ИСТИНА

Low-frequency (10–200 cm-1) Raman (LF Raman) spectroscopy provides information on high amplitude molecular motions, motions of parts of molecules and collective motions involving several molecules. Recently, it has been shown that the ratio of integral intensities of the LF Raman spectra to the high-frequency one can be used as an indicator of dynamic disorder and compactization for two classes of materials: -conjugated organic semiconductors (OSs) - promising for the use in organic electronic devices, and nucleic acids, DNA and RNA, responsible for the vitally important functions of storage, transmission and realization of the genetic information. The use of OS in high-performance organic electronic devices requires a high mobility of charge carriers, calling for rational design and efficient screening of new high-mobility OS materials. Indeed, high-amplitude intermolecular vibrations in OSs cause dynamic disorder - fluctuations of the charge transfer integrals between the molecules - which disrupts charge delocalization between the molecules and reduces the charge-carrier mobility. It has been established that the Raman intensities of LF modes are related to the contribution of these modes to dynamic disorder [1, 2]. The relative intensity of LF Raman modes shows the lower values in the OSs with a lower dynamic disorder. The corresponding, LF Raman-based approach to probing dynamic disorder has been demonstrated on various OS representatives: four series of oligomeric OSs - polyenes, oligofurans, oligoacenes, and heteroacenes [1]; derivatives of naphthalenediimides [2]; crystalline OSs consisting of π-isoelectronic small molecules (i.e., having the same number of π-electrons) [3]; co-oligomers of thiophene-phenylene CF3-PTTP-CF3 and its substituted derivative [4]. As a result, we have formulated a spectroscopic method for a fast and non-contact assessment of the charge-carrier mobility in crystalline OS [5]. We expect that the proposed approach will provide a simple and practical way to rapidly screen among many others OS with high charge mobility prior to their study in electronic devices. One of the parameters of biomolecules that is important for the integrity of hereditary information and its transmission during cellular processes is the compactization of a biomolecule [6]. It is expected that the relative intensity of the LF Raman spectra of DNA and RNA can be an indicator of their compactization, since in more compact molecules the amplitude of larger-scale molecular motions corresponding to the LF region of the Raman spectra is lower. This is shown for the samples of DNA with different compactization: “cut” and supercoiled DNA and ribosomal and “relaxed” RNA. We also track the changes in the DNA and ribosome spectra with time and find that for the former, a clear decrease of the LF intensity associated with solvent evaporation and denser packing is observed, while for the RNA, the spectrum changes only slightly because of the inherent compactization of the ribosome. Briefly, we show that LF Raman spectroscopy is a powerful tool for predicting and estimating the most important parameters for OS (carrier mobility) and DNA/RNA (molecular compactization).