Prospects and Challenges in Application of Gamma and Electron Beam Processing of Nanomaterials

Application of radiation techniques for nanotechnology has been known for years. X-ray, EB and ion beam lithography are a good example of applications. By using electron beams, ion beams and X-Rays structures as small as 10 nm can be produced. Ion track membranes with track diameters from 10 nm to 100 nm are used as such or as templates for electroplating of nanowires of metal, semiconductor and magnetic materials. In the near future X-Rays, focused ion beams and electron beams will be used for nanolithography and 3D fabrication; heavy ion beams on the other hand can be useful for fabrication of nanopores and nanowires. The use of radiation has proved to be an essential technique in the fabrication of nanostructures with high resolution as the radiation beams can be focused into a few nanomater scales or less. Three groups of products could be considered to be fabricated by radiation techniques: nanoparticles, nanogels and nanocomposites. Nanoparticles has application in electronic devices and bioactive systems. Their radiation synthesis in aqueous dispersions started in the late seventies. Literature describe the radiolytic reduction of many metal ions either single metal or in combination with another metal to generate metallic or bimetallic mixtures as well as core-shell structures. To obtain metallic particles from their parent ions one only needs to ensure reductive conditions during the irradiation. By control over the dose rate delivered to the sample the radiolytic approach can offer the fine control over the rate of generation on the growing species. Nanogels are particles of polymer gels having the dimensions in the order of nanometers. They are applied in pharmaceutical and cosmetic industries, as the bioactive substances delivery systems. Depending on the irradiation parameters (radiation dose, dose rate, polymer concentration, irradiation temperature) molecules with different structures (such as long-chain branches, nanogels, microgel or microgel particles) can be obtained. Nano-composite material encompasses a large variety of systems such as one-dimensional, two-dimensional, three-dimensional and amorphous materials, made of distinctly dissimilar components and mixed at the nanometer scale. The IAEA organized a consultants meeting on emerging applications of radiation in nanotechnology in Bologna, Italy in 2004. These and other possible fields of radiation processing applications in nanotechnology are discussed in the paper