News Release

Thermoplasmonic sensor for the detection of phase transitions in nanoscale materials

A joint paper by Kazan Federal University and King's College London appeared in ACS Photonics

Peer-Reviewed Publication

Kazan Federal University

The work was conducted under the auspices of the Russian Science Foundation; the project "Synthesis and research of a new class of nanocomposite ceramics with degenerate dielectric constant for optoplasmonic applications" is headed by Professor Sergey Kharintsev (KFU's Institute of Physics).

Professor Kharintsev, the first co-author, comments, "Under the influence of light, collective oscillations of electrons can be excited in metallic nanostructures, and as a result the electric field in the vicinity of the nanostructures strongly increases. The field of physics that studies the effects of generation and propagation of such electromagnetic excitations is called plasmonics. Its most striking achievements include optical visualization of single molecules and diagnostics of their vibrations with a spatial resolution of 0.16 nm (for example, the size of a water molecule is 0.3 nm). In practice, the achievements of plasmonics are widely used in the development of highly sensitive biomedical sensors, in the creation of new generation solar cells, in the development of the element base of nanophotonics and optoelectronics, in particular, light filters, polarizers, modulators, waveguides, etc."

Strong heating of nanostructures under plasmon resonance conditions underlies a number of unique applications of thermoplasmonics in biology and medicine. This is the basis of photothermal cancer therapy methods. It made possible to create a thermoplasmonic biosensor with a record sensitivity of 0.22 pmol per liter for the detection of SARS-CoV-2 (COVID-19 virus), as well as reusable protective masks in which copper nanoparticles are heated by sunlight to temperatures at which viruses die.

"We have developed an optical sensor, which is a metasurface composed of an ordered array of metallic titanium nitride (TiN) nanoantennas, each 500 times smaller than a human hair. By scanning ordered nanoantennas with a focused laser beam, they can be successively heated to a predetermined temperature (up to several hundred degrees) in less than one microsecond. Using such an optical sensor, we were able to determine for the first time the local glass transition temperature of a polymer with a spatial resolution of 200 nanometers," continues Kharintsev. "I would like to draw the attention of biologists, chemists and physicists to the fact that the functional properties of the created thermoplasmonic sensor go far beyond the scope of the mentioned application. This nanophotonic device can be used to study, for example, size effects in spatially limited (in three directions) 0D polymers. Using the sensor, it is possible to detect the glass transition temperature of spatially inhomogeneous polymer films, including multicomponent polymer mixtures. A thermoplasmonic optical sensor can be used to study structural changes and phase transitions, such as to determine the local crystallization (melting) temperature of nanoobjects. Attention should be paid to the possibility of using a thermoplasmonic sensor in the study of biological reactions on single cells (for instance, in the study of denaturation of individual proteins)."

As the interviewee noted, the team plans to use thermoplasmonic sensors in ultrafast calorimetry, another research priority of Kazan University chemists.


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