State of the art of nanoforest structures and their applications

Forest-like nanostructures, their syntheses, properties, and applications are reviewed. Nanoforests are mainly represented by carbon nanotubes, zinc and titanium oxides, and gold, and much less frequently by other metals, metal oxides, arsenides and phosphides. These nanostructures generally consist of more simple 1D objects, such as nanowires, nanopillars, nanorods, nanotrees, nanofibers or nanotubes. Synthesis methods for nanoforests vary from catalytic pyrolysis or thermal decomposition of hydrocarbons to electrophoretic deposition, hydrothermal routes, electron beam lithography, focused-ion-beam techniques, vapor phase transport, facet-selective etching and pulsed deep reactive etching technologies, among others. A number of applications for the forest-like nanostructures are generalized, for instance as sensors/detectors, photoanodes in solar and fuel cells, supercapacitors and energy storage devices, in SERS applications, optical and MEMs switching devices, water splitting processes, CO2 fixation, and as supports or targets for biomolecules. In general, it is expected that more varieties of compounds and materials with exciting properties can be obtained in this form in the near future, thus expanding numerous applications of forest-like nanostructures.