Junping Li

Synthesis of hydrophilic ZnS nanocrystals and their application in photocatalytic degradation of dye pollutants

Abstract Hydrophilic ZnS nanocrystals with narrow size distribution were synthesized via homogeneous precipitation using EDTA as stabilizer. The as-synthesized products were characterized with XRD, TEM, HRTEM and UV-Vis spectrum. UV-Vis spectra showed that ZnS nanocrystals exhibited strong quantum-confined effect with a blue shift in the band gap of light absorbance. The photocatalytic activity of these nanocrystals was also investigated for the liquid phase photocatalytic degradation of Basic Violet 5BN (BV5) dye under UV irradiation. It was found that the ZnS nanocrystals had good catalytic activity for photodegradation of BV5.

Martensitic transition and structural modulations in the Heusler alloy Ni2FeGa

We have found two distinctive structural modulations altering evidently along with the martensitic transition (MT) in the Ni2FeGa alloy. The first one (q(1)), corresponding to the well-known phonon anomalies in the [xixi0] TA(2) branch, occurs along the direction. The second one (q(2)), an incommensurate modulation observed for the first time, occurs along the -direction. Both modulations change gradually with the premartensitic phonon softening and discontinuously with the MT. Anomalies in magnetic properties emerging around the MT have been briefly discussed

Nanoscale phase separation of antiferromagnetic order and superconductivity in K0.75Fe1.75Se2

We report an in-plane optical spectroscopy study on the iron-selenide superconductor K0.75Fe1.75Se2. The measurement revealed the development of a sharp reflectance edge below Tc at frequency much smaller than the superconducting energy gap on a relatively incoherent electronic background, a phenomenon which was not seen in any other Fe-based superconductors so far investigated. Furthermore, the feature could be noticeably suppressed and shifted to lower frequency by a moderate magnetic field. Our analysis indicates that this edge structure arises from the development of a Josephson-coupling plasmon in the superconducting condensate. Together with the transmission electron microscopy analysis, our study yields compelling evidence for the presence of nanoscale phase separation between superconductivity and magnetism. The results also enable us to understand various seemingly controversial experimental data probed from different techniques.

Vertical variations in kinetics of alkaline phosphatase and P species in sediments of a shallow Chinese eutrophic lake (Lake Donghu)

The vertical distribution of the variables relevant to P forms in sediments were studied in a shallow Chinese freshwater lake (Lake Donghu) in 1997, 1998, 1999 and 2000, to assess the contribution of enzyme to P availability in sediment cores. Sediment P was fractionationd into iron-bound P, calcium-bound P, acid soluble organic P (ASOP) and hot NaOH extractable residual organic P. The former two species made the largest contribution to the sediment P pool. All P species exhibited significantly higher concentrations in different depths at Station I, compared with those found at Station II, except for ASOP. Coupled with these lower ASOP concentrations, the Vmax data of alkaline phosphatase, measured on the same samples, were significantly higher at station I. Taken together, ASOP were probably important in supplying the enzymatic substrate (Phosphatase Hydrolyzable Phosphorus, PHP) into interstitial water. Dissolved orthophosphate and PHP concentrations were highly heterogeneous , but peaked in subsurface, paralleled by higher Vmax and lower Km values of alkaline phosphatase, throughout the sediment core. Sediment in the eutrophic lake is not only enriched in available P (iron-bound P), or stores residual P, but also tends to release PHP, thereby inducing the production of alkaline phosphatase and releasing o-P into water column by enzymatic hydrolysis. The latter process may also occur in relatively deep sediment layers.

Single-crystal growth and optical conductivity of SrPt2As2 superconductors

SrPt2As2 single crystals with CaBe2Ge2-type structure were synthesized by self-melting technique. X-ray diffraction, transmission electron microscopy, electrical resistivity, magnetic susceptibility, specific heat, and optical spectroscopy measurements were conducted to elucidate the properties of SrPt2As2. SrPt2As2 single crystals undergo a structural phase transition well above room temperature (about 450 K) and become superconducting at 5.18 K. The superconducting and structural phase transition temperatures are reduced by 6% iridium doping. Both the pure SrPt2As2 and the Ir-doped single crystals are demonstrated to be highly metallic with rather high plasma frequencies. In particular, the optical spectroscopy measurement revealed two gaplike suppression structures: a stronger one at high energy near 12 000 cm(-1) (similar to 1.5 eV), and a less prominent one at lower energy near 3200 cm(-1) (similar to 0.4 eV) for the pure compound. We elaborate that the former is related to the correlation effect, while the latter could be attributed to the partial energy gap formation associated with structural phase transition.

Highly hydrophobic mesoporous materials as matrix for gas chromatography separation of water-alcohols mixtures

In this chapter, the hydrophobic mesoporous materials are synthesized and investigated as gas chromatography (GC) stationary phase for the separation of complicated water-alcohol systems. The hydrophobic mesoporous materials show high resolution and efficiency for the tested systems. The matrix achieves base-line separation of the propanol isomers via their different Van Der Waals interactions with functionalized surfaces in nanochannel. The chapter illustrates the representative transmission electron microscopy (TEM) image of the sample. It depicts a direct image of the 3D wormhole-like pore frameworks. The obtained hybrids are grinded and tabletted to measure the hydrophobicity. The N2 adsorption/desorption isotherms illustrate that the sample exhibits type IV isotherm with type H2 hysteresis loop, which further confirms the mesoporous sturcture of the samples. The hydrophobic materials exhibit the high resolution and efficiency for the water-alcohol mixtures. The separation order is highly consistent with the polarity of alcohol and water.

Separation of benzene and its relatives by highly hydrophobic microporous/mesoporous materials

A series of highly hydrophobic materials with different pore sizes were synthesized by non-surfactant route and then used as gas chromatography matrix for the separation of benzene and its relatives. So-produced materials with meso or micro/meso pores showed a high separation performance for the benzene and its relatives, and the highly hydrophobic microporous/mesoporous materials were shown to be good candidates for stationary phases for the separation of benzene and its relatives due to their high surface areas and highly thermal stability.

A collaborative large spatio-temporal data visual analytics architecture for emergence response

The unconventional emergency, usually outbreaks more suddenly, and is diffused more quickly, but causes more secondary damage and derives more disaster than what it is usually expected. The data volume and urgency of emergency exceeds the capacity of current emergency management systems. In this paper, we propose a three-tier collaborative spatio-temporal visual analysis architecture to support emergency management. The prototype system, based on cloud computation environment, supports aggregation of massive unstructured and semi-structured data, integration of various computing model sand algorithms; collaborative visualization and visual analytics among users with a diversity of backgrounds. The distributed data in 100TB scale is integrated in a unified platform and shared with thousands of experts and government agencies by nearly 100 models. The users explore, visualize and analyse the big data and make a collaborative countermeasures to emergencies.

Catalytic performance of chromium Schiff base complexes immobilized on mesoporous materials in benzyl alcohol oxidation

Abstract A series of chromium (III) Schiff base complexes immobilized on amorphous silica gel (SiO2), MCM-41 and SBA-15 were prepared and use for the selective oxidation of benzyl alcohol (BzOH). The results revealed that the complex immobilized on ordered mesoporous MCM-41 exhibited the highest catalytic performance. Such a significant difference in the catalytic performance of the immobilized complexes could be due to their different inner coordination structures as well as the different local concentration of reactant and objective product around their active sites, which all originated form their different support structures.

IN SITU ASSEMBLY OF ZnS NANOFIBERS WITH HIGHLY ORDERED LAMELLAR MESOSTRUCTURE

ZnS nanofibers with lamellar mesostructure could be built up from in situ generated ZnS precursors via hydrothermal routes using neutral n-alkylamines as structure-directing template and ethylene diamine tetraacetic acid (EDTA) as stabilizer. The morphology and structure of the obtained products were thoroughly investigated via scanning electron microscope (SEM), energy dispersive analysis of X-rays (EDX), transmission electron microscope (TEM), X-ray powder diffraction (XRD) and thermal analyses. HRTEM and XRD results revealed that the so-produced nanofibers were lamellar mesostructure and its framework was built of crystalline wurtzite ZnS. It was also found that the distance between the layers was proportional to the chain length of the alkylamine. The UV-visible absorption spectrum showed that the nanofibers exhibited strong quantum-confined effect with a blue shift in the band gap. Finally, a probable mechanism for the assembly of the nanofibers was also proposed.