Fluorescent NaGdF4:Yb3+/Er3+/Zr4+ hexagonal nanoprisms are synthesized for the first time through a facile hydrothermal route with the assistance of ethylene diamine tetraacetic acid (EDTA). The possible formation process for the obtained NaGdF4 samples with various phases and morphologies is investigated and discussed systematically through time-dependent experiments with the help of X-ray power diffraction (XRD) analysis, transmission electron microscopy (TEM) and field emission-scanning electron microscopy (FE-SEM) observations in this article. It is found that the intrinsic structure of NaGdF4 and external factor reaction time all play a vital role in the shape evolution of the ultimate samples. Furthermore, the photoluminescence (PL) spectra of β-NaGdF4:Yb3+/Er3+/Zr4+ nanocomposites confirm the enhancement of fluorescence intensity. According to the fluorescent results, in the case of 6% Zr4+ doping, the green and red emissions reach the highest intensities because of the asymmetrical environment around Er3+ causing by the doping of Zr4+. In addition, atomic force microscope (AFM) and electrochemical workstation are used to characterize the photoelectric property. This novel NaGdF4 nanoparticle with both luminescent and photoelectric property promises to have comprehensive applications in many fields, such as photoelectric or photovoltaic sensors, when compared with conventional up-conversion (UC) materials.

In the present work, capillary electrophoresis (CE) was used for the first time for the simultaneous analysis of azodicarbonamide (ADA) and semicarbazide (SEM), and the capillary electrophoresis separation conditions, extraction agents, and derivatization conditions were investigated. In 20 mmol L−1 sodium tetraborate, 30 mmol L−1 β-cyclodextrin (β-CD), 17 % isopropanol (v/v), and 25 mmol L−1 sodium dodecyl sulfate (SDS) running buffer, ADA and SEM previously derivatized with 9-fluorenylmethyl chloroformate (FMOC) were separated in less than 25 min with good sensitivity. The linear ranges were 8.3 × 10−4∼6.6 × 10−2 mmol L−1 and 1.9 × 10−3∼3.4 × 10−2 mmol L−1, and detection limits (S/N = 10) were 0.5 and 0.15 mg kg−1 for ADA and SEM, respectively. The proposed method was successfully applied for the simultaneous analysis of ADA and SEM in five flour samples with satisfactory recovery data from 88.0 to 93.0 % for ADA and 98.0 to 106.0 % for SEM, indicating the valuable potential application of this method for food analysis.

This paper describes the preparation and characterization of a self-assembled monolayer of per(6-deoxy6-thio)-beta-cyclodextrin (beta-CD-SH) on a gold electrode surface and the study of its inclusion interactions with D- and L-phenylalanine (Phe). The beta-CD-SH was self-synthesized and characterized by Fouriertransform infrared (FTIR) and nuclear magnetic resonance (NMR). The modified electrode surface was carefully characterized by cyclic voltammetry (CV) using potassium ferricyanide (Fe(CN)(6)](3-/4-)) and ferrocenecarboxylic acid (Fc-COOH) as redox probes. Phe was labeled with gold nanoparticles (n-Au-Phe), and the chiral recognition between them and beta-CD-SH on the surface of an electrode was carried out. The methods of gold labeling and silver staining was strengthened by SEM. Finally, silver enhancement was monitored by differential pulse voltammetry (DPV). The DPV signal was greatly amplified by the silver atoms coated on the n-Au. The proposed method distinguished D- from L-Phe with an enantioselectivity coefficient of 3.64. The association constants of o-, m- and p-ABA with beta-CD-SH at pH 4.0 were calculated to be 2.84 x 10(4), 1.94 x 10(4), and 3.43 x 10(5) mol(-1) L, respectively. (C) 2015 Elsevier B.V. All rights reserved.

The colorimetric assay for neomycin presented here is based on melamine-modified gold nanoparticles (mel-AuNPs) and the finding that hydrogen bonding between melamine and neomycin results in the aggregation of mel-AuNPs. This results in a change in the color of the solution from wine red to blue and in a red-shift of the absorption maximum of the mel-AuNPs. The concentration of neomycin can be determined by spectrophotometry. The ratio of absorptions at 680 nm and 520 nm is linearly related to the logarithm of the concentration of neomycin in the 0.1 to 5.0 nM range and in the 5 to 100 nM range, with regression coefficients of 0.997 and 0.999, respectively. The detection limit (at an S/N ratio of 3) is 30 pM. This is far below the usual safety limit. The method was applied to the detection of trace levels of neomycin in milk samples and gave recoveries between 98 and 105 %.

近年来,随着抗草甘膦转基因作物的发展,草甘膦用量逐年增大,大量草甘膦制剂的介入严重影响了土壤、水质及生态环境,危害人类身体健康.如何快速准确检测环境样品中的残留有机磷类除草剂已成为人们关注的焦点问题之一.本文从衍生方法、检测器、离线及在线富集技术等几个方面出发,总结了目前毛细管电泳在检测有机磷类除草剂方面的研究工作,并展望了未来的主要发展方向.

A label-free electrochemical immunosensor for sensitive detection of α-fetoprotein (AFP) was developed based on graphene/SnO2/Au nanocomposite. The graphene/SnO2/Au nanocomposite modified glassy carbon electrode was used to immobilize α-fetoprotein antibody (anti-AFP) and to construct the immunosensor. Results demonstrated that the peak currents of [Ru(NH3)6]3+ decreased due to the interaction between antibody and antigen on the modified electrode. Thus, a label-free immunosensor for the detection of AFP was realized by monitoring the peak current change of [Ru(NH3)6]3+. The factors influencing the performance of the immunosensor were investigated in details. Under optimal conditions, the peak currents obtained by DPV decreased linearly with the increasing AFP concentrations in the range from 0.02 to 50ngmL−1 with a linear coefficient of 0.9959. This electrochemical immunoassay has a low detection limit of 0.01ngmL−1 (S/N=3) and was successfully applied to the determination of AFP in serum samples.

The presence of melamine induces a change in the state of 1,4-dithiothreitol modified gold nanoparticles, and the concentration of melamine could be quantified by the naked eye or using a UV-vis spectrometer.

A newly-developed method of complete separation and sensitive determination of o-, m-, and p-aminobenzoic acid isomers was achieved by combining open-tubular columns for capillary electrochromatography (OT-CEC) and online sample stacking. In this study, spherical gold nanoparticles were modified by a covalent attachment of mono-6-thio-β-cyclodextrin, and OT-CEC was formed by immobilizing cyclodextrin-modified gold nanoparticles (CD-AuNP) on prederivatized 3-mercaptopropyl-trimethoxysilane fused-silica capillaries. Based on the theory of moving chemical reaction boundary, effects of several important factors such as the pH and concentration of running buffer and the conditions of stacking analytes were optimized. The optimized separations were carried out in 58 mmol/L HAc buffer at pH 3.0 using a capillary coated with CD-AuNP, while the optimized concentration was carried out in 50 mmol/L disodium hydrogen phosphate (pH 9.5). The linear ranges for m-, p-, and o-aminobenzoic acid were from 5.0 × 10−4–0.1, 5.0 × 10−4–0.1 and 1.0 × 10−4–0.1 mmol/L, respectively. And the detection limits (S/N = 3) were as low as 8.22 × 10−5, 8.21 × 10−5, and 3.76 × 10−5 mmol/L for m-, p-, and o-aminobenzoic acid, respectively. The run-to-run, day-to-day, and column-to-column reproducibilities of migration time were satisfactory with relative standard deviation values of less than 4.5 % in all cases. This method was successfully used in determining procaine hydrochloride injection sample with recoveries in the range of 96.1–106.6 % and relative standard deviations less than 5.0 %.

A new method is presented for the visual detection of dicyandiamide (DCD). Gold nanoparticles (AuNPs) capped with gallic acid (GA) were synthesized in a single step at room temperature, using GA as both the reducing agent and stabilizer. In the presence of DCD, the hydrogen-bonding interaction between GA and DCD induces the aggregation of AuNPs, associated with a color change from red to gray that can be observed with bare eye. DCD could be quantified by photometry as the red shift of the maximal absorption band is linearly related to the logarithm of concentration of DCD in the 0.1 to 500 μM concentration range, with a regression coefficient of 0.9987 and a 80 nM detection limit (at an SNR of 3). The proposed method was successfully applied to the detection of DCD in spiked dairy samples.

We reported on the one-pot synthesis of a ternary hybrid material composed of graphene functionalized with 5,10,15,20-tetrakis (4-sulfonatophenyl) porphyrin, tin oxide, and gold nanoparticles. The composite was deposited on a glassy carbon electrode to give an electrode excellent electrocatalytic activity towards the oxidation of epinephrine (EP). The oxidation peaks for EP and uric acid (UA) occur at 190 and 322 mV, respectively, and thus are well separated. This allows for a simultaneous determination of EP and UA. Under optimal conditions, the linear response range in simultaneous determination of EP and UA is from 0.5 to 100 μM for EP, and from 2.0 to 100 μM for UA. The detection limits are at 50 nM for EP and at 500 nM for UA (at an S/N ratio of 3). The sensor was employed to quantify EP and UA in spiked urine samples with satisfactory results.

A novel electrochemical biosensor for highly sensitive and selective detection of cysteine based on in situ synthesis of gold nanoparticles (AuNPs)/reduced graphene oxide (RGO) nanocomposites is proposed. Graphene oxide (GO) was reduced by dopamine, and then in situ synthesis of AuNPs by the phenolic hydroxyl groups of dopamine on the RGO surface. The sulphydryl group of cysteine could bind not only with AuNPs through Au-S bond but also with polydopamine on the RGO surface through Michael addition reaction. The combining of cysteine with the AuNPs/RGO leads to the decrease in the peak currents of electrochemical probe [Ru(NH3)(6)](3+), which could be used for indirect electrochemical sensing of cysteine. The change of the peak currents value of [Ru(NH3)(6)](3+) was linear with the concentration of cysteine in the range from 1.0 x 10(-9) to 3.0 x 10(-8) M with a linear coefficiency of 0.991. The detection limit was 1.0 x 10(-10) M (S/N = 3). The proposed electrochemical biosensor is rapid, convenient and low-cost for effective sensing of cysteine. (C) 2013 Elsevier B.V. All rights reserved.

The differential pulse catalytic adsorptive stripping voltammetry behavior of titanium(IV)-cupferron system at bismuth coated glassy carbon electrode (BiFE) has been investigated. In the piperazine-N,N'-bis(2-ethanesulfonic acid) (PIPES)-KCl solution (pH 6.4), the deposition potential at -0.70 V for 120 s, a well-defined and sensitive stripping peak of Ti(IV)-cupferron complex at -0.97 V (vs. SCE) was observed. Under optimized conditions, the peak current was linear to the concentration of Ti(IV) in the range from 10 to 60 mu g L-1 with the detection limit of 0.5 mu g L-1. To further demonstrate its possible application, the method was successfully applied to detect trace Ti(IV) in hair and water samples with satisfactory results.

A novel poly(pyrocatechol-3,5-disodiumsulfonate)/multi-walled carbon nanotubes (PPD/MWCNT) composite film modified glassy carbon electrode (GCE) was fabricated and successfully used to simultaneously determine ascorbic acid (AA), dopamine (DA) and uric acid (UA). Owing to the synergistic effects of PPD and MWCNTs, the electrochemical responses of AA, DA and UA at PPD/MWCNTs/GCE were clearly superior to those at bare GCE. Additionally, the PPD/MWCNTs composite film could reduce the potential overlap of AA, DA and UA so as to favor simultaneous determination of the three substances. Under the optimum conditions, the linear calibration curves of AA, DA and UA were obtained by differential pulse voltammetry in the range of 10-1000, 1-100 and 4-1200 microM, and the detection limits were 5, 0.5 and 0.5 microM (S/N = 3) respectively. The results showed PPD/MWCNTs/GCE possessed good reproducibility and stability, and it could be applied to determine UA in human urine with satisfying recovery by standard addition method.

A novel electrochemical biosensor for sensitive and selective detection of mercury (II) ions (Hg2+) based on a DNA grafted graphene is proposed. Graphene oxide (GO) was reduced by dopamine, and then the single-strand probe DNA modified at the 5′-end with an alkylamino modifier (NH2-ssDNA) was grafted on the reduced graphene oxide (RGO) surface via Michael addition reaction. In the presence of Hg2+, the target DNA with four thymine–thymine (T–T) mismatches would hybridize with the probe DNA on the glassy carbon electrode (GCE) through T–Hg2+–T coordination chemistry. The hybridization of the two oligonucleotides leads to the increase in the peak currents of [Ru(NH3)6]3+, which could be used for electrochemical sensing of Hg2+. The difference in the value of the peak currents of [Ru(NH3)6]3+ before and after DNA hybridization was linear with the concentration of Hg2+ in the range from 8.0×10−9 to 1.0×10−7M with a linear coefficiency of 0.996. The detection limit was 5.0×10−9M (S/N=3). The proposed electrochemical biosensor is rapid, convenient and low-cost for effective sensing of Hg2+. Particularly, the proposed method was applied successfully to the determination of Hg2+ in real environmental samples.

A novel one-pot synthesis of graphene nanosheet/SnO2 nanoparticle hybrid nanocomposites (GN/SnO2) was realized by using graphene oxide nanosheets (GONs) functionalized with sodium dodecyl sulfonate and SnCl2 as the starting materials. The morphology and structure of the synthesized SDS-GN/SnO2 nanocomposites were characterized by Raman spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction analysis. It was found that SnO2 nanoparticles were homogeneously distributed on the graphene nanosheets. The electrochemical behavior of dopamine (DA) at the SDS-GN/SnO2 nanoparticle modified electrode was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed that the modified electrode exhibited excellent electrocatalytic activity towards the electrochemical oxidation of DA. The separation of the oxidation peak potentials for ascorbic acid (AA)-DA, uric acid (UA)-DA and UA-AA obtained by DPV is about 132 mV, 128 mV and 260 mV, respectively, which allows selective and sensitive detection of DA in the presence of AA and UA. The anodic peak currents were linear with the concentration of DA in the range from 1.0 × 10-7 to 1.0 × 10-5 M with a coefficient of 0.9980. The detection limit was 80 nM (S/N = 3). The proposed method could be applied for the determination of DA in real human urine samples.

A highly sensitive and selective method was presented for colorimetric determination of melamine using gold nanoparticles (AuNPs). AuNPs were synthesized using ellagic acid (EA) as reducer in distilled water at room temperature without adding nanoparticle seeds and stabilizing agent. Melamine could interact with EA through a strong hydrogen-bonding interaction leading to weakening of the EA reducing ability, thus the formation of AuNPs was interrupted and the color of the solution changed from red to pale yellow. The concentration of melamine could be quantified visually or using a UV-vis spectrometer in the wide range from 1.6 × 10−8 M to 1.6 × 10−4 M with a correlation coefficient of 0.9961. The detection limit (3σ) was as low as 1.6 × 10−9 M. This sensor was simple, inexpensive and highly sensitive and could be successfully utilized to detect melamine in pretreated liquid milk products with high recoveries from 93% to 106%. Besides, it exhibited excellent selectivity against other interferences.

Antibiotics residues in foods are very harmful to human beings. Determination of antibiotics residues relies largely on the availability of adequate analytical techniques. Currently, there is an urgent need for on site and real time detection of antibiotics in food. In this work, a novel one step synthesis of gold nanoparticles (AuNPs) was proposed using pyrocatechol violet (PCV) as a reducer agent. Highly sensitive and selective colorimetric detection of four antibiotics kanamycin mono sulfate (KA), neomycin sulfate (NE), streptomycin sulfate (ST) and bleomycin sulfate (BL) was realized during the formation of AuNPs. PCV has -OH groups and these antibiotics have -OH, -NH2, -NH- groups, so there may be some special hydrogen-bonding interactions between PCV and these antibiotics. Therefore, the presence of KA, NE, ST and BL would influence the synthesis of AuNPs, then the color and state of AuNPs would change, which could be observed with the naked eye or a UV-vis spectrophotometer. Results showed that A670 was linear with the logarithm of KA concentration in the range from 1.0×10(-8) to 5.0×10(-7)M and 5.0×10(-7) to 5.5×10(-5)M. The detection limit of KA was 1.0×10(-9)M (S/N=3). The coexisting substances including 1.0×10(-5)M phenylalanine, alanine, glycerol, glucose, Mg(2+), Ca(2+), Na(+), K(+), CO3(2-), SO4(2-), NO3(-), Cl(-) and Br(-) did not affect the determination of 1.0×10(-7)M antibiotics. In particular, the proposed method could be applied successfully to the detection of antibiotics in the pretreated liquid milk products.

Ionic Liquid(ILs),also called room-temperature ionic liquids(RTILs),are mainly compose of specific cations and ions.Due to their unique properties such as ultralow vapour pressure,low melting ponit,wide electrochemical window,high conductivity and thermal stability,ionic liquids have been successfully applied to many areas of chemistry including organic synthesis chemistry,analytical chemistry,electrochemistry etc..The latest research progress of ionic liquids in organic synthesis and analyical chemistry is disscussed.

A simple and sensitive method for the detection of arsenic(III) using a magnetic Fe3O4 nanoparticles and gold nanoparticles modified glassy carbon electrode (Au NPs/Fe3O4/GCE) was developed. The Fe3O4 nanoparticles were dropped onto a GCE and the gold nanoparticles were electrodeposited later. The resulting electrode surfaces were characterized with both field emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (EIS). Square wave anodic stripping voltammetry (SWASV) was performed for the determination of arsenic(III). The obtained results show that the sensitivity of arsenic(III) is significantly improved on Au NPs/Fe3O4/GCE in comparison with Au NPs/GCE. Under optimal conditions, the detection limit (S/N = 3) was 0.00097 mu g L-1. In addition, the modified electrode exhibited excellent reproducibility and high stability. The developed method was successfully applied to determine arsenic(III) in real water samples with satisfactory results.

Novel upconversion NaYF4:Yb3+,Er3+/TiO2 core-shell nanoparticles (NPs) are synthesized and used to prepare the photoelectrode (PE) of dye-sensitized solar cells (DSSCs). The morphology, structure, photoluminescence characterization of the NaYF4:Yb3+,Er3+/TiO2 core-shell NPs and the photoelectric performance, alternating current impedance spectroscopy of DSSCs are characterized using transmission electron microscopy, X-ray diffraction, upconversion luminescence (UCL) spectrofluorimetry and electrochemistry. Compared with the pure TiO2 PE or the NaYF4:Yb3+,Er3+ upconversion NPs and TiO2 simply mixed prepared PE as the volume ratio of the core-shell structure, the DSSCs with the upconversion core-shell PE show a greater photovoltaic efficiency. The energy conversion efficiency of the DSSCs with a NaYF4:Yb3+,Er3+/TiO2 PE is 23.1% higher than with a pure TiO2 PE and 99.1% higher than with a mixed PE using the same conditions. This enhancement is due to the UCL core extending the spectral response range of DSSCs to the infrared region and their particular shell structure, retaining its semiconductor character. This method represents a novel approach to increase the efficiencies of DSSCs. (C) 2012 Elsevier B.V. All rights reserved.