳米颗粒和薄膜。这一策略将使各种各样的结构和成分变得容易获得，这将使我们能够找到比以前取得的任何成果都更具有可见光光活性的系统。此外，我们应该能够以一定程度的可重复性和规模来做到这一点，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.