Rongjie Gao

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.

One-step synthesis of near-infrared emitting and size tunable CuInS2 semiconductor nanocrystals by adjusting kinetic variables

This paper aims to systematically optimize the preparation process of CuInS2 (CIS) QDs by intensively manipulating kinetic variables including reaction temperature, reaction time, In/Cu ratio and surface ligand. CIS QDs were synthesized using copper iodide and indium acetate in the presence of 1-octadecene (ODE) that was used as reaction solvent, while 1-dodecanethiol (DDT) was chosen as the sulfur source and surface ligand. UV-Vis spectroscopy and fluorescence spectroscopy were applied to reveal the growth kinetics and fluorescence properties of CIS QDs. Transmission electron microscopy and X-ray diffraction were utilized to characterize the size, morphology and crystal structure of the final products. Our results reveal that the emission wavelength of CIS QDs could be found at visible light and near-infrared regions ranging from 630 to 825 nm. By scrupulous regulation of the reaction temperature, reaction time and the amount of DDT, highly dispersed and stable hydrophobic CIS QDs could be prepared directly without any further modification by one-step method. The fluorescence intensity could be enhanced by introducing Cu defects with the fluorescence quantum yield (QY%) reaching around 7%, while the particle size could be tuned from ultra-small sizes approaching 1.5 nm to 4 nm, by controlling the In/Cu ratio.

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.

Towards TiO2 nanotubes modified by WO3 species: influence of ex situ crystallization of precursor on the photocatalytic activities of WO3/TiO2 composites

TiO2 nanotubes (TNT) crystallized at different temperatures were loaded with WO3 hydrate through the reaction between (NH4)(6)W7O24 center dot 6H(2)O and an aqueous solution of HCl. The photocatalytic activities of nanocomposites firstly increase and then decrease as a function of the crystallized temperature of the TNT precursor. The structural, morphologic and optical properties of WO3/TiO2 nanocomposites were also investigated in this study. The samples, initially anatase titania (573 K-773 K), presented phase transition to rutile titania at 873 K. With the crystallized temperature increasing, an evolution of samples morphology changing from nanotube-like structure to nanorod-like structure was observed. Meanwhile, the absorption edge of samples exhibited a red shift, and correspondingly their band gap decreased. Consistent with x-ray diffraction diffractograms, the existence of rutile titania as an impurity in the precursor TNT, crystallized at higher than 873 K, depressed photocatalytic activity evidently. As a result, the degradation rate of methyl orange (MO) increased with the samples crystallinity firstly, and then reduced due to the appearance of rutile titania. In our experimental conditions, the optimal photocatalytic activity was achieved for the sample crystalized at 773 K. Its degradation rate could reach 98.76% after 90 min UV light irradiation.

Synthesis and luminescence of β-SrGe(PO4)2:RE (RE=Eu2+,Eu3+,Tb3+) phosphors for UV light-emitting diodes

Abstract A new series of β-SrGe(PO 4 ) 2 :RE (RE=Eu 2+ ,Eu 3+ ,Tb 3+ ) phosphors were synthesized and characterized by using X-ray powder diffraction as well as excitation, and emission spectroscopy. The results exhibited that the singly doping Eu 2+ , Tb 3+ and Eu 3+ of β-SrGe(PO 4 ) 2 emit strong blue, green and red light under UV irradiation, respectively. Based on the charge transfer transitions of O 2− →RE 3+ , an overlapping excitation band of the as-obtained phosphors could be found in UV region, which made β-SrGe(PO 4 ) 2 :RE (RE=Eu 2+ ,Eu 3+ ,Tb 3+ ) serve as a new series of RGB phosphors. Meanwhile, these phosphors could also be excited by 380 nm excitation simultaneously, and hence the three phosphors mixed physically could achieve the tunable hues from blue to white region by adjusting the mixed ratios.

Preparation of stable superamphiphobic surfaces on X80 pipeline steel substrates

This paper provides a simple, high efficiency and low-cost approach for the preparation of superamphiphobic surfacea on X80 pipeline steel substrates. The whole process included three simple steps: first, the metallic copper was electrochemically deposited onto the surface of X80 pipeline steel substrates under hot alkaline conditions to obtain a layer of the bi-material interface structure. Second, the treated surface was further immersed in ammonia solution at a particular temperature in order to fabricate hierarchical structure to increase the surface roughness. Finally, to reduce the surface energy of the fabricated structures, the surfaces were subsequently chemically modified with 1H,1H,2H,2H-perfluoro-decyl-triethoxysilane. After treatment using the optimum parameters, the as-prepared surfaces exhibited repellency toward distilled water, glycerol, ethylene glycol, and olive oil with contact angles at 163°, 157°, 155° and 152°, respectively, the corresponding sliding angles are all within 10°, which can be attributed to the combination of micro/nano rough reentrant and hierarchical laminated structures with low surface energy modification. Furthermore, in an attempt to improve the superamphiphobic properties of the surface, the thermal stability, long-term stability and mechanical stability of the fabricated nanostructure film surface were examined using a UV light test, immersion test, temperature test and abrasion test, which show that the created superamphiphobic surfaces possess excellent stability under harsh conditions. The developed approach presented might provide a facile, low-cost and scalable route toward the preparation of novel films on metal substrates for various industrial applications, and a high potential for large-scale applications of pipeline steel.

Hierarchical Fe3O4@titanate microspheres with superior removal capability for water treatment: in situ growth and structure tailoring via hydrothermal assisted etching

Hierarchical flower-like Fe3O4@titanate microspheres with ultrathin nanosheets-assembled shell were fabricated via an effective step-by-step approach. Superparamagnetic Fe3O4 microspheres pre-formed were used as templates for perfect deposition of the following coatings. Silica middle layer was introduced by Stober method in order to direct the formation of amorphous titania coverage via the hydrolysis of tetraisopropyl titanate. Under alkaline hydrothermal environment, titanate nanosheets crystallized and grew in situ attaching on the surface of Fe3O4 spheres, generating the flower-like microspheres which exhibit excellent adsorption properties. Meanwhile, the hierarchical structures can be tailored by varying the hydrothermal temperature and alkalinity, and the roles of sodium hydroxide and hydrogen peroxide were proposed.

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.