Caixia 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.

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.

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.

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.

Structure and Luminescence Characteristics of Terbium Hydroxide Nanosheets Doped with Eu3

Eu3+ doped terbium hydroxide nanosheets were successfully synthesized from layer compound of Tb2(OH)5NO3·1.5H2O doped by Eu3+. Firstly layer compound of Tb2(OH)5NO3·1.5H2O doped by Eu3+ was obtained by hydrothermal reaction at 1200 . After ion exchange reaction with SDS under the microwave condition, the layer space of the compound increases from 0.907 nm to 2.34 nm. Furthermore stable nanosheet sol was obtained after exfoliation under ultrasonic condition. At the mean time we discovered that microwave and ultrasonic method can greatly shorten the preparation time. The structure of layer compound and the morphology of nanosheets were determined by XRD and TEM. The luminescence properties of terbium hydroxide nanosheets doped with Eu3+ were examined; the relationship between structure and spectra was discussed

Synthesis and Characterization of CoO2 Nanosheets

The layered sodium cobalt oxide Na0.6CoO2 phase has been synthesized from Na2O2 and Co3O4 by solid-state reaction at 550°C for 12h with the heating rate about 2°C /min. The colloidal suspension of exfoliated, layered cobalt oxide nanosheets was prepared through the intercalation of tetrabutyl ammonium hydroxide ions (TBA) into protonated sodium cobalt oxide. The as-obtained composites were analyzed by powder X-ray diffraction (XRD). They were also cross-confirmed by a range of methods including UV/Vis spectroscopy, and Transmission Electron Microscopy (TEM). The Zeta-potential measurements clearly demonstrated the negative surface charge of cobalt oxide nanosheets.

Synthesis, Structure and Properties of Super Fine LiMn2O4

In this paper, super fine LiMn2O4 powder was synthesized by mechanochemical method starting from Li2CO3 and Mn2O3. The structure, size and morphology of LiMn2O4 were explored with X-ray diffraction and scanning electron microscopy (SEM). The electrochemical properties of LiMn2O4 were studied in 2 mol/L (NH4)2SO4 solution. The result showed that pure spinel LiMn204 powder was prepared after 8h grinding with 3.0KW of power and the particle size was about 1µm. Cyclic vohammetry curve indicate LiMn2O4 electrode material has better capacitive performances.

Synthesis and Characterization of FeO+ Nanosheets

The layered FeOCl has been synthesized from Fe2O3 and FeCl3 by chemical vapor transport technique at 380°C., and an intercalation of sodium benzoate into as-synthesized FeOCl was conduct. After the intercalation composites were sonicated for 4 h in butyl alcohol, the colloidal suspension of layered iron oxide nanosheets was obtained. The FeOCl and the intercalation composites were analyzed by powder X-ray diffraction (XRD). Transmission Electron Microscopy (TEM) was also used to characterize the morphologies of the FeO+ Nanosheets. Except to this, the selected area electron diffraction was also performed to examine the iron nanosheets.