Ti3C2Tx Coated with TiO2 Nanosheets for the Simultaneous Detection of Ascorbic Acid, Dopamine and Uric Acid.

Two-dimensional MXenes have become an important material for electrochemical sensing of biomolecules due to their excellent electric properties, large surface area and hydrophilicity. However, the simultaneous detection of multiple biomolecules using MXene-based electrodes is still a challenge. Here, a simple solvothermal process was used to synthesis the Ti3C2Tx coated with TiO2 nanosheets (Ti3C2Tx@TiO2 NSs). The surface modification of TiO2 NSs on Ti3C2Tx can effectively reduce the self-accumulation of Ti3C2Tx and improve stability. Glassy carbon electrode was modified by Ti3C2Tx@TiO2 NSs (Ti3C2Tx@TiO2 NSs/GCE) and was able simultaneously to detect dopamine (DA), ascorbic acid (AA) and uric acid (UA). Under concentrations ranging from 200 to 1000 µM, 40 to 300 µM and 50 to 400 µM, the limit of detection (LOD) is 2.91 µM, 0.19 µM and 0.25 µM for AA, DA and UA, respectively. Furthermore, Ti3C2Tx@TiO2 NSs/GCE demonstrated remarkable stability and reliable reproducibility for the detection of AA/DA/UA.

Improving Out-of-Plane Charge Mobility and Phase Stability of Dion-Jacobson Lead-Free Perovskites via Intercalating π-Conjugated Aromatic Spacers.

The layered quasi-2D perovskites are recognized as one of the effective strategies to resolve the big problem of intrinsic phase instability of the perovskites. However, in such configurations, their performance is fundamentally limited due to the correspondingly weakened out-of-plane charge mobility. Herein, the π-conjugated p-phenylenediamine (PPDA) is introduced as organic ligand ions for rationally designing lead-free and tin-based 2D perovskites with the aid of theoretical computation. It is evidenced that both out-of-plane charge transport capacity and stability can be significantly enhanced within as-established quasi-2D Dion-Jacobson (DJ) (PPDA)Csn -1 Snn I3 n +1 perovskites. The obviously increased electrical conductivity and reduced carrier effective masses are attributed to the enhanced interlayer interactions, limited structural distortions of diamine cations, as well as improved orbital coupling between Sn2+ and I- ions of (PPDA)Csn -1 Snn I3 n +1 perovskites. Accordingly, by dimension engineering of the inorganic layer (n), the bandgap (Eg ) of quasi-2D perovskites can be linearly tailored toward the suitable Eg (1.387 eV) with optimal photoelectric conversion efficiency (PCE) of 18.52%, representing their great potential toward promising applications in advanced solar cells.

Co-utilization of iron ore tailings and coal fly ash for porous ceramsite preparation: Optimization, mechanism, and assessment.

Maximizing the utilization of industrial by-products, such as iron ore tailings (IOTs) and coal fly ash (CFA), is crucial toward sustainable development. This study provides a meticulous insight into the optimization, mechanism, and assessment of the co-utilization of IOTs and CFA for the preparation of porous ceramsite. Micro-CT results revealed that the prepared ceramsite exhibited an exceptional porosity, peaking at 56.98%, with a wide range of pore diameters (3.55-959.10 µm) under optimal conditions (IOTs content at 76%, preheating at 550 °C for 15 min, and sintering at 1177 °C for 14 min), while maintaining good mechanical properties (water adsorption of 1.28%, comprehensive strength of 8.75 MPa, apparent density of 1.37 g/cm3, and bulk density of 0.62 g/cm3). The primary parameters affecting the porosity were identified and ranked as follows: sintering temperature > IOTs content > sintering time. The formation and growth of pores could be attributed to the equilibrium relationship between the liquid-phase surface tension and the gas expansion force, accompanied by pore wall thinning and pore merging. Notably, the prepared ceramsite is both ecologically feasible and economically rewarding, boasting a profit margin of 9.47 $/ton. The comprehensive life cycle assessment (LCA) conducted further highlights the potential of its large-scale implementation for promoting sustainable development. This study provides an innovative strategy for the co-utilization of IOTs and CFA, with advantages such as cost-effectiveness, ecological feasibility and scalability of production.

General Strategy for Rapid Production of Low-Dimensional All-Inorganic CsPbBr3 Perovskite Nanocrystals with Controlled Dimensionalities and Sizes.

Currently, all-inorganic CsPbX3 (X = Br, I, Cl) perovskite nanocrystals (NCs) are shining stars with exciting potential applications in optoelectronic devices such as solar cells, light-emitting diodes, lasers, and photodetectors, due to their superior performance in comparison to their organic-inorganic hybrid counterparts. In the present work, we report a general strategy based on a microwave technique for the rapid production of low-dimensional all-inorganic CsPbBr3 perovskite NCs with tunable morphologies within minutes. The effect of the key parameters such as the introduced ligands, solvents, and PbBr2 precursors and microwave powers as well as the irradiation times on the production of perovskite NCs was systematically investigated, which allowed their growth with tunable dimensionalities and sizes. As a proof of concept, the ratio of OA to OAm as well as the concentration of PbBr2 precursor played important roles in triggering the anisotropic growth of the perovskite NCs, favoring their growth into 1D/2D single-crystalline nanostructures. Meanwhile, their sizes could be tailored by controlling the microwave powers and irradiation times. The mechanism for the tunable growth of perovskite NCs is discussed.

Boron doping induced thermal conductivity enhancement of water-based 3C-Si(B)C nanofluids.

In this paper, the fabrication and thermal conductivity (TC) of water-based nanofluids using boron (B)-doped SiC as dispersions are reported. Doping B into the ß-SiC phase leads to the shrinkage of the SiC lattice due to the substitution of Si atoms (0.134 nm radius) by smaller B atoms (0.095 nm radius). The presence of B in the SiC phase also promotes crystallization and grain growth of obtained particles. The tailored crystal structure and morphology of B-doped SiC nanoparticles are beneficial for the TC improvement of the nanofluids by using them as dispersions. Using B-doped SiC nanoparticles as dispersions for nanofluids, a remarkable improvement in stability was achieved in SiC-B6 nanofluid at pH 11 by means of the Zeta potential measurement. By dispersing B-doped SiC nanoparticles in water-based fluids, the TC of the as-prepared nanofluids containing only 0.3 vol.% SiC-B6 nanoparticles is remarkably raised to 39.3% at 30 °C compared to the base fluids, and is further enhanced with the increased temperature. The main reasons for the improvement in TC of SiC-B6 nanofluids are more stable dispersion and intensive charge ions vibration around the surface of nanoparticles as well as the enhanced TC of the SiC-B dispersions.

The effective determination of Cd(ii) and Pb(ii) simultaneously based on an aluminum silicon carbide-reduced graphene oxide nanocomposite electrode.

A platform for the simultaneous determination of Cd(ii) and Pb(ii) in aqueous solution has been applied based on an aluminum silicon carbide-reduced graphene oxide nanocomposite (Al4SiC4-RGO) modified bismuth film glassy carbon electrode (GCE) using square wave anodic stripping voltammetry (SWASV) for the first time. The Al4SiC4-RGO nanocomposite electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared with the Al4SiC4 modified GCE and bare GCE, the electrochemical performance of the Al4SiC4-RGO nanocomposite electrode is obviously enhanced resulting from the synergistic effects of Al4SiC4, RGO and bismuth film. The chemical and electrochemical parameters that exert an influence on the deposition and stripping of metal ions, such as supporting electrolytes, pH values, concentrations of Bi3+, deposition potentials and deposition times, were carefully studied. Under optimal conditions, a linear relationship exists between the currents and the concentrations of Cd(ii) and Pb(ii) in the range of 50 to 2700 µg L-1. The limits of detection (S/N = 3) are estimated to be 1.30 µg L-1 for Pb(ii) and 2.15 µg L-1 for Cd(ii). Compared with the related work reported in the literature, the analytical performance in this work has a lower determination limit and a wider detection linear range. In addition, this electrode also exhibits good stability and reproducibility. These results imply that the Al4SiC4-RGO nanocomposite might be a promising candidate for practical applications in the electrochemical detection of metal ions.

SiC Nanowires with Tunable Hydrophobicity/Hydrophilicity and Their Application as Nanofluids.

In this paper, several methods including HF, NaOH, TEOS, and PVP treatment were adopted to modify the wettability of silicon carbide (SiC) nanowires switching from hydrophobic to hydrophilic. The phase and microstructure investigated by XRD, FT-IR, XPS, TGA, SEM, and TEM demonstrated SiC nanowires switching from hydrophobic to hydrophilic due to the surface-tethered hydrophilic layer as well as increasing interspace between nanowires. Besides this, SiC nanowires with hydrophilicity may effectively improve the thermal conductivity of a fluid. The thermal conductivity of aqueous SiC nanowires after TEOS treatment with just 0.3 vol % was remarkably improved up to ca. 13.0%.

A titanium nitride nanotube array for potentiometric sensing of pH.

A titanium nitride nanotube array (TiN NTA) electrode was fabricated through anodic oxidation of titanium and reduction and nitridation of TiO2 NTA. The microstructure of TiN NTA was characterized to be uniform with inner diameters of about 120 nm, a wall thickness of 15-20 nm and an average length of 10 µm. Open-circuit potentials were measured to evaluate the TiN TNA electrode related to pH sensitivity, response time, stability, selectivity, hysteresis and reproducibility in the pH range of 2.0-11.0 at 20 ± 1 °C. The prepared TiN NTA electrode exhibits a near-Nernstian slope of 55.33 mV per pH with the correlation coefficient value of 0.995. It shows good selectivity for H(+) ions in the presence of cations and anions, especially in fluoride-containing media. It also has good stability and reproducibility with a response time of 4.4 s. These make it a promising candidate as a pH electrode sensor.

Improvement in surface-enhanced Raman spectroscopy from cubic SiC semiconductor nanowhiskers by adjustment of energy levels.

Enhanced reproducible Raman signals of the 4-MBA molecule were observed on the surface of semiconducting SiC nanowhiskers (SiCNWs) by surface-enhanced Raman spectroscopy (SERS). The SERS enhancement was further tuned and boosted by doping with B. Theoretical calculations were performed to unravel the mechanism of the SERS enhancement and it was found that the SERS effect was strongly associated with the energy level structure between the substrate and analyte. Appropriate energy level matching facilitated the charge transfer process during laser illumination, enhancing the SERS signal. This proposed mechanism was verified through multiple control experiments.

Preparation of TiOxNy/TiN composites for photocatalytic hydrogen evolution under visible light.

TiOxNy/TiN heterojunction composites with tunable chamber structures were prepared through reduction and nitridation of organotitania obtained via solvothermal alcoholysis at 900 °C for 4 h in partially cracked NH3. Owing to the low synthesis temperature, TiOxNy/TiN duplicates the original structure of organotitania. It also demonstrates an outstanding activity toward hydrogen production as high as 34.9 µmol h(-1) g(-1), which is about 1.5 times higher than the highest value reported in the literature for the TiN material. The enhanced photoactivity can be ascribed to the heterojunction structure, which is beneficial for separating the photogenerated carriers in space.

Simulation of the Service Environment and Selection of the Refractory Lining for a Heat Recovery Coke Oven.

A heat recovery coke oven (HRCO) is one of important approaches to achieving a carbon peak and carbon neutrality in China. However, the steady operation of an HRCO is significantly influenced by the internal working conditions and the quality of lining refractories. In this work, a comprehensive study of the internal working conditions of an HRCO was carried out. The results suggest that the partition wall (PW) between the carbonization and combustion chambers is the most vulnerable area, with the corresponding traditional silica bricks inadequate for the service requirements. A reference based on a comparison of the average thermal stress and high-temperature compressive strength is offered for evaluating and selecting silica bricks for the PW. New optimized silica bricks within the reference are verified to be more applicable to the actual working conditions of an HRCO than the traditional silica bricks. As such, this work provides valuable guidance for the optimization and selection of silica bricks for the PW in an HRCO.

Intense interaction between biochar/g-C3N4 promotes the photocatalytic performance of heterojunction catalysts.

In recent decades, environmental protection and energy issues have gained significant attention, and the development of efficient, environmentally friendly catalysts has become especially crucial for the advancement of photocatalytic technology. This study employs the sintering method to produce biochar. A hybrid photocatalyst for the degradation of RHB under visible light was prepared by loading varying proportions of biochar onto g-C3N4 using ultrasonic technology. Among them, 2% CGCD (2% biochar/g-C3N4) achieved a degradation rate of 91.3% for RHB after 30 minutes of visible light exposure, which was more than 25% higher than GCD (g-C3N4), and exhibited a higher photocurrent intensity and lower impedance value. The enhancement in photocatalytic activity is primarily attributed to the increased utilization efficiency of visible light and the electron transfer channel effect from a minor amount of biochar, effectively reducing the recombination of photo-generated charge carriers on the g-C3N4 surface, thereby significantly improving photocatalytic activity. The degradation of RHB is synergistically mediated by O2 -, h+ (photo-generated holes), and ˙OH. The free radical capture experiment indicates that O2 - and ˙OH are the primary active components, followed by h+.

Ni3 S2 -Ni Hybrid Nanospheres with Intra-Core Void Structure Encapsulated in N-Doped Carbon Shells for Efficient and Stable K-ion Storage.

Iron group metals chalcogenides, especially NiS, are promising candidates for K-ion battery anodes due to their high theoretical specific capacity and abundant reserves. However, the practical application of NiS-based anodes is hindered by slow electrochemical kinetics and unstable structure. Herein, a novel structure of Ni3 S2 -Ni hybrid nanosphere with intra-core voids encapsulated by N-doped carbon shells (Ni3 S2 -Ni@NC-AE) is constructed, based on the first electrodeposited NiS nanosphere particles, dopamine coating outer layer, oxygen-free annealing treatment to form Ni3 S2 -Ni core and N-doped carbon shell, and selective etching of the Ni phase to form intra-core void. The electron/K+ transport and K+ storage reaction kinetics are enhanced due to shortened diffusion pathways, increased active sites, generation of built-in electric field, high K+ adsorption energies, and large electronic density of states at Fermi energy level, resulting from the multi-structures synergistic effect of Ni3 S2 -Ni@NC-AE. Simultaneously, the volume expansion is alleviated due to the sufficient buffer space and strong chemical bonding provided by intra-core void and yolk-shell structure. Consequently, the Ni3 S2 -Ni@NC-AE exhibits excellent specific capacity (438 mAh g-1 at 0.1 A g-1 up to 150 cycles), outstanding rate performances, and ultra-stable long-cycle performance (176.4 mAh g-1 at 1 A g-1 up to 5000 cycles) for K-ion storage.

Are formation and adsorption energies enough to evaluate the stability of surface-passivated tin-based halide perovskites?

Surface passivation is one of the effective and widely-used strategies to enhance the stability of halide perovskites with reduced surface defects and suppressed hysteresis. Among all existing reports, the formation and adsorption energies are popularly used as the decisive descriptors for screening passivators. Here, we propose that the often-ignored local surface structure should be another critically important factor governing the stability of tin-based perovskites after surface passivation, but has no detrimental effect on the stability of lead-based perovskites. It is verified that poor surface structure stability and deformation of the chemical bonding framework of Sn-I caused by surface passivation are ascribed to the weakened Sn-I bond strength and facilitated formation of surface iodine vacancy (VI). Therefore, the surface structure stability represented by the formation energy of VI and Sn-I bond strength should be used to accurately screen preferred surface passivators of tin-based perovskites.

Exploring Inhibition Mechanism of Si on Cementite Nucleation in Hypereutectoid Steel: Experiments and First-Principles Calculations.

To clarify the influence of Si on cementite nucleation during the solidification of hypereutectoid steel, the types and microstructure of cementite in hypereutectoid steel with various Si concentrations were investigated by X-ray diffraction and scanning electron microscopy. Additionally, the interfacial properties of γ-Fe/Fe3C were studied using the first-principles density functional theory, including work on adhesion, interfacial energy, and electronic structure, with the aim of elucidating the impact mechanism of Si on the cementite nucleation. The results showed that increasing Si concentrations (0-0.42 wt.%) had a negligible effect on the types of cementite in as-cast hypereutectoid steel. However, the average number of cementite lamellae per unit area decreased significantly, indicating that an increase in Si concentrations has an inhibitory effect on cementite nucleation. This can be attributed to the effect of Si on the interfacial properties of γ-Fe (010)/Fe3C (010), where the presence of Si disrupts the charge distribution of the γ-Fe (010)/Fe3C (010) interface and decreases the hybridization of atom orbits on each side of the interface, resulting in a decrease in the interatomic interaction force. This is reflected in the decrease in the work of adhesion (from 6.92 J·m-2 to 6.78 J·m-2) and the increase in the interfacial energy (from -1.42 J·m-2 to -1.31 J·m-2). As a result, the stability of the γ-Fe (010)/Fe3C (010) interface is reduced, making it difficult for the composite structure to form. This indicates that Si doping inhibits cementite nucleation on austenite.

Energy Level Matching and Band Edge Reconfiguration for Enhanced Charge Transport in Dion-Jacobson 3D/2D Perovskite Heterojunctions.

Generally, the 2D CsPbI3 layer capping on 3D counterparts has been considered as an effective strategy for both enhancing photovoltaic efficiency and stability. However, the intrinsically poor out-of-plane charge transport through the 2D layer remarkably hinders the overall performance of solar devices. To overcome such a challenge, we report the rationally designed 3D-CsPbI3/2D-(PYn)PbI4 (n = 1-4) heterojunctions with desirable energy level matching. It is evidenced that the valence band (VB) edge reconfiguration would occur with the increase of n, accompanied by the VB maximum (VBM) of the 2D component moving down from the higher level above that of the 3D component to the underneath. Consequently, the as-constructed 3D/2D-(PYn)PbI4 (n = 1, 2) heterojunctions exhibit optimal energy level matching, with accelerated transport of holes from 3D to 2D component and limited backflow of electrons. These findings might provide some meaningful insights on the energy level matching in 3D/2D perovskite heterojunctions.

Built-in Electric Field in Quasi-2D CsPbI3 Perovskites Using High-Polarized Zwitterionic Spacer for Enhanced Charge Separation/Transport.

Two-dimensional (2D) halide perovskites are promising candidates for the fabrication of stable and high-efficiency solar cells. However, the low power conversion efficiency (PCE) of cell devices using 2D perovskites is attributed to reduced charge transport caused by poor organic barrier conductivity. In this study, we propose the use of a high-polarized organic zwitterionic spacer, p-aminobenzoic acid (PABA), to construct novel quasi-2D perovskite structures with enhanced self-driven charge separation and transfer. The NH3+ and COO- groups in PABA generate an aligned electric field, promoting carrier separation and aggregation on the opposite edges of the inorganic layer. This enables efficient in-plane transportation along the inorganic layer. Additionally, PABA intercalated quasi-2D perovskite exhibits improved stability compared with counterparts with diamine cation spacers due to the strong interaction between -COO- and inorganic layers. Our findings suggest that high-polarized organic zwitterionic spacers, with NH3+ and COO- functionality, hold promise for stable and efficient quasi-2D perovskite solar cells.

Heterojunction Engineering Enhanced Self-Polarization of PVDF/CsPbBr3 /Ti3 C2 Tx Composite Fiber for Ultra-High Voltage Piezoelectric Nanogenerator.

Piezoelectric nanogenerator (PENG) for practical application is constrained by low output and difficult polarization. In this work, a kind of flexible PENG with high output and self-polarization is fabricated by constructing CsPbBr3 -Ti3 C2 Tx heterojunctions in PVDF fiber. The polarized charges rapidly migrate to the electrodes from the Ti3 C2 Tx nanosheets by forming heterojunctions, achieving the maximum utilization of polarized charges and leading to enhanced piezoelectric output macroscopically. Optimally, PVDF/4wt%CsPbBr3 /0.6wt%Ti3 C2 Tx -PENG exhibits an excellent voltage output of 160 V under self-polarization conditions, which is higher than other self-polarized PENG previously. Further, the working principle and self-polarization mechanism are uncovered by calculating the interfacial charge and electric field using first-principles calculation. In addition, PVDF/4wt%CsPbBr3 /0.6wt%Ti3 C2 Tx -PENG exhibits better water and thermal stability attributed to the protection of PVDF. It is also evaluated in practice by harvesting the energy from human palm taps and successfully lighting up 150 LEDs and an electronic watch. This work presents a new idea of design for high-performance self-polarization PENG.

A general thermodynamics-triggered competitive growth model to guide the synthesis of two-dimensional nonlayered materials.

Two-dimensional (2D) nonlayered materials have recently provoked a surge of interest due to their abundant species and attractive properties with promising applications in catalysis, nanoelectronics, and spintronics. However, their 2D anisotropic growth still faces considerable challenges and lacks systematic theoretical guidance. Here, we propose a general thermodynamics-triggered competitive growth (TTCG) model providing a multivariate quantitative criterion to predict and guide 2D nonlayered materials growth. Based on this model, we design a universal hydrate-assisted chemical vapor deposition strategy for the controllable synthesis of various 2D nonlayered transition metal oxides. Four unique phases of iron oxides with distinct topological structures have also been selectively grown. More importantly, ultra-thin oxides display high-temperature magnetic ordering and large coercivity. MnxFeyCo3-x-yO4 alloy is also demonstrated to be a promising room-temperature magnetic semiconductor. Our work sheds light on the synthesis of 2D nonlayered materials and promotes their application for room-temperature spintronic devices.

Ti3C2Tx (MXene)/Pt nanoparticle electrode for the accurate detection of DA coexisting with AA and UA.

Dopamine (DA), uric acid (UA) and ascorbic acid (AA) are biomolecules widely distributed in the human body and play an important role in many physiological processes. An abnormal concentration of them is associated with various diseases. Thus, the accurate and fast detection of them has been one of the major demands in the healthcare industry. In this study, we demonstrate that Ti3C2Tx/PtNP modified glassy carbon electrodes (GCEs) show a good electrochemical performance in the detection of DA and UA. However, there is no response signal to AA for either the CV or DPV curve due to the electrostatic repulsion between the negatively charged electrode surface and the negatively charged AA. Ti3C2Tx(MXene)/Pt nanoparticles (PtNPs) are prepared by etching Ti3AlC2(MAX) with HF and reducing H2PtCl6 with a NaBH4 aqueous solution. The morphology of Ti3C2Tx/PtNPs is multilayered accordion-like Ti3C2Tx decorated with PtNPs with a diameter of 10-20 nm. Furthermore, it is found that the electrochemical detection of DA will be enhanced by AA. The electrochemical detection rule of AA enhanced DA can be expressed as follows: I(DA+AA) = 0.011216CAA + 0.039950CDA + 1.1175(I(DA+AA) is the peak current of DA coexisting with AA. CAA is the concentration of AA. CDA is the concentration of DA). This can be used as a calibration to correct the concentration of DA when AA and DA coexist. Notably, AA promotes the stability of the electrode because it cleans the oxidation products from the electrode surface in time. In addition, the sensor exhibits good reproducibility and satisfactory recovery results in a real sample.