Mesocrystals (MCs) are a relatively new class of materials with superb potential in many applications e.g. photocatalysis, dye-sensitized solar cells, fibre optics, sensors, bioimplants, etc. MCs are best viewed as ordered assemblies (superstructures) of individual single crystals, each of which often have critical dimensions of the order of nanometres. Such structures are common in nature and in recent years chemists have developed routes to, and some models of, MC formation. At the start of POLYCOMP though approaches to mesocrystal (MC) formation were still largely ad hoc and thus many of the applications of these fascinating materials detailed above remained largely unachievable. The principle underlying reason for this is that complex MC formation processes were (and in many cases still are) too poorly understood. Based on natural crystallisation phenomena, chemists had developed a working model of MC formation whereby polymers can be used to form organised inorganic structures. This said, the shape, period, size and morphology of self-organized structures (MCs) generated in this manner show strong structural dependence upon the polymer used. As its overall objective POLYCOMP sought to address this issue by focussing on a well-studied system, formation of NH4TiOF3 MCs and their subsequent thermally-mediated transition into TiO2 MCs. A better understanding of how to form MCs is important for society because of the long term promise they offer. This potential is based on the fact that although they are micro/macroscopic materials they have the potential to possess the properties of their constituent nano-sized building blocks. Such properties include unique light emitting properties (cf quantum dots ), superparamagnetism (cf Fe3O4 nanoparticles ) etc. Consequently, there are myriad potential high tech applications possible including in: photocatalysis, Li-ion battery and electrode applications, photovoltaics (especially generation3 cells), sensors, low energy lighting systems, etc.
