New ITMO-Developed Method for Silver Nanostructure Synthesis to Accelerate Drug Development

As a wave, light has an electric field that oscillates perpendicular to its direction of travel. In sunlight, the direction of these oscillations constantly changes in a random way – such light is called unpolarized. Polarized light, on the other hand, exhibits ordered polarization. In linear polarization, for example, the light oscillates in a single fixed plane; conversely, in the case of circular polarization, the oscillation vector rotates continuously. Following along the light’s propagation path, the rotation coils into a helix, like a screw or a spring. This can be left- or right-handed, depending on the direction of rotation. 

There are materials sensitive to light polarization; they can be used to locate molecules of specific polarizations – left- or right-handed. Typically, these materials are manufactured using lithography, which requires expensive equipment and is not conducive to producing large-scale elements rapidly. Therefore, researchers are looking for alternative ways to overcome these limitations. 

Researchers from ITMO University, alongside their colleagues from other countries, developed a laser-induced method for creating polarization-sensitive nanostructures on material surfaces. The scientists used silver nanostructures with a thin surface oxide layer necessary for silver atoms to smoothly redistribute under laser radiation.

The pre-oxidized film was exposed to circularly-polarized laser light, i.e. light with a fixed direction of its wave twist. As a result, computer simulations confirmed that light with different polarizations generates asymmetric energy distribution around nanoparticles, causing silver atoms to build up nanostructures that selectively absorb light with a particular polarization. For example, exposing a film to a right-circularly polarized light leads to the prevalence of nanoparticles sensitive to right-handed polarization. Thus, by employing a laser, the team was able to “code” the desired polarization into a material structure.

The obtained material can be used to produce sensors that can rapidly and efficiently separate molecules based on their polarization. Such devices can be beneficial for drug development, as well as advanced biosensors and photodetectors.

“Our findings open up new opportunities for developing affordable and small-scale polarized detectors without any need for high-cost lithographic methods. In the future, we’re planning to design a photodetector for photonic integrated circuits using our coating and apply this technology for the needs of optoelectronics,” says Daler Dadadzhanov, PhD, a team lead and a senior researcher at ITMO’s International Research and Educational Center for Physics of Nanostructures. 

This article was written by the press office of the Russian Science Foundation