Showing papers by "Anhui Normal University published in 2011"

Chiral inorganic nanoparticles: origin, optical properties and bioapplications.

Abstract: Chirality of inorganic nanoparticles (NPs) is an emerging and hot topic in nanoresearch in the past several years. Many novel and interesting properties of chiral NPs have been explored and studied, which highlight their importance in both fundamental research and potential applications. This review summarizes recent progress in the study of origins, optical properties and bioapplications of chiral NPs, and future developments in this research area are also discussed.

Regioselective stepwise bromination of boron dipyrromethene (BODIPY) dyes.

Abstract: Halogenated BODIPYs are important synthetic precursors and potential sensitizers for photodynamic therapy (PDT). Electrophilic bromination of pyrrolic-unsubstituted BODIPYs using bromine regioselectively generated mono- to heptabromoBODIPYs in a stepwise fashion in good to excellent yields. These resultant bromoBODIPYs were applied for regioselective substitution and Suzuki coupling reaction to generate BODIPYs 4, 5, 6, and 7 in good to excellent yields. According to NMR and X-ray analysis results, the stepwise bromination first takes place at 2,6-, then at 3,5-, and eventually at 1,7-positions, whereas the regioselective substitution occurs first at 3,5- then at 1,7-positions of the chromophore. The spectroscopic properties of these resultant BODIPYs were studied, which shows the potential application of these bromoBODIPYs as sensitizers for PDT.

On the approximate controllability of semilinear fractional differential systems

Abstract: Fractional differential equations have wide applications in science and engineering. In this paper, we consider a class of control systems governed by the semilinear fractional differential equations in Hilbert spaces. By using the semigroup theory, the fractional power theory and fixed point strategy, a new set of sufficient conditions are formulated which guarantees the approximate controllability of semilinear fractional differential systems. The results are established under the assumption that the associated linear system is approximately controllable. Further, we extend the result to study the approximate controllability of fractional systems with nonlocal conditions. An example is provided to illustrate the application of the obtained theory.

Turn-on and near-infrared fluorescent sensing for 2,4,6-trinitrotoluene based on hybrid (gold nanorod)-(quantum dots) assembly.

Abstract: In this study, we design a FRET system consisting of gold nanorod (AuNR) and quantum dots (QDs) for turn-on fluorescent sensing of 2,4,6-trinitrotoluene (TNT) in near-infrared region. The amine-terminated AuNR and carboxyl-terminated QDs first form a compact hybrid assembly through amine−carboxyl attractive interaction, which leads to a high-efficiency (>92%) FRET from QDs to AuNRs and an almost complete emission quenching. Next, added TNT molecules break the preformed assembly because they can replace the QDs around AuNRs, based on the specific reaction of forming Meisenheimer complexes between TNT and primary amines. Thus, the FRET is switched off, and a more than 10 times fluorescent enhancement is obtained. The fluorescence turn-on is immediate, and the limit of detection for TNT is as low as 0.1 nM. Importantly, TNT can be well distinguished from its analogues due to their electron deficiency difference. The developed method is successfully applied to TNT sensing in real environmental samples.

Epitaxial Growth of CdS Nanoparticle on Bi2S3 Nanowire and Photocatalytic Application of the Heterostructure

Abstract: Bi2S3 nanowire/CdS nanoparticle heterostructure has been designed and constructed through an easy wet-chemistry approach at 140 °C for 8 h. The product is mainly composed of Bi2S3 nanowires, several hundred nanometers long and 10 nm wide, and epitaxially grown triangle-like CdS nanoparticles with size of 20 nm at their surfaces. A possible sequential deposition growth mechanism is proposed on the basis of experimental results to reveal the formation of the nanoscale heterostructure. Under the irradiation of UV light, the as-prepared nanoscale Bi2S3/CdS heterostructure exhibits enhanced photochemical efficiency that can be mainly attributed to the microstructure of the product. In the nanoscale heterostructure, the CdS nanoparticle not only determines the overall band gap energy, but also controls the charge carrier transition, recombination, and separation, while the Bi2S3 nanowire serves as support for the CdS nanoparticle, defines the specific surface area of the product and thus influences the photocat...

Contrasting patterns in elevational diversity between microorganisms and macroorganisms

Abstract: Aim Data and analyses of elevational gradients in diversity have been central to the development and evaluation of a range of general theories of biodiversity. Elevational diversity patterns have, however, been severely understudied for microbes, which often represent decomposer subsystems. Consequently, generalities in the patterns of elevational diversity across different trophic levels remain poorly understood. Our aim was to examine elevational gradients in the diversity of macroinvertebrates, diatoms and bacteria along a stony stream that covered a large elevational gradient.

Photocatalytic synthesis of M/Cu2O (M = Ag, Au) heterogeneous nanocrystals and their photocatalytic properties

Abstract: M/Cu2O (M = Ag, Au) heterogeneous nanocrystals are successfully prepared by depositing noble metal nanoparticles onto the surfaces of Cu2O octahedral nanocrystals through a simple photocatalytic process. The samples are characterized by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDX). The influence of the light source and solution temperature on the deposition of noble metal (taking Ag as an example) nanoparticles has been studied. The experimental results show that visible light is more favorable for the deposition of Ag nanoparticles onto Cu2O nanocrystals, and a solution temperature of more than 30 °C can prevent the erosion of Cu2O. The photocatalytic properties of the prepared M/Cu2O heterogeneous nanocrystals are studied, showing enhanced photocatalytic activities.

Dual amplification strategy for the fabrication of highly sensitive interleukin-6 amperometric immunosensor based on poly-dopamine.

Abstract: An electrochemical immunosensor was studied for sensitive detection of Interleukin-6 (IL-6) based on a dual amplification mechanism resulting from Au nanoparticles (AuNP)−Poly-dopamine (PDOP) as the sensor platform and multienzyme−antibody functionalized AuNP-PDOP@carbon nanotubes (CNT). The stable and robust film, PDOP, was used to immoblize biomolecules not only for the construction of the sensor platform, but also for the signal labeling. Sensitivity was greatly amplified by using the special platform of AuNP-PDOP and synthesizing horseradish peroxidase (HRP)-antibody (Ab2) functionalized AuNP-PDOP@carbon nanotubes (CNT). A linear response range of IL-6 from 4.0 to 8.0 × 102 pg mL−1 with a low detection limit of 1.0 pg mL−1 was obtained by the amperometry determination. Measurements of IL-6 in human serum gave excellent correlations with standard ELISA assays. Moreover, the immunosensor exhibited high selectivity, good reproducibility, and stability.

Do patterns of bacterial diversity along salinity gradients differ from those observed for macroorganisms

Abstract: It is widely accepted that biodiversity is lower in more extreme environments. In this study, we sought to determine whether this trend, well documented for macroorganisms, also holds at the microbial level for bacteria. We used denaturing gradient gel electrophoresis (DGGE) with phylum-specific primers to quantify the taxon richness (i.e., the DGGE band numbers) of the bacterioplankton communities of 32 pristine Tibetan lakes that represent a broad salinity range (freshwater to hypersaline). For the lakes investigated, salinity was found to be the environmental variable with the strongest influence on the bacterial community composition. We found that the bacterial taxon richness in freshwater habitats increased with increasing salinity up to a value of 1‰. In saline systems (systems with >1‰ salinity), the expected decrease of taxon richness along a gradient of further increasing salinity was not observed. These patterns were consistently observed for two sets of samples taken in two different years. A comparison of 16S rRNA gene clone libraries revealed that the bacterial community of the lake with the highest salinity was characterized by a higher recent accelerated diversification than the community of a freshwater lake, whereas the phylogenetic diversity in the hypersaline lake was lower than that in the freshwater lake. These results suggest that different evolutionary forces may act on bacterial populations in freshwater and hypersaline lakes on the Tibetan Plateau, potentially resulting in different community structures and diversity patterns.

Solvent dependent fluorescent properties of a 1,2,3-triazole linked 8-hydroxyquinoline chemosensor: tunable detection from zinc(II) to iron(III) in the CH3CN/H2O system.

Abstract: A triazole-containing 8-hydroxyquinoline (8-HQ) ether 2 was efficiently synthesized in two steps from the “click” strategy. Compound 2 gave a strong fluorescence (Φ = 0.21) in nonprotic solvent like CH3CN, and a weak fluorescence (Φ = 0.06) in protic solvent like water. In water, a more than 100 nm red shift of the fluorescence maximum was observed for compound 2 in comparison with that in CH3CN. This fluorescence difference may be attributed to the intermolecular photoinduced proton transfer (PPT) process involving the protic solvent water molecules. Similarly, this intermolecular PPT process was also observed in the high-water-content CH3CN aqueous solution (e.g., CH3CN/H2O = 5/95, v/v). The water content in the CH3CN/H2O binary solvent mixture greatly affected the fluorescence intensity (e.g., Φ = 0.06 and 0.25 when CH3CN/H2O = 5/95 and 95/5, v/v, respectively) and emission wavelength. Using this interesting property, by simple variation of the water content in the CH3CN aqueous solution, compound 2 wa...

A glucose oxidase immobilization platform for glucose biosensor using ZnO hollow nanospheres

Abstract: A good route (template-directed synthetic route) for the fabrication of ZnO hollow nanospheres (ZnO-HNSPs) was proposed. ZnO hollow nanosphere is a wonderful platform to immobilize glucose oxidase for glucose biosensor owing to the high specific surface area and high isoelectric point (IEP). Along with nafion and glucose oxidase (GOD), a glucose sensor was designed. Nafion/ZnO-HNSPs/GOD/GCE displays higher catalytic activity toward the glucose oxidation than Nafion/ZnO nano-Flowers/GOD/GCE. Linear response was obtained over a concentration range from 5.0 × 10 −3 mM to 13.15 mM with a detection limit of 1.0 μM (S/N = 3), and the sensitivity was 65.82 μA/(mM cm 2 ). Satisfyingly, the Nafion/ZnO-HNSPs/GOD/GCE could effectively avoid the interferences from the common interfering species such as uric acid (UA), ascorbic acid (AA), dopamine (DA) and fructose. The Nafion/ZnO-HNSPs/GOD modified electrode allows high sensitivity, excellently selective, stable, and fast amperometric sensing of glucose and thus is promising for the future development of glucose sensors.

Single-crystalline α-Fe2O3 oblique nanoparallelepipeds: High-yield synthesis, growth mechanism and structure enhanced gas-sensing properties

Abstract: In this paper, single-crystalline α-Fe2O3 oblique nanoparallelepipeds are fabricated in high yield via a facile surfactant-free hydrothermal method, which involves oriented aggregation and Ostwald ripening. The obtained nanocrystals have exposed facets of {012}, {01–4} and {−210} with a rhombohedral α-Fe2O3 structure. The gas sensors based on the as-synthesized α-Fe2O3 nanostructures exhibit high sensitivity, short recovery time, and good reproducibility in ethanol and acetone. The superiority of the gas-sensing properties of the obtained nanostructures should be attributed to the surface structure of the nanocrystals. The as-prepared α-Fe2O3 nanocrystals are significant for exploiting their other applications in the future.

Large-scale synthesis of hydrated tungsten oxide 3D architectures by a simple chemical solution route and their gas-sensing properties

Abstract: Square slab-like and flower-like hydrated tungsten oxide three-dimensional architectures were synthesized by acidic precipitation of sodium tungstate solution at mild temperature. Techniques of X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermalgravimetric analysis, and transmission electron microscopy were used to characterize the structure and morphology of the products. The experimental results show that the square slab-like and flower-like WO3·H2O architectures can be obtained by addition of a varying amount of 10.0 M HCl solution. The corresponding tungsten oxide three-dimensional architectures were obtained after calcinations at 400 °C. Finally, the obtained WO3 three-dimensional architectures were used as sensitive materials in the experiments. Compared with WO3 square slabs, the as-prepared WO3 microflowers exhibit a good response and reversibility to some organic gases, such as toluene and acetone. The responses to 100 ppm toluene and acetone are 16.7 and 17.4, respectively, at a working temperature of 320 °C. In addition, the sensors also exhibit a good response to ethanol, methanol and n-butanol, which indicates that the flower-like WO3 nanostructures are highly promising for applications of gas sensors.

Existence result for fractional neutral stochastic integro-differential equations with infinite delay

Abstract: This paper is concerned with the existence of mild solutions for a class of fractional neutral stochastic integro-differential equations with infinite delay in Hilbert spaces. A sufficient condition for the existence is obtained under non–Lipschitz conditions by means of Sadovskii's fixed point theorem. An example is given to illustrate the theory.

Fabrication and gas-sensing properties of hierarchically porous ZnO architectures

Abstract: Hierarchically three-dimensional (3D) porous ZnO architectures are synthesized by a template-free, economical aqueous solution method combined with subsequent calcination. First, the precursors of interlaced and monodisperse basic zinc nitrate (BZN) nanosheets are prepared. Then calcination of the precursors produces hierarchically 3D porous ZnO architectures composed of interlaced ZnO nanosheets with high porosity resulting from the thermal decomposition of the precursors. The products are characterized by X-ray diffraction, thermogravimetric–differential thermalgravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller N2 adsorption–desorption analyses. The BET surface area of the hierarchically porous ZnO nanostructures was calculated to be 12.8 m2 g−1. Compared with ZnO rods, the as-prepared porous ZnO nanosheets exhibit a good response and reversibility to some organic gases, such as ethanol and acetone. The responses to 100 ppm ethanol and acetone are 24.3 and 31.6, respectively, at a working temperature of 320 °C. These results show that the porous ZnO architectures are highly promising for gas sensor applications, as the gas diffusion and mass transportation in sensing materials are significantly enhanced by their unique structures. Moreover, it is believed that this solution-based approach can be extended to fabricate other porous metal oxide materials with a unique morphology or shape.

Single-walled carbon nanotube/pyrenecyclodextrin nanohybrids for ultrahighly sensitive and selective detection of p-nitrophenol.

Abstract: Electrochemical detection of p-nitrophenol (P-NP) using a highly sensitive and selective platform based on single-walled carbon nanotube/pyrenecyclodextrin (SWCNT/PyCD) nanohybrids is described for the first time. The electrochemical performance of the SWCNT/PyCD nanohybrid electrode was fully compared with bare glassy carbon, single-SWCNT, single-PyCD, and SWCNT/CD (without pyrene rings) electrodes. Besides the techniques of cyclic voltammetry and chronoamperometric transients, differential pulse voltammetry (DPV) has been used for the detection of P-NP without any interference from o-nitrophenol (O-NP) at the potentials of -0.80 and -0.67 V, respectively. The SWCNT/PyCD nanohybrid electrode is highly sensitive, and it shows an ultrahigh sensitivity of 18.7 μA/μM toward P-NP in contrast to the values reported previously. The detection limit (S/N = 3) of the SWCNT/PyCD nanohybrid electrode toward P-NP is 0.00086 μM (0.12 ppb), which is well below the allowed limit in drinking water, 0.43 μM, given by the U.S. Environmental Protection Agency (EPA). The analytical performance of the SWCNT/PyCD nanohybrid electrode toward P-NP is superior to the existing electrodes.

3-D flower-like NiCo alloy nano/microstructures grown by a surfactant-assisted solvothermal process

Abstract: Uniform 3-D flower-like NiCo crystalline nano/microstructures were synthesized by a surfactant-assisted solvothermal process at 120 °C for 10–15 h, which were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX) and vibrating sample magnetometry (VSM). The effects of synthetic parameters such as surfactant, solvent and molar ratio of metal ions on the formation and morphology of NiCo samples were investigated. The experimental results showed that sodium dodecylbenzenesulfonate (SDBS) and solvent ethanol play critical roles in the formation of novel flower-like NiCo alloy assemblies, and the self-assembly evolution was found to be a two-stage growth process. Magnetic hysteresis measurements revealed that the flower-like Ni48Co52 alloy spheres with an average diameter of ca. 800 nm and hierarchical flower-like Ni47Co53 alloys with a size of ca. 5 μm display ferromagnetic behaviors with saturation magnetizations of 111.33 emu g−1 and 103.58 emu g−1, and coercivities of 84.27 Oe and 52.71 Oe, respectively, at room temperature.

Selective growth of Au nanoparticles on (111) facets of Cu2O microcrystals with an enhanced electrocatalytic property.

Abstract: The selective growth of Au nanoparticles on (111) facets of truncated octahedral and cuboctahedral Cu2O crystals has been achieved by exploiting the differences in the standard potential between AuCl4–/Au and Cu2+/Cu2O pairs and in surface energies between (111) and (100) planes. The density and size of Au nanoparticles can be controlled by tuning the concentration of the gold precursor. Truncated octahedral Cu2O–Au nanocomposites have a 10 times higher electrochemically catalytic activity toward H2O2 reduction than do pure Cu2O crystals. The enhanced catalysis may be derived from the polarization of Au NPs at the interface, which makes Cu2O more active for H2O2 reduction.

Ligand-free CuO nanospindle catalyzed arylation of heterocycle C-H bonds.

Abstract: CuO nanospindles have been developed to efficiently catalyze the direct arylation of heterocycle C–H bonds with moderate to excellent yields This reaction can be applied to heterocycles such as benzoxazole, benzothiazole, and 1-methylbenzimidazole in the presence of a more environmentally friendly inorganic base like K2CO3 under ligand-free catalytic conditions In addition, the catalyst can be recycled and reused without any significant decrease in catalytic activity