Ge Su

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.

Water-soluble silica-coated ZnS : Mn nanoparticles as fluorescent sensors for the detection of ultratrace copper(II) ions in seawater

Quantum dots (QDs), semiconductor particles with all three dimensions confined to the nanometer length scale, are good choices for the detection of heavy metals in aqueous media. In this study, silica-coated ZnS : Mn nanoparticles (ZnS : Mn/SiO2) were synthesized by coating hydrophobic ZnS : Mn nanoparticles with silica shells through a microemulsion method. The ZnS : Mn/SiO2 QDs exhibited satisfying dispersibility and luminescence properties in seawater. After a series of experiments were conducted in real seawater, the ZnS : Mn/SiO2 QDs were proven to be sensitive and selective for Cu2+ detection. The quenching of the fluorescence of the QDs with the addition of Cu2+ is well described by the Stern–Volmer pattern. The detection of Cu2+ concentrations in seawater can be achieved over a linear range from 8.16 × 10−8 to 4.96 × 10−4 mol L−1. Studies show that ZnS : Mn/SiO2 QDs have great potential to be used as sensors for Cu2+ analysis from low to high concentrations in seawater.

Fabrication of intelligent photonic crystal hydrogel sensors for selective detection of trace mercury ions in seawater

A hydrogel sensing material has been fabricated using three dimensional (3-D), polymerized colloidal photonic crystals (PCPCs) for highly sensitive and selective detection of mercury ions (Hg2+) in seawater. Due a to periodically ordered lattice of the embedded photonic crystals, the hydrogel diffracts light in visible spectral range according to the Braggs law. The hydrogel has been functionalized by spatially distributed –SH groups through cleaving –S–S– bonds in grafted N,N′-cystaminebisacrylamide molecules and can selectively bind with Hg2+ ions to form –S–Hg–S– bridge bonds in seawater. The Hg2+ binding causes the volume of the hydrogel to shrink, corresponding to a wavelength shift of the light diffracted by the hydrogel. The shifted wavelength is proportional to the amount of bound Hg2+ ions, which enables the quantitative evaluation of Hg2+ ions with a limit of detection at 10−9 M level in seawater, as measured by a portable spectrometer. With this intelligent hydrogel sensors, we demonstrate a simple method for the rapid in situ monitoring and detection of Hg2+ ions at low concentrations in seawater.

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.

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.

Construction of layer-by-layer g-C3N4/Ag/Bi2WO6 Z-scheme system with enhanced photocatalytic activity

A highly active Z-scheme layer-by-layer g-C3N4/Ag/Bi2WO6 system was designed and prepared by a facile in situ growth strategy, which led to superior visible-light photocatalytic efficiency with excellent stability and reusability. The photocatalytic degradation rate of Rhodamine B with CN/Ag/BWO was proved to be 3 times higher than g-C3N4 and 4 times higher than Bi2WO6, further demonstrating the necessity of the layer-by-layer structure and the suitable electron mediator Ag in Z-scheme system. A probable mechanism for the enhanced photocatalytic efficiency of CN/Ag/BWO system was proposed. The results demonstrated that ·O2− or direct h+ was the primary reactive radicals involved, which confirmed that the Z-scheme mechanism of charge carrier transfer conducted the higher photocatalytic activity. This work provided scientific basis for rational construction of Z-scheme photocatalytic system.