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Combination of two-dimensional (2D) materials and semiconductors is considered to be an effective way for fabricating photocatalysts for solving the environmental pollution and energy crisis. In this work, novel 2D/2D heterojunction of R-scheme Ti3C2 MXene/MoS2 nanosheets is successfully synthesized by hydrothermal reaction. The photocatalytic activity of the Ti3C2 MXene/MoS2 composites is evaluated by photocatalytic degradation and hydrogen evolution reaction. Especially, 0.5 wt% Ti3C2 MXene/MoS2 sample exhibits optimum methyl orange (MO) degradation and H2 evolution rate of 97.4% and H2 evolution rate of 380.2 μmol h−1 g−1, respectively, which is attributed to the enhanced optical absorption ability and increased specific surface area. Additionally, Ti3C2 MXene coupled with MoS2 nanosheets is favorable for improving the photocurrent response and reducing the electrochemical impedance, leading to the enhanced electron transfer of excited semiconductor and inhibition of charge recombination. This work demonstrates that Ti3C2 MXene could be a promising carrier to construct 2D/2D heterojunction in photocatalytic degradation and hydrogen evolution reaction.

The effect of etching environment (opened or closed) on the synthesis and electrochemical properties of V 2 C MXene was studied. V 2 C MXene samples were synthesized by selectively etching of V 2 AlC at 90 °C in two different environments: opened environment (OE) in oil bath pans under atmosphere pressure and closed environment (CE) in hydrothermal reaction kettles under higher pressures. In OE, only NaF (sodium fluoride) + HCl (hydrochloric acid) etching solution can be used to synthesize highly pure V 2 C MXene. However, in CE, both LiF (lithium fluoride) + HCl and NaF+HCl etchant can be used to prepare V 2 C MXene. Moreover, the V 2 C MXene samples made in CE had higher purity and better-layered structure than those made in OE. Although the purity of V 2 C obtained by LiF+HCl is lower than that of V 2 C obtained using NaF+HCl, it shows better electrochemical performance as anodes of lithium-ion batteries (LIBs). Therefore, etching in CE is a better method for preparing highly pure V 2 C MXene, which provides a reference for expanding the synthesis methods of V 2 C with better electrochemical properties.

In this work, we report the synthesis method of carbon quantum dots (CDs) using the one-step method for fast and effective metal ion determination. Ascorbic acid was used as an inexpensive and environmentally friendly precursor. High-pressure and high-temperature reactors were used for this purpose. Microscopic characterization revealed the size of CDs was in the range of 2–6 nm and they had an ordered structure. The photoluminescence properties of the CDs depend on the process temperature, and we obtained the highest PL spectra for 6 h of hydrothermal reaction. The maximum emission spectra depend poorly on synthesis time. Further characterization shows that CDs are a good contender for sensing Fe3+ in aqueous systems and can detect concentrations up to 0.49 ppm. The emission spectra efficiency was enhanced by up to 200% with synthesis time.

In this study, the reaction mechanism of CO2 reduction by using Zn under mild hydrothermal condition was investigated by DFT calculation method. Based on the calculation of the transition state, as well as the IRC and HOMO/LUMO, the Zn-H was considered as a key intermediate for the high formate production from CO2. This study provides information on the reaction pathway of metal reduction with the metal hydrogen bond under hydrothermal conditions. The energy diagram showed that the Zn-H has high reducing activity, which induced that the formate was easily produced through hydrothermal reactions. From the viewpoint of energy, in the CO2 reaction system, the HCOO- was easily produced than that in the HCO3- reaction system. This process provides new concept for the high efficient production of value-added chemicals in the carbon dioxide utilization research area.

Ammonia borane (AB, NH 3 BH 3 ) is a promising candidate for a hydrogen-storage material because of its high stability as a solid state at room temperature under atmospheric pressure. This study demonstrated a novel catalyst design for highly efficient hydrolysis of AB by hybridizing Pt catalyst with hydroxyapatite (HAp, Ca 10 (PO4) 6 (OH) 2 ) as an “active support”, possessing Lewis-acidic Ca 2+ sites in the a-plane and Lewis-basic PO 4 3- sites in the c-plane. Facet-engineered HAp particles were synthesized via the microwave-assisted hydrothermal reaction using Ca-EDTA chelates. Varying the Ca/P ratio of HAp precursor (from 1.5 to 1.8) affected the particle morphology, exposed facet ratio of {300} to {002}, and the percentage of phosphate anion species (PO 4 3- and HPO 4 2- ). The rod-like HAp sole catalysts performed approximately 2-fold higher activity for the hydrolysis of AB, compared with spherical HAp with low crystallinity. Moreover, the Pt/rod-like HAp co-catalyst demonstrated superior catalytic performance with a turnover frequency (TOF) of 623 mol H2 mol Pt -1 min -1 than the Pt/spherical HAp (<232 mol H2 mol Pt -1 min -1 ). We proposed a possible mechanism of a synergistic effect in the significant enhancement of the hydrogen release rate from AB. Lewis basic PO 4 3- and Lewis acidic Ca 2+ sites on HAp would affect preferential adsorption of electron-deficient BH 3 and electron-rich NH 3 groups in AB, catalyzing cleavage of B-N bonds. Besides, PO 4 3- sites play a critical role in anchoring Pt particles towards electron transfer from Pt to PO 4 3- , resulting in considerable enhancement of catalytic performance in dissociative adsorption of water molecules, which is a rate-determining step in the hydrolysis. Graphical Abstract

In this work, a novel isatin-Schiff base L2 had been synthesized through a simple reaction between isatin and 2-amino-5-methylthio-1,3,4-thiadiazole. The produced Schiff base L2 was then subjected to a hydrothermal reaction with cerium chloride to produce the cerium (III)-Schiff base complex C2. Several spectroscopic methods, including mass spectra, FT-IR, elemental analysis, UV–vis, 13 C-NMR, 1 H-NMR, Thermogravimetric Analysis, HR-TEM, and FE-SEM/EDX, were used to completely characterize the produced L2 and C2. A computer simulation was performed using the MOE software program to find out the probable biological resistance of studied compounds against the proteins in some types of bacteria or fungi. To investigate the interaction between the ligand and its complex, we conducted molecular docking simulations using the molecular operating environment (MOE). The docking simulation findings revealed that the complex displayed greater efficacy and demonstrated a stronger affinity for Avr2 effector protein from the fungal plant pathogen Fusarium oxysporum (code 5OD4) than the original ligand. The antibacterial activity of the ligand and its Ce 3+ complex were applied in vitro tests against different microorganism. The study showed that the complex was found to be more effective than the ligand.

In this study, an eco-friendly superhydrophobic cotton fabric (CF) with water contact angle of 155° was fabricated via a facile two-step approach: imparting surface roughness through hydrothermal growth of ZnO particles, and using stearic acid to create a low-energy surface. ZnO prepared by hydrothermal reaction was in a rod-like shape and had nano- or micro-scale sizes. It was located on the surface in loose aggregates. After modification with stearic acid, the aggregate structure of ZnO particles was changed from loose packing to compact packing. The superhydrophobic CF could be wetted by oil but could not be wetted by water, showing excellent oil/water separation performance. The superhydrophobic CF was able to absorb oils selectively from their mixtures with water and could be used as a filtering membrane to separate oil/water mixtures directly with separation efficiency and oil flux of 96–99% and 2000–9000 L m −2  h −1 , respectively, depending on the intrinsic property of the oils. In addition, the superhydrophobic CF showed excellent mechanical robustness and environmental durability with water contact angle almost remaining unchanged after exposure to sandpaper abrasion, ultrasonication, boiling water treatment and organic solvents erosion. With excellent robustness and durability, the superhydrophobic CF exhibits great potential in oil/water separation even under some harsh conditions. Graphic abstract

Although preparation conditions are known to affect the morphology and catalytic performance of hydrothermally synthesized MoS2, the influence of pH remains unclear. Herein, unsupported MoS2 was prepared from ammonium tetrathiomolybdate (ATTM) by a hydrothermal reaction at various pH values under a reaction pressure of 2 MPa. The physical and chemical properties of the MoS2 samples were characterized, and the catalytic performance for CO methanation was examined. With increasing pH, the morphology of the MoS2 particles transformed from aggregates of irregular grain-like particles to flower-like particles through the agglomeration of fine mesoporous nanoflakes. Hydrothermal synthesis at a pH of 9.5 increased the MoS2 crystallinity by enhancing the stacking of the (0 0 2) lattice plane. The MoS2 samples prepared at pH 7.0 and 9.5 showed increased CO conversion during methanation, which was associated with a low concentration of Mo5+ species and the presence of surface sulfate species. Thus, a high pH during catalyst preparation may promote the complete decomposition of ATTM to MoS2 and the formation of sulfur vacancies, which can facilitate methanation.

A facile and efficient approach to prepare carboxylated cellulose nanocrystals (CCNCs) is presented through a novel one-step hydrothermal procedure by using a mixed acid system of hydrochloric acid and nitric acid (HCl/HNO 3 ). The as-prepared cellulose nanoparticles were characterized by scanning electron microscopy, wide angle X-ray diffraction, conductometric titrations, Fourier transform infrared spectrometry and thermal gravimetric analysis. The results showed that the combination of the mixed acid and hydrothermal reaction can speed up the process of CCNC preparation, and then high quality of the product could be obtained at relatively low acid concentration. It is found that the addition of nitric acid could not only promote the conversion of surface groups on the cellulose nanocrystals (CNCs), but also have significant influences on the yield, particle size and microstructure of CNCs. For the volume ratio of HCl/HNO 3 of 7:3, the as-prepared CCNCs exhibited the largest length to diameter ratio and narrowest dimension distributions as well as maximum degree of oxidation of 0.12. In addition, high dispersion stability for the CCNCs could be observed due to the existence of negative carboxyl groups. This approach based on one-step oxidative carboxylation greatly simplified the preparation of CCNCs with high yield and high crystallinity under mild hydrothermal condition.

We present an investigation on carbon quantum dots (CQDs) synthesized from wastewater induced during the production of tofu. We find that tofu wastewater is a good source of raw material in making fluorescent CQDs. The corresponding CQDs can be fabricated simply via hydrothermal reaction to carbonize the organic matter in the yellow serofluid of tofu wastewater. Two sorts of CQDs can be obtained within the deionized water and NaOH solution, respectively, where the CQDs in water (NaOH solution) can emit blue (green) light under the UV irradiation. It is found from X-ray photoelectron spectroscopy (XPS) that the basic difference between these two sorts of CQDs is the contents of C–O and C=O bonds on the surface of the CQDs. This difference can cause different features of the photoluminescence (PL) spectra of the CQDs. On the basis of the obtained results from the XPS and PL measurements, we propose a mechanism in understanding and explaining the photon-induced light emission from CQDs. This study is relevant to the fabrication and application of fluorescent CQDs as, e.g., light display materials.