Doped nanostructures

The goal of this themed issue is to gather a representative collection of high quality articles in the general field of doping of nanoparticles or nanostructures. As with conventional thin films, virtually all the envisaged applications for nanoparticles and nanostructures will require tailoring of the chemical and physical properties of these functional materials. This will be achieved by addition of appropriate lattice elements to control the bandgap and absorption properties and through incorporation of dopants to achieve the requisite conductivity. The possibility to engineer the electronic, optical, photochemical and magnetic properties of nanomaterials towards specific applications through a careful selection of the dopants has great implications on almost all areas of nanoscience and nanotechnology. The need to achieve a very high degree of substitutionality of these dopants is critical because of the small active volume of the nanostructures, but there is also the opportunity to create near-ideal properties without extended defects such as dislocations and to control electron, photon and phonon transport.

The applications for doped nanostructures range from drug delivery, cancer therapy, label-free and functionalized detection of biological agents and gases (including transforming DNA molecuales into fluorescent magnetic nanoparticles for detection of genetic variations), photonic bandgap structures, water purification, plasmonics, storage of gases, micro-filters, biomimetic structures efficient light emitters, energy storage, advanced batteries, non-linear optics, optical switches and high speed electronics based on graphene sheets or semiconductor nanowires. In the latter case, one need not be limited to conventional substrates, and the use of nanostructures allows for realization of flexible electronics that will revolutionalize how we view and store information. Numerous demonstrations of tunable light emission with high quantum yield and control of polarization have been reported. To achieve practical emission intensities, it is necessary to develop core/shell nanoheterostructures with high degrees of carrier confinement. The characterization of these types of nanostructures represents a tremendous challenge to existing metrology methods and the nanomaterials are themselves being developed for new probe methods for mapping of electrical, structural and optical properties at the nanoscale.

The interaction between nanostructures, the ability to individually address the active elements, the ability to scale up memory or processor units based on nanostructures, the reproducibility of synthesis, patterning and assembly, control of size, composition, the reliability and modeling of nanoscale devices, the need for both axial and radial heterostructures and even the public health aspects are all important fields of current research. The range of nanomaterials requiring doping control is also extensive, ranging from group IV, II–VI, III–V semiconductors and nitrides to oxides, chalcopyrites, chalcogenides and other optical materials and it is expected that integration of these different types of materials might be simplified at the nanoscale. The remaining challenges include how to control the properties of these doped nanostructures through the application of external electric, magnetic or optical fields and how to normalize or standardize the response of nanomaterial devices.

This themed issue brings together an outstanding group of papers that address many of the issues raised in the discussion above. As is evident in the table of contents the articles cover a broad range of topics within the field of doped nanostructures and provide an excellent snapshot of the current state of the field. We hope that this issue will stimulate further advances in the field and help to advance both the basic science and potential applications of these fascinating entities.

Stephen Pearton, The University of Florida, USA

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