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.

Recovery of Ni matte from Ni-bearing electroplating sludge.

In this study, a novel process for the recovery of Ni from Ni-bearing electroplating sludge (ES) is proposed, which involves the carbothermic reduction stage and smelting stage. In the reduction stage, the CaSO4, Fe2O3, and NiO in the ES were reduced by carbon at 1000 °C, and the Ni3S2 and Fe4Ni5S8(Ni-rich phases) were generated. After that, the reduced ES was mixed with SiO2 and smelted at 1500 °C. During the smelting stage, Ni3S2 and Fe4Ni5S8 were melted to form liquid Ni-Fe-S matte and separated from the molten slag by gravity. Finally, 58.5%Ni-13.8%Fe-27.7%S (in weight) matte and vitrified slag were obtained. The recovery ratio of Ni (97.2%) was much higher than that of Fe (14.7%). Besides, the Ni/Fe mass ratio of the ES was 0.7, while the ratio of the prepared matte was about 4.2. Therefore, the selective recovery of Ni was achieved. The obtained Ni matte can be used as the raw material for pure Ni or Ni-bearing chemicals.

Controllable synthesis of Mo2C with different morphology and application to electrocatalytic hydrogen evolution reaction.

In order to evaluate the effect of precursors and synthesis strategies on catalytic ability of Mo2C in the hydrogen evolution reaction (HER), four kinds of Mo2C were synthesized using two kinds of MoO3by two strategies. Compared with the one-step direct carbonization strategy, Mo2C with a large special surface area and a better performance could be synthesized by the two-step strategy composed of a nitridation reaction and a carbonization reaction. Additionally, the as-prepared porous Mo2C nanobelts (NBs) exhibit good electrocatalytic performance with a small overpotential of 165 mV (0.5 M H2SO4) and 124 mV (1 M KOH) at 10 mA cm-2, as well as a Tafel slope of 58 mV dec-1(0.5 M H2SO4) and 59 mV dec-1(1 M KOH). The excellent catalytic activity is ascribed to the nano crystallites and porous structure. What's more, the belt structure also facilitates the charge transport in the materials during the electrocatalytic HER process. Therefore, the two-step strategy provides a new insight into the structural design with superior performance for electrocatalytic HER.

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.

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.

FeNi LDH/V2CTx/NF as Self-Supported Bifunctional Electrocatalyst for Highly Effective Overall Water Splitting.

The development of bifunctional electrocatalysts with efficient oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is still a key challenge at the current stage. Herein, FeNi LDH/V2CTx/nickel foam (NF) self-supported bifunctional electrode was prepared via deposition of FeNi LDH on V2CTx/NF substrate by hydrothermal method. Strong interfacial interaction between V2CTx/NF and FeNi LDH effectively prevented the aggregation of FeNi LDH, thus exposing more catalytic active sites, which improved electrical conductivity of the nanohybrids and structural stability. The results indicated that the prepared FeNi LDH/V2CTx/NF required 222 mV and 151 mV overpotential for OER and HER in 1 M KOH to provide 10 mA cm-2, respectively. Besides, the FeNi LDH/V2CTx/NF electrocatalysts were applied to overall water splitting, which achieved a current density of 10 mA cm-2 at 1.74 V. This work provides ideas for improving the electrocatalytic performance of electrocatalysts through simple synthesis strategies, structural adjustment, use of conductive substrates and formation of hierarchical structures.

Innovative method for minimization of waste containing Fe, Mn and Ti during comprehensive utilization of vanadium slag.

More than 1.2 million tons of tailings containing approximately 30 wt% of Fe from traditional vanadium extraction processes are discarded every year as solid waste, which waste resources. In order to achieve effective and green utilization of waste, a novel process was proposed to keep Cr and V at Cr3+ and V3+ during extraction by using AlCl3-NaCl-KCl molten salt in Ar gas atmosphere to control the valuable elements (Cr, V, Mn and Fe) from oxidized. The morphological features of vanadium slag reacted in the temperature range from 200 °C to 800 °C and volatilization of samples under different AlCl3/slag ratios were analyzed. Meanwhile, the chlorinated kinetics of V, Cr, Mn and Fe in vanadium slag were systemically investigated in temperature range of 850 °C-950 °C. The kinetics investigation indicated that the chlorination processes of Fe and Mn were restricted by mass transfer in product layer (Al-Si-O mixture) and the chlorination processes of V and Cr were controlled by surface reaction. The apparent activation energies for Fe, Mn, V, and Cr are 105.28 kJ/mol, 94.26 kJ/mol, 64.64 kJ/mol, and 63.30 kJ/mol, respectively. After chlorination, the separation of metal chlorides was achieved. TiCl4 is hydrolyzed to obtain TiO2. Mn can be separated from VCl3, CrCl3, FeCl2, and MnCl2 by controlling the electrolytic voltages. Fe-V-Cr alloy was obtained by electrolysis at 2.3 V.

Electrochemical properties of La0.5Sr0.5Fe0.95Mo0.05O3-δ as cathode materials for IT-SOEC.

Solid oxide electrolysis cells (SOECs) are a new type of high-efficiency energy conversion device that can electrolyze CO2 efficiently and convert electricity into chemical energy. However, the lack of efficient and stable cathodes hinders the practical application of CO2 electrolysis in SOECs. Herein, a novel perovskite oxide La0.5Sr0.5Fe0.95Mo0.05O3-δ (LSFMo) is synthesized and used as a cathode for SOECs. The introduction of Mo significantly improves the CO2 tolerance of the material in a reducing atmosphere and solves the problem of SrCO3 generation in the La0.5Sr0.5FeO3-δ material. Mo ion doping promotes the conductivity in a reducing atmosphere and increases the oxygen deficiencies of the material, which lowers the ohmic resistance (R s) of the material and significantly improves the CO2 adsorption and dissociation in the middle-frequency of polarization resistance (R p). For example, R p decreases from 0.49 to 0.24 Ω cm2 at 800 °C under 1.2 V. Further, the reduction of R s and R p increases the performance improvement, and the current density is increased from 1.56 to 2.13 A cm-2 at 800 °C under 2 V. Furthermore, LSFMo shows reasonable short-term stability during the 60 h stability test.

Excellent Electrochemical Performance of La0.3Sr0.7Fe0.9Ti0.1O3-δ as a Symmetric Electrode for Solid Oxide Cells.

Solid oxide cells (SOCs) can switch between fuel cell and electrolysis cell modes, which alleviate environmental and energy problems. In this study, the La0.3Sr0.7Fe0.9Ti0.1O3-δ (LSFTi 91) perovskite is innovatively used as a symmetric electrode for solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs). LSFTi 91 exhibits a pure perovskite phase in both oxidizing and reducing atmospheres, and the maximum conductivity in air and 5% H2/Ar is 150 and 1.1 S cm-1, respectively, which meets the requirement of the symmetric electrode. The polarization resistance (Rp) at 1.5 V is as low as 0.09 Ω cm2 in the SOEC mode due to the excellent CO2 adsorption capacity. The current density can reach 1.9 A cm-2 at 1.5 V and 800 °C, which is the highest electrolytic performance in the reported single-phase electrodes. LSFTi 91 also exhibits eminent oxygen reduction reaction and hydrogen oxidation reaction (ORR and HOR) activities, with Rp of 0.022 and 0.15 Ω cm2 in air and wet H2, respectively. The peak power density of SOFC could reach 847 mW cm-2 at 800 °C. In addition, good reversibility is confirmed in the cyclic operation of SOFC and SOEC.

Ultra-Stable and Durable Piezoelectric Nanogenerator with All-Weather Service Capability Based on N Doped 4H-SiC Nanohole Arrays.

Ultra-stable piezoelectric nanogenerator (PENG) driven by environmental actuation sources with all-weather service capability is highly desirable. Here, the PENG based on N doped 4H-SiC nanohole arrays (NHAs) is proposed to harvest ambient energy under low/high temperature and relative humidity (RH) conditions. Finite element method simulation of N doped 4H-SiC NHAs in compression mode is developed to evaluate the relationship between nanohole diameter and piezoelectric performance. The density of short circuit current of the assembled PENG reaches 313 nA cm-2, which is 1.57 times the output of PENG based on N doped 4H-SiC nanowire arrays. The enhancement can be attributed to the existence of nanohole sidewalls in NHAs. All-weather service capability of the PENG is verified after being treated at -80/80 ℃ and 0%/100% RH for 50 days. The PENG is promising to be widely used in practice worldwide to harvest biomechanical energy and mechanical energy.

Enhancing the Stability of Orthorhombic CsSnI3 Perovskite via Oriented π-Conjugated Ligand Passivation.

Lead-free orthorhombic CsSnI3 (Bγ-CsSnI3) perovskite has been emerging as one of the potential candidates of photovoltaic materials with superior performance. However, the instability induced by rapid reconstructive phase transition and the oxidation of Sn2+ greatly limits their future application. We thus reported a strategy, oriented π-conjugated ligand passivation, for enhancing the stability of Bγ-CsSnI3, simulated using a Bγ-CsSnI3 slab model based on the first-principles computation. The phase stability was found to be strongly dependent on the orientations of phenylethylammonium (PEA+) ligands. The passivated Bγ-CsSnI3 slab with the ligand molecule axis along [414] was demonstrated as the most stable with the lowest adsorption energy (Eads). Based on this configuration, the calculated formation energies (Eform) of half- and full-monolayer coverage were even more negative than that of yellow phase (Y-) CsSnI3 passivated by PEA+ ligands, verifying the enhanced phase stability. Furthermore, the surface states could be effectively suppressed and the downshifted conduction band minimum (CBM) resulted in a reduced band gap for the completely capped Bγ-CsSnI3. Moreover, the CBM and the valence band maximum (VBM) of the system with complete coverage were respectively donated by the surface and bulky components of the slab, which might benefit the separation and transfer of photogenerated carriers.

Inadvertent tracheobronchial placement of feeding tube in a mechanically ventilated patient.

Nasogastric (NG) tube misplacement into the airways is a rare complication. The presence of a cuffed endotracheal or tracheostomic tube often gives primary care providers a false sense of security. This report presents a case of inadvertent NG tube insertion into the right lower lobe bronchus of a 79-year-old patient with advanced chronic obstructive pulmonary disease, resulting in pneumonia and septic shock. In this report, the literature is reviewed, the influence of tube size on complications is compared, and the reliability of different methods to verify correct tube position is discussed. We conclude that a cuffed tracheostomic tube does not prevent advancement of a large-bore feeding tube into the tracheobronchial system. If any doubt exists regarding proper tube position, a chest radiograph should be obtained prior to initiation of feeding.

Wurtzite AlN(0001) Surface Oxidation: Hints from Ab Initio Calculations.

With superior electrical and thermal properties, aluminum nitride (AlN) exhibits wide application. However, AlN is rather oxygen-sensitive and tends to be oxidized at high temperature. The surface oxidation of AlN remains a major challenge, while the underlying physics of AlN surface oxidation is still elusive. Here, First-principles calculations were performed to study wurtzite AlN(0001) surface oxidation process. The adsorption energy of oxygen was calculated to be site-dependent on the surface with varying O coverage. Calculation indicates that oxygen atoms are preferentially adsorbed at the hollow site (H3) of the AlN(0001) surface regardless of the O coverage. N2 is determined as the dominant gas product. The procedure of N3- removal and the formation of N vacancies (VN) take place step by step. VN plays an accelerating role in the oxidation of AlN, and O2- prefers to occupy the site of VN via consuming the Al p lone-pair electrons and passivating the dangling bond states of Al. An O-Al-O layer is formed when the first Al-N bilayer is fully oxidized, which could be regarded as a precursor of γ-Al2O3. On the basis of our atomic-level simulation, a possible phase transformation mechanism from γ-Al2O3 to α-Al2O3 was further proposed.

A novel method for vanadium slag comprehensive utilization to synthesize Zn-Mn ferrite and Fe-V-Cr alloy.

Vanadium slag is a by-product from steelmaking process of vanadium-titanium magnetite, which mainly contains FeO, MnO, V2O3, and Cr2O3, The elements Fe and Mn are major components of Mn-Zn ferrite. The elements V and Cr are major components of V-Cr alloy. In view of the potential application in these study, a Mn0.8Zn0.2Fe2O4 of high saturation magnetization (Ms = 68.6 emu/g) and low coercivity (Hc = 3.3 Oe) was successfully synthesized from the leaching solutions of vanadium slag by adding appropriate chemical reagents, ZnCl2 and MnCl2·4H2O, via roasting at 1300 °C for 1 h. The minor components (CaO and SiO2) in the leaching solution of vanadium slag segregated to the grain boundaries resulting in increasing the resistivity of ferrite. The value of DC resistivity of Mn0.8Zn0.2Fe2O4 at 25 °C reached 1230.7Ω m. The residue containing Fe, V and Cr was chlorinated by AlCl3 and the Fe3+, V3+, and Cr3+ ions were released into the NaCl-KCl eutectic. The current-time curve for the electrolysis of molten salt was investigated. Alloy (Fe, V, and Cr) of granular shape was obtained. The residue can be used to produce the mulite. This process provided a new approach to utilize slag from steelmaking.