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The binding of dopamine (DA) with bovine serum albumin (BSA) was investigated for the first time by fluorescence and Fourier transform–infrared spectroscopy. The association constants, thermodynamic parameters, quenching rate constants at three different temperatures and the number of binding sites were also determined. The fluorescence results revealed that the fluorescence of BSA was quenched by DA through a static quenching procedure and a DA–BSA complex was formed. Synchronous fluorescence spectroscopy illustrated that DA interacted with both tyrosine residues and tryptophan residues of BSA. IR spectra revealed the structure changes of the BSA functional groups with the addition of DA. The thermodynamic study and IR spectra confirmed that hydrophobic and hydrogen bonds interactions were both the predominant intermolecular forces to stabilise the complex.

The electrochemical polymerization of glycine on carbon ionic liquid electrode (CILE) was described. The presence of ionic liquid on the surface of CILE facilitated the electropolymerization of glycine. The polyglycine modified CILE provided a valid and simple approach to selectively detect dopamine in the presence of AA in physiological environment. The proposed sensor not only decreased the voltammetric responses of AA but also dramatically enhanced the oxidation peak current of DA compared to bare CILE. Using square wave voltammetry, the modified CILE showed good electrochemical behavior to DA, a linear range of 1.0×10−7–3.0×10−4 M in the presence of 1 mM ascorbic acid (AA) and a detection limit of 5.0×10−9 M was estimated (S/N=3).

A simple, sensitive, and reliable method based on a multi-walled carbon nanotubes (MWNTs) modified carbon ionic liquid electrode (CILE) has been successfully developed for determination of dopamine (DA) in the presence of ascorbic acid (AA). The acid-treated MWNTs with carboxylic acid functional groups could promote the electron-transfer reaction of DA and inhibit the voltammetric response of AA. Due to the good performance of the ionic liquid, the electrochemical response of DA on the MWNTs/CILE was better than that of other MWNTs modified electrodes. Under the optimum conditions a linear calibration plot was obtained in the range 5.0 × 10 −8 to 2.0 × 10 −4 mol L −1 and the detection limit was 1.0 × 10 −8 mol L −1 .

A simple sensor based on bare carbon ionic liquid electrode was fabricated for simultaneous determination of dihydroxybenzene isomers in 0.1 mol L−1 phosphate buffer solution (pH 6.0). The oxidation peak potential of hydroquinone was about 0.136 V, catechol was about 0.240 V, and resorcinol 0.632 V by differential pulse voltammetric measurements, which indicated that the dihydroxybenzene isomers could be separated absolutely. The sensor showed wide linear behaviors in the range of 5.0 × 10−7–2.0 × 10−4 mol L−1 for hydroquinone and catechol, 3.5 × 10−6–1.535 × 10−4 mol L−1 for resorcinol, respectively. And the detection limits of the three dihydroxybenzene isomers were 5.0 × 10−8, 2.0 × 10−7, 5.0 × 10−7 mol L−1, respectively (S/N = 3). The proposed method could be applied to the determination of dihydroxybenzene isomers in artificial wastewater and the recovery was from 93.9% to 104.6%.

An electrode was developed for the determination of hydrogen peroxide (H 2 O 2 ). It contains a chitosan–copper complex onto which multi-wall carbon nanotubes in an ionic liquid were deposited. The modified electrode exhibited excellent electrocatalytic activity that was applied to the detection of H 2 O 2 . The pH value and the effect of electrical potential on the current response were optimized. The electrode displays good stability, an expanded linear response range, improved electrocatalytic activity towards H 2 O 2 , and enables detection of H 2 O 2 with a linear response from 0.02 to 13 mM of H 2 O 2 , with a correlation coefficient of 0.997 and a response time of S / N = 3).

In this paper, we described a novel sensor based on tiron-doped polypyrrole and carbon nanotubes (CNTs) fabricated on low resistance monolayer-modified glassy carbon electrode. First, the dodecylamine monolayer was chemically modified. Second, CNTs were controllably adsorbed onto dodecylamine. Then, tiron doped polypyrrole was electro-deposited on the CNTs film. The layer-by-layer modified electrode was sensitive to dopamine, while it made no response to even high concentration of ascorbic acid. Parameters influencing the dopamine response were optimized. High performance of the sensor was obtained, such as wide concentration range, low detection limit (3 nM), low background current, high stability, and reproducibility.

Deoxyribonucleic acid (DNA) was electrochemically deposited on a carbon ionic liquid electrode to give a biosensor with excellent redox activity towards paraquat as shown by cyclic voltammetry and differential pulse voltammetry. Experimental conditions were optimized with respect to sensing paraquat by varying the electrochemical parameters, solution pH, and accumulation time of DNA. Under the optimized conditions, a linear relation exists between the reduction peak current and the concentration of paraquat in the range from 5 × 10−8 mol L−1 to 7 × 10−5 mol L−1, with a detection limit of 3.6 × 10−9 mol L−1. The utility of the method is illustrated by successful analysis of paraquat in spiked real water samples.

A new composite film comprising cationic gemini surfactant butane-α,ω-bis(dimethyl dodeculammonium bromide) (BDDA, C12-C4-C12) and poly (allylamine) hydrochloride(PAH) have been prepared. The composite film showed good biocompatibility and could promote the direct electron transfer between hemoglobin (Hb) and glassy carbon (GC) electrode. The immobilized Hb exhibited a pair of well-defined, quasi-reversible, and stable redox peaks with a formal potential of −0.158 V (vs. SCE) in 0.10 M pH 7 phosphate buffer solutions, and showed high affinity to hydrogen peroxide. The cathodic peak current of the electrode was linear with increasing concentration of H2O2 in the range of 5.14 to 200 μM.

A simple, sensitive, and reliable method based on a molecular sieve/ionic liquids composite electrode has been successfully developed for selective determination of dopamine (DA). The electrochemical behavior of dopamine (DA) at the modified electrode was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). The influence of experimental parameters including pH of solution, amount of modifier, accumulation potential and time on the response of DA was investigated. At the optimum conditions, the peak current of DA was linear with the concentration of DA in the wide range of 5.0 × 10 −8 mol L −1 to 8 × 10 −4 mol L −1 , with the correlation coefficient of 0.9982. The detection limit was 1.0 × 10 −8 mol L −1 ( S / N = 3) in the presence of 0.2 mM ascorbic acid (AA). The interference studies showed that the modified electrode had excellent selectivity. What's more, the modified electrode also exhibited good reproducibility and stability for determination of DA, and could be applied to determine human serum samples.

Heavy metal bioremediation by a multi-metal resistant endophytic bacteria L14 (EB L14) isolated from the cadmium hyperaccumulator Solanum nigrum L. was characterized for its potential application in metal treatment. 16S rDNA analysis revealed that this endophyte belonged to Bacillus sp. The hormesis of EB L14 were observed in presence of divalent heavy metals (Cu (II), Cd (II) and Pb (II)) at a relatively lower concentration (10 mg/L). Such hormesis was the side effect of abnormal activities increases of ATPase which was planned to provide energy to help EB L14 reduce the toxicity of heavy metals by exporting the cations. Within 24 h incubation, EB L14 could specifically uptake 75.78%, 80.48%, 21.25% of Cd (II), Pb (II) and Cu (II) under the initial concentration of 10 mg/L. However, nearly no chromium uptake was observed. The mechanism study indicated that its remediation efficiencies may be greatly promoted through inhibiting the activities of ATPase. The excellent adaptation abilities and promising remediation efficiencies strongly indicated the superiority of this endophyte in heavy metal bioremediation at low concentrations, which could be useful for developing efficient metal removal system.

We describe a novel sensor for dopamine. It is based on the use of polypyrrole doped with a carbon nanotube-DNA hybrid. The composite material can be used as a matrix for immobilizing doping anions such as tiron which assist in electrostatic repulsion of anions such as ascorbate and others. The sensor was used for highly selective and sensitive determination of dopamine. Parameters affecting the response were optimized. The sensor displays a wide dynamic range, a detection limit as low as 0.5 pM, high stability, and good reproducibility.

In this paper, DNA functionalized single-wall carbon nanotubes/Cu(2+) (DNA-CNTs/Cu(2+)) complex was one-step electrodeposited onto the glassy carbon electrode (GCE), which fabricated a DNA-CNTs/Cu(2+)/GCE sensor to detect nitrite. Cyclic voltammogram of DNA-CNTs/Cu(2+)/GCE showed a pair of well-defined redox peaks for Cu(2+)/Cu(+). Compared with DNA-CNTs/GCE and DNA-Cu(2+)/GCE, the prepared DNA-CNTs/Cu(2+)/GCE exhibited more excellent electrochemical properties. Thus, the prepared DNA-CNTs/Cu(2+)/GCE was proposed as nitrite sensor. The effects of Cu(2+), CNTs and DNA concentration in the mixture together with electrodeposition time and determination conditions such as applied potential, pH value on the current response of DNA-CNTs/Cu(2+)/GCE toward nitrite were optimized to obtain the maximal sensitivity. In addition, electrochemical experiments revealed that the modified electrode showed high electrocatalytic activity to the reduction of nitrite ion (NO(2)(-)). The linear range for the detection of NO(2)(-) was 3x10(-8) to 2.6x10(-3)M, and the response was very fast (less than 3s). A low detection limit of 3x10(-8)M (S/N=3) for NO(2)(-) was achieved.

A rapid, simple and reliable analytical procedure has been developed for the determination of polyphenols, including chlorogenic acid, rutin and scopoletin, in tobacco samples. After extraction, the polyphenols were analyzed by micellar liquid chromatography coupled with UV detection at 340 nm without sample preparation step. The compositions of the micellar mobile phase for the separation of these polyphenols were selected adequately by a chemometric method. The optimal resolution and satisfactory peak shapes were achieved with 0.022 mol L−1 sodium dodecyl sulfate and 0.45% (volume fraction) 1-propanol solution at pH 5.0 using Eclipse XDB-C18 (250 mm × 3.0 mm, 5 μm) column. The limits of detection for chlorogenic acid, rutin and scopoletin were 0.15, 0.29 and 0.22 μg mL−1, respectively. This validated method was successfully applied to qualitatively and quantitatively analyze the polyphenols in tobacco in less than 10 min.

In this paper, Cu nanoparticles/carbon nanotube/chitosan (Cu nano /CNTs/CS) film was one-step electrodeposited onto the glassy carbon electrode (GCE), which fabricated a Cu nano /CNTs/CS/GCE sensor to detect nitrite. One-step electrodeposition of CNTs and Cu nano with the chitosan (CS) hydrogel was achieved, and the whole procedure takes only several minutes. Scanning electron microscopy (SEM) image demonstrated that the Cu nanoparticles coated on CNTs/CS were uniform, with an average size of 30 nm. The effects of Cu 2+ , CNTs and CS concentration in the mixture together with electrodeposition time and determination conditions such as applied potential, pH value on the current response of Cu nano /CNTs/CS/GCE toward nitrite were optimized to obtain the maximal sensitivity. In addition, electrochemical experiments revealed that the modified electrode showed high electrocatalytic activity to the reduction of nitrite ion (NO 2 − ). The linear range for the detection of NO 2 − was 1.0 × 10 −7 M to 2.5 × 10 −3 M with a high sensitivity of −48.92 μA mM −1 , and the response was very fast (less than 2 s). A low detection limit of 2.4 × 10 −8 M (S/N = 3) for NO 2 − was achieved.

Simultaneous determination of dihydroxybenzene isomers was investigated at a multi-wall carbon nanotubes (MWCNTs)/β-cyclodextrin composite modified carbon ionic liquid electrode in phosphate buffer solution (pH 7.0, 1/15 mol/L) in the presence of cationic surfactant cetylpyridinium bromide (CPB). With the great enhancement of surfactant CPB, the voltammetric responses of dihydroxybenzene isomers were more sensitive and selective. The oxidation peak potential of hydroquinone was about 0.024 V, catechol was about 0.140 V and resorcinol 0.520 V in differential pulse voltammetric (DPV) measurements, which indicated that the dihydroxybenzene isomers could be separated entirely. The electrode showed wide linear behaviors in the range of 1.2×10−7–2.2×10−3, 7.0×10−7–1.0×10−3, 2.6×10−6–9.0×10−4 mol/L for hydroquinone, catechol and resorcinol, respectively. And the detection limits of the three dihydroxybenzene isomers were 4.0×10−8, 8.0×10−8, 9.0×10−7 mol/L, respectively. The proposed method could be applied to the determination of dihydroxybenzene isomers in artificial wastewater, and the recovery was from 97.4% to 104.2%.

In this paper, Cu nanoparticles were electrodeposited onto the film of Nafion (Nf)-solubilized multi-walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE), which fabricated a sensitive nano-copper coated multi-walled carbon nanotubes modified glassy carbon electrode (Cunano/CNTs–Nf/GCE) to detect nitrite. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) demonstrated that the Cu nanoparticles coated on MWCNTs were uniform, with an average size of 30 nm. The effects of electrodeposition circles, CNTs–Nf solution concentration and determination conditions such as pH value and applied potential on the current response of Cunano/CNTs–Nf/GCE toward nitrite were optimized to obtain the maximal sensitivity. Moreover, electrochemical experiments revealed that the modified electrode sensor showed high electrocatalytic activity for the reduction of nitrite ion ( NO 2 - ). The linear range of the determination of NO 2 - was from 1.0 × 10−6 M to 6.0 × 10−4 M and the response was fast (less than 5 s). A low detection limit of 8.0 × 10−8 M (S/N = 3) for NO 2 - was achieved.

A carbon ionic liquid electrode (CILE) was modified with a polythionine (PTh)/multi-walled carbon nanotubes (MWCNTs) composite and used for the detection of reduced nicotinamide adenine dinucleotide (NADH). The electrode was prepared by electrochemical polymerization of thionine on the MWCNTs in neutral medium. Cyclic voltammetry indicated that the electrode was capable of mediating the oxidation of NADH at an overpotential as low as 0.03 V. Amperometric experiments showed that a sensitive and stable response towards NADH is obtained within 5 s. The linear range for the determination of NADH is from 0.8 μmol L−1 to 422 μmol L−1, with a detection limit of 0.26 μmol L−1 (S/N = 3). The wide linear range, lower detection limit and faster response towards NADH suggests that the new method potentially is useful for developing NAD+-dependent enzyme-based biosensors.

Glassy carbon electrode modified with DNA-functionalized single-walled carbon nanotube hybrids by layer-by-layer was developed for the detection of 2,4,6-trinitrotoluene. The characteristic of the DNA-functionalized single-walled carbon nanotube hybrids was examined by atomic force microscope. Compares with single-walled carbon nanotubes-alone modified electrode, DNA-functionalized single-walled carbon nanotube hybrids-modified one exhibited the more superior ability of detecting 2,4,6-trinitrotoluene, including the higher sensitivity and the lower overpotentials, due to plenty of π-electrons and hydrogen bond binding sites were provided. This modified electrode showed a fast response towards 2,4,6-trinitrotoluene and the detection could be finished within 15 s. A limit of detection of 0.5 μg L−1 was obtained by this modified electrode with a linear range at lest up to 800 μg L−1. Stability test showed an average relative standard deviation of 3.5% for 40 consecutive runs with a same modified electrode and the reproducibility of the responses of 2,4,6-trinitrotoluene was within 5.1% from one electrode preparation to another (n = 10). And also, the applicability of this modified electrode was demonstrated for the analysis of 2,4,6-trinitrotoluene in spiked groundwater.

The interaction between urea and guanidinium chloride (GuHCl) on lysozyme refolding was investigated in this work. Live micrococcus lysodeikticus was successfully introduced into a refolding system. Lysozyme can be refolded from the GuHCl-denatured, DTT-reduced state in a good yield of 96.54% at final protein concentration as high as 0.2 mg·mL−1. A model could be employed to elucidate refolding kinetics behavior and the kinetics constants were studied. In the coexistence of GuHCl and urea, the aggregation rate decreased by increasing urea concentration to a proper value. The cooperation of GuHCl and urea not only suppressed the competition of the aggregation reaction but also increased the yield of refolding efficiently.

A novel carbon nanotubes (CNTs) film-modified electrode was developed by controllable adsorption of the CNTs onto the monolayer of dodecylamine chemically modified glassy carbon electrode (GCE). The electrochemical characteristics of the dodecylamine monolayer-modified GCE were examined by electrochemical impedance spectroscopy and cyclic voltammetry. Compared with the self-assembled monolayer (SAM) of dodecanethiol-modified gold electrode, the prepared dodecylamine monolayer-modified GCE presented a smaller resistance and a higher capacitance. In addition, after single wall carbon nanotubes (SWCNTs) were controllably adsorbed onto the both modified electrodes by hydrophobic interaction, the dodecylamine monolayer-modified GCE showed a larger capacitance than that of bare GCE for its small resistance and good conductivity of CNTs, but the SAM of dodecanethiol-modified gold electrode was failed to achieve the same result. Furthermore, the proposed SWCNTs dodecylamine monolayer-modified GCE was successfully used to determine dopamine in the presence of ascorbic acid after it adsorbed the ssDNA.

The kinetics of chromium(VI) reduction by Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli) was studied under both pure and mixed cultures. Initially, the study of kinetics was performed in pure culture. It was observed that the growth of the two bacteria was both inhibited in the presence of chromium(VI). The maximum specific growth rate (μ m ) of P. aeruginosa decreased from 2.3942 h−1 (without Cr(VI)) to 1.8551 h−1 (with Cr(VI)). Under the mixed culture, the growth of E. coli was inhibited by P. aeruginosa. The maximum specific growth rate (μ m ) of E. coli decreased form 0.871 h−1 (in pure culture) to 0.153 h−1 (in mixed culture). When the concentration of each bacterium was 4.5 × 108 cells ml−1, the half-velocity reduction rate constant (K C) and the maximum specific reduction rate constant (v max) of chromium(VI) were 80.05 mg chromium(VI) l−1 and 3.674 mg chromium(VI) cells−1 h−1, respectively. The results showed that the simulation appeared in good agreement with the experimental data, supporting the series of mathematical models represented the bacteria growth and chromium(VI) reduction in both pure and mixed cultures usefully.

A novel method for the simultaneous determination of cadmium(II) and copper(II) during the adsorption process onto Pseudomonas aeruginosa was developed. The concentration of the free metal ions was successfully detected by square wave anodic stripping voltammetry (SWASV) on the mercaptoethane sulfonate (MES) modified gold electrode, while the P. aeruginosa was efficiently avoided approaching to the electrode surface by the MES monolayer. And the anodic stripping peaks of Cd(2+) and Cu(2+) appear at -0.13 and 0.34V respectively, at the concentration range of 5-50 microM, the peak currents of SWASV present linear relationships with the concentrations of cadmium and copper respectively. As the determination of Cd(2+) and Cu(2+) was in real time and without pretreatment, the kinetic characteristics of the adsorption process were studied and all the corresponding regression parameters were obtained by fitting the electrochemical experimental data to the pseudo-second-order kinetic model. Moreover, Langmuir and Freundlich models well described the biosorption isotherms. And there were some differences in the amount of metal ion adsorbed at equilibrium (q(e)) and other kinetics parameters when the two ions coexisted were compared with the unaccompanied condition, which were also discussed in this paper. The proposed electrode system provides excellent platform for the simultaneous determination of trace metals in complex biosorption process.

In this paper, a hydroxyapatite-modified carbon ionic liquid electrode (HAP-CILE) for the simultaneous determination of lead and cadmium was developed. The hydroxyapatite which combines with ionic liquid plays an important role in remarkable responses of metals. Trace analysis of the selected heavy metals was performed by square-wave anodic stripping voltammetry (SWASV). The oxidation of two metals yielded well-defined, separated square-wave peak currents. The peak currents at about −0.34 V for Pb 2+ and −0.88 V for Cd 2+ were measured. The affecting factors containing supporting electrolyte, pH of solution, accumulation time, deposition potential, amount of hydroxyapatite and possible interferences were investigated. The sensor exhibited linear behavior in the range of 1 × 10 −9 mol L −1 to 1 × 10 −7 mol L −1 for lead and cadmium (correlation coefficients: 0.995 and 0.997, respectively) with detection limits of 2 × 10 −10 mol L −1 for lead and 5 × 10 −10 mol L −1 for cadmium. The results indicate that the sensor is sensitive and effective for the simultaneous determination of lead and cadmium.

A sensitive method for the determination of estradiol is presented that is based on an electrode modified with multi-walled carbon nanotubes (MWNTs) along with an ionic liquid. The resulting electrode showed more sensitive voltammetric response to estradiol than other electrodes modified with MWNTs. The peak current for estradiol is linearly related to concentration over two decades, and the limit of detection is 5 nM. The method was applied to the determination of estradiol in rabbit blood serum and in environmental waters. The recoveries were 95.3-104.0% and 97.0-104.7%, respectively.

The electrocatalytic reduction of hydrogen peroxide (H2O2) was investigated using an electrode that was obtained by electropolymerization of Prussian Blue (PB) on a carbon ionic liquid electrode (CILE). The electrochemical reduction of H2O2 in buffer of pH 7.4 was performed using cyclic voltammetry and the amperometric I–t curve technique. A PB-modified CILE was applied to detect H2O2 at −0.10 V (versus the Ag/AgCl electrode). The linear dynamic range is from 0.05 to 6.0 mM, the detection limit is 1.0 µM (S/N = 3). The electrode displays good stability, a response time of

A new method for monitoring Pseudomonas aeruginosa growth with dimethoate (DMA) as sole carbon using the series piezoelectric quartz crystal (SPQC) and high-performance liquid chromatography (HPLC) was described. Compared with the general methods, SPQC gives real-time, multidimensional information. The determination limit of HPLC was 1.08 ng. A combined novel response model for Pseudomonas aeruginosa degrading DMA was derived. By fitting DMA reducing data, the value of the reduction rate constant (k) was obtained and in line with the actual trend. The proposed kinetic model was successfully applied to Pseudomonas aeruginosa degrading DMA.

Pseudomonas aeruginosa immobilized multiwalled carbon nanotubes were used as a novel kind of solid-phase extraction adsorbents of heavy metals, and the concentration of copper ions in the aqueous solution was obtained with the use of linear sweep anodic stripping voltammetry (LSASV). The adsorption of copper ions was rapid, and equilibrium was attained within 30 min. The combination technique provides fast, real-time information for adsorption process. Based on the electrochemical results, the kinetics and equilibrium were systematically examined. The pseudo-second-order kinetic model was used to correlate the kinetic experimental data, and the kinetic parameters were evaluated. The Langmuir and Freundlich models were applied to describe the adsorption isotherms.

A new amperometric glucose biosensor was constructed, based on the immobilization of glucose oxidase (GOx) with cross-linking in the matrix of chitosan on a glassy carbon electrode, which was modified by layer-by-layer assembled carbon nanotube (CNT)/chitosan (CHIT)/gold nanoparticles (GNp) multilayer films. With the increasing of CNT/CHIT/GNp layers, the response current to H2O2 was changed regularly and the response current reached a maximum value when the number of CNT/CHIT/GNp layers was 8. The assembling process of multilayer films was simple to operate. With GOx as an enzyme model, a new glucose biosensor was fabricated. The excellent electocatalytic activity and special structure of the enzyme electrode resulted in good characteristics. The linear range was 6 × 10− 6 ∼ 5 × 10− 3 M, with a detection limit of 3 × 10− 6 M estimated at a signal-to-noise ratio of 3, fast response time (less than 6 s). Moreover, it exhibited good reproducibility and stability.

Taking advantages of the larger specific surface area of single-walled carbon nanotubes and the lower contact resistance of –NH–C than that of multiple-walled carbon nanotubes and that of –S–Au, respectively, a ethylenediamine monolayer modified glassy carbon electrode (GCE) grafted by non-covalent and covalent sulphydryl groups jointly modified single-walled carbon nanotubes for arsenic(III) detection was developed. The resistance of ethylenediamine monolayer modified GCE was examined by electrochemical impedance spectroscopy. The characters of the non-covalent sulphydryl groups and the organized non-covalently modified single-walled carbon nanotubes were examined by detecting arsenic(III) and atomic force microscopy, respectively. After end-capped the remaining carboxylic groups of single-walled carbon nanotubes by covalent sulphydryl groups, the last electrode was applied to detect arsenic(III) and a limit of detection (LOD) ( S/N = 3) of 0.008 μg L −1 was obtained. And also, common contaminants at levels presenting in natural water did not interfere with the assay.

The present work describes the dectection of cytochrome c (cyt c) at biocompatible aurum (Au) nanoparticle-structured supported bilayer lipid membrane (sBLM) modified with anionic sites. Au nanoparticles were directly deposited through sBLM modified with lauric acid (LA) to build a hybrid device of nanoscale electrode array via potential cycling in 10 mM HAuCl4 solution containing 0.1 M KCl. The properties of Au nanoparticle-doped sBLM composite were then characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Results indicated that Au nanoparticles grew in voids of the sBLM with size around 20 - 30 nm. With SWV, after optimization, the results of the experiments indicate that the currents of cyt c were linear functions of its concentrations over the range from 1.0 x 10(-7) to 3.2 x 10(-6) M and the limit of detection (LOD, S/N = 3) was 5 x 10(-8) M. The influences of several common base pairs, amino acids and metal ions on determination of cyt c via this Au nanoparticle-doped sBLM composite were relatively low in experiments, suggesting the excellent biocompatibility of this detection method.

In this paper, DNA–Cu2+ complex was electrodeposited onto the surface of glassy carbon (GC) electrode, which fabricated a DNA–Cu2+/GC electrode sensor to detect H2O2 with nonenzyme. Cyclic voltammogram of DNA–Cu2+/GC electrode showed a pair of well-defined redox peaks for Cu2+/Cu+. Moreover, the electrodeposited DNA–Cu2+ complex exhibited excellent electrocatalytic behavior and good stability for the detection of H2O2. The effects of Cu2+ concentration, electrodeposition time and determination conditions such as pH value, applied potential on the current response of the DNA–Cu2+/GC electrode toward H2O2 were optimized to obtain the maximal sensitivity. The linear range for the detection of H2O2 is 8.0 × 10−7 M to 4.5 × 10−3 M with a high sensitivity of −40.25 μA mM−1, a low detection limit of 2.5 × 10−7 M and a fast response time of within 4 s. In addition, the sensor has good reproducibility and long-term stability and is interference free.

Based on layer-by-layer assembled DNA functionalized single-walled carbon nanotube hybrids, a DNA biosensor for the detection of arsenic(III) in a nearly physiological pH environment was developed. The redox process between arsenic(III) and arsenic(0) on the biosensor was proved. The growth of those hybrids on glassy carbon electrode was monitored by detecting arsenic(III). The arsenic(III) current on the biosensor was similar over a broad pH range (3.0–8.0) and the limit of detection (S/N = 3) was 0.05 μg L−1 at pH 7.0. The biosensor can be reused up to 16 times. Keywords: DNA functionalized single-walled carbon nanotube hybrids, DNA biosensor, In a nearly physiological pH environment, Redox process, The detection of arsenic(III)

A sensor for methanol was fabricated by incorporating the antibiotic cefixime (CEF) along with Ni(II) ion into a chitosan membrane matrix. Sensing is based on the electrocatalytic effect that the complex membrane exerts on the electro-oxidation of methanol. The resulting CEF-Ni(II)/chitosan glassy carbon (GC) electrode had a good electrocatalytic activity to the electro-oxidation of methanol in alkaline medium. The modified electrode had an immense electrocatalytic activity on the second process of methanol oxidation (methanol oxidation intermediate(s) to the final product). The modified electrode had a wide linear range from 20 μM to 12 mM for the determination of methanol in alkaline medium, and a detection limit of 5.24 μM based on a signal-to-noise ratio of 3. In addition, the sensor exhibited good stability.

A modified electrode has been fabricated with nano-silver/multi-walled carbon nanotube composites and characterized with scanning electron microscopy, X-ray powder diffraction and cyclic voltammetry. The electrochemical characteristics of the modified electrode have been studied. It has been found that the modified electrode can be used for the direct electroanalysis of hydrogen peroxide. A wave appeared at −0.64 V (vs. SCE) on the modified electrode due to the reduction of hydrogen peroxide. There was a linear relationship between hydrogen peroxide concentration and the cathodic differential pulse voltammetric current in the range 0.35–15 mM with a detection limit of 0.2 mM (S/N = 3). A medical hydrogen peroxide disinfection liquid was analyzed and recoveries were obtained between 97.5 and 103.8%.

An electrochemical sensor for hydroquinone (HQ) using β‐cyclodextrin/poly(N‐acetylaniline)/carbon nanotube composite (β‐CD/PAA/MWNTs) modified glassy carbon electrode has been successfully developed. Based on the synergistic effect of MWNTs and conducting PAA polymer and the accumulation effect of β‐CD, the analytical response of the β‐CD/PAA/MWNTs film to the electrochemical behavior of HQ was better than that of a β‐CD/PAA film, a PAA/MWNTs film, a PAA film, or a bare glassy carbon (GC) electrode. Under the conditions chosen, the anodic currents increased linearly with HQ concentration from 1×10−6 to 5×10−3 mol l−1 and the detection limit was 8×10−7 mol l−1. This electrochemical sensor showed excellent reproducibility, stability and recovery for the determination of HQ.

A high-performance amperometric glucose biosensor was developed, based on immobilization of glucose oxidase (GOx) on a copper (Cu) nanoparticles/chitosan (CHIT)/carbon nanotube (CNT)-modified glassy carbon (GC) electrode. The Cu and CNT had a synergistic electrocatalytic effect toward the reduction of hydrogen peroxide in the matrix of biopolymer CHIT. The Cu/CHIT/CNT modified GC electrode could amplify the reduction current of hydrogen peroxide greatly. Besides, the Cu/CHIT/CNT modified GC electrode reduces hydrogen peroxide at a much lower applied potential and inhibit the responses of interferents. With GOx as an enzyme model, a new glucose biosensor was fabricated. The sensitivity of the sensor is due not only to the large microscopic area but also to the high efficiency of transformation of H2O2 generated by enzymatic reaction to current signal. The biosensor exhibited excellent sensitivity (the detection limit is down to 0.02 mM), fast response time (less than 4 sec), wide linear range (from 0.05 to 12 mM), and perfect selectivity.

A novel Prussian Blue nanoparticles/carbon nanotubes/poly(1,2-diaminobenzene) based glucose biosensor was fabricated by a simple and fast method. Firstly, the Prussian Blue (PB) nanoparticles were direct electrodeposited onto the surface of a glassy carbon electrode modified with multiwall carbon nanotubes (MWNTs) in a short time. Then an ultrathin conducting poly(1,2-diaminobenzene) film was electrodeposited onto the surface of PB/MWNTs nanocomposite to immobilize the glucose oxidase via glutaraldehyde cross-linking. The experiments results showed that the stability of the PB nanoparticles was greatly improved by the MWNTs and the PB/MWNTs nanocomposite exhibited an excellent synergistic electrocatalytic effect toward reduction of hydrogen peroxide. The biosensor showed excellent performances toward determination of glucose. The linear range of the glucose biosensor is from 10 µM to 2.5 mM, with a detection limit of about 5 µM. The response is within less than 5 sec.

A novel method for the determination of Pb2+ with bismuth film electrodes (BFEs) based on magneto-voltammetry was investigated. In the presence of a 0.6 T external magnetic field, square wave voltammetry of Pb2+ was performed with BFEs. A high concentration of Fe3+ was added to the analytes to generate a large cathodic current during the preconcentration step. A Lorentz force from the flux of net current through the magnetic field resulted in convection. Then, more Pb2+ deposited onto the electrode and larger stripping peak currents were observed. BFEs that were prepared by simultaneously depositing the bismuth and Pb2+ on an electrode offered a mercury-free environment for this determination. This method exhibits a high sensitivity of 4.61 µA µM−1 for Pb2+ over the 1 × 10−8 to 1 × 10−6 M range. A detection limit as low as 8.5 × 10−10 M was obtained with only 1-min preconcentration. The method was successfully applied to determine Pb2+ in real water samples.

A novel biosensor was fabricated by using a DNA-Ni(II)/MWNTs/Chitosan complex membrane, and the synergistic electrocatalytic effect of the complex membrane for the electro-oxidation of methanol was observed. The membrane composed of DNA, MWNTs and chitosan functioned as a support matrix for the immobilization of the electrocatalytic nickel cation. The good electrocatalytic activity of the resulting DNA-Ni(II)/MWNTs/chitosan/GC electrode was demonstrated by electro-oxidation of methanol in alkaline medium. A linear range from 0.2 to 5.0 mM for the detection of methanol in alkaline medium was observed with a rapid response (within 3 s) and a detection limit of 10 µM based on a signal-to-noise ratio of 3. In addition, the sensor exhibited good stability.

This paper provided information on the use of linear sweep anodic stripping voltammetry for evaluating the process of copper biosorption onto Pseudomonas aeruginosa. This technique was suited to determine the concentration of free copper ion on site on the mercaptoethane sulfonate modified gold electrode surface without any pretreatment. It was in favor of the study of kinetic process as the fast changing kinetic data characteristic just after the beginning of biosorption could be accurately depicted. Based on the electrochemical results, the kinetics and equilibrium of biosorption were systematically examined. The pseudo-second-order kinetic model was used to correlate the kinetic experimental data and the kinetic parameters were evaluated. The Langmuir and Freundlich models were applied to describe the biosorption equilibrium. It was found that the Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. Maximum adsorption capacity of copper ion onto Pseudomonas aeruginosa was 0.9355 μmol mg−1 (about 59.4417 mg g−1).

Novel nano-silver coated multi-walled carbon nanotube composites were prepared and used to fabricate a modified electrode. The application of the nano-silver coated multi-walled carbon nanotube composites modified electrode for determination of trace thiocyanate is demonstrated for the first time. The influence of substrate, pH and interference of coexisting substances was investigated for response properties of the electrode. There was a linear relationship at the range 2.5 × 10 −9 to 5 × 10 −8 mol L −1 and 5 × 10 −8 to 1 × 10 −6 mol L −1 of thiocyanate with the decrement of anodic DPV peak currents. The limit of detection was 1 × 10 −9 mol L −1 (S/N = 3). The constructed electrode showed excellent reproducibility and stability. Actual urine and saliva samples of smoker and non-smoker were analyzed and satisfactory results were obtained. This method provides a new way to construct any electrode for biological and environmental analysis.

A novel method was proposed for fabrication of a carbon nanotubes/poly(1,2-diaminobenzene) nanoporous composite based electrode. The poly(1,2-diaminobenzene) was deposited onto the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotubes (MWNTs) via multipulse chronoamperometric electropolymerization (MCE) process. Compared with the composite prepared by conventional electropolymerization (CE), the electronic and ionic transport capacity of the MCE-based composite were significantly improved due to its unique nanoporous structure. The surface of the composite-modified GCE was characterized with scanning electron microscopy (SEM) and cyclic voltammetry (CV). The nanoporous MCE-based electrode was applied to determination of NADH at a much low potential of 70 mV, and a linear range from 2.0 μM to 4.0 mM was observed with fast response (within 5 s) and a lower detection limit of 0.5 μM (based on S/N = 3). In comparison, a narrow linear range from 5.0 μM to 2.0 mM, slower response (up to 15 s) and a higher detection limit of 3.0 μM (based on S/N = 3) was obtained with the electrode prepared by CE. The wider linear range, lower detection limit and fast response of the MCE-based electrode implies that the new method proposed can provide more excellent platforms for sensitive electrochemical sensing and biosensing.

A new nanocomposite material for construction of glucose biosensor was prepared. The biosensor was formed by entrapping glucose oxidase(Gox) into chitosan/nanoporous ZrO2/multiwalled carbon nanotubes nanocomposite film. In this biosensing thin film, the multiwalled carbon nanotubes can effectively catalyze hydrogen peroxide and nanoporous ZrO2 can enhance the stability of the immobilized enzyme. The resulting biosensor provides a very effective matrix for the immobilization of glucose oxidase and exhibits a wide linear response range from 8 μmol/L to 3 mmol/L with a correlation coefficient of 0.994 for the detection of glucose. And the response time and detection limit of the biosensor are determined to be 6 s and 3.5 μmol/L, respectively. Another attractive characteristic is that the biosensor is inexpensive, stable and reliable.

A novel modified electrode was fabricated by electropolymerization of acid chrome blue K at a multi-walled carbon nanotubes modified glassy carbon electrode. The electrode developed was used for simultaneous determination of the isomers of dihydroxybenzene in environmental samples using first order linear sweep derivative voltammetry with background subtraction. A linear relationship between peak current and concentration of hydroquinone, catechol and resorcinol was obtained in the range of 1 × 10−6–1 × 10−4 mol L−1, and the detection limits were estimated to be 1 × 10−7, 1 × 10−7 and 9 × 10−8 mol L−1, respectively. The constructed electrode showed excellent reproducibility and stability. Real water samples were analyzed and satisfactory results were obtained. This method provides a new way of constructing electrodes for environmental and biological analysis.

A new type of poly(toluidine blue O)/multiwall carbon nanotube (PTBO/MWNTs) composite nanowires was fabricated by two steps: first, the TBO monomer was assembled onto multiwall carbon nanotubes (MWNTs) to form TBO/MWNTs adduct. Then, the obtained TBO/MWNTs adduct was electropolymerized on a glassy carbon electrode (GCE) surface by cyclic voltammetry. The nanowires modified GCE was characterized with scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The PTBO/MWNTs composite nanowires modified electrode was applied to determinate NADH. Compared with bare GCE and MWNTs modified GCE, the PTBO/MWNTs composite nanowires modified GCE decreased the NADH oxidization overpotential by about 650 mV and 260 mV, respectively, with a much low peak potential at about 0.0 V (vs. SCE). The peak current response at PTBO/MWNTs composite nanowires modified GCE was about 4.5 times higher than that of ultrathin PTBO modified GCE, at the same peak potential. A linear range from 2.0 μM to 4.5 mM was observed with fast response (within 5 s) and a low detection limit of 0.5 μM (based on S / N = 3). The current diminution to 1.0 mM NADH is lower than 10% in a period over 70 min shows that the PTBO/MWNTs composite nanowires modified GCE is quite stable. The better electrocatalytic behavior toward NADH oxidation at PTBO/MWNTs composite nanowires modified GCE suggests that the composite nanowires is an excellent platform for electrochemical sensing and biosensing.

A novel capacitive immunosensor was successfully developed for the direct detection of transferrin based on an ultrathin γ-alumina sol–gel-derived film and gold nanoparticles. The thin film was formed and air-dried by dripping Al2O3 sol with a microliter syringe on a gold electrode modified with a self-assembled mercaptoacetic acid (MAA) monolayer. After defects in the film were blocked with a long-chain alkylthiol, gold nanoparticles were deposited on the surface of the modified film via a potential step from +1.1 to 0.0 V (versus Ag|AgCl|KCl) for 15 s in a 0.5 M H2SO4 solution containing 0.1 mM HAuCl4. Finally, the antibody was immobilized on the gold nanoparticles under the optimized experimental conditions. The capacitive sensor prepared by the present method can provide high sensitivity because of the ultrathin inorganic film with high permittivity and good biocompatibility of gold nanoparticles. Compared with a capacitive immunoassay based on antibody-embedded ultrathin γ-alumina sol–gel-derived films, the novel immunosensor presented a lower detection limit of 0.05 ng/ml and a wider linear response range of 1–75 ng/ml for transferrin detection. The prepared procedure of the novel immunosensor also provided a new approach to fabrication of capacitive immunosensors.

A novel system combining acoustic wave impedance (AWI) analyzer with UV-vis spectrophotometer was developed for the study of chromium (VI) reduction kinetics by Pseudomonas aeruginosa. AWI gave information about the growth of Pseudomonas aeruginosa, and UV-vis spectrophotometer gave information about the concentration of chromium (VI) simultaneously. A combined system response model, for chromium (VI) reduction kinetics at lower initial chromium (VI) concentrations, was derived and proved based on the novel system. Taking into account the effect of bacterial growth on chromium (VI) reduction, the new model successfully simulated chromium (VI) bioremediation process. By fitting chromium (VI) reduction data toward the derived model, the kinetic parameters related to the process were obtained. When the concentration of peptone was 10 g L(-1), the half-velocity reduction rate constant K (C) and the maximum specific chromium (VI) reduction rate constant nu(max) were 0.7682 mg chromium (VI) L(-1) and 2.5814 x 10(-12) mg chromium (VI) cells(-1) h(-1), respectively. It was found that the combined system can provide real-time, reliable, and two-dimensional kinetic information, and can be applied to study other biological processes.