Qiang Li

Controlled Synthesis of ZnS Quantum Dots and ZnS Quantum Flakes with Graphene as a Template

Novel ZnS quantum dots (QDs) and ZnS quantum flakes (QFs) were successfully prepared with graphene nanosheets (GNs) as a special template, and two unique heterostructures of ZnS/GNs were also obtained. Due to the structure-directing template effect of GNs, the as-synthesized ZnS with different morphologies, dots or flakes, were uniformly distributed on the surface of GNs by controlling nucleation and growth. The two different heterostructures of ZnS/GNs exhibited obvious photovoltaic response, and ZnS/GN QFs-on-sheet heterostructures show higher photovoltage than that of ZnS/GN QDs-on-sheet.

Novel luminescent yttrium oxide nanosheets doped with Eu3+ and Tb3+

Novel single-layer rare-earth oxide nanosheets were obtained by the exfoliation of Y(1−X)REXOBr (RE = Eu/Tb) layer. First, the Br− ions in Y(1−X)REXOBr were exchanged by benzoate ions under microwave conditions. The interlayer benzoate can chelate RE ions in the oxide layer, and change the structure and luminescence properties of the new layer compound. Then, a colloid of yttrium oxide nanosheets was obtained in n-butanol after the ultrasonic treatment of the benzoate-inserted layer for 30 min. The size and thickness of the yttrium oxide nanosheets were ∼800 nm and 0.8 nm, as measured by transmission electron and atomic force microscopies, respectively. A transparent thin film of the yttrium oxide nanosheets on indium tin oxide glass was prepared by electrophoretic deposition. The thin film showed strong red or green emission upon UV-light excitation based on Eu3+ and Tb3+ ions, respectively.

Luminescent Properties of Eu3+-Doped HfO2 Powders Prepared by Combustion

Scintillators are ideal candidates used in detectors for X-ray ,γ-ray and high energy ray , and have been widely applied in nuclear medicine , high energy physics ,geologic survey , security inspection and material flaw detection. The high density of HfO2 is an attractive compound for host lattice activated by rare earth for applications as scintillating materials. This paper reported the synthesis of Eu3+ doped HfO2 nanopowders by chemical self-combustion method at low temperature. Analytical grade Eu(NO3)3 and high pure HfOCl2 were used as raw materials. The requisite amount of urea and glycine as the mixed fuel were added to the mixed solution. A little EDTA was used as a complexant. The mixed solution was dried at 200°C, and fired at 450°C. The powders synthesized by self-combustion were then calcined at 800°C to profit the crystal growth and improve the luminescent properties. XRD, TEM were employed to analyze the phase composition and the characteristics of as-obtained powders. The TEM images display typical nano-structured morphology of Eu3+ doped HfO2. Analysis of XRD indicates that Eu3+ doped HfO2 nanopowders are cubic phase. The excitation and emission spectra were analyzed by the fluorescence photometer. There are two peaks in emission spectra .One is at 595nm, and another is at 614nm. The luminescent properties also reveal the structure of cubic phase.

Near-infrared-emitting colloidal Ag2S quantum dots excited by an 808 nm diode laser

Thioglycolic acid (TGA)-coated colloidal Ag2S quantum dots (QDs) emitting in the near-infrared (NIR) region upon excitation by an 808 nm diode laser were synthesized. The observed photoluminescence (PL) was attributed to the presence of ligand-modified Ag2S on the QD surfaces and could be easily controlled by a simple dilution process due to the concentration-dependent surface structure of the colloidal QDs. Upon dilution of the solution, the PL intensity initially increased before later decreasing, with a blueshift being observed in the PL spectra. These phenomena can be accounted for by the aggregation of QDs due to a decrease in the content of ligand-modified Ag2S on the QD surfaces upon dilution, which in turn affected the fluorescence resonance energy transfer (FRET), and re-emission of the surface energy level.

Enhanced fluorescence of europium-doped yttrium hydroxide nanosheets modified by 2-thenoyltrifluoroacetone

A novel luminescent inorganic/organic hybrid nanosheet [Y2(1−x)Eu2x(OH)5(TTA)n]+ was successfully synthesized. The photoluminescence of the hybrid nanosheet was significantly different from that of the unmodified nanosheet. The main charge transfer band Eu–O of the nanosheet was replaced by the more efficient π–π* electron transition band of the organic ligands in the hybrid. The emission bands of the 5D0–7F2 electric dipole transition in the hybrid were enhanced greatly. We also prepared a novel transparent thin film of the luminescent inorganic/organic hybrid on FTO glass by electrophoretic deposition. On being excited by ultraviolet radiation, the thin films show strong red emission.

One-Step Approach for the Fabrication and Characterization of Hydroxyapatite/TiO2 Composite Ceramic Coatings by Micro-Arc Oxidation In Situ on the Surface of Pure Titanium

The hydroxyapatite (HA)/ TiO2 composite ceramic coatings were formed by micro-arc oxidation (MAO) on pure titanium in mixed electrolyte of calcium glycerophosphate and calcium acetate with DC pulse power. Microstructure, phase composition, porosity and thickness of the coatings were examined using SEM, XRD, Image-Pro Plus 6.0 Image analysis system and Eddy current thickness gauge. Results indicate that MAO coatings containing calcium and phosphorus were formed in situ on pure titanium surface. Pores formed by the discharge channels distribute uniformly on the coatings surface, and the inner layer is dense. The principal crystalline phases of the MAO coatings are anatase TiO2, rutile TiO2, HA, Ca3(PO4)2 and matrix Ti. The interface is metallurgical bonding and the bonding strength is strong. And reaction time makes a greater influence than voltage in thickness and voltage makes a greater influence than time in porosity.

Synthesis and Photo-Catalytic Performance of ZnO/Graphene Composites

Zinc acetate dehydrate and Graphene oxide (GO) were employed as raw materials, the ZnO/Graphene composites were simply and quickly synthesized by solvothermal reaction at 180°C for 12 h. The phase structure and morphologies of the as-obtained composites were characterized and observed by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Using RhB solution simulated dye wastewater, the composites’ photo-catalytic performance were preliminary tested and observed with the visible light irradiation. The results indicated that the concentrations of zinc acetate and the mass ratio of zinc acetate dihydratio and graphene oxide all had an impact on the photo-degradation rate. The photo-degradation rate of the composites prepared with the concentrations of zinc acetate of 0.01 mol/L was higher than that of zinc acetate of 0.001 mol/L. The mass ratio of zinc acetate dehydratio and graphene oxide of 4:1 was higher than that of 8:1.

Synthesis and Photo-Catalytic Properties of MOO3 Nanosheets

Layered Molybdenum trioxide MOO3, with a two-dimensional (2D) structure was successfully delaminated into colloidal nanosheets in n-butanol via a soft-chemical process involving intercalation of dodecylamine. X-ray diffration (XRD) showd that: after intercalation spacing of the layered material expend from 1.38nm to 2.69nm. Furthermore, stable nanosheet sol was obtained after exfoliation under ultrasonic condition, Characterizations by transmission electron microscopy (TEM) and scan electron microscopy (SEM) confirmed the formation of unilamellar 2D nanosheet crystallites with an average lateral size of 400 nm, those also suggests that the samples we got is Lamellar structured. Selected Area Electron Diffraction (SEDA) indicates that the obtained nanosheets were crystalline. And the obtained nanosheets exhibited photo-catalytic decolorization properties. Which was evaluated by monitoring the degradation of Methylene Blue, after 40 minutes 90% methylene blue was degradated.

The Characteristics of Graphene Prepared by Different Methods

Graphene becomes a hot topic in the fields of materials science and condensed matter physics. Many synthesis methods were developed. This paper reported the characteristics of graphene prepared by different methods. Graphene was respectively prepared by oxidation-reduction method, ultrasonic peeling method and grinding methods. The structure and morphology were determined by TEM, Raman spectra,UV-Vis,ets. and compared. It was confirmed that morphology is little different but structure is similar among graphene from different preparation methods.

Synthesis and Characterization of Graphene/Cu2SnS3 Quantum Dots Composites

In this paper, employing Cu(AC)2•H2O, SnCl2•2H2O and thiourea as raw materials, the composites of graphene/Cu2SnS3 quantum dots (QDs) were prepared simply and quickly using the hydrothermal method. Meanwhile, the separate Cu2SnS3 QDs were also synthesized in the same way. The as-obtained Cu2SnS3 QDs and composites’ phase structures were analyzed and characterized by powder X-ray diffraction (XRD), and the results indicated that the size of the Cu2SnS3 QDs in the composites were less than that of the separate Cu2SnS3 QDs. At the same time, their morphologies were also observed and cross-confirmed by Transmission Electron Microscopy (TEM), and the measurements manifested that Cu2SnS3 QDs were uniformly dispersed on the surface of the graphene, while the separate Cu2SnS3 QDs have obvious glomeration. In addition to this, elemental analysis was also made to verify the existence of Cu2SnS3 on the surface of graphene.