Methods for studying the coherent 4D structural dynamics of free molecules and condensed state of matter

Studies in the coupled 4D spatial and temporal continuum are necessary for understanding the dynamic features of molecular systems with a complex profile of the potential energy surface. The introduction of time sweep into diffraction methods and the development of principles for studying coherent processes have revealed new approaches to the analysis of the dynamics of wave packets, the intermediate products and the transition state of the reaction center, and short-lived compounds in gaseous and condensed media. The use of picosecond and femtosecond electron probe pulses, synchronized with excitation laser pulses, determined the development of ultrafast electron crystallography, time-resolved X-ray diffraction, and dynamic transmission electron microscopy (DTEM). One of the most promising applications of the developed diffraction methods is the characterization and visualization of the processes occurring upon the photoexcitation of free molecules and biological objects and the analysis of surface and thin films. The whole set of spectral and diffraction methods based on different physical principles, which are complementary and make it possible to perform the photoexcitation of nuclei and electrons and carry out diagnostics of their dynamics at ultrashort time sequences, reveal new possibilities for studies with the necessary integration of the “structure-dynamics-function” triad in chemistry, biology, and materials science.     

Selective modification of polylactide by introducing acrylate groups: IR spectroscopy,gel permeation chromatography,and differential thermal analysis

One-stage modification of polylactide has been performed to obtain the acrylate derivatives of the polymer capable of further polymerization and preparation of cross-linked polymer materials suitable for creating implants. The reaction mechanism was determined by IR spectroscopy, gel permeation chromatography, and differential thermal analysis. It was shown for the first time that the reaction path changes depending on the ratio of components so that the desired product polylactide acrylate forms with a ~90% yield only in the presence of large (approximately tenfold) excesses of the isocyanate and acrylate components; at the equimolar ratio of components generally used in urethane formation, a mixture of the desired product (~30%), oligourethane diacrylates, and unchanged polylactide forms.     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.     

Gold nanorods as a perspective technology platform for SERS analytics

We discuss the application of gold nanorods for forming SERS substrates for chemical and biological sensing. Two approaches are considered: (1) formation of planar arrays on silicon wafers by using suspensions of gold nanorods; and (2) a new approach based on gold nanorod powders that can be easily dissolved in aqueous media. Both SERS platforms are characterized and their SERS enhancement factors are compared.     

Spectra of copper and europium β-diketonates in alcoholic solutions and transparent dielectrics

We have used optical and EPR spectroscopy to study the mechanisms for color center formation in nanoporous glasses, polymethylmethacrylate, and alcoholic solutions containing ?-diketonate molecules: Cu(hfac)₂, Ba(hfac)₂, Pr(hfac)₃, and Eu(fod)₃. We have observed and studied the complex structure of the absorption bands in the 300 nm region belonging to the intraligand π-π* transition. Analogous results were obtained when studying the photoluminescence spectra of ⁵D₀ → ⁷F₀ transitions of Eu³⁺ ions and the EPR spectra of Cu²⁺ ions in matrices doped with Cu(hfac)₂. We propose a model according to which for β-diketonate molecules (except for basic diketonates), a hydrolyzed form exists that is formed during synthesis of the polycrystalline powder due to the presence of water molecules. The model allows us to explain the spectral manifestations of β-diketonates in different matrices.     

Thermostimulated formation of silver and gold nanoparticles in porous silicon dioxide matrices

Manifestations of thermostimulated formation and subsequent transformation of silver and gold nanoparticles in porous opal and Vycor glass matrices are studied using optical spectroscopy. Two temperature ranges for silver nanoparticles are revealed, where first-type particles transform into another type of particles. With gold nanoparticles in these matrices, a temperature range in which one type of particles transforms into another type is established. An effect of complete blackening of Vycor glass samples, caused by their annealing, is revealed, and a rationalization of this effect is given.     

AFM study of the extracellular connective tissue matrix in patients with pelvic organ prolapse

The method of atomic force microscopy (AFM) is used for the first time for morphological investigation of pathological changes in the extracellular matrix of skin connective tissue upon the prolapse of pelvic organs (common disorder among women). Skin samples of patients with clinically proven pelvic-organ prolapse and of patients that do not have any connective tissue related disease (control group) are investigated via AFM. The AFM study reveals that the extracellular matrix of the skin connective tissues from patients with pelvic-organ prolapse diverges from the normal in various organization levels including both micro- and nanotexture (packing of collagen fibers and fibrils, respectively). The results of AFM study of the normal and pathologically changed skin connective tissues are in good agreement with the data of clinical morphological analysis, which indicates the potential of AFM as an independent diagnostic tool.     

An EPR and Optical Spectroscopy Study of the Effect of Laser Radiation on Biological Tissues

The formation of radicals upon UV (248 nm) and IR (1.56 m) laser irradiation of some biological tissues (cartilage, bone tissue, fish scale) and their components (chondroitin sulfate, collagen) was studied by the EPR technique. The radical decay kinetics in bony tissue specimens after their irradiation with UV light were described. By the spin trapping technique, it was shown that radicals were not produced during IR (1.56 m) laser irradiation of cartilaginous tissue. A change in optical absorption spectra and the dynamics of optical density of cartilaginous tissue, fish scale, and a collagen film under exposure to laser radiation (248 nm) in an air, oxygen, and nitrogen atmosphere was studied.     

Impregnation of polymers with 2,2,6,6-tetramethyl-4-oxo-piperidine-1-oxyl (TEMPONE) paramagnetic probe in sub- and supercritical CO<Subscript>2</Subscript>

The spin probe method is used to study the impregnation of polycarbonate (PC) based on bisphenol A, polyethylene oxide (PEO), and crosslinked acrylamide–acrylic acid copolymer (PAA) with organic molecules in sub- and supercritical CO₂ media. Electron spin resonance (EPR) data show that, at 196 bar and 307 K, 2,2,6,6-tetramethyl-4-oxo-piperidine-1-oxyl (TEMPONE) paramagnetic spin probe molecules penetrate into the PC and PEO matrices, which are, respectively, in the glassy and elastic states under normal conditions. The degree of impregnation of PAA under these conditions is negligibly small. Estimates of the local concentration of probe molecules show that, in the PEO matrix, TEMPONE is distributed much more uniformly than in the PC matrix. Analysis of the effect of temperature on the shape of the EPR spectra of the radical in the polymer matrix shows that, under the same conditions, the mobility of TEMPONE molecules in the PEO matrix is much higher than in the PC matrix. The results suggest that the spin probe method is promising for studying the characteristics of macro- and micro-processes in polymer–supercritical fluid solvent–organic molecule ternary systems.