Researchers at the University of Cantabria have participated in an international study on the electromagnetic behaviour of metals on a nano-scale, with the aim of identifying the most suitable materials for certain technological applications in biology, medicine, analysis of matter, and especially in those where miniaturization is important, such as in communications and the storage of information on an optical level.
The work is framed within the field of nanoplasmonics, a branch of Nanophotonics whose aim is to study the electromagnetic behaviour of metals at a nano level. On this scale, metal particles excited by electromagnetic radiation present interesting phenomena of great practical interest, such as the intensification of the electromagnetic field at nanometric distances from particles.
Gold, silver and copper have traditionally been used to form part of those plasmonic nanostructures because of their optimal response in certain lengths of visible wavelengths, but in the UV range its efficiency is very weak and provides a challenge in order to find alternative solutions. After three years of work, scientists have pointed to rhodium as a good candidate, as it allows plasmonics and photocatalysis to be combined.
The results of this study have been published under the title "Rhodium Nanoparticles for Ultraviolet Plasmonics", in the prestigious scientific journal Nano-Letters, of the American Chemical Society. Experts from the UC - Fernando Moreno, Francisco González, Juan M. Sanz and Rodrigo Alcaraz de la Osa-, as well as others from the University of Duke and the Army Research Laboratory, both in the United States, have taken part. The project is funded by the Ministry of Science and Innovation and USAITCA (United States International Technology Center-Atlantic).
Today there is a great demand for the use of these technologies in more energetics areas of the spectrum, such as in the ultraviolet area, due to their importance in biological applications (biomolecules, as well as aromatic amino acids or DNA itself have a response in this range). There are also applications related to the analysis of the matter, based on the Raman effect, and in assistance to photochemical reactions (photocatalysis, photodissociation).
A direct application would be the generation of permanent biocides elements to use them in self-cleaning tissues. So far, silver nanoparticles have been used. Its ease of oxidation, as well as its low plasmonic efficiency in the ultraviolet area, rule it out for use in these frequencies. To develop structures in this range, it was necessary to find more suitable metals and scientists' work has focused more on this search. Rhodium proved to be an excellent candidate.
This is commonly used in the industrial field as a catalyst for different types of chemical compounds and hydrocarbons, often mixed with Platinum and Palladium to increase their already high resistance to corrosion. Moreover, it is a tremendously promising metal to combine plasmonic and catalysis.
The study in which the UC participated has shown that this material has a strong response in the ultraviolet range and the American groups were able to manufacture, through chemical means, nanoparticles of rhodium in the shape of a three-pointed star, smaller than 10 nanometers.
With these particles, they managed the intensification of local electromagnetic fields as well as the effects of charge transfer and they analyzed the possibilities that exist to achieve assisted photocatalysis by plasmonicos effects.
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