A fast method for preparing aqueous graphene oxide (GO) dispersions by electrochemical oxidation of a graphite anode without preliminary intercalation with oxidizing agents is proposed. Ultrasonic probing was used in the modulation mode of ultrasonic waves (work/rest) for more efficient graphite oxidation–exfoliation. It is shown that the 4/2 s mode of ultrasonic modulation is the most effective due to the probe material’s low corrosion while maintaining the optimum synthesis temperature not exceeding 30–35 °C and achieving the best characteristics of the resulting product. Three cases of anodic oxidation of graphite to obtain graphene oxide were considered: (1) a combined cathode–anode compartment, (2) a split cathode–anode salt-bridged compartment, and (3) separated anode compartment with a 3.5 kDa dialysis membrane. It was determined that the approach to synthesis with a divided cathode–anode compartment makes it possible to obtain GO sheets with fewer defects compared to chemical methods or methods with a combined cathode–anode compartment and makes it possible to control the oxidation degree of the material (C:O ratio) by varying the current density. The prepared samples showed good stability for more than six months. The spectral and morphological characteristics were studied. Using chemiluminometry in the luminol/Co(II)/H2O2 system, the antioxidant properties concerning three key reactive oxygen species (H2O2, superoxide anion radical, and hydroxyl radical) were demonstrated. It was also shown that the prepared GO dispersions do not induce lipid and phospholipid peroxidation.

Modern heat-conducting materials require special attention to analyze their thermophysical properties. Compared to classical methods, thermal lens spectrometry (TLS) has advantages due to its high sensitivity to physical and chemical composition. To avoid a systematic error in the analysis of complex systems, it is necessary to realize the limits of the applicability of the method. This study considers the features of thermal-diffusivity measurements by TLS in the stationary state for dispersed systems with absorbances up to 0.05. The limits of applicability of the method in analyzing heterogeneous systems are shown, and a mathematical apparatus is proposed for indicating a systematic error in finding thermal diffusivity that does not exceed 1%. Graphene oxide (GO), which has attractive physicochemical properties, was used as the object of analysis. GO belongs to 2D objects, the study of which requires highly sensitive methods and special attention when discussing the results. The thermophysical properties of aqueous dispersions of graphene oxide in a wide range of concentrations (up to 2 g/L) and lateral sizes (up to 4 µm) were studied by TLS. It has been found that with increasing nanophase concentration, the thermal diffusivity of graphene oxide dispersions passes through a minimum, which can be used in solving thermal insulation problems. It has been established that prolonged laser irradiation of the dispersion leads to a change in thermal diffusivity, which indicates the photochemical reduction of graphene oxide.

A new ionic cyclopropanation process involving the addition of diazo esters to donor–acceptor cyclopropanes (DAC) activated by GaCl3 has been developed. The reactions occur via 1,2-zwitterionic gallium complexes with elimination of nitrogen in all cases to give 1,1,2,3-tetrasubstituted cyclopropanes as the main products. Also, a number of related processes with the formation of various polysubstituted cyclopropanes, alkenes, and cyclobutanes, including products of multiple diazo ester addition, have been developed. Obtained by the developed method tetrasubstituted cyclopropanes are activated cyclopropanes such as DAC and can be used for further synthesis in this capacity. Their new reaction with benzaldehyde promoted by TiCl4 and involving one of the additional functional groups has been demonstrated, which leads to five-membered lactones. The mechanisms of the occurring processes, as well as the structures and stereochemistry of a rich range of products formed, are discussed in detail.