The Role of Alkali Cation Intercalates on the Electrochemical Characteristics of Nb2CTX MXene for Energy Storage

The intercalation of cations into layered-structure electrode materials has long been studied in depth for energy storage applications. In particular, Li⁺-, Na⁺-, and K⁺-based cation transport in energy storage devices such as batteries and electrochemical capacitors is closely related to the capacitance behavior. We have exploited different sizes of cations from aqueous salt electrolytes intercalating into a layered Nb₂CT_x electrode in a supercapacitor for the first time. As a result, we have demonstrated that capacitive performance was dependent on cation intercalation behavior. The interlayer spacing expansion of the electrode material can be observed in Li₂SO₄, Na₂SO₄, and K₂SO₄ electrolytes with d-spacing. Additionally, our results showed that the Nb₂CT_x electrode exhibited higher electrochemical performance in the presence of Li₂SO₄ than in that of Na₂SO₄ and K₂SO₄. This is partly because the smaller-sized Li⁺ transports quickly and intercalates between the layers of Nb₂CT_x easily. Poor ion transport in the Na₂SO₄ electrolyte limited the electrode capacitance and presented the lowest electrochemical performance, although the cation radius follows Li⁺>Na⁺>K⁺. Our experimental studies provide direct evidence for the intercalation mechanism of Li⁺, Na⁺, and K⁺ on the 2D layered Nb₂CT_x electrode, which provides a new path for exploring the relationship between intercalated cations and other MXene electrodes.     

Formation of Chiral β-Silyl-Vinyl Ethers

Chiral formates derived from propane-1,2-diol, 1,2- O -isopropylidene- f - D -xylo- and f - D -gluco-furanoses were subjected to treatment with cyclopentadienyl [tris(trimethylsilylmethyl)] titanium (IV). A mixture of the corresponding ( E )- and ( Z )- g -silylvinyl ethers were obtained with predominance of the former. It was found that in contrast to ( Z )-vinyl ethers, which give g -lactams with chlorosulfonyl isocyanate, the ( E )-vinyl ethers gave unstable cycloadducts which undergo rapid elimination reaction leading to ( E )- f , g -unsaturated amides.     

Study of carbon black obtained by pyrolysis of waste scrap tyres

Waste scrap tyres were thermally decomposed under various conditions. Decompositions were followed by the TGA method. Specific heating regimes were tested to obtain optimal structural properties of resulting pyrolytic carbon black produced by pyrolysis of scrap tyres and the process was characterized in temperature interval from 380 to 1,200 °C and heating rate 10, 20 and 50 °C min^?1 under nitrogen atmosphere. The original scrap tyres and pyrolytic carbon black were characterized by Raman and Fourier transform infrared spectroscopy methods. Textural properties were also determined. Effect of temperature and heating rate on process of pyrolysis of scrap tyres was observed. Shifting of temperature of maximum pyrolysis rate to lower value and spreading of DTG peak is caused by increasing heating rate. Temperature 570 °C was sufficient for total scrap tyres pyrolysis. Graphitic and disordered structure was distinguished in the formed carbon black by Raman spectroscopy. With increasing temperature, heating rate and weight loss, the amount of the graphitic structure was reduced at the expense of disordered structure. Destruction of nonporous scrap tyres and formation of porous structure took place at higher temperature. Porous carbon black is formed above 380 °C, specific surface area increased up to 88 m² g^?1 .     

Thermal stability and flammability of styrene–butadiene rubber (SBR) composites

The article presents the effect of attapulgite (ATT) and its synergic action with carbon or silica on the thermal properties and flammability of cross-linked styrene–butadiene rubber. It has been shown that ATT is active filler improving the thermal and mechanical properties of composites containing this aluminosilicate. The decreased flammability of vulcanizates containing ATT compared to that of unfilled vulcanizates results from good insulating properties of the ATT used. The considerable reduction in the flammability of composites containing ATT and carbon nanofiber or silica is connected, first of all, with the formation of a homogeneous boundary layer.     

Comparison of Oxidative Aromatic Coupling and the Scholl Reaction

Does the dehydrogenative coupling of aromatic compounds mediated by AlCl₃ at high temperatures and also by FeCl₃, MoCl₅, PIFA, or K₃[Fe(CN)₆] at room temperature proceed by the same mechanism in all cases? With the growing importance of the synthesis of aromatic compounds by double C? H activation to give various biaryl structures, this question becomes pressing. Since some of these reactions proceed only in the presence of non‐oxidizing Lewis acids and some only in the presence of certain oxidants, the authors venture the hypothesis that, depending on the electronic structure of the substrates and the nature of the “catalyst”, two different mechanisms can operate. One involves the intermediacy of a radical cation and the other the formation of a sigma complex between the acid and the substrate. The goal of this Review is to encourage further mechanistic studies hopefully leading to an in‐depth understanding of this phenomenon.     

Electrochemical DNA biosensor for human papillomavirus 16 detection in real samples

An electrochemical DNA biosensor for human papillomavirus (HPV) 16 detection has been developed. For this proposed biosensor, l-cysteine was first electrodeposited on the gold electrode surface to form l-cysteine film (CYSFILM). Subsequently, HPV16-specific probe was immobilized on the electrode surface with CYSFILM. Electrochemistry measurement was studied by differential pulse voltammetry method (DPV). The measurement was based on the reduction signals of methylene blue (MB) before and after hybridization either between probe and synthetic target or extracted DNA from clinical samples. The effect of probe concentration was analyzed and the best results were seen at 1000 nM. The hybridization detection presented high sensitivity and broad linear response to the synthetic-target concentration comprised between 18.75 nM and 250 nM as well as to a detection limit of 18.13 nM. The performance of this biosensor was also investigated by checking probe-modified electrode hybridization with extracted DNA from samples. The results showed that the biosensor was successfully developed and exhibited high sensitivity and satisfactory selectivity to HPV16. These results allow for the possibility of developing a new portable detection system for HPVs and for providing help in making an effective diagnosis in the early stages of infection.