International research and
education center for
Physics of Nanostructures

Scientists from the Centre "Information Optical Technologies" (СIOT) have developed a new approach to nanoobject construction that allows to study and predict how deformations and defects in the crystal lattice affect the optical properties of semiconductor nanocrystals. This model allows to calculate both the linear and non-linear optical properties of various nanoobjects such as nanorolls, nanorods, and nanoplatelets, among others. The method can be used to create optical materials and devices with new functionalities, with potential applications in drug delivery, chiral exciton-based devices and chiral catalysis devices, biosensing and spintronics. Results of the research were published in Nano Letters and ACS Nano.

Interest in the creation of new devices and tools based on the use of semiconductor nanocrystals has grown greatly in recent years. This technology is seeing a great deal of use in biology, medicine, optical materials, electronics, solar energy, and other areas. The reason for this steadfast adoption of semiconductor nanocrystals are their unique properties -  scientists can easily modify the optical response of semiconductor nanocrystals simply by changing their chemical composition and shape.

Another powerful tool that may be used to change the optical response of nanocrystals is lattice distortion. The authors have proposed a theoretical description of a new method of studying the optical properties of semiconductor nanocrystals with crystal lattice defects. They have considered nanostructures of various shapes and developed general methods for calculating their linear and non-linear optical properties.

“The fundamental significance of our research lies in that it offers a new method of constructing semiconductor nanoobjects. It is known that nanoobjects can be used both as stand-alone quantum structures and as elements in the creation of more complex quantum superstructures. In our study, we model the properties of a single nanoblock. We do that on two levels simultaneously - the crystal lattice and the crystal shape. By choosing a shape and adding defects and deformations of the crystal lattice, we can significantly change its properties and amplify the desired effects. This approach, in particular, lets us turn nanoblocks that were not previously optically active into such. Structuring these nanoblocks will later facilitate the creation of next-generation optical devices,” - comments Anvar Baitmuratov, one of the authors of the research.

The developed theoretical approach has found further development in another study focused on semiconductor nanorolls. A nanoroll is a nanoplatelet that, due to a particular mechanical impact, has taken the form of a multi-layered tube. What makes these objects unique is their structure: unlike nanoplatelets, nanorolls take up relatively little space while preserving the large area of nanoplatelets. All this allows them to interact with other nanoobjects, including molecules, with high efficiency.

In the article published in ACS Nano, the researchers developed a new method of geometric transformation that makes it possible to “unfold” a nanoroll into a nanoplatelet and, therefore, calculate the optical properties of a nanoplatelet in a curved space.

“This method is analogous to the one that is used, for example, in Einstein’s general theory of relativity. Using this transformation, we have been able to calculate the optical properties of such a nanoplate in a curved space and recording the nanoroll’s optical response,” - says Nikita Teplyakov, one of the authors of the article. - “So far, such objects have been  studied only experimentally. Thanks to their large contact area, nanorolls are used in medicine and chemistry as catalyzers in chemical reactions, as tools for capturing and transferring molecules, and in molecular sensing. In addition, since nanorolls are chiral objects, another promising application for such objects is in spintronics, which, unlike traditional electronics, implies energy and data transfer not through electrical charges, but through their currents’ spin. Nanorolls also allow us to study the spin transfer in chiral molecules".