Highly Efficient NO2 Sensors Based on Al-ZnOHF under UV Assistance.

Zinc hydroxyfluoride (ZnOHF) is a newly found resistive semiconductor used as a gas-sensing material with excellent selectivity to NO2 because of its unique energy band structure. In this paper, Al3+ doping and UV radiation were used to further improve the gas-sensing performance of ZnOHF. The optimized 0.5 at.% Al-ZnOHF sample exhibits improved sensitivity to 10 ppm NO2 at a lower temperature (100 °C) under UV assistance, as well as a short response/recovery time (35 s/96 s). The gas-sensing mechanism demonstrates that Al3+ doping increases electron concentration and promotes electron transfer of the nanorods by reducing the bandgap of ZnOHF, and the photogenerated electrons and holes with high activity under UV irradiation provide new reaction routes in the gas adsorption and desorption process, effectively promoting the gas-sensing process. The synergistic effect of Al3+ and UV radiation contribute to the enhanced performance of Al-ZnOHF.

UV-excited single-component white phosphor of Lu2WO6 with broad-band emission for pc-WLED.

Obtaining white light from a single-component phosphor is still a significant challenge due to the complex energy transfer between multiple luminescent centers. Herein, white light emission is obtained in a single-component lutetium tungstate without any doping elements. By tuning the pH values during the hydrothermal synthesis, the orthorhombic Lu2W3O12 transformed into monocline Lu6WO12 and rhombohedra Lu6WO12. Only the monoclinic Lu2WO6 phase emitted light, whereas the other two phases did not. The main reason was that the exciton binding energy of Lu2WO6 was larger than that of Lu2W3O12 and Lu6WO12. Except for the 480 nm intrinsic emission of Lu2WO6, new long-wavelength excitation and emission bands were observed with the center at 340 nm and 520 nm. Based on the first-principle calculation, this new photoluminescence band comes from the electron transition between the local states of oxygen vacancies and valence band. Owing to this new broad-band emission, the white light LED lamp is fabricated by combining Lu2WO6 phosphor synthesized at pH values of 4.5 and 6 and 365 nm LED chips. The CIE coordinates of the pc-WLEDs are (0.346, 0.359) and (0.380, 0.380), respectively, and both are located in the white light region. Our research demonstrated a facile way to obtain a single-component white light emission phosphor without any doping components for pc-WLED applications.

2H-MoS2/Co3O4 nanohybrid with type I nitroreductase-mimicking activity for the electrochemical assays of nitroaromatic compounds.

A type I nitroreductase-mimicking nanocatalyst based on 2H-MoS2/Co3O4 nanohybrids for trace nitroaromatic compounds detection is reported in this work. For the preparation of nanocatalyst, ultrathin Co3O4 nanoflakes array was in-situ grown onto 2H-MoS2 nanosheets forming three-dimensional (3D) nanohybrid with large specific surface area as well as abundant active sites. The as-prepared nanocatalyst shows a specific affinity as well as high catalytic activity towards nitroaromatic compounds. Given the favorable nitroreductase-mimicking catalytic activity of 2H-MoS2/Co3O4 nanohybrid, a sensitive and efficient electrochemical microsensor has been constructed for the detection of 2, 4, 6-trinitrotoluene (TNT). Under optimized conditions, the microsensor displayed sensitive response from µM to pM levels with a limit of detection (LOD) of 1 pM. We further employed photoelectron spectroscopy (XPS) analysis and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method to identify the nitroreductase-mimicking mechanism of 2H-MoS2/Co3O4 nanohybrids towards 2, 4, 6- TNT. It was found that the abundant oxygen vacancies in ultrathin Co3O4 nanoflakes played an essential role in determining its catalytic performance. Moreover, the developed MoS2/Co3O4 nanozyme has a lower Michaelis-Menten constant (km) than that of nature nitroreductase demonstrating a good enzymatic affinity towards its substrates, and further generating a high catalytic activity. This research not only proposed a new type of nanozyme, but also developed a portable electrochemical microsensor for the detection of 2, 4, 6-TNT.

1T-Phase molybdenum sulfide/cobalt oxide nanopillars hybrid nanostructure coupled with nitrogen-doped carbon thin-film as high efficiency electrocatalyst for oxygen evolution.

High efficient and durable catalysts are always needed to lower the kinetic barriers as well as prolong the service life associated with oxygen evolution reaction (OER). Herein, a sequential synthetic strategy is considered to prepare a hierarchical nanostructure, in which each component can be configured to achieve their full potential so that endows the resulting nanocatalyst a good overall performance. In order to realize this, well-organized cobalt oxide (Co3O4) nanopillars are firstly grown onto ultrathin 1T-molybdenum sulfide (1T-MoS2) to obtain high surface area electrocatalyst, providing electron transfer pathways and structural stability. After that, zeolitic imidazolate framework-67 (ZIF-67) derived carbonization film is further in situ deposited on the surface of nanopillars to generate plentiful active sites, thereby accelerating OER kinetics. Based on the combination of different components, the electron transfer capability, catalytic activity and durability are optimized and fully implemented. The obtained nanocatalyst (defined as 1T-MoS2/Co3O4/CN) exhibits the superior OER catalytic ability with the overpotential of 202 mV and Tafel slope of 57 mV·dec-1 at 10 mA·cm-2 in 0.1 M KOH, and good durability with a minor chronoamperometric decay of 9.15 % after 60,000 s of polarization.

Flower-like Hydroxyfluoride-Sensing Platform toward NO2 Detection.

We report for the first time using zinc hydroxyfluoride (ZnOHF) for efficient NO2 gas detection. The prepared ZnOHF had a unique flower-like architecture self-assembled by nanorods with a diameter of 150 nm and length of 2-3 µm. The sensing performance toward NO2 detection indicated that the prepared ZnOHF exhibited high response (82.71), short response/recovery time (13 s/35 s) to 10 ppm of NO2, and excellent selectivity at 200 °C, greatly outperforming the ZnO raw material. ZnOHF could work in a wide detection window ranging from 100 ppb to 50 ppm, implying its practical application prospects in both industry and daily life. The excellent sensing behavior of ZnOHF originated mainly from the negligible oxygen ions adsorbed on the material surface, which was caused by the higher work function of ZnOHF. Therefore, almost all conduction band electrons can be used in the NO2 gas sensing.

Understanding the varying mechanisms between the conformal interlayer and overlayer in the silicon/hematite dual-absorber photoanode for solar water splitting.

Dual-absorber photoelectrodes have been proved to have great potential in the photoelectrochemical (PEC) water splitting application due to their broadband absorption and suitable energy-band position, while the surface/interface issues are still not clearly resolved and understood. Here, during the preparation of a silicon/hematite dual-absorber photoanode achieved via synthesizing a Sn-doped hematite film on the silicon nanowire (SiNW) substrate, we separately introduced the conformal overlayer and interlayer of an Al2O3 thin film by atomic layer deposition. With the thickness-optimized interlayer (overlayer) of the Al2O3 thin film, the photocurrent density at 1.23VRHE can be enhanced from 0.85 mA cm-2 to 1.51 mA cm-2 (1.25 mA cm-2), and the on-set potential has a cathodic shift of ∼0.32 V. Although both the overlayer and interlayer modification can substantially improve the PEC performance, the underlying mechanisms are obviously different. The overlayer can only reduce the carrier recombination on the top surface and in the bulk of the hematite film; in contrast, the interlayer not only passivates the SiNW surface and bottom surface of the hematite film, but also the top surface of the photoanode due to Al3+ thermal diffusion from the bottom to the top surface of the hematite film and the resultant Al2O3 formation. This work deepens our understanding for the roles of the surface and interface engineering in the achievement of high-performance PEC systems based on dual or more absorbers.

Conductive Metal-Organic Frameworks for Amperometric Sensing of Paracetamol.

An electrochemical sensor for paracetamol is executed by using conductive MOF (NiCu-CAT), which is synthesized by 2, 3, 6, 7, 10, 11-hexahydroxytriphenylene (HHTP) ligand. The utility of this 2D NiCu-CAT is measured by the detection of paracetamol, p-stacking within the MOF layers is essential to achieve high electrical conductivity, redox activity, and catalytic activity. In particular, NiCu-CAT demonstrated detection Limit of determination near 5µM for paracetamol through a wide concentration range (5-190 µM). The NiCu-CAT/GCE exhibits excellent reproducibility, stability, and interference for paracetamol.

Effects of Transition Metal Substituents on Interfacial and Electronic Structure of CH3NH3PbI3/TiO2 Interface: A First-Principles Comparative Study.

To evaluate the influence of transition metal substituents on the characteristics of CH3NH3PbI3/TiO2, we investigated the geometrical and electronic properties of transition metal-substituted CH3NH3PbI3/TiO2 by first-principles calculations. The results suggested that the substitution of Ti4+ at the five-fold coordinated (Ti5c) sites by transition metals is energetically favored. The substituted interface has enhanced visible light sensitivity and photoelectrocatalytic activity by reducing the transition energies. The transition metal substitution can effectively tune the band gap of the interface, which significantly improves the photo-reactivity. The substituted systems are expected to be more efficient in separating the photo-generated electrons-holes and active in the visible spectrum.

Syntheses, crystal-solution structures and magnetic properties of a series of decanuclear heterometallic [LnCoCo] (Ln = Eu, Gd, Tb, Dy) clusters.

Four unprecedented decanuclear heterometallic [Ln2CoII4CoIII4] clusters based on a diethanolamine ligand (H2dea), namely [Eu2CoII4CoIII4(dea)8(HCOO)4(OH)2(Cl)2(CH3OH)2]Cl2·4CH3OH·2H2O (1), [Gd2CoII4CoIII4(dea)8(HCOO)4(OH)2(Cl)2(CH3OH)2]Cl2·4CH3OH·2H2O (2), [Tb2CoII4CoIII4(dea)8(HCOO)4(OH)2(Cl)2(CH3OH)2]Cl2·2CH3OH·4H2O (3) and [Dy2CoII4CoIII4(dea)8(HCOO)4(OH)2(Cl)2(CH3OH)2]Cl2·2CH3OH·4H2O (4) were synthesized through a facile solution method. Single-crystal X-ray diffraction analyses reveal that complexes 1-4 consist of a [Ln2CoII4CoIII4] core, which is constructed by bridging a quasi-double cuboidal [Ln2CoII2CoIII2] core with two [CoIICoIII] units. Electrospray ionization mass spectrometry (ESI-MS) using methanol solution reveals that complexes 1-4 are stable in the solution, and the clusters undergo three different substitution reactions (Cl- replaced by OH-, OH- replaced by CH3O- and HCOO- replaced by OH-/CH3O-) at the same time in the ionization state. Magnetic susceptibilities reveal ferromagnetic couplings within complexes 3 and 4, and the magnetocaloric effect (MCE) for 2 was also evaluated and the maximum entropy change (-ΔSm) value reaches 16.3 J kg-1 K-1 at about 3 K and 5 T.

[Effect of triptolide on urinary monocyte chemottractant protein-1 in patients with diabetic nephropathy].

OBJECTIVE: To observe the change of urinary monocyte chemottractant protein-1 (MCP-1) in patients with diabetic nephropathy (DN), and to explore the therapeutic effect and mechanism of triptolide (TL) in treating DN. METHODS: Thirty-five patients in the treated group were treated with TL plus benazepril and thirty two patients in the control group were treated with benazepril alone for six months. The change of urinary MCP-1 was measured before and after treatment. RESULTS: Level of urinary MCP-1 in DN patients was significantly higher than that in healthy subjects (P < 0.01), but it could be significantly decreased after TL treatment, showing significant difference as compared with that in the control group (P < 0.05). CONCLUSION: Determination of urinary MCP-1 level is beneficial to know the degree of kidney inflammation in DN patients. TL can inhibit inflammatory reaction to decrease the level of urinary MCP-1, and thus improve the renal function.