Molecular Dynamics Simulation and Viscosity Analysis of Red Mud-Steel Slag Glass-Ceramics.

The preparation of glass-ceramics with red mud and steel slag can not only solve the pollution problem caused by industrial waste slag but also produce economic benefits. It is difficult to analyze the high-temperature melt with the existing test methods, so the simulation experiment with molecular dynamics calculation becomes an important research method. The effects of steel slag content on the microstructure of red mud glass-ceramics were studied by molecular dynamics method. The results show that the binding ability of Si-O, Al-O, and Fe-O decreases with the increase in steel slag content. The number of Si-O-Si bridge oxygen increased gradually, while the number of Al-O-Al, Al-O-Fe, and Fe-O-Fe bridge oxygen decreased significantly. The number of tetrahedrons [SiO4] increased, the number of tetrahedrons [FeO4] and [AlO4] decreased, and the total number of three tetrahedrons decreased. The mean square displacement value of Si4+ and O2- increases first and then decreases, resulting in the viscosity of the system decreasing first and then increasing. The molecular dynamics method is used to analyze the structure of red mud-steel slag glass-ceramics on the microscopic scale, which can better understand the role of steel slag and has guiding significance for the experiment of this kind of glass-ceramics.

Co(II)-Based Metal-Organic Framework Derived CA-CoNiMn-CLDHs with Peroxidase-like Activity for Colorimetric Detection of Phenol.

Given the serious harm of toxic phenol to human health and the ecological environment, it is urgent to develop an efficient, low-cost and sensitive nanoenzyme-based method to monitor phenol. MOF-derived nanozyme has attracted wide interest due to its hollow polyhedra structure and porous micro-nano frameworks. However, it is still a great challenge to synthesize MOF-derived multimetal synergistic catalytic nanoenzymes in large quantities with low cost. Herein, we reported the synthetic strategy of porous hollow CA-CoNiMn-CLDHs with ZIF-67 as templates through a facile solvothermal reaction. The prepared trimetallic catalyst exhibits excellent peroxidase-like activity to trigger the oxidative coupling reaction of 4-AAP and phenol in the presence of H2O2. The visual detection platform for phenol based on CA-CoNiMn-CLDHs is constructed, and satisfactory results are obtained. The Km value for CA-CoNiMn-CLDHs (0.21 mM) is lower than that of HRP (0.43 mM) with TMB as the chromogenic substrate. Because of the synergistic effect of peroxidase-like activity and citric acid functionalization, the built colorimetric sensor displayed a good linear response to phenol from 1 to 100 µM with a detection limit of 0.163 µM (3σ/slope). Additionally, the CA-CoNiMn-CLDHs-based visual detection platform possesses high-chemical stability and excellent reusability, which can greatly improve economic benefits in practical applications.

Zinc vacancy modulated quaternary metallic oxynitride GeZn1.7ON1.8: as a high-performance anode for lithium-ion storage.

The development of alternative anode materials to achieve high lithium-ion storage performance is crucial for the next-generation lithium-ion batteries (LIBs). In this study, a new anode material, Zn-defected GeZn1.7ON1.8 (GeZn1.7-x ON1.8), was rationally designed and successfully synthesized by a simple ammoniation and acid etching method. The introduced zinc vacancy can increase the capacity by more than 100%, originating from the additional space for the lithium-ion insertion. This GeZn1.7-x ON1.8 particle anode delivers a high capacity (868 mA h g-1 at 0.1 A g-1 after 200 cycles) and ultralong cyclic stability (2000 cycles at 1.0 A g-1 with a maintained capacity of 458.6 mA h g-1). Electrochemical kinetic analysis corroborates the enhanced pseudocapacitive contribution and lithium-ion reaction kinetics in the GeZn1.7-x ON1.8 particle anode. Furthermore, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses at different electrochemical reaction states confirm the reversible intercalation lithium-ion storage mechanism of this GeZn1.7-x ON1.8 particle anode. This study offers a new vision toward designing high-performance quaternary metallic oxynitride-based materials for large-scale energy storage applications.

Enhancing the Heat Storage Performance of a Na2HPO4·12H2O System via Introducing Multiwalled Carbon Nanotubes.

The hydrated salt disodium hydrogen phosphate dodecahydrate (DHPD, Na2HPO4·12H2O) has a suitable phase transition temperature and high latent heat of phase transition. Still there are problems such as supercooling, phase separation, and low thermal conductivity. In this paper, DHPD, sodium carboxymethyl cellulose (CMC), aluminum oxide (Al2O3), and poly(vinylpyrrolidone) (PVP) are used to configure DHPD-CAP to suppress supercooling and phase separation successfully. Multiwalled carbon nanotubes (MWCNTs) are used to stabilize DHPD-CAP phase-change materials and improve the thermal conductivity of pure DHPD. Further studies show only a physical interaction between MWCNTs and DHPD, and no new phases are generated. The addition of MWCNTs can also promote the nucleation of the DHPD-CAP composite, and the corresponding latent heat of phase change shows a trend of increasing and then decreasing with the increase of MWCNT content. Compared with DHPD after one cycle, the latent heat of DHPD-CAP/MWCNT4 increases by 36.19%. With the addition of MWCNTs, the thermal stability of the composites is improved compared to pure DHPD. The DHPD-CAP/MWCNT4 composite has good stability after many cycles.

Band gap-Tunable Porous Borocarbonitride Nanosheets for High Energy-Density Supercapacitors.

Band gap-tunable porous borocarbonitride (BCN) nanosheets were successfully fabricated with cheap and readily available precursors by annealing and exfoliating. The band gap of the as-prepared BCN materials ranges from 5.5 to 1.0 eV; these samples exhibit beneficial structural features suitable for the application in supercapacitors. Especially, the BCN material with a band gap of 1.0 eV exhibits a great specific surface area (600.9 m2 g-1), massive active sites, and excellent conductivity (10.8 S m-1). In addition, this example displays great specific capacitance (464.5 F g-1), excellent cycle stability (98.5% performance retention after 10 000 cycles), and ultrahigh energy density (50.4 W h kg-1, in 1 M Et4NBF4 electrolyte). This excellent electrochemical performance and facile effective synthesis of band gap-tunable BCN materials will provide a promising strategy for configuring nanostructured multiple compound electrodes for other energy storage and conversion devices.

Ultra-broadband nonlinear optical response of two-dimensional h-BN nanosheets and their hybrid gel glasses.

Hydrophilic hydroxylated hexagonal boron nitride nanosheets (BNNSs), also called 'white graphene', exhibit high water solubility, compatibility, dispersity with physical and/or chemical effects on the gel matrix, and unexpected but outstanding near-infrared adsorption and nonlinear optical limiting properties. These properties mean that hydroxylated BNNSs are suitable for practical applications in solidification and devices. Hydroxylated BNNSs are doped into an organically modified silicate matrix through a facile sol-gel process. The resulting BNNS-organically modified silicate glass hybrids demonstrate various solid structures (glass, coating, and film), good uniformity, thermostability, toughness, and high linear transmittance in the visible and near-infrared regions. Hybrid glasses showed large optical limiting effects and high doping concentrations without the addition of a compatibiliser, and their limiting thresholds and concentration exceed those of the corresponding suspensions by factors of 1.3-2 and 20-130, respectively. The optical limiting performance of BNNSs is almost equal to or may exceed those of graphene oxide and graphene in solutions and doped glasses. The combined mechanisms of nonlinear absorption, refraction, and scattering are deduced. A solid organically modified silicate hybrid transparent system doped with BNNSs is a promising candidate material for optical limiters and nonlinear optical devices. This system could be an efficient solid-state optical limiter in the visible and long-wavelength near-infrared regions (532-2000 nm).

Metal-free Ternary BCN Nanosheets with Synergetic Effect of Band Gap Engineering and Magnetic Properties.

Introducing the synergy effect of magnetic properties and band gap engineering is highly desired for two-dimensional (2D) nanosheets. Here, we prepare metal-free ternary 2D carbon (C) doped boron nitride (BN) nanosheets (BCN) with band gap engineering and magnetic properties by a synergetic way. The substitutional occupation of C atoms, as revealed by X-ray absorption spectrum, in BCN nanosheets induces tunable band gap reduction (5.5 eV to 2.6 eV) and intensive intrinsic ferromagnetism at room temperature. First-principle calculations also reveal that substituted C atoms in BCN nanosheets can broaden the light adsorption region and reduce the optical band gap, and ferromagnetic ordering is energetically more favorable than antiferromagnetic. This design opens up new possibility for synergetic manipulation of exchange interactions and band gap engineering in 2D nanostructures.

Fabrication of two-dimensional nanosheets via water freezing expansion exfoliation.

Layered materials, if exfoliated effectively, will exhibit several unique properties, offering great potential for diverse applications. To this end, in this study, we develop a novel, universal, and environmentally friendly method named as 'water freezing expansion exfoliation' for producing two-dimensional nanosheets. This method exploits the expansion in the volume of water upon freezing. When the water freezing expansion condition is reproduced in layered materials, the layers exfoliate to overcome the van der Waals force between them. The expansion process is performed by repeated cycling between 4 °C and -20 °C to effectively exfoliate layered materials of graphite, hexagonal boron nitride (h-BN), MoS2 and WS2. Systematic characterization of the samples thus obtained using electron microscopy and optical studies substantiate the formation of thin flakes (graphene, h-BN, MoS2, and WS2 nanosheets). The method demonstrated in this study is cost-effective and does not demand sophisticated equipment and stringent high temperature conditions. Given this general applicability, this method holds great promise for exfoliating layered materials that are sensitive to elevated temperature.