They Mold Nanometric Gold Particles To Behave Like Clones In Biomedicine

A special laser system ensures that billions of gold nanoparticles act as if they were one. The research, published in Science and in which the Complutense University of Madrid has participated , in collaboration with the CIC biomaGUNE and the Polytechnic University of Madrid, takes advantage of these new properties for applications in biomedicine and photonics, from the treatment of tumors to the production of energy, thanks to the ability of these particles to absorb or reflect light of a certain color, depending on their geometry.

Molding the shape of nano-sized gold particles - size of millionths of millimeters - to improve their properties in biomedicine and photonics is possible thanks to a special laser system in a work in which the Complutense University of Madrid (UCM) participates and which has published in Science.

The research, which also includes the CIC biomaGUNE and the Polytechnic University of Madrid (UPM), in addition to representing a record of optical quality in which billions of gold nanoparticles behave as if they were one, opens a new way to manipulate and improve nanomaterials, using lasers as chisels in the hands of a sculptor.

"Through the use of ultra-fast lasers, very intense, but of very short duration - one billion trillion flashes in a second - we can say that we have obtained the world record of optical quality, until we can get all the molded particles to behave like nanometric clones ", explains Andrés Guerrero Martínez, researcher of the Ramón y Cajal program of the Faculty of Chemical Sciences of the UCM.

The study provides the physical and chemical keys that are necessary to understand and control to obtain nanomaterials that can be considered "perfect" from a point of view of their optical properties.

"We have tried during the last fifteen years to obtain identical nanoparticles, so that they all have the same color, so that their applications are more efficient. In this work we have focused on the use of gold nano-sticks , where minimal variations in length or width cause significant changes in the color of the light they absorb, "says Luis Liz Marzán, scientific director of CIC biomaGUNE and researcher of the Ikerbasque program.

From the treatment of tumors to contamination

The applications of nanoparticles are based on their ability to absorb and reflect light of a specific color and in a surprisingly efficient way. These effects, called plasmonic, generate optical properties that can not be obtained with metals of much larger dimensions, even millimeters.

These properties can be used for a large number of useful applications that in many cases were not possible until now. In medicine, the light reflected by these particles can be used to diagnose diseases; but the absorption of light can also be used to cause the release of heat, for example, for the treatment of tumors in a localized manner and minimizing the usual side effects in current treatments.

"Plasmonic particles have also found applications in areas such as information technology, energy production or control of environmental pollution, among others," says Guillermo González Rubio, co-author of the work and who has recently obtained the title of doctor for the UCM under the co-direction of Andrés Guerrero Martínez and Luis Liz Marzán.

Another novelty of this work is the application of ultra-fast lasers for the modulation of the geometry of the particles and the improvement of their properties. To this end, the Ultrarrápidos Laser Center - CLUR (UCM), managed by Luis Bañares, professor of the UCM and co-author of the work, has been used.

Also, to understand the chemical and physical nature of the molding process, standard characterization techniques (spectroscopy and electron microscopy) have been used, as well as new theoretical models and advanced computer simulation techniques.

According to Ovidio Rodríguez Peña, researcher at UPM, "the demonstration of this objective and the explanation of the processes that allow it, represent a change of mentality that can open new avenues for the development of nanomaterials with improved properties and applications".