Herein we show the effect of heat treatment of two dimensional layered titanium carbide structure (Ti 3 C 2 T x ), so called MXene. As prepared MXene has functional groups -OH, -F, -Cl. In order to remove the functional groups we heat treated the MXene in Ar (with 0.01% O 2 ) and H 2 (with 0.01% H 2 O) atmospheres. We discovered the significant decrease in the amount of functional groups (-F and -Cl) and increase in the -O content, which refers to the oxidation of the material. Also we determined the optimal regime for Raman spectroscopy in order to avoid any changes in the structure of the material. We revealed that titanium carbide changes its structure at 700 °C and 900 °C into two different titanium dioxide modifications like rutile and anatase in Ar (with 0.01% O 2 ) atmosphere. Also there are small changes occurred in Ti 3 C 2 Tx structure and formation of amorphous carbon after 700 °C treatment in H 2 (with 0.01% H 2 O) atmosphere and formation of TiO 2 (rutile) at 900 °C. Energydispersive X-ray spectroscopy (EDX) revealed the reduction of functional groups at 700 °C in both atmospheres and total disappearance of -F and -Cl and increasing the oxygen at 900 °C. The huge increase of oxygen by atomic percent, can be explained by the initial oxygen content in argon and hydrogen gases.

No abstract

Information on vitamin C—ascorbic acid (AA)—content is important as it facilitates the provision of dietary advice and strategies for the prevention and treatment of conditions associated with AA deficiency or excess. The methods of determining AA content include chromatographic techniques, spectrophotometry, and electrochemical methods of analysis. In the present work, an electrochemical enzyme-free ascorbic acid sensor for a neutral medium has been developed. The sensor is based on zinc oxide nanowire (ZnO NW) arrays synthesized via low-temperature chemical deposition (Chemical Bath Deposition) on the surface of an ITO substrate. The sensitivity of the electrochemical enzyme-free sensor was found to be dependent on the process treatments. The AA sensitivity values measured in a neutral PBS electrolyte were found to be 73, 44, and 92 µA mM−1 cm−2 for the ZnO NW-based sensors of the pristine, air-annealed (AT), and air-annealed followed by hydrogen plasma treatment (AT+PT), respectively. The simple H-plasma treatment of ZnO nanowire arrays synthesized via low-temperature chemical deposition has been shown to be an effective process step to produce an enzyme-free sensor for biological molecules in a neutral electrolyte for applications in health care and biomedical safety.

In this work, the synthesis of nickel particles encapsulated in a few-layer graphene shell was carried out using the method of electric arc discharge in the liquid phase, in various media: deionized water, alcohol, and toluene. Nickel and graphite were used as electrodes. The study was carried out to analyze how various liquids, acting as a cooling medium and a source of carbon, affect the formation of a protective shell around metal particles. Raman studies, analysis of X-ray diffraction data, and scanning electron microscopy confirmed the formation of spherical encapsulated nickel particles in all types of liquid media. It was found out that the use of toluene as a cooling medium increased the number of particles with a graphite shell and allowed obtaining micro- and nanoparticles covered with monolayer graphene. The absence of oxygen in the composition of toluene, in contrast with alcohol and especially water, prevents the oxidation of nickel particles during the synthesis. This fact, along with the initial basic hexagonal carbon structure of toluene, makes it a good medium for the formation of metal particles covered with a protecting graphite shell as a result of arc discharge in the liquid phase.

In this work, the photocatalytic activity of layered GaSe flakes obtained by liquid-phase exfoliation of bulk crystals was tested on the photodegradation of an organic dye under UV irradiation. The initial bulk GaSe crystals were synthesized by stoichiometric fusion method. Investigation of the structure and composition showed that as-grown crystal corresponds to β-polytype of GaSe. Analysis of the kinetics of the decomposition MB molecules showed that the obtained flakes demonstrate good photocatalytic activity in the UV range. The efficiency of the dye photodegradation was 86% within 3 hours under UV irradiation.