A sensitive and selective sensor‐coated molecularly imprinted sol–gel film incorporating β‐cyclodextrin‐multi‐walled carbon nanotubes and cobalt nanoparticles‐chitosan for oxacillin determination

A sensitive and selective imprinted electrochemical sensor for the determination of oxacillin was developed based on indium tin oxide electrode. The proposed sensor was decorated with imprinted sol–gel film and cobalt nanoparticles‐chitosan/β‐cyclodextrin‐multiwalled carbon nanotubes nanocomposites. The surface morphologies of the modified electrodes were characterized by scanning electron microscopy and transmission electron microscope. The stepwise assembly process and electrochemical behavior of the novel sensor were characterized by differential pulse voltammetry, cyclic voltammetry and Amperometric i‐t response. The imprinted sensor displayed excellent selectivity toward oxacillin. Meanwhile, the introduced cobalt nanoparticles‐chitosan and β‐cyclodextrin‐multi‐walled carbon nanotubes exhibited noticeable amplified electrochemical response signal. The differential voltammetric anodic peak current was linear to oxacillin concentration in the range from 2.0 × 10^?7 to 1.0 × 10^?4 mol·l^?1, and the detection limit was 6.9 × 10^?9 mol·l^?1. The proposed imprinted sensor was applied to the determination of oxacillin in human blood serum samples successfully. Copyright © 2011 John Wiley & Sons, Ltd.     

Asymmetric hydrogenation of ketones catalyzed by silica‐supported chitosan‐iron‐nickel complex

A new silica‐supported biopolymer‐metal complex, silica‐supported chitosan‐iron‐nickel complex was prepared by a very simple method. This complex catalyst can be used as a catalyst in the asymmetric hydrogenation of propiophenone to (R)‐(+)‐1‐phenyl‐1‐propanol and acetophenone to (R)‐(+)‐1‐phenyl ethanol in 91.7 and 77.7% optical yields, respectively, at 110°C and under 70 kg/cm² pressure. The catalyst could be reused several times without any remarkable change in the catalytic activity. Copyright © 2004 John Wiley & Sons, Ltd.     

Spectroscopic characterization and preparation of low molecular,water‐soluble chitosan with free‐amine group by novel method

Low molecular, water‐soluble chitosan (LMWSC) with a free amine group was prepared by the novel salts‐removal method described in this study. A weight‐average molecular weight and degree of deacetylation (DDA) of LMWSC were determined by viscometry and Kina titration, resulting in 18,579 Da and 93% DDA, respectively. In the Fourier transform infrared spectroscopic, ¹H NMR, and ¹³C NMR spectra the absorption band by the carboxyl group derived from lactic acid and the impurities formed in the enzymatic process disappeared or were significantly lower than that of the control chitosan. Also, from the ¹H NMR and ¹³C NMR spectra the empirical value for the area ratio of the proton and carbon corresponds nearly to its theoretical values. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum identified the difference in the two adjacent peaks as 161. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3796–3803, 2002     

Extraction of neodymium from other fission products by co‐reduction of Sn and Nd

High temperature processing is an important method for recovering long‐lived elements from spent nuclear fuel. Electrolysis is the key technology for high temperature processing. The electrochemical behaviors of Sn²⁺, Nd³⁺ and the mechanisms of Sn‐Nd alloy formation were investigated on a Mo electrode at 873 K by conducting a series of electrochemical techniques. The results showed the deposition of Nd on inert electrode is a two‐step process in LiCl‐KCl‐SnCl₂ (2.0 wt.%) melt system. Subsequently, the electrochemical extraction of Nd from molten chlorides were carried out on the Mo electrode at temperature of 873 K by the potentiostatic electrolysis at ?1.2 V for 40 hr. Besides, the extraction efficiency is 97.6%. A series of potentiostatic electrolysis were carried out at potential range between ?1.0 and ? 1.4 V. The NdSn₃ alloy was obtained by electrolysis at ?1.2 V. This deposition potential is consistent with the predicted results of the mathematical model. The micro‐chemical analysis and morphology analysis of the deposits was characterized by energy dispersive spectrometry (EDS) with scanning electron microscopy (SEM) equipped. The composition of the deposits was analyzed by X‐ray diffraction (XRD) and inductive coupled plasma atomic emission spectrometer (ICP‐AES).     

基于酶标抗体和媒介体共吸附于金胶壳聚糖膜的PSA免疫传感器的制备

本文研制了一种用金胶壳聚糖仿生膜来同时固定四甲基联苯胺（TMB）和酶标抗体的新型电化学免疫传感器,用于检测血清肿瘤标志物前列腺特异性抗原（PSA）的含量。固定的TMB作为电子传递媒介体,在扫速小于45 mV/s时,电极表现为一个表面控制过程,而在扫速大于45 mV/s时则表现为一个扩散控制过程。将固定有酶标抗体和TMB的免疫传感器与待测PSA抗原一起培育,在该传感器上形成的免疫复合物通过TMB-H₂O₂-HRP电化学体系进行了测定。在优化实验条件下,PSA的线性检测范围为5-30 ng·mL^-1,检测限为1.0 ng·mL^-1。该PSA免疫传感器制备方法简单,成本低廉,具有较好的稳定性和重现性。     

Insights into the Oxidation Chemistry of 2‐Hydroxypurine by Electrochemical Methods

The oxidation chemistry of 2‐hydroxypurine has been investigated in phosphate containing supporting electrolytes at pH 1.4–9.8 at a pyrolytic graphite electrode by voltammetric studies, spectral studies, controlled potential electrolysis and related techniques. The kinetics of decay of the UV‐absorbing intermediate generated during electrooxidation was followed spectrophotometrically and the decay occurred in a pseudo‐first‐order reaction. The course of the electrode reaction has been deduced to involve a 6e, 6H⁺ oxidation of 2‐hydroxypurine via the formation of 2, 8‐dihydroxypurine. The electrooxidation of 2‐hydroxypurine has been found to be an EC reaction (electrode reaction followed by chemical reactions) in which charge transfer is followed by competitive chemical reactions. A detailed interpretation of the redox mechanism of 2‐hydroxypurine has been presented.     

Self‐Assembled Mercapto‐Compound‐Gold‐Nanoparticle‐Modified Carbon Paste Electrode for Potentiometric Determination of Cadmium(II)

A new modified carbon paste electrode (CPE) based on a recently synthesized ligand [2‐mercapto‐5‐(3‐nitrophenyl)‐1,3,4‐thiadiazole] (MNT), self‐assembled to gold nanoparticles (GNP) as suitable carrier for Cd(II) ion with potentiometric method are described. The proposed electrode exhibits a Nernstian slope of 29.4±1.0 mV per decade for Cd(II) ion over a wide concentration range from 3.1×10^?8 to 3.1×10^?4 mol L^?1. The detection limit of electrode was 2.0×10^?8 mol L^?1 of cadmium ion. The potentiometric responses of electrode based on MNT is independent of the pH of test solution in the pH range 2.0–4.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. Finally, the proposed electrode was successfully employed to detect Cd(II) ion in hair and water samples.     

在离子液体中电化学还原合成2-氨基苯甲醚

利用循环伏安法研究了2-硝基苯甲醚在离子液体中的电化学还原行为。以Cu为工作电极,石墨电极为对电极,饱和甘汞电极(SCE)为参比电极,在室温离子液体中电化学还原2-硝基苯甲醚合成2-氨基苯甲醚。优化了电解实验条件,在最佳实验条件(E= -1.0 V, T=50 ℃, c=74.4 mmol·L-1, Q=6 F·mol-1, Y=10:1)下2-氨基苯甲醚的产率最高可达51.3%。在离子液体中电化学合成2-氨基苯甲醚,反应条件温和,避免了有毒易挥发的溶剂、催化剂及其他支持电解质等的使用;并实现了离子液体的重复利用,为2-氨基苯甲醚提供了一条新的绿色化合成路线。     

Fabrication of Chitosan‐Multiwall Carbon Nanotube Nanocomposite Containing Ferri/Ferrocyanide: Application for Simultaneous Detection of D‐Penicillamine and Tryptophan

We report a simple and effective strategy for fabrication of the nanocomposite containing chitosan (CS) and multiwall carbon nanotube (MWNT) coated on a glassy carbon electrode (GCE). The characterization of the modified electrode (CS‐MWNT/GC) was carried out using scanning electron microscopy (SEM) and UV–vis absorption spectroscopy. The electrochemical behavior of CS‐MWNT/GC electrode was investigated and compared with the electrochemical behavior of chitosan modified GC (CS/GC), multiwalled carbon nanotube modified GC (MWNT/GC) and unmodified GC using cyclic voltammetry (CV) and electron impedance spectroscopy (EIS). The chitosan films are electrochemically inactive; similar background charging currents are observed at bare GC. The chitosan films are permeable to anionic Fe(CN)₆^3?/4? (FC) redox couple. Electrochemical parameters, including apparent diffusion coefficient for the Fe(CN)₆^3?/4? redox probe at FC/CS‐MWNT/GC electrode is comparable to values reported for cast chitosan films. This modified electrode also showed electrocatalytic effect for the simultaneous determination of D‐penicillamine (D‐PA) and tryptophan (Trp). The detection limit of 0.9 μM and 4.0 μM for D‐PA and Trp, respectively, makes this nanocomposite very suitable for determination of them with good sensitivity.     

Click‐Conjugation of Nanogold‐Functionalized PAMAM Dendrimer: Toward a Novel Electrochemical Detection Platform

This work reports a new electrochemical monitoring platform for sensitive detection of Cu²⁺ coupling click chemistry with nanogold‐functionalized PAMAM dendrimer (AuNP‐PAMAM). The system involved an alkyne‐modified carbon electrode and an azide‐functionalized AuNP‐PAMAM. Initially, the added Cu²⁺ was reduced to Cu⁺ by the ascorbate, and then the azide‐modified AuNP‐PAMAM was covalently conjugated to the electrode via Cu⁺‐catalyzed azide‐alkyne click reaction. The carried AuNPs accompanying PAMAM dendrimer could be directly monitored by stripping voltammetry after acidic pretreatment. By introduction of high‐loading PAMAM dendrimer with gold nanoparticles, as low as 2.8 pM Cu²⁺ (ppt) could be detected, which was 125‐fold lower than that of gold nanoparticle‐based labeling strategy. The method exhibited high specificity toward target Cu²⁺ against other potentially interfering ions, and was applicable for monitoring Cu²⁺ in drinking water with satisfactory results.     

Dissociation behaviors of carboxyl and amine groups on carboxymethyl‐chitosan in aqueous system

Several carboxymethyl‐chitosan (CMCS) samples with different deacetylation degree and/or substituted degree were prepared from the carboxymethylation reaction of chitosan under soft conditions. The products were dissolved in standard HCl aqueous solution to carry out potentiometric titration by using NaOH as titrating solution at different ionic strengths. Then the dissociation behaviors of protonated carboxyl and amine groups were investigated under their degree of dissociation (α) and protonation constant (pK_α) had been calculated. Moreover, influences of the intrinsic and extrinsic parameters on the dissociation behavior of CMCS were also considered in this article. As a result, dissociations of carboxyl and amine on CMCS exhibited unusual behaviors in comparison with carboxyl of carboxymethyl‐cellulose and amine groups of chitosan, respectively. The pK_α values of carboxyl declined slightly at early dissociation stage but subsequently maintained constant. In contrast, the pK_α of ammonium increased with its dissociation degree despite that there was an inflexed change on its dissociation curve. The potentiometric behavior of carboxyl was hardly affected by variation of deacetylation degree or substituted degree. However, these intrinsic parameters played more important role on dissociations of ammonium on CMCS. The ionic strength of media could bring screening effect on dissociaciation of both sorts of ionizable groups of CMCS. By increasing the ionic strength of media, screening effect on dissociations increased significantly. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1419–1429, 2008     

Electrodeposition of dendritic gold/silver nanaoparticles on disposable screen‐printed carbon electrode and its application of 4‐mercaptopyridine in in situ electrochemical surface‐enhanced Raman scattering

Column electrodes pretreated through oxidation–reduction cycles were traditionally used in electrochemical surface‐enhanced Raman scattering (SERS). In this study, a disposable screen‐printed carbon electrode was introduced into in situ electrochemical SERS through the electrodeposition of dendritic gold/silver nanoparticles (Au/AgNPs) onto the surface of the carbon working electrode to induce the SERS enhancement effect on the electrode. Scanning electron microscopy images showed that dendritic Au/AgNPs nanostructures could be fabricated under appropriate electrodeposition conditions and could present a minimum SERS factor of 4.25 × 10⁵. Furthermore, the absorbed behavior of 4‐mercaptopyridine was investigated under different potentials. The adsorption configuration was inferred to transform from ‘vertical’ to ‘lying‐flat’. The proposed new electrode combined with a portable Raman spectrometer could be useful in the identifying products or intermediates during electrochemical synthesis or electrochemical catalysis in in situ electrochemical SERS. Copyright © 2016 John Wiley & Sons, Ltd.     

Determination of Iodide and Idoxuridine at a Glutaraldehyde‐Cross‐Linked Poly‐L‐Lysine Modified Glassy Carbon Electrode

The detection limit (about 0.017 μg mL^?1) for voltammetric determination of iodide (peak at +0.87 V vs. Ag/AgCl at pH 2) at a glutaraldehyde‐cross‐linked poly‐L ‐lysine modified glassy carbon electrode involving oxidation to iodine was found to be several orders of magnitude lower than that for the voltammetric determination on a bare glassy carbon electrode. This method was applied successfully to the determination of iodide in two medicinal formulations. Idoxuridine was determined indirectly at the same electrode by accumulating it first at ?0.8 V vs. Ag/AgCl. At this potential the C? I bond in the adsorbed idoxuridine is reduced giving iodide, which is then determined at the modified electrode. The method was successfully applied to the determination of idoxuridine in a urine sample.     

Well‐defined succinylated chitosan‐O‐poly(oligo(ethylene glycol)methacrylate) for pH‐reversible shielding of cationic nanocarriers

A novel type of well‐defined graft copolymer, succinylated chitosan‐O‐poly(oligo(ethylene glycol)methacrylate) (SC‐POEGMA), was developed for pH‐reversible poly(ethylene glyocol) (PEG) shielding of cationic nanocarriers. Chitosan‐O‐POEGMA (CS‐POEGMA) was first synthesized via single electron transfer‐living radical polymerization of oligo(ethylene glyol) methacrylate (OEGMA) using O‐brominated chitosan (CS‐Br) as a macromolecular initiator and Cu(I)Br/1,1,4,7,10,10‐hexamethyltriethylenetetramine as a catalyst. The subsequent succinylation of the chitosan backbone gave the titled copolymers. The content of POEGMA in CS‐POEGMA could be widely modulated by varying the degree of bromination and feed ratio of OEGMA to CS‐Br, without compromising the amino density of chitosan backbone. The hierarchical assembly between SC‐POEGMA and trimethylated chitosan‐O‐poly(ε‐caprolactone) (TMC‐PCL) micelles was further studied. At pH 7.4, the stoichiometric interactions between SC and TMC segments to form polyampholyte–polyelectrolyte complexes led to the formation of PEG‐shielded micelles. The hierarchially assembled micelles could be disassembled into the pristine TMC‐PCL micelles, when the medium pH was below a certain pH (pH_φ). By varying the degree of succinylation of SC‐POEGMA, the pH_φ value could be facilely modulated from 6.5 to 3.5 to meet the needs for specific biomedical applications. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Highly Selective and Sensitive Copper(II) Membrane Sensors Based on 6‐Methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one as a New Neutral Ionophore

A new Cu(II) ion‐selective PVC membrane sensor based on 6‐methyl‐4‐(1‐phenylmethylidene)amino‐3‐thioxo‐1,2,4‐triazin‐5‐one (MATTO) as an excellent sensing material was developed. The electrode exhibits a Nernstian slope of 29.2±0.4 mV per decade over a very wide concentration range between 1.0×10^?1 and 1.0×10^?6 M, with a detection limit of 4.8×10^?7 M (30.5 ng/mL). The sensor possesses the advantages of short conditioning time, fast response time (<10 s), and especially, very good selectivity towards transition and heavy metal, and some mono, di and trivalent cations. The proposed electrode was successfully applied to the determination of copper in wastewater of copper electroplating samples and as an indicator electrode in potentiometric titration of Cu(II) ions with EDTA.     

2‐Azido‐2‐deoxycellulose: Synthesis and 1,3‐Dipolar Cycloaddition

Chitosan ( 1 ) was prepared by basic hydrolysis of chitin of an average molecular weight of 70000 Da, ¹H‐NMR spectra indicating almost complete deacetylation. N‐Phthaloylation of 1 yielded the known N‐phthaloylchitosan ( 2 ), which was tritylated to provide 3a and methoxytritylated to 3b . Dephthaloylation of 3a with NH₂NH₂?H₂O gave the 6‐O‐tritylated chitosan 4a . Similarly, 3b gave the 6‐O‐methoxytritylated 4b . CuSO₄‐Catalyzed diazo transfer to 4a yielded 95% of the azide 5a , and uncatalyzed diazo transfer to 4b gave 82% of azide 5b . Further treatment of 5a with CuSO₄ produced 2‐azido‐2‐deoxycellulose ( 7 ). Demethoxytritylation of 5b in HCOOH gave 2‐azido‐2‐deoxy‐3,6‐di‐O‐formylcellulose ( 6 ), which was deformylated to 7 . The 1,3‐dipolar cycloaddition of 7 to a range of phenyl‐, (phenyl)alkyl‐, and alkyl‐monosubstituted alkynes in DMSO in the presence of CuI gave the 1,2,3‐triazoles 8 – 15 in high yields.     

An Immunosensor for Ultrasensitive Detection of 1‐Pyrenebutyric Acid with Enhanced Electrochemical Performance Based on a Graphene‐Ionic Liquid Doped Chitosan Film Modified Glassy Carbon Electrode

This paper describes a highly sensitive and label‐free electrochemical immunosensor for the detection of 1‐pyrenebutyric acid (PBA) which is based on a graphene (GS), chitosan (CS), and ionic liquid (IL) composite modified glassy carbon electrode (GS‐CS‐IL/GCE). The modification process was monitored by transmission electron microscopy (TEM) and cyclic voltammetry (CV). Due to the synergistic effects of GS, CS, and IL, the biosensor exhibits excellent selectivity to PBA. The current response of the proposed immunosensor decreases linearly at two concentration ranges from 0.01 to 5 and from 5 to 150 ng mL^?1 with a detection limit of 0.01 ng mL^?1.     

Electrocatalytic and selective determination of d‐penicillamine in the presence of tryptophan using a benzoylferrocene‐modified carbon nanotube paste electrode

Two amino acids – d ‐penicillamine (D‐PA) and tryptophan (TRP) – could be simultaneously determined in an aqueous solution (pH 7.0) using a novel benzoylferrocene‐modified carbon nanotube paste electrode. The results indicate that the electrode is efficient in terms of its electrocatalytic activity for the oxidation of D‐PA, leading to an overpotential reduction by more than 155 mV. Using square wave voltammetry, measurement of D‐PA and TRP in one mixture could be done independently from each other with a potential difference of about 205 mV. The proposed electrochemical sensor exhibited a linear calibration plot ranging from 1.0 × 10^?6 to 8.0 × 10^?4 m with a detection limit of 1.3 × 10^?7 m for D‐PA. Finally, the proposed method was applied to the determination of D‐PA in a D‐PA capsule. Copyright © 2012 John Wiley & Sons, Ltd.     

Highly Selective and Sensitive Triiodide PVC‐Membrane Electrode Based on a New Charge‐Transfer Complex of Bis(2,4‐Dimethoxybenzaldehyde)butane‐2,3‐Dihydrazone with Iodine

In this work, a highly selective membrane triiodide sensor based on a new charge‐transfer complex of bis(2,4‐dimethoxybenzaldehyde)butane‐2,3‐dihydrazone with iodine (Iodide Charge Transfer complex: ICT) as membrane carrier is introduced. The influences of five different solvent mediators on sensitivity and selectivity of the proposed sensor were considered. The best performance was obtained with the membrane composition containing 30% poly (vinyl chloride), 63% DBP, 5% ICT and 2% HTAB. The electrode shows a Nernstian behavior over a very wide triiodide ion concentration range (1.0 × 10^?7‐1.0 × 10^?2 M), and a detection limit value of 8.0 × 10^?8 M. The effect of pH on the potentiometric response of the sensor was also studied, and it was found that the response of the electrode is independent of the pH of the solution in the pH range of 4.0–10. The proposed sensor has a very fast response time (< 12 s), and good selectivities relative to a wide variety of common inorganic and organic anions, including iodide, acetate, bromide, chloride, fluoride, nitrite, nitrate, sulfite, sulfate, cyanide and thiocyanate. In fact the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for triiodide ion. The proposed membrane sensor can be used for at least 6 months without any divergence in the potentials. The electrode was successfully applied as an indicator electrode in the titration of triiodide with thiosulfate ion.     

Immobilization of Enzymes on the Nano‐Au Film Modified Glassy Carbon Electrode for the Determination of Hydrogen Peroxide and Glucose

A new enzyme‐based amperometric biosensor for hydrogen peroxide was developed relying on the efficient immobilization of horseradish peroxidase (HRP) to a nano‐scaled particulate gold (nano‐Au) film modified glassy carbon electrode (GC). The nano‐Au film was obtained by a chitosan film which was first formed on the surface of GC. The high affinity of chitosan for nano‐Au associated with its amino groups resulted in the formation of nano‐Au film on the surface of GC. The film formed served as an intermediator to retain high efficient and stable immobilization of the enzyme. H₂O₂ was detected using hydroquinone as an electron mediator to transfer electrons between the electrode and HRP. The HRP immobilized on nano‐Au film maintained excellent electrocatalytical activity to the reduction of H₂O₂. The experimental parameters such as the operating potential of the working electrode, mediator concentration and pH of background electrolyte were optimized for best analytical performance of amperometry. The linear range of detection for H₂O₂ is from 6.1×10^?6 to 1.8×10^?3 mol L^?1 with a detection limit of 6.1 μmol L^?1 based on signal/noise=3. The proposed HRP enzyme sensor has the features of high sensitivity (0.25 Almol^?1cm^?2), fast response time (t_90%≤10 s) and a long‐term stability (>1 month). As an extension, glucose oxidase (GOD) was chemically bound to HRP‐modified electrode. A GOD/HRP bienzyme‐modified electrode formed in this way can be applied to the determination of glucose with satisfactory performance.