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

Greatly enhanced dielectric charge storage capabilities of layered polymer composites incorporated with low loading fractions of ultrathin amorphous iron phosphate nanosheets

Two-dimensional nanomaterials are promising fillers for dielectric nanocomposites because of their high specific surface areas which can induce strong interfacial polarization and result in improved dielectric permittivity. In this work, ultrathin amorphous FePO4 nanosheets with a thickness of about 3.7 nm are successfully obtained using a one-step solvothermal method and are further dispersed into a P(VDF-HFP) matrix, forming FePO4/P(VDF-HFP) nanocomposites. Obviously enhanced dielectric permittivities are achieved owing to the strong interfacial polarization at the huge interfaces between the FePO4 nanosheets and the P(VDF-HFP) matrix. A greatly enhanced dielectric permittivity of 18.5@10 kHz, which is about 240% that of the P(VDF-HFP) matrix, is obtained in the composite with merely 2 wt% FePO4 nanosheets. Furthermore, bilayer paraelectric/ferroelectric composites, in which pure polyetherimide acts as the paraelectric layer and the FePO4/P(VDF-HFP) composite as the ferroelectric layer, are fabricated. It is found that, the synergistic effect between the two layers results in a substantially suppressed loss and elevated breakdown strengths, as well as obviously improved energy density and discharge efficiency in comparison with the single layer FePO4/P(VDF-HFP) composites. Consequently, a high energy density of 7.58 J cm(-3) and a high discharge efficiency of 81.6% are concurrently achieved in the bilayer composite with merely 0.5 wt% FePO4 nanosheets. The excellent dielectric energy storage performances make these composites promising candidates for advanced electrostatic capacitors

Spatial Distribution, Source Identification, and Potential Ecological Risk Assessment of Heavy Metal in Surface Sediments from River-Reservoir System in the Feiyun River Basin, China

To investigate the pollution characteristics of the surface sediments of the river–reservoir system in the Feiyun River basin, a sediment heavy metal survey was conducted for the first time in the Feiyun River basin. Surface sediments from 21 sampling sites in the Feiyun River basin were collected, and the concentrations and spatial distribution characteristics of 15 heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Mn, V, Co, Mo, Sb, W, Fe, and Se) were analyzed. Three heavy metal ecological risk assessment methods were used to evaluate the potential risks of heavy metals in sediments, and the sources of major heavy metals were traced by correlation analysis and principal component analysis. The results show that (1) the average concentration of heavy metals (As) (212.64 mg/kg) and (Sb) (4.89 mg/kg) in Feiyun River Basin is 33.3 and 6.89 times the background value of Zhejiang Province; the overall spatial distribution of heavy metals is: the mainstream of Feiyun River > Zhaoshandu Reservoir > Shanxi Reservoir, thereby, the pollution is relatively significant; (2) by processing the geo-accumulation index and enrichment index methods, As and Sb are classified as ‘severely polluted’, ‘moderately severely polluted’ and ‘severely polluted’, ‘very severe polluted’ respectively; (3) the potential ecological index evaluates the surface sediments in the Feiyun River Basin as a very high risk level, the main environmental risk factors are As, Sb, Cd and Mo; (4) the principal component analysis results show that the heavy metals in the sediments of the Feiyun River Basin may be mainly affected by human activities such as sewage from domestic and agricultural activities, mining and smelting, and the others are affected by natural factors

Facile Synthesis of Highly Photoluminescent Ag₂Se Quantum Dots as a New Fluorescent Probe in the Second Near-Infrared Window for in Vivo Imaging

A facile solvothermal method is reported to synthesize highly photoluminescent Ag₂Se quantum dots (QDs) with emission at 1300 nm in the second near-infrared window. After surface modification of C18-PMH-PEG, the Ag₂Se QDs possess bright photoluminescence, good water-solubility, high colloidal stability and photostability, as well as decent biocompatibility, which are further successfully performed in in vivo deep imaging of organs and vascular structures with high spatial resolution. This new NIR-II fluorescent nanoprobe with small sizes, ideal optical properties, and decent biocompatibility opens up exciting opportunities for future biomedical applications

Well-Defined, Nanostructured, Amorphous Metal Phosphate as Electrochemical Pseudocapacitor Materials with High Capacitance

Amorphous micro/nanomaterials are very important members of the noncrystalline materials family and have attracted tremendous interest and exhibited their excellent performance in the application of electrical catalysis and energy storage. The complexity of this research field is limited ultimately by the lack of a facile and practicable strategy to synthesize well-defined ultrathin amorphous nanomaterials. Here, for the first time, we report the random attachment of Co₃(PO₄)₂ amorphous nanoplate building blocks into ultrathin nanosheets with dimensions on the micrometer scale. We found the structure of obtained Co₃(PO₄)₂ amorphous nanosheet can be converted into nanowire by a split process. On the basis of our observations, an assemble-split mechanism for synthesizing ultrathin amorphous nanostructure is proposed. Furthermore, our strategy is general and can be used to prepare other metal phosphate amorphous ultrathin nanostructures. As a demonstration, the synthesized Co₃(PO₄)₂ ultrathin nanowire has been proven to show extraordinary performance as an electrode material for a pseudocapacitor with the specific capacitance of up to 1174 F g^–1, which is much higher than that of crystalline cobalt phosphate and even comparable to that of cobaltous hydroxide nanomaterials