A new method for changing the behavior of nanoparticles using artificial lighting may lead, among other things, to the development of new applications in computerized information storage
A new method for changing the behavior of nanoparticles using artificial lighting may lead, among other things, to the development of new applications in computerized information storage. In a published study Recently in the scientific journal Nature Chemistry, scientists from the Weizmann Institute of Science proposed using a medium containing light-sensitive molecules (photoswitchable or photoresponsive), and placing the nanoparticles inside it, unlike the methods tried so far, in which the nanoparticles themselves were coated with light-sensitive molecules.
The mechanism of action of the new method, developed in the research group of Dr. Raphael Klein from the Department of Organic Chemistry at the Weizmann Institute of Science, is based on the fact that under exposure to light the configuration of molecules called spiropyrans, found in the medium, changes and becomes more acidic. In the next step, the "floating" nanoparticles react in the medium to the change in acidity. This move causes them to organize in the dark, and disperse in the light. Nanoparticles tend to have different properties when they are randomly dispersed, compared to when they are organized. Hence, nanoparticles that respond to changes in acidity (which are a much larger group of materials than the group of materials that respond to light), now have the potential to be used in applications based on exposure to light. These are very many application possibilities, from paper that allows erasing and rewriting, to water purification, and to the controlled release of medicines, or other substances.
Dr. Klein says that these molecules have a long history at the Weizmann Institute of Science: "In 1952, two researchers from the institute, Ernst Fischer and Yehuda Hirschberg, were the first to demonstrate the unique behavior of spiropyrans that react to light. Later, in the 80s of the last century, Prof. Valery Krongause carried out many important studies on spiropyrans, and used them to develop a variety of materials that allow, among other things, the darkening of glasses when they are exposed to sunlight. Today, 63 years after the first demonstration of the properties of photochemical materials, we use the same simple molecules for a new purpose."
The stability of nanoparticles coated with light-sensitive molecules does not last long. On the other hand, in the new method, in which the nanoparticles "float" in the medium, it was found that they are stable over time. "We ran 100 cycles of writing with the nanoparticles dispersed in a gel-like medium, that is, we essentially performed reversible information storage," says Dr. Klein, "and there was no deterioration in the system, so the same system can be used many times."
