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Polydopamine coated TiO2nanofiber fillers have been synthesized by the hydrothermal method combined with PDA coating, and can significantly enhance the electrochemical properties and interfacial stability of the PEO polymer electrolyte.

A hierarchical porous LiMn0.8Fe0.2PO4/C (N-LMFP) was synthesized by a simple solid-state method beneficial for engineering applications. The fine particle and hierarchical porous structure enable a superior rate performance of the N-LMFP sample.

A "pea-pod"-like composite of graphene-wrapped silicon nanoparticles (P–Si@GS) was successfully prepared via a new and facial technique utilizing freeze-drying and subsequent solvothermal process. The cross-linked "pods" formed by curled few-layer graphene sheets constituted a conductive network, in which silicon nanoparticles were tightly wrapped. The unique graphene-wrapped structure with mesopores on the surface can effectively enhance the conductivity of silicon, alleviate its volume effect and provide rapid transport channels for electrons and ions, thus resulting in excellent electrochemical performance. The strategy of combining freeze-drying and solvothermal methods is facile, low-cost and effective, which provides new ideas for the preparation of high-performance graphene-wrapped nanoparticles composites.

Serious damage caused by oily wastewater makes the development of efficient superhydrophobic and superoleophilic materials for oil/water separation processes critical and urgent. Herein, durable superhydrophobic nanometer-scale TiO2 grains with low-surface-energy substance composite-modified materials were fabricated by using a cost-effective and facile synthesis method for the gravity-driven separation of oil/water mixtures under harsh conditions. Different substrates, such as sawdust, wheat straw, cotton, sponge and fabric, were applied for superhydrophobic surface preparation, and various low-surface-energy reagents could interact with deposited TiO2 nanoparticles, including cetylamine, dodecanethiol, stearic acid and HDTMS. The resultant materials showed superhydrophobic properties with a water contact angle (WCA) higher than 150.8°. The separation of various oil/water mixtures with high efficiency and purity was acquired by using the as-prepared sponge. More importantly, the coated sponge exhibited good resistance to various harsh environmental solutions. Moreover, its superhydrophobicity also remained even after 12 months of storage in air or 10 cycles of abrasion. The durable superhydrophobic coating prepared in this work could be practically used for the highly efficient separation of oil/water mixtures under various harsh conditions.

Transition metal phosphides are used as anode materials for lithium-ion batteries because of their high theoretical capacity and low polarization. In this work, a core-shell GaP@C nanocomposite was successfully synthesized by a simple chemical vapor deposition (CVD) method, utilizing commercial GaP as the raw material and xylene as the carbon source. The uniform thin carbon shell could alleviate the volumetric variation and improve the conductivity of the inner GaP. When used as an anode in lithium-ion batteries, the GaP@C nanocomposite has a capacity of 812 mA h g-1 at a current density of 0.5 A g-1 after 100 cycles. At a high current density of 2 A g-1, the GaP@C anode delivers a good capacity value of 1087 mA h g-1.

A uric acid (UA) electrochemical biosensor was constructed using ferrocene (Fc) decorated cuprous oxide (Cu2O) enhanced electro-active characteristics and covalently immobilized with uricase (UOx) on glassy carbon electrode (GCE). The electrochemical characteristics of the fabricated electrode was analysed by cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV). DPV studies revealed rapid response of fabricated electrode UOx/Fc/Cu2O/GCE towards UA in a wide concentration range of 0.1–1,000 μM with a sensitivity of 1.900 μA mM−1 cm−2 and very low detection limit of 0.0596 μM. A very low magnitude Michaelis–Menten constant (Km) value was evaluated as 34.7351 μM which indicated the chemical attraction of the enzyme towards the UA was much higher. The developed biosensor was successfully applied to detect UA in human urine samples. Moreover, reproducibility and stability studies demonstrated the fabricated UOx/Fc/Cu2O/GCE biosensor had high reproducibility with a RSD of 2.8% and good reusability with a RSD of 3.2%. Specificity studies results showed the fabricated biosensor had strong anti-interference ability. The improved sensor performance was attributed to the synergistic electronic properties of Cu2O and Fc that provided enhances delectrocatalytic activity and electron transfer. The present biosensor can be extended for use in clinical settings.

Synthesis method is crucial to the improved electrochemical performances of LiMnPO4 materials with poor electronic and ionic conductivity for large-scale preparation. Here, carbon-coated LiMn0.8Fe0.2PO4 materials were synthesized through a rheological phase-assisted solid-state method combined with freeze-drying. Effect of different carbon sources on the structure, morphology, and electrochemical performance of as-prepared LiMn0.8Fe0.2PO4 materials was investigated. The results suggest that LiMn0.8Fe0.2PO4 materials with citric acid as carbon sources show a high discharge capacity with 164, 122, and 106 mA h g−1 at 0.1, 1, and 5 C, and a capacity retention of around 99.6% after 100 cycles at 1 C. This can be attributed to higher surface area, intense peak of sp2 N–C=N bonds, and uniform particle distribution resulting from the rheological phase formed using citric acid as carbon sources combined with freeze-drying. The rheological phase-assisted solid-state method is a promising route for production of LiMn0.8Fe0.2PO4 materials with excellent performances.

The polyethylene oxide (PEO) solid electrolyte is a promising candidate for all solid state lithium-ion batteries (ASSLIBs), but its low ionic conductivity and poor interfacial compatibility against lithium limit the rate and cycling performance of the cell. Herein, the novel and efficient TiO

Li1.3Al0.3Ti1.7(PO4)3 is regarded as one of the most promising solid electrolytes for all solid state lithium ion batteries (ASSLIBS). However, its grain boundary conductivity is still low, which reduces the total conductivity of electrolyte. In this work, in order to further improve the electrical conductivity of Li1.3Al0.3Ti1.7(PO4)3, a series of Y doped Li1.3Al0.3-xYxTi1.7(PO4)3 (x = 0, 0.025, 0.05, 0.075 and 0.15) solid electrolytes were synthesized using a modified solid state method. Effects of Y doping content on morphology, phase and electrical conductivity of Li1.3Al0.3Ti1.7(PO4)3 electrolyte materials were systematically investigated. All synthetic electrolyte powders show Nasicon-like structure, well-shaped polyhedral morphology as well as good crystallinity. Y dopant content has a great influence on electrochemical properties of electrolytes. The high total conductivity of 7.8 × 10−4 S/cm at room temperature and a low activation energy of 0.17 eV is obtained for the electrolyte with the Y doping content of 0.075 due to the increasing of grain boundary conductivity, and its electrical conductivity is about 2 times larger than that of the undoped electrolyte. The excellent electrochemical performance is mainly attributed to high electrolyte density which results from the good sintering property of electrolyte materials as well as the existence of YPO4 phase at grain boundaries. Additionally, this electrolyte has a negligible electronic conductivity. These results suggest that Y doped Li1.3Al0.3Ti1.7(PO4)3 can be used as an alternative solid electrolyte for all solid state lithium ion batteries.

Liquid food adhesion on containers has increased food waste and pollution, which could be effectively alleviated with a superhydrophobic surface. In this research, the superhydrophobic coating was fabricated with edible soybean wax on different substrates by a spraying method. The coated surface showed excellent superhydrophobicity due to its microstructure formed by self-roughening, which could repel a variety of viscous liquid food with the apparent contact angle of 159 &plusmn, 2&deg, The coated surface was still liquid-repellent after hot water immersion (45 &deg, C), abrasion test with sandpaper, water impact, finger touch and immersion into yogurt. The liquid-repellent coating with soybean wax, which is natural and green, is promising for application in the food industry to reduce waste.

A bagasse-based 3D carbon matrix (BC) with high specific surface area and high conductivity was obtained by carbonization and pore-forming processes with bagasse as the carbon precursor and K2FeO4 as the pore-former. The microporous structure and nitrogenous functional groups were determined in the prepared carbon matrix, which could allow high sulfur loading and improve the polysulfide absorption capacity during cycling. After sulfur infusion, the S/BC composite with 68.8% sulfur content was obtained. The lithium–sulfur (Li–S) battery with the S/BC cathode shows high specific capacity and good cycling performance. It delivers a specific capacity of 1360 mA h g−1 at 0.2C and remains at 790 mA h g−1 after 200 cycles. At 1C, the Li–S with this composite cathode exhibits 601 mA h g−1 after 150 cycles. This work offers a new kind of green material and a new method for Li–S batteries.

This research demonstrated the development of a simple, cost-effective, and label-free immunosensor for the detection of &alpha, synuclein (&alpha, Syn) based on a cystamine (CYS) self-assembled monolayer (SAM) decorated fluorine-doped tin oxide (FTO) electrode. CYS-SAM was formed onto the FTO electrode by the adsorption of CYS molecules through the head sulfur groups. The free amine (&ndash, NH2) groups at the tail of the CYS-SAM enabled the immobilization of anti-&alpha, Syn-antibody, which concurrently allowed the formation of immunocomplex by covalent bonding with &alpha, Syn-antigen. The variation of the concentrations of the attached &alpha, Syn at the immunosensor probe induced the alternation of the current and the charge transfer resistance (Rct) for the redox response of [Fe(CN)6]3&minus, /4&minus, which displayed a linear dynamic range from 10 to 1000 ng/mL with a low detection limit (S/N = 3) of ca. 3.62 and 1.13 ng/mL in differential pulse voltammetry (DPV) and electrochemical impedance spectra (EIS) measurements, respectively. The immunosensor displayed good reproducibility, anti-interference ability, and good recoveries of &alpha, Syn detection in diluted human serum samples. The proposed immunosensor is a promising platform to detect &alpha, Syn for the early diagnose of Parkinson&rsquo, s disease, which can be extended for the determination of other biologically important biomarkers.

Biomass was wet-torrefied to improve its properties prior to gasification. Two kinds of biomass were employed as feedstock, including the larch wood and corn stalk. For both larch wood and corn stalk, the oxygen content of torrefied samples reduced greatly, while the carbon content increased. All of these features had a positive effect on the gasification process, which was discussed in the research. During steam gasification, all of the wet-torrified biomass samples yielded higher amounts of H2 and CO compared to the raw biomass samples, showing the superiority of the wet torrefaction (WT). During CO2 gasification, the CO production was also significantly improved by WT. The kinetic characteristic parameters for the gasification of raw and torrefied biomass samples were determined using the random pore model. It was found that the activation energy of gasification could be reduced by the WT process.

In this paper, a novel superhydrophobic magnetic sawdust (SMSD) was fabricated as an oil sorbent. The SMSD was functionalized with Fe3O4 nanoparticles using melamine formaldehyde resin (MFR) as a coupling agent and subsequently hydrophobically-treated with hexadecyltrimethoxysilane (HDTMS). The SMSD showed excellent superhydrophobicity with the water contact angle of 155.3 &plusmn, 0.9&deg, Meanwhile it had remarkable environmental durability, long-term stability, and mechanical durable properties. Taking advantage of its magnetic characteristics, the SMSD could be easily controlled to absorb oil to separate oil&ndash, water mixtures with high oil absorption capacity and good reusability. Moreover, the emulsion was successfully separated by SMSD, including water-in-oil and oil-in-water emulsions. This study developed an effective oil absorbent, which was low cost and environmentally-friendly.

A comparative study was carried out on the electrochemical behavior of three carbonized zeolitic imidazolate frameworks (ZIFs) synthesized through solvothermal pyrolysis. An electrochemical sensor for acetaminophen (ACT) was subsequently developed. The sensor was made by coating the glassy carbon electrode (GCE) with cobalt-nitrogen co-doped carbon nanotube hollow polyhedron (Co-NCNHP), which was prepared from core shell ZIF-8@ZIF-67, before electrodeposition of gold nanoparticles. Due to the high specific surface area, good electrical conductivity and stability of both Co-NCNHP and the gold nanoparticles, the resultant sensor displayed excellent electrocatalytic activity towards ACT with the catalytic rate constant Kcat of 4.9 × 105 M−1 s−1, diffusion coefficient D of 1.8 × 10−6 cm2 s−1, high sensitivity of 1.75 μA μM−1 cm−2, and best at a working voltage of 0.35 V (vs. Ag/AgCl). Benefitting from the synergistic effect of both Co-NCNHP and gold nanoparticles, the modified GCE had a linear response in the 0.1 μM–250 μM ACT and detection limit of 0.05 μM (at S/N = 3). The sensor was successfully applied to quantify ACT in tablets and spiked urine samples with recoveries ranged between 96.0% and 105.2%.

Herein, a novel electrochemical sensor based on core-shell zeolitic imidazolate framework-8 @zeolitic imidazolate framework-8 (ZIF-8@ZIF-67) derived cobalt and nitrogen co-doped carbon polyhedron (Co, N-CP) and electrodeposited nickel nanoparticles (Ni NPs) was developed for nitrite (NO2−) detection. The Co, N-CP was prepared by direct pyrolysis of the core-shell structured ZIF-8@ZIF-67 at Zn/Co at 900 °C in an Ar atmosphere. Ni NPs were electrodeposited on Co, N-CP modified glass carbon electrode (Co, N-CP/GCE) using potentiostatic method. The Ni NPs decorated Co, N-CP displays a synergetic electrocatalytic effect for the oxidation of NO2− due to the large surface area and ordered porosity of Co, N-CP integrating the good conductivity and catalytic activity of Ni NPs. The proposed sensor exhibited good electrocatalytic activity, sensitivity and selectivity towards NO2− with the catalytic rate constant (Kcat) of 5.49 × 106 M−1 s−1 and the diffusion coefficient (D) of 5.12 × 10−6 cm2 s−1. The Ni/Co, N-CP/GCE showed a wide linear response (5–1000 μM) and a low detection limit (LOD) of 0.094 μM (S/N = 3). Additionally, the sensor was successfully applied to monitor NO2− in real samples with satisfactory recoveries, indicating that Ni/Co, N-CP could be a promising candidate for sensing of other biologically important molecules.

To circumvent the binder’s adverse effect on the performance of electrochemical sensor and improve the analysis efficiency, a binder-free cobalt-doped Ni-MOF (Co/Ni-MOF) film, with honeycomb-like structure, is fast electrodeposited on glassy carbon electrode (GCE) by cathodic reduction. No conductive agent added, the Co/Ni-MOF/GCE can be directly used as a sensor for levofloxacin (LEV) determination. Under the optimal condition, a wider linear range of 0.1 μM–500 μM LEV is obtained with the limit of detection (LOD, 3S/N) being 22 nM and the sensitivity of 2.85 μA μM−1 cm−2. Further, when being used to analysis of LEV in eye drop and spiked milk, satisfactory recoveries of 94.0%–108.2% are achieved. Particularly, benefiting of the synergistic effect of Co2+ and Ni2+, as well as and the binder-free film, the sensor exhibits an excellent sensitivity and a robust long-term stability. This work develops a facile and efficient strategy to synthesis of Co and Ni based MOF film, and provides them a new way in electrochemistry application.

A sensitive and selective sensor was fabricated to determine melamine (Mel), based on MIL-53@XC-72 nanohybrid modified glassy carbon electrode (GCE). The MIL-53@XC-72 nanohybrid was synthesized from MIL-53 via hydrothermal method, followed by adulterating with XC-72. The prepared sensor possessed high sensitivity and selectivity due to the synergistic effect of the large surface of MIL-53, the bonding interaction between Mel and MIL-53 as well as the high conductivity of XC-72. Under the optimal conditions, the sensor exhibited rapid electrochemical response to Mel at the potential of 0.7 V in 0.1 M HCl solution. A linear concentration range of Mel was obtained from 0.04 to 10 μM with a linear correlation coefficient of 0.998 and detection limit of 0.005 μM (S/N = 3). In addition, the sensor presented excellent reproducibility, high stability and selectivity, and was successfully applied for the determination of Mel in liquid milk with a good recoveries. Hence, the MOFs@XC-72-Nafion-GCE sensor could be considered as promising applicability for the determination of other electrochemically inactive analytes.

Nasicon-type Li1+xAlxGe2-x(PO4)3 (x = 0–0.5) electrolytes have been prepared via a facile and economic method. All synthetic electrolyte samples show Nasicon structure and good crystallinity. The Al doping content has a great influence on the electrical conductivity of electrolyte. The electrolyte with the composition of Li1.4Al0.4Ge1.6(PO4)3 exhibits a highest electrical conductivity of 2.72 × 10−4 S/cm at room temperature, which is mainly attributable to fewer impurity and dense electrolyte structure. The LiFePO4/Li cell assembled with this electrolyte delivers an initial specific discharge capacity of 127.86 mAh g−1 at a charge/discharge current density of 0.5C at 60 °C, which shows an excellent cycling performance with high discharge capacity of 131.2 mAhg−1 after 150 cycles. These results suggest that the Li1.4Al0.4Ge1.6(PO4)3 electrolyte is a potential electrolyte for all solid state lithium-ion battery.

Herein, we fabricated a sensitive rutin electrochemical sensor via modifying glassy carbon electrode (GCE) with zeolitic imidazolate framework-8 (ZIF-8) and acetylene black (AB) in the presence of chitosan (CS). The electrochemical activity and experimental parameters of the ZIF-8-AB-CS/GCE sensor were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Under the optimal conditions, the sensor presented a reasonable linear response in the range of 0.1–10 μM with a limit of detection (LOD) as low as 0.004 μM (S/N = 3). The sensor possessed good reproducibility and high stability, and was successfully applied to detect rutin tablet samples with satisfactory results, which was attributed to the synergistic effect between ZIF-8 and AB. Meanwhile, the sensor displayed a potential application for detection of other analytes in real samples. Furthermore, a probable interaction mechanism was proposed to account for the interaction between rutin and the nanocomposite electrode, which was not discussed in previous reports.

A highly sensitive and selective electrochemical method based on a poly(chromotrope 2B)-modified anodized glassy carbon electrode (PCHAGCE) was developed for the determination of dopamine (DA) in the presence of uric acid (UA) and ascorbic acid (AA). The PCHAGCE sensor exhibited excellent electron-mediating behavior towards the oxidation of DA in 0.1 M phosphate buffer solution (PBS) (pH 7.0). It was found that the electrocatalytic activity was significantly dependent on the charge status and molecular structure of the target molecules. Differential pulse voltammetry (DPV) measurements revealed oxidation signals for DA, UA, and AA that were well-resolved into three distinct peaks with AA–DA, DA–UA, and AA–UA peak potential separations (Δ E p ) of 172, 132, and 304 mV, respectively. A detection limit of 0.04 ± 0.001 μM ( S/N = 3) and a quantification limit ( S/N = 10) of 0.149 ± 0.03 μM were obtained for DA sensing in a linear range of 1 to 40 μM in PBS (pH 7.0) with a very high sensitivity of 1.522 ± 0.032 μA·μM −1 . The DA concentrations in human urine samples were also successfully determined with recoveries of 94.0–98.0%. This approach provides a simple, easy, sensitive, and selective method to detect DA in the presence of AA and UA.

A highly sensitive electrochemical method for the simultaneous and quantitative detection of hydroquinone (HQ) and catechol (CC) was developed, based on covalent immobilization of thionine (TH) by Schiff-base reaction between –NH2 of TH and –COH onto graphene oxide modified glassy carbon electrodes (GO/GCE). The modified electrode showed excellent electrocatalytic activity and reversibility toward the oxidation of both HQ and CC in 0.1 M phosphate buffer solution (PBS, pH 7.0). The redox responses from the mixture of HQ and CC were clearly resolved in both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) with the peak differences of 100 mV and 110 mV, respectively. The oxidation peak currents of HQ and CC were linear over the range from 1 to 200 μM in the presence of 150 μM of counterpart. The detection limits (S/N = 3) for HQ and CC were 20 and 25 nM, respectively. Furthermore, the electrochemical performances with some interference were studied. The developed sensor was successfully examined for real sample analysis with tap water and revealed stable and reliable recovery data. © The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any

Herein, we developed a sensitive and non-enzymatic glucose sensor based on a dendritic Cu-Cu2S nanocomposite-modified glassy carbon electrode (GCE). Dendritic Cu-Cu2S were successfully deposited with high purity and crystallinity onto a GCE by a simple and single-step potentiostatic deposition method from an aqueous solution of CuCl2 and thiourea (TU). The electrocatalytic activity of the Cu-Cu2S/GCE sensor towards glucose oxidation was investigated by cyclic voltammetric and amperometric methods. The sensor exhibited high sensitivity (5.02 mA/mM/cm2) in the concentration range from 0.1 μM to 0.5 mM with a limit of detection of 0.33 μM (S/N = 3). In addition, this sensor showed high selectivity for glucose detection with good accuracy and recovery in human serum samples. Thus, the present sensor can be used as a simple and effective sensing platform for non-enzymatic detection of glucose.

In the original article, Fengzhang Ren’s and Jingjing Ma’s first names are spelled wrong. They are correct as shown here.

In this paper, reactive polyvinylsilazane (PVSZ) is employed as silicate source for poly(dimethylsiloxane) (PDMS) channel surface modification. The PVSZ submicron layer is simply constructed by flushing 1 wt.% PVSZ-anhydrous DMF solution into PDMS channel for 1 min. After UV and thermal curing, the reactive coating is subjected to hydrolysis reaction in an alkali solution for 1 h to convert the consolidated polymer surface to silicate phase. The surface is characterized by SEM, AFM and contact angle measurement. The PVSZ silicate channel is of optical transparence and solvent resistance, and provides a long-term stable electroosmotic flow (EOF) with 4.3 ± 0.1 × 10 − 4 cm 2 V − 1 s − 1 at pH 9.00, and a reliable capillary electrophoresis (CE) performance. Theoretical plate numbers of five FITC-labeled amino acids were all over 14,000 (2.8 μm height), and EOF repeatability is much superior to that of PDMS channel.

A simple and highly sensitive electrochemical method for the simultaneous and quantitative detection of hydroquinone (HQ) and catechol (CT) was developed, based on a poly(thionine)-modified glassy carbon electrode (GCE). The modified electrode showed excellent electrocatalytic activity and reversibility towards the oxidation of both HQ and CT in 0.1 M phosphate buffer solution (PBS, pH 7.0). The peak-to-peak separations (Δ E p ) between oxidation and reduction waves in CV were decreased significantly from 262 and 204 mV at the bare GCE, to 63 and 56 mV, respectively for HQ and CT at the poly(thionine) modified GCE. Furthermore, the redox responses from the mixture of HQ and CT were easily resolved in both CV and DPV due to a difference in the catalytic activity of the modified GCE to each component. The peak potential separation of ca. 0.1 V was large enough for the simultaneous determination of HQ and CT electrochemically. The oxidation peak currents of HQ and CT were linear over the range from 1 to 120 μM in the presence of 100 and 200 μM of HQ and CT, respectively. The modified electrode showed very high sensitivity of 1.8 and 1.2 μA μM −1 cm −2 for HQ and CT, respectively. The detection limits ( S / N = 3) for HQ and CT were 30 and 25 nM, respectively. The developed sensor was successfully examined for real sample analysis with tap water and revealed stable and reliable recovery data.

A highly selective and sensitive electrochemical method, based on a poly(thionine)-modified glassy carbon electrode (PTH-GCE), was developed for the determination of dopamine (DA). The modified electrode was characterized by electrochemical techniques and an atomic force microscope (AFM). The modified GCE exhibited catalytic behavior towards the oxidation of DA in 0.1 M pH 7.0 phosphate buffer solution (PBS). In differential pulse voltammetry (DPV) measurements, the oxidation peak potential of ascorbic acid (AA), uric acid (UA) and serotonin (5-HT) overlapped with that of DA at the bare GCE. However, the oxidation peak of 5-HT was separated from that of DA at the PTH-GCE while the oxidation of AA and UA were suppressed at the same time. The peak potential separation of ca. 0.2 V was large enough for selective determination of DA from the interference of 5-HT. A linear range of 5.0–35.0 μM and a detection limit (S/N = 3) of 0.2 μM were obtained for DA detection in PBS (pH 7.0). This approach provides a simple and easy method to detect DA selectively from the interferences of AA, UA and 5-HT.

A quercetin monolayer has been prepared on top of the self-assembled 3-mercaptopropionic acid (MPA) layer for the copper ion determination. Cu2+ ions are readily accumulated on this modified electrode through the complex formation and electrochemically detected. With a quercetin layer, the redox process of Cu2+ became more reversible than at the MPA-modified electrode. Complexation sites in MPA and quercetin were occupied within five min when the electrode was immersed in 10 μM Cu2+ solution. The MPA and quercetin layers were stable enough to allow repeated EDTA treatment to remove adsorbed Cu2+ for the surface regeneration. Only 7% decrease was found after ten times regeneration and use. Linear current response was found over the concentration range of 1 nM and 10 μM with detection limit of 0.1 nM. Common interfering ions such as Cd2+, Zn2+, and Fe2+/3+ did not show any electrochemical response in the potential range of Cu2+ determination.

Electrodes for the dopamine (DA) determination in biological samples have been developed with improved selectivity and sensitivity in an excess of ascorbic acid (AA). Negatively charged Ni(II) complex was synthesized and electropolymerized on the glassy carbon electrode to impart the surface with anionic characteristics that could act both as a catalyst and as a discriminating layer against AA based on the electrostatic interaction. Thus prepared electrodes enabled selective determination of DA even in a large excess of AA by differential pulse voltammetry at physiological pH. Linear response was found down to 1.0 × 10 − 7 M with 5.0 × 10 − 9 M of LOD (Limit of Detection). In a flow injection analysis performed in an amperometric mode, the detection limit was lowered by two orders of magnitude down to 1.0 × 10 − 9 M with a linear range of 1.0 × 10 − 9 to 1.0 × 10 − 6 M. The relative standard deviation was found to be 3.36% from 25 independent measurements for 1.0 × 10 − 5 M of DA. Stable oxidation current of DA was observed even after 30 days storage in air. The recoveries of DA in the 100-fold diluted human urine samples were 97.7% for 4 measurements. The rate constant for the DA oxidation was 1.3 × 10 − 3 cm s − 1 from hydrodynamic experiments using a rotating disk electrode.

Quercetin, Metal complex, SpectroelectrochemistryPolyphenols having a benzo-γ-pyrone structure constitutea family known as flavonoids. Flavonoids are widelydistributed among higher plants. By virtue of astringenttaste, they are believed to serve as defensive molecules,protecting plant tissues from herbivorous attack.

In this paper, we describe the double modification of the glassy carbon electrode surface with two polymer layers for the selective determination of dopamine. The first layer was the electropolymerized macrocyclic nickel complex acting as an electrocatalyst for the dopamine oxidation and the second layer the polyurethane benzyl L-glutamate (PUBLG) for screening interfering species. Hydrolyzed PUBLG (PU-C) showed a better screening effect. Thus prepared GC/Ni(II) complex film/PU-C electrodes exhibited improved selectivity and better performance than unmodified counterparts, with minimum passivation even in the presence of large excess of interferents. Under optimal conditions, these electrodes showed a linear response over a dopamine concentration range of 2.5×10−7 and 3.0×10−5 M with a correlation coefficient of 0.999 and detection limit (at S/N=3) of 8.0×10−8 M. The recoveries of dopamine in the 5-fold diluted human urine sample were 96.9% for 4 measurements. The rate constant for the dopamine oxidation measured by the rotating disk electrode was found to be 1.1×10−3 cm s−1.

A simple and sensitive electrochemical method for the simultaneous and quantitative detection of ranitidine (RT) and metronidazole (MT) was developed, based on a poly(chromotrope 2B) modified activated glassy carbon electrode (PCHAGCE). The PCHAGCE showed excellent electrocatalytic activity toward the reduction of both RT and MT in 0.1 mol/L phosphate buffer solution (pH 6.0). The peak-to-peak separations for the simultaneous detection of RT and MT between the two reduction waves in cyclic voltammetry were increased significantly from ∼0.1 V at activated GCE, to ∼0.55 V at PCHAGCE. By differential pulse voltammetry techniques, the reduction peak currents of RT and MT were both linear over the range of 1.0 × 10−5–4.0×10−4 mol/L. The detection limits (S/N = 3) were 5.4 × 10−7 mol/L and 3.3 × 10−7 mol/L for RT and MT, respectively. The modified electrode was successfully applied to the determination of RT and MT in pharmaceutical preparations and human serum as real samples with stable and reliable recovery data.

A glassy carbon electrode having two polymer layers has been applied to selectively detect epinephrine. The inner layer formed by electropolymerization of macrocyclic nickel complex functioned as an electrocatalyst for epinephrine oxidation and the outer layer composed of hydrolyzed polyurethane γ-benzyl L-glutamate as a screening layer. Differential pulse voltammetry showed almost 100% recovery of epinephrine even in 100-fold excess of interferents. When applied to a dual glassy carbon electrode as an amperometric detector in flow injection analysis, a linear response over 0.1 μM and 10 μM was obtained. Recovery tested for 5-fold diluted human urine samples was 97.5%.