Over the last two decades nanomaterials have attracted
growing interest because of their unique, potentially
useful electronic, magnetic, and optical properties. For
example, carbon nanotubes possess tunable electronic
structure from metals to insulators. Nanoparticles can act
as ‘‘artificial atoms’’ which, when assembled into mesoor
macroscopic structures may lead to novel functional
materials. Thus self-assembled particle arrays not only
preserve the properties of individual particles but can also
exhibit new behaviors due to interparticle correlations and
coupling. The ability to organize nanoscale components
into specific geometrical arrangements, with defined interconnections,
underpins much of their promise for future
applications as well as current fundamental studies. Here
we focus on the organization of nanoparticles and, to a
lesser extent, other nanoscopic building blocks into
ringlike arrangements ranging over five decades of length
scale, from macroscopic (
1 mm) to nanoscopic (
10
nm). In addition to the simple geometry or a ring, a variety
of other arrangements have been realized. For example,
following earlier reports of close-packed crystalline
nanoparticle superstructures,[1–5] Korgel et al. analyzed
nanoparticle self-assembly into superlattices in detail
highlighting the effects of size-selection, ligand coverage,
and interparticle attraction.[6] Detailed reviews on the
fabrication and properties of nanoparticle superlattices are
now available.[7,8] Other efforts have focused on organizing
nanoparticles according to highly specific biological
interactions[9–19] or using self-organized polymeric media
such as block copolymers to spatially template nanoparticle
synthesis and distribution.[20–28] Albeit the focus of
this review restricts it from broadly considering the
general theme of nanomaterial self-assembly, the above
and related efforts continue to make critical advances
toward functional materials and devices incorporating
nanoscale components