ABSTRACT
Wheel-like nanostructures as nanoparticle forms are very rare. In addition to the description of a nanowheel as a geometric form of nanoparticles, this term is also used to discuss molecular parts in organic or coordination compounds,1,2 which can be used, in particular, in the creation of nanocars.3 A few examples of nanowheels are as follows. Various platinum nanostructures with size and shape control (globular nanodendrites, –at dendritic nanosheets, foam-like nanospheres, porous nanocages, nanowheels [Figures 5.1 and 5.2], nanowire networks, and hollow nanospheres) were synthesized by using a series of templates with/without porphyrin photocatalysts.4 The porphyrin molecules rapidly reduced the platinum complex into a tunable number of initial seed particles under white light irradiation. This provided a nearly equal growth time for each seed, leading to £nal products with uniform and predictable sizes. Hierarchical ZnO nanoarchitectures, such as microtrepangs, microbelts, nano–owers, nanocombs, nanowheels (Figure 5.3), and nanofans assembled by ZnO nanocones, nanobowling pins, nanobottles, nanoarrows, and nanonails, have had their growth controlled by the thermal evaporation of Zn and a mixture of In and In2S3.5 These novel hierarchical ZnO nanoarchitectures may be attractive building blocks for creating optical or other nanodevices. A –ow system was employed to study the steps underlying the assembly of molybdenum oxide wheel of 3.6 nm diameter.6 Crystallization of an intermediate structure in which a central {Mo36} cluster appears to template the assembly of the surrounding {Mo150} wheel was observed (Figure 5.4). In addition, various ZnSe nanostructures (nanowires, nanorings, nanowheels, and tricrystal nanobelts) were fabricated by thermal evaporation method.7,8
In addition, a very rare example of a large polynuclear lanthanide complex nanowheel (Figure 5.5) with a very symmetric ring structure leading to a system containing europium ions in two different coordination environments was described.1
