Theoretical and Experimental Chemistry最新文献

The role of nanostructuring of a conductive polymer phase and the nature of a dopant in composites of carbon nanotubes (CNTs) and poly(3-methylthiophene) (P3MT) with core-shell morphology is considered. It is found that sharp changes occur in the crystallinity of the P3MT phase of the composite at a polymer shell thickness of ~9 monomolecular layers; sharp changes occur in its thermal stability, electrical conductivity, and spectral characteristics at 4-6 layers; and sharp changes occur in the magnitude of sensor responses to isopropanol vapor and their time at ~3 layers. It is shown that the nature of a surface active dopant (anions of dodecylbenzenesulfonic and perfluorooctanoic acids) significantly affects the crystallinity, doping degree, and thermal stability of P3MT in composites, as well as the charge transfer from CNTs to doped P3MT.

Nanoscale CuO was synthesized by precipitating Cu₂O in an alkaline medium in presence of potato extract, followed by oxidation in air. It was shown that the material consisted of nanoparticles with an average size of 25 nm. It was found that the obtained CuO had high antibacterial activity against Escherichia coli and Staphylococcus aureus, which exceeded the activity of copper oxide obtained without the use of potato extract.

It is shown that an increase in the BEA zeolite dealumination degree in the composition of NiBEA catalysts leads to an increase in the conversion of methane and carbon dioxide in the process of dry reforming of methane. The activity of catalysts increases with a decrease in the ratio of acid/basic sites. CO₂ is activated at basic sites during both the conversion of methane to carbon dioxide and in the accompanying reverse water-gas shift reaction. Changing the Si/Al ratio is an effective tool for regulating the activity and selectivity of NiBEA catalysts, thus providing the obtaining of synthesis gas with different CO/H₂ ratios.

The catalytic properties of reduced graphene oxide (rGO) deposited on aluminium oxide in the ethane dehydrogenation reaction have been studied. It is shown that the deposition of 1wt.% of rGO on aluminium oxide increases the ethane conversion when compared to a pure support. The rGO/Al₂O₃ catalyst exhibits 100% selectivity for ethylene at temperatures below 650°C. Based on the use of Raman and infrared spectroscopy, as well as nitrogen adsorption and desorption isotherms, the structural characteristics before and after the dehydrogenation process have been determined, and the carbonization of rGO/Al₂O₃ and the initial Al₂O₃ during ethane dehydrogenation has been confirmed. Carbonization of the catalyst does not lead to a complete loss of its activity, which may be associated with the formation of graphene-like nanostructures, which also reveal catalytic activity.

The review considers pivotal and novel research on developing organocatalysts that imitate key enzyme classes devoid of metal ions, such as lyases, hydrolases, transferases, and oxidoreductases. Special attention is paid to enantioselective transformations facilitated by organocatalysts. It is demonstrated that the development of enzyme mimetics has significant potential for the creation of new catalytic systems. Some classes of enzymes still have no analogues among organocatalysts.

It has been established that during the biogas reforming process (CH₄:CO₂ > 1) over Ni-Al₂O₃/cordierite catalysts modified with rare earth metal oxides (CeO₂, La₂O₃) reactant activation occurs at different surface sites: CH₄ on Ni⁰ and CO₂ on MeO_x (Me = La, Ce). This allows to avoid the competition between CH₄ and CO₂ molecules for active surface sites, facilitating a stable process under methane excess.

It has been shown that a series of indenyl-hydrazono-thiazole derivatives could be obtained in quantitative yields by a mechanochemical method without the use of solvents. According to the results of the study by NMR and electron spectroscopy it was found that the tautomeric amino-form of the thiazole ring in indenyl-hydrazono-thiazolidin-4-one was more stable compared to the imino form. Thiazole derivatives containing chlorophenyl and nitrophenyl groups in the thiazole ring possessed significant activity against S. Aureus.

It has been established that crystalline carbon nitride (CCN) in acidic solutions of C1-C4 alcohols in the presence of a palladium cocatalyst exhibits high photocatalytic activity in the process of chemoselective hydrogenation of benzaldehyde (BA) and 5-hydroxymethylfurfural (HMF) to benzyl alcohol and 2,5-dihydroxymethylfuran, respectively. The apparent quantum yield of BA conversion reaches ~90 % in ethanol under optimal conditions, while HMF reaches 30% (at λ_irr = 405 nm). A probable process scheme is proposed, which involves the initiation of transformations of substrate molecules with the participation of photogenerated charges, in particular, oxidation of alcohols by holes of the CCN valence band, reduction of carbonyl groups by photogenerated electrons, and further transformations of intermediate compounds of a radical nature with the formation of final products.

The effect of modification of nanostructured TiO₂ films with lanthanum ions on their electrocatalytic, photoelectrochemical, and sensor properties is investigated. La-TiO₂ films were prepared by sol–gel method and characterized by X-ray diffraction analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and photoelectrochemical current spectroscopy. It is shown that modification with lanthanum ions leads to an increase in the photosensitivity of La-TiO₂ electrodes in the UV range and a batochromic shift in the photocurrent spectra, and also improves their catalytic activity in the reaction of oxygen reduction and sensor properties in determining the concentration of heavy metal ions in liquids.

The possibility of obtaining 2D GeH by mechanochemical treatment of bulk germanane in the presence of NaCl with subsequent sonochemical treatment and liquid-phase exfoliation has been demonstrated for the first time. It has been established that the preliminary mechanochemical nanostructuring of germanane promotes the formation of predominantly monolayer particles with a thickness of <1 nm and a lateral size of up to 200 nm, and also leads to a red shift of the E_2g mode in the Raman spectrum by 10 cm^–1. It is shown that the dispersion of mechanochemically obtained germanane has three times higher photocatalytic activity in the hydrogen evolution reaction from an aqueous solution of lactic acid than the sample obtained without mechanochemical treatment.