Nanostructured titanium dioxide (TiO2) with a crystallite size from 10 to 85 nm, photocatalytically active for organic reactions under illumination with visible light, has been prepared by a sol–gel process using a titanium tetrabutoxide solution in ethanol with an initial pH of 6. According to X-ray diffraction characterization results, the as-prepared titanium dioxide was amorphous. Annealing in a hydrogen atmosphere for 1 h at 400°C led to the formation of an anatase phase, and annealing in the temperature range from 600 to 800°C resulted in the anatase–rutile phase transition. The crystallite size of titanium dioxide increased from 10 to 75 nm as the annealing temperature was raised from 400 to 1000°C (furnace annealing for 1 h) and from 60 to 85 nm as the annealing time at a temperature of 800°C was increased from 30 to 240 min. Diffuse reflection spectra showed that the band gap of TiO2 decreased from 3.3 to 2.6 eV as the annealing temperature was raised from 200 to 1000°C. The specific surface area data obtained by BET measurements showed that the samples annealed at the highest temperature (1000°C) had the smallest surface area, which dropped from 307 to 1 m2/g. The efficiency of the synthesized TiO2 tested as a catalyst for oxidative $$S_{{\text{N}}}^{{\text{H}}}$$ cross-coupling of acridine with indole demonstrated an in crease in product yield from 35 to 80% as the annealing temperature was raised to 800°C. Varying the 800°C annealing time from 30 to 180 min had no effect on the reaction product yield, which ranged from 70 to 80%.

— Nanostructured titanium dioxide (TiO2) with a particle size from 7 to 50 nm, photocatalytically active for organic reactions under illumination with visible light, has been prepared by...

Titanium dioxide (TiO₂) was synthesized by sol-gel method at different values of pH = 3, 7, 8, 9, or 10. X-ray phase analysis has shown that in an acid rout an anatase phase was crystallized, and in an alkaline rout an amorphous phase of TiO₂ was achieved. After annealing for 4 hours at 350 °C, all samples was transformed in the anatase phase. The particle size in the different samples varies from 7 to 49 nm depending on the pH. The diffuse reflection spectra revealed a high value of the band gap in the range from 3.2 to 3.7 eV and its narrowing after annealing to the range from 3.2 to 3.5 eV.

Studying the electrophysical properties and conduction mechanisms of Au/TiO₂/Ti memristive structures based on nanoporous and nanotubular layers made of anodized titanium dioxide contributes to the improvement of quality indicators of prospective elements and nano-electronic devices derived from them. The paper measures the current–voltage characteristics and temperature dependencies of conductance in high-(HRS) and low-resistance states (LRS) for Au/TiO₂/Ti memristors with different thickness of nanoporous/nanotubular active layer. The importance of forming a nanotubular structure of the oxide layer with a thickness of 155–200 nm and an internal diameter of nanotubes of 21 ± 4 nm for improving the main characteristics of Au/TiO₂/Ti memristors when realizing the filamentary mechanism of resistive switching with the participation of oxygen vacancies is shown. The main parameters of electron transport, such as activation energy of electron conduction, electron mobility, dielectric relaxation time, and concentration of allowed states in the conduction band, are calculated for nanoporous and nanotubular TiO₂ layers in HRS using the framework of charge limited conduction mechanism. The parameters of the electron trap distribution are determined, such as concentration, capture cross-section, energy depth, distribution type, and characteristic temperature. It is shown that electron transport in LRS occurs by the Poole–Frenkel emission through filaments with metallic conduction type. Band diagrams are proposed to describe the conduction mechanisms involving oxygen vacancies for Au/TiO₂/Ti memristors in high- and low-resistance states.

Nonstoichiometric titanium dioxide (TiO_2-x) with different oxygen content was synthesized by sol‒gel method and, subsequently, annealed in the hydrogen flow for one hour at 200, 400, 600, 800, or 1000 °C. Synthesized powders were studied by XRD, BET and DRS methods. X-ray phase analysis showed that an annealing at temperatures of 400 and 600 °C leads to the formation of the crystalline phase of anatase, but at 800 and 1000 °C annealing rutile phase is formed. Particle size increases from 10 to 45 nm at annealing. The diffuse reflectance spectra show a narrowing of the energy band gap from 3.3 down to 2.6 eV with increasing of annealing temperature. The specific surface area decreases from 306 to 1 m²/g after annealing.

Oxidative C-H/C-H coupling reactions of dipyrromethanes with azines in the presence of a heterophase oxidative photocatalytic system (O₂/TiO₂/visible light irradiation) were carried out. As a result of cyclization of obtained compounds with boron trifluoride etherate, new hetaryl-containing derivatives of 4,4-difluoro-4-boron-3a,4a-diaza-s-indacene were synthesized. For the obtained compounds, absorption and luminescence spectra, quantum yields of luminescence as well as cyclic volt-amperograms were measured.