Showing papers by "Henan Normal University published in 2006"

Synthesis, properties, and environmental applications of nanoscale iron-based materials: A review

Abstract: Due to their special properties, people have been increasingly interested in studying applications of nanoscale metal materials in environmental engineering. Literature about the current research on the synthesis, properties, and environmental applications of nanoscale iron-based materials is reviewed and summarized in this article. Different physical and chemical methods used for synthesizing nano-iron-based particles with desired size, structure, and surface properties are described. We also emphasize important properties of nano-iron-based particles, including the density and intrinsic reactivity of surface sites. These properties directly influence the chemical behavior of such particles and, consequently, affect their applications in water and wastewater treatment and in air pollution control. Environmental applications of nano-iron particles are discussed in detail, including removal of chlorinated organics, heavy metals, and inorganics.

Photocatalytic degradation and kinetics of Orange G using nano-sized Sn(IV)/TiO2/AC photocatalyst

Abstract: Sn(IV) doped and nano-sized TiO 2 immobilized on active carbon (AC) (Sn(IV)/TiO 2 /AC) were prepared by the sol–gel and dip-calcination method. An azo dye, Orange G (OG), was used as a model compound to study its photocatalytic activity in a fluidized bed photoreactor. The addition of Sn(IV) on TiO 2 could greatly improve the activity of TiO 2 , and the optimal amount of tin was 2.5 at.%. The effects of calcination temperature, pH value, the initial hydrogen peroxide concentration ([H 2 O 2 ] 0 ), the catalyst amount ([TiO 2 ]), the initial OG concentration ([dye] 0 ) and co-existing negative ions on the photocatalytic activity of Sn(IV)/TiO 2 /AC were studied. The optimal conditions were as follows: pH 2.00, [H 2 O 2 ] 0 = 1.5mL/L, [dye] 0 = 50 mg/L, [TiO 2 ] = 12.5 g/L, when the 300 W high pressure mercury light was used as the light source. Under these conditions, the degradation efficiency of OG reached 99.1% after 60 min reaction. The kinetics of the OG degradation was also analyzed. The results showed that the kinetics of this reaction fit the Langmiur–Hinshelwood kinetics model well and the absorption of OG on the Sn(IV)/TiO 2 /AC surface was the controlling step in the whole degradation process. In addition, the catalyst, liquid and gas were separated effectively, and the integrative process of reaction and separation was achieved during the experiment.

Effects of Zr doping on stoichiometric and reduced ceria: A first-principles study

Abstract: The Zr doping in CeO(2) may change the reduction properties and therefore the redox properties of CeO(2). Using first-principles density functional theory with the inclusion of on-site Coulomb interaction for a 96-atom supercell, these effects are studied by comparing the differences in atomic structures, electronic structures, and reduction energies of the doped CeO(2) and those of the nondoped CeO(2). It is found that (1) Zr doping of the ceria structure results in important modifications involving nonequivalent O atoms; (2) the oxygen anions (still four-coordinated) next to the doping center show considerably lower reduction energies (by 0.6 eV) and larger displacements ("higher mobilities"); (3) an O vacancy is most easily created close to the Zr centers, therefore the Zr-doping centers might serve as nucleation centers for vacancy clustering; and (4) the electrons left by the released oxygen localize on two Ce cations neighboring the vacancy, which results in the reduction of two Ce(4+) ions.

Fabrication of protein-conjugated silver sulfide nanorods in the bovine serum albumin solution.

Abstract: Highly ordered silver sulfide nanorods conjugated with the Bovine Serum Albumin (BSA) protein have been successfully achieved at ambient temperature. Such a process is very simple and controllable, directly using silver nitrate and thioacetamide (TAA) as the reactants in the aqueous solution of BSA. The products have been characterized by XRD, HRTEM-SAED, SEM-EDS, TG-DTA, FT-IR, and CD spectroscopy. The results of the research show that the as-prepared Ag2S nanorods are monodispersed with sizes about 40 nm in diameter and 220 nm in length, and exhibit a high degree of crystallinity and good photoluminescence. Furthermore, an interesting mechanism is discussed for the formation of the Ag2S nanorods.

Volumetric and Viscosity Properties of Monosaccharides in Aqueous Amino Acid Solutions at 298.15 K

Abstract: Apparent molar volumes VΦ,S and viscosity B-coefficients for d-(+)-glucose, d-(+)-galactose, d-(+)-xylose, and d-(−)-ribose in aqueous amino acid (glycine or l-alanine) solutions have been determined respectively from density and viscosity measurements at 298.15 K. Infinite-dilution apparent molar volumes for the saccharides in aqueous glycine or l-alanine solutions have been evaluated, together with the standard transfer volumes Δt of the saccharides from water to aqueous amino acid solutions. It is shown that values of transfer volumes and viscosity B-coefficients are positive and increase with increasing amino acid contents. Volumetric parameters indicating the interactions of saccharides with amino acids in water have been obtained from the transfer volumes of the saccharides. The interactions between saccharides and amino acids are discussed in terms of the structural interaction model and the stereo structure of monosaccharide molecules.

Sensitive determination of thiamethoxam, imidacloprid and acetamiprid in environmental water samples with solid-phase extraction packed with multiwalled carbon nanotubes prior to high-performance liquid chromatography.

Abstract: This paper describes a novel method for sensitive determination of thiamethoxam, imidacloprid and acetamiprid based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials. Factors that maybe influence the enrichment efficiency, such as sample flow rate, sample pH, and sample volume, were investigated in detail. Under the optimized conditions, the detection limits of thiamethoxam, imidacloprid and acetamiprid were 6.1, 5.4 and 6.7 ng L−1, respectively. The experimental results indicated that there was good linearity (R 2>0.9993) over the range of 0.08~100 ng mL−1 and good reproducibility with the relative standard deviations over the range of 0.7~1.1% (n=6). The proposed method has been applied to the analysis of real-world water samples, and satisfactory achievements were obtained. The average spiked recoveries were in the range of 87.5~109.8%. All the results indicated that the proposed method could be used for the simultaneous determination of the three pesticides in environmental water samples at trace levels.

h-index sequence and h-index matrix: Constructions and applications

Abstract: The calculation of Hirsch's h-index is a detail-ignoring way, therefore, single h-index could not reflect the difference of time spans for scientists to accumulate their papers and citations. In this study the h-index sequence and the h-index matrix are constructed, which complement the absent details of single h-index, reveal different increasing manner and the increasing mechanism of the h-index, and make the scientists at different scientific age comparable.

One-step hydrothermal synthesis and gas sensing property of ZnSnO3 microparticles

Abstract: The paper reports the preparation and gas sensing characteristic of ZnSnO3. The perovskite structure ZnSnO3 was prepared by hydrothermal process directly. Its crystal structure and ceramic microstructure were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Its grain size is about 500 nm, and homogeneous as well as monodispersive in shape. Furthermore, the gas sensing properties of the materials were tested in static state. It is found that the sensors have good sensitivity and selectivity to H2S.

Hydrothermal synthesis, characterization and photocatalytic properties of Zn2SnO4 nanocrystal

Abstract: Spinel zinc stannate (Zn2SnO4) samples were prepared one-step by a hydrothermal process at 200 °C for 24 h. The crystal structure of the samples was characterized by X-ray diffraction (XRD). The specific surface areas of the nanocrystal powders were measured by Brunauer–Emmett–Teller (BET) method with a gas adsorption analyzer. The crystal morphology and particle size were analyzed using a transmission electron microscopy (TEM). The results show that the product is polycrystalline Zn2SnO4, and the average specific surface area of nanocrystal powder is about 62 m2/g, the particles have mono-dispersive cubic shape and the grain size is about 20 nm. Furthermore, the photocatalytic activity of the samples was appraised by means of the liquid phase photocatalytic degradation of various water-soluble dyes (K-NR, B-RN and B-GFF) under UV and visible light irradiation. The effects of catalyst loading and reacting time on the photocatalytic activity were also investigated. The results show that Zn2SnO4 can photocatalytically decompose dyes in water solution after 2 h irradiation and the degradation can reach about 100%.

Sensing properties of rare earth oxide doped In2O3 by a sol–gel method

Abstract: The powders of pure In2O3 and Eu3+, Gd3+, Ho3+-doped In2O3 with the structure of bixbyite-type were synthesized by a sol–gel method in the citric acid system. The structure and crystal phase of the powders were characterized by using an X-ray diffractometer. The gas sensing characteristics were obtained by measuring the response magnitude as a function of various controlling factors like dopant, operating temperature, concentrations of the test gases and the response time. The results showed that pure In2O3 had poor selectivity, while the In2O3 sensors doped with 5 wt.% Eu2O3, 5 wt.% Gd2O3, and 5 wt.% Ho2O3 increased the gas-sensing performance towards H2S as a reducing gas, but decreased gas towards Cl2 as an oxidizing gas at 195 °C. Namely, doping of the rare earth oxides remarkably improved the selectivity for H2S. In addition, it was found that among the dopants, 5 wt.% Ho2O3 gave the highest the response value, selectivity, stability and the most excellent response and recovery characteristics to H2S at 195 °C. Thus, the Ho2O3-doped In2O3 is a promising candidate for detection of H2S in environments.

Simultaneous Determination of Cyanazine, Chlorotoluron and Chlorbenzuron in Environmental Water Samples with SPE Multiwalled Carbon Nanotubes and LC

Abstract: In this paper, a new method based on solid-phase extraction with multiwalled carbon nanotubes as the packed materials for sensitive determination of cyanazine, chlorotoluron and chlorbenzuron in environmental water samples was demonstrated. Related parameters that may influence the enrichment efficiency of multiwalled carbon nanotubes such as the kind and volume of elute, sample flow rate, sample pH, and volume of the water samples were investigated. Under the optimum conditions, the detection limits of cyanazine, chlorbenzuron and chlorotoluron were 0.015, 0.012, 0.034 ng mL−1, respectively. The experimental results indicated a good linearity (R 2 > 0.9947) over the concentration range of 0.4–40 ng mL−1 for cyanazine and chlorotoluron, and 0.8–80 ng mL−1 for chlorbenzuron. The relative standard deviations of the three analytes were 3.54, 1.55 and 1.38%, respectively. The established method also was applied to the analysis of the real-world water samples and excellent achievements were obtained with average spiked recoveries from 87.8 to 110.1%. All the results indicated that this procedure could allow the simultaneous determination of these three compounds in environmental water samples at trace levels.

Comparison of the Enrichment Efficiency of Multiwalled Carbon Nanotubes, C18 Silica, and Activated Carbon as the Adsorbents for the Solid Phase Extraction of Atrazine and Simazine in Water Samples

Abstract: Multiwalled carbon nanotubes with exceptional merits as SPE adsorbents for enrichment of environmental pollutants have absorbed much attention. The goal of this paper was to make a comparison with it and regular adsorbents such as C18 silica and activated carbon in the extraction capacity of atrazine and simazine. The results indicated that multiwalled carbon nanotubes were very suitable for determination of atrazine and simazine because of an enrichment performance similar to that of C18 silica. In contrast, the spiked recovery of simazine was higher than that of atrazine using multiwalled carbon nanotubes as packing material for SPE. However, reverse results were obtained when the extraction was performed with packing of C18 silica. Moreover, as the extraction of simazine was concerned, multiwalled carbon nanotubes were much better than C18 silica. As for the enrichment of atrazine, C18 silica achieved greater extraction factor than multiwalled carbon nanotubes. Activated carbon did not give the expected extraction efficiency because of its large size and blank volume and less active sites for adsorption. All these experimental results indicated that multiwalled carbon nanotubes could be used as a valuable alternative adsorbent for SPE of atrazine and simazine in many real water samples.

Discovery of a daunorubicin analogue that exhibits potent antitumor activity and overcomes P-gp-mediated drug resistance

Abstract: Anthracyclines are considered to be some of the most effective anticancer drugs for cancer therapy. However, drug resistance and cardiotoxicity of anthracyclines limit their clinical application. We hypothesize that direct modifications of the sugar moiety of anthracyclines avert P-glycoprotein (P-gp) recognition and efflux, increase drug intracellular concentration in cancer cells, and thus overcome P-gp-mediated drug resistance. Daunorubicin (DNR) analogues with sugar modifications were synthesized by directly transforming the amino group of DNR to an azido group or triazole group. Molecular docking showed that the lead compound (3'-azidodaunorubicin, ADNR) averts P-gp binding, while daunorubicin (DNR) extensively interacts with multidrug-resistance (MDR) protein through H-bonds and electrostatic interactions. FACS assay demonstrated that these new compounds abolished P-gp drug efflux and accumulated high intracellular concentration in the drug-resistant leukemia K562/Dox. P-gp inhibition by CsA confirmed that these new analogues are no longer P-gp substrates. ADNR exhibited potent anticancer activity in both drug-sensitive (K562) and drug-resistant leukemia cells (K562/Dox), with a 25-fold lower drug resistance index than DNR. An in vivo xenograft model demonstrated that ADNR showed more than 2.5-fold higher maximum growth inhibition rate against drug-resistant cancers and significant improvement for animal survival rate versus DNR. No significant body weight reduction in mice was observed for ADNR at the maximum tolerable dose, as compared to more than 70% body weight reduction for DNR. These data suggest that sugar modifications of anthracyclines avert P-gp binding, abolish P-gp-mediated drug efflux, increase intracellular drug concentration, and thus overcome P-gp-mediated drug resistance in cancer therapy.

Hausdorff Dimension of Ruptures for Solutions of a Semilinear Elliptic Equation with Singular Nonlinearity

Abstract: We consider the following semilinear elliptic equation with singular nonlinearity: $$\Delta u - \frac{1}{ u^\alpha} + h(x) =0 \quad \hbox{in}\, \Omega $$ where $$\alpha >1, h(x) \in C^1 (\Omega)$$ and Ω is an open subset in $${\mathbb R}^n, n\geq 2$$ . Let u be a non-negative finite energy stationary solution and $$\Sigma=\Big\{ x \in \Omega: \; \lim_{r \to 0^+}{1}/{|B_r (x)|} \int_{B_r (x)} |u| \hbox{exists, and is equal to}\, 0\Big\}$$ be the rupture set of u. We show that the Hausdorff dimension of Σ is less than or equal to [(n−2) α+(n+2)]/(α +1).