Bohua Dong

Synthesis and characterization of the water-soluble silica-coated ZnS:Mn nanoparticles as fluorescent sensor for Cu2+ ions

Silica-coated ZnS:Mn nanoparticles were synthesized by coating hydrophobic ZnS:Mn nanoparticles with silica shell through microemulsion. The core-shell structural nanoparticles were confirmed by X-ray diffraction (XRD) patterns, high-resolution transmission electron microscope (HRTEM) images and energy dispersive spectroscopy (EDS) measurements. Results show that each core-shell nanoparticle contains single ZnS:Mn nanoparticle within monodisperse silica nanospheres (40nm). Photoluminescence (PL) spectroscopy and UV-vis spectrum were used to investigate the optical properties of the nanoparticles. Compared to uncoated ZnS:Mn nanoparticles, the silica-coated ZnS:Mn nanoparticles have the improved PL intensity as well as good photostability. The obtained silica-coated ZnS:Mn nanoparticles are water-soluble and have fluorescence sensitivity to Cu(2+) ions. Quenching of fluorescence intensity of the silica-coated nanoparticles allows the detection of Cu(2+) concentrations as low as 7.3x10(-9)molL(-1), thus affording a very sensitive detection system for this chemical species. The possible quenching mechanism is discussed.

Synthesis and Luminescence Properties of Core/Shell ZnS:Mn/ZnO Nanoparticles

In this paper the influence of ZnO shell thickness on the luminescence properties of Mn-doped ZnS nanoparticles is studied. Transmission electron microscopy (TEM) images showed that the average diameter of ZnS:Mn nanoparticles is around 14 nm. The formation of ZnO shells on the surface of ZnS:Mn nanoparticles was confirmed by X-ray diffraction (XRD) patterns, high-resolution TEM (HRTEM) images, and X-ray photoelectron spectroscopy (XPS) measurements. A strong increase followed by a gradual decline was observed in the room temperature photoluminescence (PL) spectra with the thickening of the ZnO shell. The photoluminescence excitation (PLE) spectra exhibited a blue shift in ZnO-coated ZnS:Mn nanoparticles compared with the uncoated ones. It is shown that the PL enhancement and the blue shift of optimum excitation wavelength are led by the ZnO-induced surface passivation and compressive stress on the ZnS:Mn cores.

Facile synthesis of highly luminescent UV-blue emitting ZnSe/ZnS core/shell quantum dots by a two-step method

New water-soluble and highly luminescent ZnSe/ZnS core/shell quantum dots with tunable emission ranging between 390 and 460 nm were synthesized via a two-step method.

Synthesis and characterization of Mn doped ZnS d-dots with controllable dual-color emissions.

High-quality Mn doped ZnS d-dots were successfully synthesized via an alternative route based on the solvothermal method using oleic acid as stabilizing agent. X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as photoluminescence (PL) spectra were employed to characterize the obtained samples. The as-obtained d-dots are highly crystalline and uniform sized, and they can be well dispersed in hexane to form stable and clear colloidal solution. The optical properties of the d-dots with different Mn doped concentration are investigated in detail. The Mn doped ZnS d-dots have two emission bands, including surface state emission (blue) and Mn emission (orange), which are both sensitivity to the Mn doped concentration. By varying the Mn doped concentration, the relative PL intensities of dual-color emissions can be well manipulated, showing their application in tunable color output. Furthermore, a subsequent ligand exchange has been introduced to give the d-dots hydrophilic surfaces, which are favorable for biological applications.

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.

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.

Effect of ultraviolet irradiation on luminescence properties of undoped ZnS and ZnS:Ag nanoparticles

Undoped ZnS and ZnS:Ag nanoparticles have been prepared through hydrothemal synthesis. The changes of luminescence properties induced by ultraviolet irradiation have been investigated. For both samples, the initial slight increase in luminescence is ascribed to the fast electron filling, while the succedent decrease is supposed to be caused by nonradiative pathways originating from some unknown photochemical products. The more remarkable decrease in ZnS:Ag is put down to the segregation of Ag on the surfaces of ZnS:Ag nanoparticles. Multipeaks Gaussian fitting is applied to the emission spectra. The fitting peaks around 490 nm in both samples are related with the surface states emission and the fitting peaks around 456 nm in ZnS nanoparticles and 443 nm in ZnS:Ag nanoparticles are attributed to the type of donor-acceptor pair luminescence, which corresponds to the transition between different donor levels and acceptor levels in different samples. A model of stretched exponential function is used to fit th...

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.