Showing papers by "Anhui Normal University published in 2013"

Non-enzymatic electrochemical sensing of glucose

Abstract: This article reviews the progress made in the past 5 years in the field of direct and non-enzymatic electrochemical sensing of glucose. Following a brief discussion of the merits and limitations of enzymatic glucose sensors, we discuss the history of unraveling the mechanism of direct oxidation of glucose and theories of non-enzymatic electrocatalysis. We then review non-enzymatic glucose electrodes based on the use of the metals platinum, gold, nickel, copper, of alloys and bimetals, of carbon materials (including graphene and graphene-based composites), and of metal-metal oxides and layered double hydroxides. This review contains more than 200 refs.

Colorimetric Visualization of Glucose at the Submicromole Level in Serum by a Homogenous Silver Nanoprism–Glucose Oxidase System

Abstract: In this study, we design a homogeneous system consisting of Ag nanoprisms and glucose oxidase (GOx) for simple, sensitive, and low-cost colorimetric sensing of glucose in serum. The unmodified Ag nanoprisms and GOx are first mixed with each other. Glucose is then added in the homogeneous mixture. Finally, the nanoplates are etched from triangle to round by H2O2 produced by the enzymatic oxidation, which leads to a more than 120 nm blue shift of the surface plasmon resonance (SPR) absorption band of the Ag nanoplates. This large wavelength shift can be used not only for visual detection (from blue to mauve) of glucose by naked eyes but for reliable and convenient glucose quantification in the range from 2.0 × 10–7 to 1.0 × 10–4 M. The detection limit is as low as 2.0 × 10–7 M, because the used Ag nanoprisms possess (1) highly reactive edges/tips and (2) strongly tip sharpness and aspect ratio dependent SPR absorption. Owing to ultrahigh sensitivity, only 10–20 μL of serum is enough for a one-time determina...

Existence of solutions for nonlinear fractional stochastic differential equations

Abstract: The fractional stochastic differential equations have wide applications in various fields of science and engineering. This paper addresses the issue of existence of mild solutions for a class of fractional stochastic differential equations with impulses in Hilbert spaces. Using fractional calculations, fixed point technique, stochastic analysis theory and methods adopted directly from deterministic fractional equations, new set of sufficient conditions are formulated and proved for the existence of mild solutions for the fractional impulsive stochastic differential equation with infinite delay. Further, we study the existence of solutions for fractional stochastic semilinear differential equations with nonlocal conditions. Examples are provided to illustrate the obtained theory.

MoS2/MX2 heterobilayers: Bandgap engineering via tensile strain or external electrical field

Abstract: We have performed a comprehensive first-principles study of the electronic and magnetic properties of two-dimensional (2D) transition-metal dichalcogenide (TMD) heterobilayers MX2/MoS2 (M = Mo, Cr, W, Fe, V; X = S, Se). For M = Mo, Cr, W; X=S, Se, all heterobilayers show semiconducting characteristics with an indirect bandgap with the exception of the WSe2/MoS2 heterobilayer which retains the direct-band-gap character of the constituent monolayer. For M = Fe, V; X = S, Se, the MX2/MoS2 heterobilayers exhibit metallic characters. Particular attention of this study has been focused on engineering bandgap of the TMD heterobilayer materials via application of either a tensile strain or an external electric field. We find that with increasing either the biaxial or uniaxial tensile strain, the MX2/MoS2 (M=Mo, Cr, W; X=S, Se) heterobilayers can undergo a semiconductor-to-metal transition. For the WSe2/MoS2 heterobilayer, a direct-to-indirect bandgap transition may occur beyond a critical biaxial or uniaxial strain. For M (=Fe, V) and X (=S, Se), the magnetic moments of both metal and chalcogen atoms are enhanced when the MX2/MoS2 heterobilayers are under a biaxial tensile strain. Moreover, the bandgap of MX2/MoS2 (M=Mo, Cr, W; X=S, Se) heterobilayers can be reduced by the electric field. For two heterobilayers MSe2/MoS2 (M=Mo, Cr), PBE calculations suggest that the indirect-to-direct bandgap transition may occur under an external electric field. The transition is attributed to the enhanced spontaneous polarization. The tunable bandgaps in general and possible indirect-direct bandgap transitions due to tensile strain or external electric field endow the TMD heterobilayer materials a viable candidate for optoelectronic applications.

Origin and Molecular Characteristics of a Novel 2013 Avian Influenza A(H6N1) Virus Causing Human Infection in Taiwan

Abstract: TO THE EDITOR—On 20 May 2013, the world’s first human-infected case of H6N1 bird flu was reported in Taiwan. A novel avian-origin influenza A(H6N1) virus was confirmed by the National Influenza Center, Centers for Disease Control, Taiwan, and the patient has already recovered. The H6 subtype influenza viruses were first identified in turkeys in 1965, and make up one of the most commonly recognized subtypes in domestic ducks in southern China [1]. Previous studies indicated that the H6N1 virus is low pathogenic [2]. In this study, we investigated the molecular characteristics of the novel avian influenza A(H6N1) virus and performed phylogenetic and coalescent analyses to infer the potential origins. We first conducted a sequence identical analysis using nucleotide BLAST for all 8 segments of the novel H6N1 virus across 2 Avian influenza virus sequence databases (GISAID, NCBI). The PB1 gene of the novel human influenza A/Taiwan/ 2/2013(H6N1) (EPI_ISL_143275) has the highest nucleotide sequence similarity to A/ chicken/Taiwan/PF3/02(H6N1) at 95.8%, whereas the remaining 7 genes showed that the highest nucleotide sequence similarity to A/chicken/Taiwan/A2837/2013 (H6N1) ranged from 96.2% (NA) to 99.5% (NP). We also constructed the maximum likelihood phylogenetic trees for each genome segment using the program PhyML3.0 [3]. The results of phylogenetic analyses showed that all 8 genes of this virus were clustered in the Taiwan lineage. Taking sampling collection schedules into consideration, the closest relative of A/Taiwan/2/2013(H6N1) is A/chicken/ Taiwan/A2837/2013, suggesting the latter might be the precursor of the novel virus. Our results indicated A/Taiwan/2/2013 (H6N1) was reassorted from A/chicken/ Taiwan/0101/2012(H5N2) (PB2 and PA genes), A/chicken/Taiwan/A1997/2012

Transcriptome sequences resolve deep relationships of the grape family.

Abstract: Previous phylogenetic studies of the grape family (Vitaceae) yielded poorly resolved deep relationships, thus impeding our understanding of the evolution of the family. Next-generation sequencing now offers access to protein coding sequences very easily, quickly and cost-effectively. To improve upon earlier work, we extracted 417 orthologous single-copy nuclear genes from the transcriptomes of 15 species of the Vitaceae, covering its phylogenetic diversity. The resulting transcriptome phylogeny provides robust support for the deep relationships, showing the phylogenetic utility of transcriptome data for plants over a time scale at least since the mid-Cretaceous. The pros and cons of transcriptome data for phylogenetic inference in plants are also evaluated.

Preferential growth of long ZnO nanowires and its application in gas sensor

Abstract: Long single crystalline ZnO nanowires with an average diameter of 50 nm and lengths of up to 9 μm were synthesized by a sudden hydrothermal reaction of Zn(NO3)2·6H2O aqueous solution and NaOH aqueous solution. The formation mechanism of the long ZnO nanowires was studied in detail. In addition, Au nanoparticles were introduced on the surface of ZnO nanowires using a wet-chemical reduction method. Both the long ZnO nanowires and Au-nanoparticle-functionalized ZnO nanowires (Au NPs-ZnO NWs) were applied to fabricate gas sensors for the detection of some organic vapors. The as-fabricated gas sensors exhibit high gas-sensing response, and short response and recovery time. Compared with the ZnO nanowires, the Au NPs-ZnO NWs exhibit a higher response and lower working temperature to some organic vapors, such as ethanol and n-butanol. Such behaviors can be attributed to catalytic activity of Au nanoparticles and Schottky contact at the Au/ZnO interface.

A gold nanorods-based fluorescent biosensor for the detection of hepatitis B virus DNA based on fluorescence resonance energy transfer

Abstract: In this study, we designed a fluorescence resonance energy transfer system containing gold nanorods (AuNRs) and fluorescein (FAM) for the detection of hepatitis B virus DNA sequences. AuNRs were synthesized according to the seed-mediated surfactant-directed approach, and the surface of the AuNRs was wrapped with a thin layer of cetyltrimethylammonium bromide (CTAB), resulting in the AuNRs being positively charged. When FAM-tagged single-stranded DNA (FAM-ssDNA) was added into the AuNRs suspension, it was adsorbed onto the surface of the positively charged AuNRs and formed a FAM-ssDNA–CTAB–AuNRs ternary complex, the resulting structure led to a fluorescence resonance energy transfer (FRET) process from FAM to AuNRs and the fluorescence intensity of FAM was consequently quenched. When complementary target DNA was added to the FAM-ssDNA–CTAB–AuNRs complex solution, a further decrease in fluorescence intensity was observed because of an increased FRET efficiency. Under optimal conditions, the decline of the fluorescence intensity of FAM (ΔF) was linear with the concentration of the complementary DNA from 0.045 to 6.0 nmol L−1 and the detection limit was as low as 15 pmol L−1 (signal/noise ratio of 3). When this fluorescent DNA sensor was used to detect the polymerase chain reaction product of hepatitis B virus gene extracted from a positive real sample, a positive response was obtained. Impressively, the biosensor exhibits good selectivity, even for single-mismatched DNA detection.

Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu (Crassulaceae): a new species from Zhejiang Province, China

Abstract: Sedum plumbizincicola X.H. Guo et S.B. Zhou ex L.H. Wu (Crassulaceae), a new species restricted to lead–zinc mining areas in Zhejiang Province, China, is described and illustrated. This taxon belongs to sect. Sedum (H. Ohba) S.H. Fu based on the adaxially gibbous carpels and follicles. It superficially resembles S. alfredii Hance and three other Sedum species found in the same area, but differs from these other taxa in bearing 4-merous flowers. Differences in geographical distribution, growth habit, phenology, macromorphology, leaf and stem anatomy, as well as seed micromorphology among S. plumbizincicola, S. alfredii and other related taxa in the genus Sedum are also reported. nrDNA internal transcribed spacers (ITS) sequences from seven populations of S. plumbizincicola support the recognition of this as a taxonomic entity distinct from S. alfredii.

Collective total synthesis of englerin A and B, orientalol E and F, and oxyphyllol: application of the organocatalytic [4+3] cycloaddition reaction.

Abstract: The concise collective total synthesis of englerinA and B, orientalolE and F, and oxyphyllol has been accomplished in 1015 steps, with the total synthesis of orientalolE and oxyphyllol being achieved for the first time. The success obtained was enabled by

Approximate Controllability of Fractional Differential Equations with State-Dependent Delay

Abstract: The systems governed by delay differential equations come up in different fields of science and engineering but often demand the use of non-constant or state-dependent delays The corresponding model equation is a delay differential equation with state-dependent delay as opposed to the standard models with constant delay The concept of controllability plays an important role in physics and mathematics In this paper, first we study the approximate controllability for a class of nonlinear fractional differential equations with state-dependent delays Then, the result is extended to study the approximate controllability fractional systems with state-dependent delays and resolvent operators A set of sufficient conditions are established to obtain the required result by employing semigroup theory, fixed point technique and fractional calculus In particular, the approximate controllability of nonlinear fractional control systems is established under the assumption that the corresponding linear control system is approximately controllable Also, an example is presented to illustrate the applicability of the obtained theory

Synthesis of polycrystalline cobalt selenide nanotubes and their catalytic and capacitive behaviors

Abstract: Polycrystalline Co0.85Se nanotubes are successfully prepared by using Co(CO3)0.35Cl0.20(OH)1.10 nanorods as precursor through a solvothermal process. The as-prepared Co0.85Se nanotubes show efficient catalytic performance for decomposition of hydrazine hydrate at room temperature. The catalysts can be repeatedly used and their repeatability is also excellent. The Co0.85Se nanotubes can also be applied as supercapacitor electrode materials. Galvanostatic charge–discharge measurements show that the Co0.85Se nanotube electrode has a specific capacitance of 238 F g−1 at a current density of 1 A g−1 after 100 cycles of activation, and retaining 90.3% of the capacitance after the next 1900 cycles.

A highly efficient, clean-surface, porous platinum electrocatalyst and the inhibition effect of surfactants on catalytic activity.

Abstract: Herein we report a gentle seedless and surfactant-free method for the preparation of clean-surface porous platinum nanoparticles. In terms of electrocatalytic CH(3)OH oxidation, the clean-surface porous platinum exhibited better performance than platinum nanoparticles and a commercial Pt/C catalyst. The porous nanostructures exhibited 2.26-fold higher mass activity and 2.8-fold greater specific activity than the Pt/C catalyst. More importantly, three typical surfactants, cetyltrimethylammonium bromide/chloride (CTAB/C), poly(vinylpyrrolidone), and sodium dodecyl sulfate, were chosen to study the inhibition effect of surfactants on electrocatalytic performance. It was observed that the surfactants led to a clear selective decrease in electrocatalytic performance. CTAB/C inhibited the catalytic activity the most due to the stronger interaction between the OH-enriched platinum surface and the positively charged molecules. Thus, this work indicates that these clean-surface porous platinum nanoparticles may be used as efficient catalysts for direct methanol fuel cells and provides a greater understanding of the inhibition effects of surfactants on catalytic activity.

Ag–Au bimetallic nanostructures: co-reduction synthesis and their component-dependent performance for enzyme-free H2O2 sensing

Abstract: In this work, Ag–Au bimetallic nanostructures with various component ratios were successfully synthesized through a simple kinetic controlled co-reduction route at room temperature. The structure and composition of the as-obtained products has been adjusted and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDX) elemental mapping, inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and UV-visible spectra. Meanwhile, Ag67.3Au32.7 bimetallic nanostructures were identified to show the best sensing performance in the enzyme-free detection of H2O2 with a short response time (<5 s) at an applied potential of −0.5 V, a linear range from 0.01 to 68 mM (R2 = 0.998) with a lower detection limit of 0.2 μM and higher sensitivity of 600 μA mM−1 cm−2. More importantly, the component-dependent electrochemical sensor data of different component nanostructures has been studied, and the synergistic effect between Ag and Au can lead to the best performance of H2O2 sensing. The interaction of diffusion and adsorption we raised reasonably has been used to explain the component-depended performance. Significantly, this work supplies an understanding of the bimetallic component effect for H2O2 sensing by the control of the components of the Ag–Au bimetal, and find out the Ag67.3Au32.7 bimetallic nanostructures are the most excellent candidate for enzyme-free H2O2 sensing.

High-Capacity Gas Storage by a Microporous Oxalamide-Functionalized NbO-Type Metal–Organic Framework

Abstract: A microporous oxalamide-functionalized NbO-type metal–organic framework, HNUST-3, has been designed and synthesized by self-assembling [Cu2(COO)4] paddlewheel SBUs and a novel tetracarboxylate ligand with linking oxalamide groups. HNUST-3 represents the first example of a porous oxalamide-functionalized MOF, which exhibits a high BET surface area of 2412 m2·g–1, large H2 uptake (unsaturated total capacity of 6.1 wt % at 20 bar and 77 K), and excellent CH4 storage (135.8 cm3(STP)cm–3 at 20 bar and 298 K) as well as high CO2 adsorption capacity (20.2 mmol·g–1 at 20 bar and 298 K) with good selectivity for CO2 over CH4 (7.9) and N2 (26.1) at 298 K.

Label-free electrochemical immunosensor for the carcinoembryonic antigen using a glassy carbon electrode modified with electrodeposited Prussian Blue, a graphene and carbon nanotube assembly and an antibody immobilized on gold nanoparticles

Abstract: We described a sensitive, label-free electrochemical immunosensor for the detection of carcinoembryonic antigen. It is based on the use of a glassy carbon electrode (GCE) modified with a multi-layer films made from Prussian Blue (PB), graphene and carbon nanotubes by electrodeposition and assembling techniques. Gold nanoparticles were electrostatically absorbed on the surface of the film and used for the immobilization of antibody, while PB acts as signaling molecule. The stepwise assembly process was investigated by differential pulse voltammetry and scanning electron microscopy. It is found that the formation of antibody-antigen complexes partially inhibits the electron transfer of PB and decreased its peak current. Under the optimal conditions, the decrease of intensity of the peak current of PB is linearly related to the concentration of carcinoembryonic antigen in two ranges (0.2–1.0, and 1.0–40.0 ng·mL−1), with a detection limit of 60 pg·mL−1 (S/N = 3). The immunosensor was applied to analyze five clinical samples, and the results obtained were in agreement with clinical data. In addition, the immunosensor exhibited good precision, acceptable stability and reproducibility.

3D porous gear-like copper oxide and their high electrochemical performance as supercapacitors

Abstract: A facile and mild approach was used for the controlled synthesis of 3D porous gear-like CuO on a Cu substrate (PGC) based on annealing gear-like Cu(OH)2 (GC) at 200 °C in air. There are 3–10 edges that build up a gear-like structure and a huge number of holes formed on each edge. As an integrated nanostructure, the binder-free PGC can be used as a supercapacitors electrode (SC) directly. Due to its 3D porous structure and the highly conductive Cu substrate as a current collector, the integrated electrode exhibited excellent electrochemical properties. These were demonstrated by excellent specific capacitance as high as 348 F g−1 at a discharge current density of 1 A g−1, which corresponds to the energy density of 43.5 Wh kg−1. The electrochemical tests also showed that the as-synthesized PGC exhibited excellent cycling stability.

Stochastic functional differential equations with infinite delay driven by G-Brownian motion

Abstract: In this paper, we consider a class of stochastic functional differential equations with infinite delay at phase space BC ( − ∞ ,0]; Rd) driven by G-Brownian motion (SFDEGs) in the framework of sublinear expectation spaces . We prove the existence and uniqueness of the solutions to SFDEGs with the coefficients satisfying the linear growth condition and the classical Lipschitz condition. In addition, we establish the exponential estimate of the solution. Copyright © 2013 John Wiley & Sons, Ltd.

Aptamer‐Based Turn‐On Detection of Thrombin in Biological Fluids Based on Efficient Phosphorescence Energy Transfer from Mn‐Doped ZnS Quantum Dots to Carbon Nanodots

Abstract: This paper presents the first example of a sensitive, selective, and stable phosphorescent sensor based on phosphorescence energy transfer (PET) for thrombin that functions through thrombin-aptamer recognition events. In this work, an efficient PET donor-acceptor pair using Mn-doped ZnS quantum dots labeled with thrombin-binding aptamers (TBA QDs) as donors, and carbon nanodots (CNDs) as acceptors has been constructed. Due to the π-π stacking interaction between aptamer and CNDs, the energy donor and acceptor are taken into close proximity, leading to the phosphorescence quenching of donors, TBA QDs. A maximum phosphorescence quenching efficiency as high as 95.9% is acquired. With the introduction of thrombin to the "off state" of the TBA-QDs-CNDs system, the phosphorescence is "turned on" due to the formation of quadruplex-thrombin complexes, which releases the energy acceptor CNDs from the energy donors. Based on the restored phosphorescence, an aptamer-based turn-on thrombin biosensor has been demonstrated by using the phosphorescence as a signal transduction method. The sensor displays a linear range of 0-40 nM for thrombin, with a detection limit as low as 0.013 nM in pure buffers. The proposed aptasensor has also been used to monitor thrombin in complex biological fluids, including serum and plasma, with satisfactory recovery ranging from 96.8 to 104.3%. This is the first time that Mn-doped ZnS quantum dots and CNDs have been employed as a donor-acceptor pair to construct PET-based biosensors, which combines both the photophysical merits of phosphorescence QDs and the superquenching ability of CNDs and thus affords excellent analytical performance. We believe this proposed method could pave the way to a new design of biosensors using PET systems.