Manganese Cadmium Sulfide Nanoparticles Solid Solution on Cobalt Acid Nickel Nanoflakes: A Robust Photocatalyst for Hydrogen Evolution.

Photocatalytic water splitting for hydrogen evolution is one of the most promising methods to mitigate environmental and energy-related issues. In this study, manganese cadmium sulfide (Mnx Cd1-x S) solid solution is used to construct a p-n heterostructure with NiCo2 O4 through a hydrothermal method. The Mn0.25 Cd0.75 S/NiCo2 O4 composites are used for photocatalytic hydrogen evolution reaction, and the optimal hydrogen rate with 40 mg of Mn0.25 Cd0.75 S/NiCo2 O4 40 mg (MCS/NCO 40) is 61159 µmol g-1 h-1 , which is about 16.3 times than that of pure Mn0.25 Cd0.75 S. After combining with NiCo2 O4 , the light absorption scale, the separation efficiency of photogenerated carriers, and the reaction kinetics are enhanced. Moreover, the band offset of MCS/NCO composites is calculated by the core level alignment method, demonstrating the formation of a p-n heterostructure. The built-in electric field from the p-n heterostructure drives charge transfer and enhances separation efficiency, which results in improved photocatalytic performance.

Fabrication of the Ni/ZnO/BiOI foam for the improved electrochemical biosensing performance to glucose.

The Ni foam decorated with ZnO/BiOI core-shell p-n junction nanorods was prepared and employed as an enzyme loading matrix to detect glucose. The detection potential was decreased significantly (0.3 V) and the sensitivity was enhanced largely (115.2 µA mM-1 cm-2). The metal-semiconductor foam can afford the porous surface for loading enzymes and achieving the multiple catalysis. More important, the built-in electric field and electron well in the p-n junction interface provide the driving force for electron transport. It was an effective strategy to enhance the biosensing performance by the rational design of p-n junction.

Mn and Co co-doped perovskite fluorides KNiF3 with enhanced capacitive performance.

Perovskite-based aqueous supercapacitors have important development prospects due to their advantages of high energy density, low cost, environmental benignity. Here, bimetallic Ni-Mn and trimetallic Ni-Co-Mn perovskite fluorides are prepared via facile solvothermal method and characterized as positive electrode materials for supercapacitors. The structure, composition, chemical states and the electrochemical properties of these samples are investigated in detail. Three electrode measurements indicate that the electrochemical properties of the perovskite fluorides KNiF3 depend on the nature and amount of dopants. Partial doping of Ni by Mn increases the rate capability but decreases the specific capacity, while Co and Mn co-doping improve both the rate capability and specific capacity of perovskite fluoride KNiF3. The K-Ni-Co-Mn-F (Ni/Co/Mn = 12:2:1) sample exhibits the maximum specific capacity of 211 mAh g-1, low internal resistance and a high rate capability (82% capacity retention from 1 to 16 A g-1). Furthermore, the AC//K-Ni-Co-Mn-F (Ni/Co/Mn = 12:2:1) asymmetric supercapacitor delivers a maximum energy density of 50.2 Wh kg-1. These results prove that Co and Mn co-doped KNiF3 can be a promising material for supercapacitor.

Synthesis and characterization of Mn-doped CsPb(Cl/Br)3 perovskite nanocrystals with controllable dual-color emission.

Metal-halide perovskite nanocrystals (NCs) are considered to be promising types of optoelectronic and photonic materials. The emission colors of the cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) NCs depend on the joint influence of the emission peaks of the host and its dopant ions. Herein, we report a phosphine-free strategy to synthesize Mn-doped CsPb(Cl/Br)3 NCs to tune their optical properties in a wide color gamut. Colloidal Mn-doped CsPb(Cl/Br)3 NCs were synthesized by injecting Cs-oleate solution into the MnCl2 and PbBr2 precursor solution. The as-prepared Mn-doped CsPb(Cl/Br)3 NCs are highly crystalline and uniform sized nanocubes with two emission peaks, including the host emission around 450 nm and the Mn2+ dopant emission around 600 nm, which are sensitive to the MnCl2-to-PbBr2 molar feed ratio and the reaction temperature. By varying the MnCl2-to-PbBr2 molar feed ratio or the reaction temperature, the relative PL intensities of dual color emission can be manipulated, showing their ability in tunable color output.

Vertical Growth of 2D Amorphous FePO4 Nanosheet on Ni Foam: Outer and Inner Structural Design for Superior Water Splitting.

Rational design of highly efficient bifunctional electrocatalysts based on 3D transition-metal-based materials for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is of great importance for sustainable energy conversion processes. Herein, a novel strategy involving outer and inner structural engineering is developed for superior water splitting via in situ vertical growth of 2D amorphous FePO4 nanosheets on Ni foam (Am FePO4 /NF). Careful experiments and density functional theory calculations show that the inner and outer structural engineering contributing to the synergistic effects of 2D morphology, amorphous structure, conductive substrate, and Ni-Fe mixed phosphate lead to superior electrocatalytic activity toward OER and HER. Furthermore, a two-electrode electrolyzer assembled using Am FePO4 /NF as an electrocatalyst at both electrodes gives current densities of 10 and 100 mA cm-2 at potentials of 1.54 and 1.72 V, respectively, which is comparable to the best bifunctional electrocatalyst reported in the literature. The strategies, introduced in the present work, may open new opportunities for the rational design of other 3D transition-metal-based electrocatalyst through an outer and inner structural control to strengthen the electrocatalytic performance.

Rapid synthesis of CuInTe2 ultrathin nanoplates with enhanced photoelectrochemical properties.

Ultrathin (2.1 ± 0.1 nm) single-crystal CuInTe2 two-dimensional (2D) nanoplates were synthesized via a rapid colloidal synthesis method. The growth mechanism was investigated in detail. Crystal seeds grew via a 2D assembly process of initially formed small CuInTe2 nanoparticles followed by recrystallization into single crystal nanoplates. The obtained CuInTe2 nanoplates exhibited significantly enhanced photoelectrochemical properties compared with the CuInTe2 nanoparticles, benefitting from their ultrathin 2D characteristics.

Controllable synthesis and luminescent properties of rare earth doped Gd2(MoO4)3 nanoplates.

For the first time, we have successfully synthesized rare-earth doped Gd2(MoO4)3: RE3+ (RE=Eu, Tb) nanoplates by solvothermal method. The morphology of Gd2(MoO4)3 can be manipulated by changing the reaction times and reaction temperatures. The composition and surface morphology have been investigated by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM), respectively. Under the excitation of UV, Photoluminescence (PL) has been used to explore the excellent luminescence properties of the synthesized nanophosphors. The Gd2(MoO4)3: Eu3+ phosphors shows a hypersensitive red emission (612nm) when excitation wavelength within the scope of 200-350nm corresponding to a 5D0-7F2 transition. Similarly, the Gd2(MoO4)3: Tb3+ phosphors certificate a highly strong green emission at 544nm at an excitation wavelength of 298nm corresponding to a 5D4-7F5 transition. Furthermore, the characteristic spectrum peak of the Gd2(MoO4)3: Eu3+/Tb3+ nanophosphor exhibits the corresponding spectra position (green emission at 544nm and red emission at 612nm). Hence, the obtained Gd2(MoO4)3: RE3+ nanoplates may establish highly potentiality in light field applications.

Colloidal synthesis of VSe2 single-layer nanosheets as novel electrocatalysts for the hydrogen evolution reaction.

We present a one-pot colloidal route to synthesize VSe2, a new type of metallic single-layer nanosheet. The ∼0.4 nm thick VSe2 single-layer nanosheets possess extraordinary electrocatalytic hydrogen evolution reaction (HER) performance with a low onset overpotential of 108 mV, a small Tafel slope of 88 mV per decade, and an exceptional overpotential of 206 mV at a current density of 10 mA cm(-2).

The key role of nanoparticle seeds during site-selective growth of silver to fabricate core-shell or asymmetric dumbbell heterostructures.

Herein, a novel method to induce site-specific deposition of plasmonic silver domain on controlled sites of seeded AgBr nanoparticles is designed. Novel core-shell heterostructures and dumbbell heterostructures are fabricated by heterogeneous silver growth. A curved silver shell with thickness up to 5 nm is generated covering the AgBr core in the core-shell metal-semiconductor hybrids. However, in the dumbbell hybrids, a large silver domain is exclusively grown on a single side of the AgBr seed with a solid contact like relationship between the head and the tail. Photogenerated electrons are facilitated to transfer from the semiconductor head to the metal tail enhancing charge separations. The significant role of seed size during seeded silver growth has been demonstrated.

[Detection of firmness and surface color of pear by near infrared spectroscopy based on Monte Carlo uninformative variables elimination method].

In the present study, NIRS was applied to nondestructive and rapid measurement of firmness and surface color of pear. In order to improve the prediction precision and eliminate the influence of uninformative variables on model robustness, Monte Carlo uninformative variables elimination (MC-UVE) and Monte Carlo uninformative variables elimination based on wavelet transform (WT-MC-UVE) methods were proposed for variable selection in firmness and surface color NIR spectral modeling. Results show that WT-MC-UVE can reduce the modeling variables from 1451 to 210, and get similar prediction results for firmness. WT-MC-UVE improved the prediction precision for surface color, the root mean square error of prediction (RMSEP) and calibration variables were reduced from 1.06 and 1451 to 0.90 and 220 respectively, and the correlation coefficient (r) was improved from 0.975 to 0.981. The proposed method is able to select important wavelength from the NIR spectra, and makes the prediction more robust and accurate in quantitative analysis of firmness and surface color.

[Research on optimization of model for detecting sugar content of navel orange by online near infrared spectroscopy].

The objective of the present research was to optimize the model of sugar content in navel orange for improving the detection presicion by the online near infrared spectroscopy. The reference wavelength was chosen by coefficient of variation of the different wavelengths in the calibration set in the wavelength range of 700.28 - 933.79 nm. Then the spectra were transformed into ratio specra. The absorbance and ration spectra were pretreated by different preprocessing methods. The models of sugar content were developed by partial least squares (PLS) and least squares support vector regression (LSSVR). The 30 unknown navel orange samples were applied to evaluate the performance of the models. By comparison of the predictive performances, the LSSVR model was the best among the models with the first derivative preprocessing and ration spectra. The correlation coeffiecient (R(P)) of the best model was 0.85, the root mean square error of prediction (RMSEP) was 0.41 Brix. The results suggested that it was feasible to improve the precision of online near infrared spectroscopy detecting sugar content in navel orange by the optimization of reference wavelengths, the first derivative preprocessing and LSSVR.

[Review of portable NIR instruments for detecting fruit interior quality].

The detection principle of NIR technology for nondestructive measurement of fruit internal quality was briefly introtive analysis was given among several instruments. The latest progress was summarized at home and abroad. Finally, the development and trend of NIR instruments for detecting fruit quality was analyzed.