Nanostructured surfaces can be broadly defined as substrates in which the typical
features have dimensions in the range 1–100 nm (although the upper limit of 100 nm
may be relaxed to greater sizes in some cases, depending on the material and
the specific property being investigated). The recent surge of interest in these
systems stems from the remarkable effects that may arise from the critical size
reduction. Interesting novel properties (catalytic, magnetic, ferroelectric, mechanical,
optical and electronic) occur as we reduce the dimensions from a practically infinite
(and periodic) solid crystal to a system composed of a relatively small number of
atoms. So far, nanostructured materials or nanomaterials are perhaps the only
sub-field of nanoscience that has made the transition from fundamental science to
real world applications, thus becoming a technology (a good example of this are
nanostructured surface coatings). This paper describes some selected examples of recent
progress in the study of nanostructured surfaces. Surface reconstructions, which
occur either naturally or as a consequence of the interaction with adsorbates, are
discussed because of their importance in model chemical reactions and for their
potential use as templates for the ordered growth of nanostructures. Supramolecular
assemblies and molecular nanostructures, resulting from the balance between
molecule–molecule and molecule–surface interactions, are described because of their
fundamental interest and their potential use in nanoelectronic devices. Recent
progress in the growth of semiconductor nanostructures, in particular Ge–Si and
InAs–GaAs, is briefly reviewed. A few selected examples of nanostructured functional
materials, such as ferroelectric and magnetic nanostructures, are discussed in view of
their potential for applications in future data storage devices. Nanostructured
materials used in catalysis and gas sensor applications are briefly described. Finally,
perspectives and future challenges in this emerging field of research are also discussed.