Sensitive detection of potassium ion using Prussian blue nanotube sensor

A model K⁺ sensor using Prussian blue nanotubes is fabricated by electrochemical deposition of Prussian blue (PB) within the nanochannels of a porous metal-coated membrane with partially covered pore openings. The PB nanotube sensor exhibits excellent stability giving reproducible peak potentials up to 500 measurement cycles, a very low detection limit of 2.0 × 10⁻⁸ M and extremely wide logarithmic linear ranges between 5.0 × 10⁻⁸–7.0 × 10⁻⁴ M and 7.0 × 10⁻⁴–1.0 M. Negligible interferences by Na⁺, Mg²⁺ and Ca²⁺ are observed and a rapid analysis time of 30 s is readily achieved. The ease of electrodeposition, high stability of PB nanotubes and outstanding analytical performance which surpasses conventional PB voltammetric and potentiometric sensors demonstrates potential sensing applications including ion sensors and biosensors using PB and other metal hexacyanoferrate nanotubes.     

Palladized aluminum electrode covered by Prussian blue film as an effective transducer for electrocatalytic oxidation and hydrodynamic amperometry of N-acetyl-cysteine and glutathione

The mediated oxidation of N-acetyl cysteine (NAC) and glutathione (GL) at the palladized aluminum electrode modified by Prussian blue film (PB/Pd–Al) is described. The catalytic activity of PB/Pd–Al was explored in terms of Fe^III[Fe^III(CN)₆]/Fe^III[Fe^II(CN)₆]¹⁻ system by taking advantage of the metallic palladium layer inserted between PB film and Al, as an electron-transfer bridge. The best mediated oxidation of NAC and GL on the PB/Pd–Al electrode was achieved in 0.5 M KNO₃ + 0.2 M potassium acetate of pH 2. The mechanism and kinetics of the catalytic oxidation reactions of the both compounds were monitored by cyclic voltammetry and chronoamperometry. The charge transfer-rate limiting step as well as overall oxidation reaction of NAC or GL is found to be a one-electron abstraction. The values of transfer coefficients α, catalytic rate constant k and diffusion coefficient D are 0.5, 3.2 × 10² M⁻¹ s⁻¹ and 2.45 × 10⁻⁵ cm² s⁻¹ for NAC and 0.5, 2.1 × 10² M⁻¹ s⁻¹ and 3.7 × 10⁻⁵ cm² s⁻¹ for GL, respectively. The modifying layers on the Pd–Al substrate have reproducible behavior and a high level of stability in the electrolyte solutions. The modified electrode is exploited for hydrodynamic amperometry of NAC and GL. The amperometric calibration graph is linear in concentration ranges 2 × 10⁻⁶–40 × 10⁻⁶ for NAC and 5 × 10⁻⁷–18 × 10⁻⁶ M for GL and the detection limits are 5.4 × 10⁻⁷ and 4.6 × 10⁻⁷ M, respectively.     

A new hydrogen peroxide biosensor based on gold nanoelectrode ensembles/multiwalled carbon nanotubes/chitosan film-modified electrode

Gold nanoelectrode ensembles were produced by electrodeposition using multiwalled carbon nanotubes (MWNTs) as template. A new third generation amperometric biosensor for hydrogen peroxide was developed based on adsorption of horseradish peroxidase (HRP) at the glassy carbon (GC) electrode modified with Au nanoelectrode ensembles/multiwalled carbon nanotubes/chitosan film. The resulting HRP biosensor offered an excellent detection for hydrogen peroxide at −0.11 V with a linear response range of 2.08 × 10⁻⁷ to 7.6 × 10⁻³ M with a correlation coefficient of 0.998, and response time <5 s. The detection limit was 1.02 × 10⁻⁷ M at 3σ. The biosensor displays rapid response, expanded linear response range, and excellent repeatability. The simple and fast fabrication of the sensor makes it superior to other techniques.     

A Prussian blue-based flow-through renewable surface optosensor for analysis of ascorbic acid

Ascorbic acid is determined by a simple Bead Injection Spectroscopy–Flow Injection Analysis (BIS–FIA) system with spectrophotometric detection. The sensor is based on the decrease of absorbance obtained (720 nm) when Prussian blue (PB) is reduced by ascorbic acid. Commercial available flow-cell (Hellma 138-OS) is used and an appropriate volume of homogeneous bead suspension of Sephadex QAE A-25 was injected to fill this flow-cell for each measurement. The chromogenic reagent (PB) is injected into the carrier and immobilized on beads. When sample is injected, reaching the bead surface where PB is sorbed, ascorbic acid converts it to Prussian white form, which is transparent, producing the discoloration of the detection zone. At the end of the analysis, beads are discarded by reversing the flow and instantaneously transported out of the system.The calibration graph was linear over the range 5.1×10⁻⁶–6.8×10⁻⁵ M. The detection limit and RSD (%) were 4.5×10⁻⁷ M and 5.0%, respectively, using 800 μl of sample volume. This method is highly selective in the presence of other species that are normally encountered with the analyte. The sensor was applied satisfactorily to the determination ascorbic acid in fruit juices, pharmaceuticals, sweets and conservative liquids.     

Electroanalysis of myoglobin and hemoglobin with a boron-doped diamond electrode

The electrochemical behavior of myoglobin (Mb) and hemoglobin (Hb) was investigated with a boron-doped diamond (BDD) electrode by cyclic voltammetry. In acetate buffer solutions, the oxygen reduction at the BDD electrode showed a very high overpotential while the reduction of Mb or Hb was observed in the more positive potential region. Owing to the electrocatalytic reaction of O₂ and the participation of H⁺ following the electrochemical reduction of ferric proteins, the voltammetric responses for Mb and Hb on the BDD electrode in the negative going scans became remarkable in acidic buffer solutions in air. The peak current was linearly proportional to the concentration of Mb in the range 1×10⁻⁶–2×10⁻⁵ M or the concentration of Hb from 1×10⁻⁶ to 1×10⁻⁵ M.     

基于树状高分子固定DNA的电化学生物传感器的研究

用电化学氧化法使玻碳电极表面氧化生成羧基,利用偶联活化试剂将1.0G树状高分子(PAMAM)固定在玻碳电极表面,并通过共价结合固定ssDNA。以亚甲基蓝为指示剂,采用循环伏安法、示差脉冲伏安法等电化学方法对DNA电化学生物传感器进行了表征。结果发现,通过亚甲基蓝与双链dsDNA作用的氧化还原电流的变化,可以识别和定量检测溶液中互补的ssDNA片段。经过条件优化,本法测定DNA的浓度线性范围为2×10-9～2×10-7mol/L,检出限为1×10-9mol/L。     

C60 trianion-mediated electrocatalysis and amperometric sensing of hydrogen peroxide

Heterogeneous electrocatalytic reduction of hydrogen peroxide (H₂O₂) by C₆₀ is reported for the first time. C₆₀ is embedded in tetraoctylammonium bromide (TOAB) film and is characterized by scanning electron microscopy and cyclic voltammetry. Electrocatalytic studies show that the trianion of C₆₀ mediates the electrocatalytic reduction of H₂O₂ in aqueous solution containing 0.1 M KCl. Application of such film modified electrode as an amperometric sensor for H₂O₂ determination is also examined. The sensor shows a fast response within 1 s and a linear response is obtained (R = 0.9986) in the concentration range from 3.33 × 10⁻⁵ to 2.05 × 10⁻³ mol L⁻¹ for H₂O₂, with the detection limit of 2 × 10⁻⁵ mol L⁻¹ and the sensitivity of 1.65 μA mM⁻¹. A good repeatability and stability is shown for the sensor during the experiment.     

Indirect kinetic microdetermination of oxalate, citrate, and fluoride ions

An indirect catalytic method for the separate microdetermination of oxalate, citrate, and fluoride ions is described. The method is based on the inhibition action of oxalate, citrate, and fluoride ions on the catalytic oxidation reaction of 2,4-diaminophenol-hydrogen peroxide by iron(III).Procedures for the determination of 1.76 × 10⁻² to 17.6 × 10⁻² μg/ml for oxalate ion, 3.78 × 10⁻² to 30.24 × 10⁻² μg/ml for citrate ion, and 0.38 to 4.18 μg/ml for fluoride ion are given.Quantities of 1.76 × 10⁻² to 17.6 × 10⁻² μg/ml for oxalate ion, 3.78 × 10⁻² to 30.24 × 10⁻² μg/ml for citrate ion, and 0.38 to 4.18 μg/ml for fluoride ion could be determinated with a relative error of about 1–3.5% for oxalate and citrate ions and 1–2% for fluoride ion.     

Synthesis,characterization and the electrocatalytic application of prussian blue/titanate nanotubes nanocomposite

A novel kind of nanocomposite, titanate nanotubes (TNTs) decorated by electroactive Prussian blue (PB), was fabricated by a simple chemical method. The as-prepared nanocomposite was characterized by XRD, XPS, TEM, FT-IR and Cyclic voltammetry (CV). Experimental results revealed that PB was adsorbed on the surface of TNTs, and the adsorption capacity of TNTs was stronger than that of anatase-type TiO₂ powder (TNP). The PB-TNTs nanocomposite was modified onto a glassy carbon electrode and the electrode showed excellent electroactivity. The modified electrode also exhibited outstanding electrocatalytic activity towards the reduction of hydrogen peroxide and can serve as an amperometric sensor for H₂O₂ detection. The sensor fabricated by casting Nafion (NF) above the PB-TNTs composite film (NF/PB-TNTs/GCE) showed two linear ranges of 2 × 10^?5–5 × 10^?4 M and 2 × 10^?3–7 × 10^?3 M, with a detection limit of 1 × 10^?6 M. Furthermore, PB-TNTs modified electrode with Nafion (NF/PB-TNTs/GCE) showed wider linear range and better stability compared with PB-TNTs modified electrode without Nafion (PB-TNTs/GCE) and PB modified electrode with Nafion (NF/PB/GCE).     

Catalytic microdetermination of iron

A reaction rate method is described for the microdetermination of iron. The method is based on the catalytic action of iron on the reaction of 2,4-diaminophenol with hydrogen peroxide. The effect of reagent concentration is studied and the maximum tolerable amounts of interfering ions are determined. Procedures for the determination of 2.8 × 10⁻³ to 2.8 × 10⁻² μg/ml are given.Quantities of 2.8 × 10⁻³ to 2.8 × 10⁻² μg/ml could be determinated with a relative error of about 2%.     

Application ofo-Hydroxyphenylfluorone as a Fluorogenic Indicator to the Determination of Hydrogen Peroxide and Oxidase Substrates Based on the Catalytic Effect of Hemin

A highly sensitive fluorescence quenching method has been developed for selective determination of hydrogen peroxide based on the catalytic effect of hemin on theo-hydroxyphenylfluorone (a new fluorogenic substrate) and hydrogen peroxide system. Under optimum conditions, the calibration graph was linear over the range 0–1.0 × 10⁻⁶mol/liter hydrogen peroxide, with a limit of detection of 8.0 × 10⁻⁹mol/liter in a 10-min reaction period. It can easily be incorporated into the determination of biochemical substances that produce hydrogen peroxide under catalytic oxidation by their oxidase. This possibility has been tested for the determination of glucose in human sera as an example.     

Voltammetric determination of quercetin at a multi-walled carbon nanotubes paste electrode

Quercetin can effectively accumulate at multi-walled carbon nanotubes-paraffin oil paste electrodes (CNTPE) and cause a sensitive anodic peak at around 0.32 V (vs. SCE) in a 0.10 M phosphate buffer solution (pH = 4.0). Under optimized conditions, the anodic peak current is linear to quercetin concentration in the ranges of 2.0 × 10^− 9−1.0 × 10^− 7 M and 1.0 × 10^− 7−2.0 × 10^− 5 M, and the regression equations are i_p (μA) = 0.0017 + 0.928c (μM, r = 0.999) and i_p (μA) = 0.183 + 0.0731c (μM, r = 0.995), respectively. This paste electrode can be regenerated by repetitively cycling in a blank solution for about 2 min. A 1.0 × 10^− 6 M quercetin solution is measured for 10 times using the same electrode regenerated after every determination, and the relative standard deviation of the peak current is 1.7%. The method has been applied to the determination of quercetin in hydrolysate product of rutin and the recovery is 99.2–102.6%. In comparison with graphite paste electrode, carbon nanotubes-nujol paste electrode and carbon nanotubes casting film modified glassy carbon electrode, the CNTPE gives higher ratio of signal to background current and better defined voltammetric peak.     

Preparation of L-Cys–Au colloid self-assembled nanoarray electrode based on the microporous aluminium anodic oxide film and its application to the measurement of dopamine

A novel method for fabricating a nanoarray electrode combining the template technique with the self-assembled approach was developed. The glassy carbon electrode was modified with the Au nanoarray using micropores of aluminum anodic film as template. Then, the Au nanoarray electrode was self-assembled with L-cysteine (L-Cys) and gold colloid, respectively. In order to evaluate the electrochemical characteristics of L-Cys–Au colloid self-assembled nanoarray electrode, was chosen as molecule probe and cyclic voltammetry was used. In addition, the functional nanoarray electrode was applied to measuring dopamine (DA). The resulting L-Cys–Au colloid self-assembled nanoarray electrode demonstrated that the linear calibration range extended over three orders of magnitude of DA concentrations (1.0 × 10⁻⁹–1.0 × 10⁻⁶ mol/L) and the detection limit was 5.0 × 10⁻¹⁰ mol/L.     

Effect of Various Deposition Techniques,Electrode Materials and Posttreatment with Tetrabutylammonium and Tetrabutylphosphonium Salts on the Electrochemical Behavior and Stability of Various Prussian Blue Modified Electrodes

The effect of various deposition techniques, electrode materials and posttreatment with tetrabutylammonium and tetrabutylphosphonium salts on the electrochemical behavior and stability of various Prussian blue (PB) modified electrodes, namely PB modified glassy carbon electrodes, silicate‐film supported PB modified glassy carbon electrodes, PB‐doped silicate glassy carbon electrodes, PB modified carbon ceramic electrodes using electrochemical deposition and PB modified carbon ceramic electrodes using chemical deposition is reported. Cyclic voltammetry and amperometric measurements of hydrogen peroxide were performed in a flow injection system while the carrier phosphate buffer (pH 7.0) with a flow rate of 0.8 mL min^?1 was propelled into the electrochemical flow through cell housing the PB modified working electrode as well as an Ag|AgCl|0.1 M KCl reference and a Pt auxiliary electrode. The results showed that the deposition procedure, electrode material and posttreatment with additional chemicals can significantly alter the stability and electrochemical behavior of the PB film. Among the studied PB modified electrodes, those based on carbon ceramic electrodes modified with a film of electropolymerized PB showed the best electrochemical stability.     

磁性普鲁士蓝纳米颗粒的合成及其化学修饰电极的制作

利用FeSO₄与FeCl₃合成了超细磁性Fe₃O₄纳米颗粒, 并进一步利用该纳米颗粒与铁氰酸钾在酸性溶液(pH～2)中的化学反应成功制备了一种新型的磁性普鲁士蓝纳米颗粒; 研究了该磁性颗粒的磁学性能, 通过磁力将其修饰于固体石蜡碳糊电极表面制成了化学修饰电极, 考察了该电极对过氧化氢的电催化还原及对水合肼的电催化氧化特性. 该化学修饰电极可对过氧化氢和水合肼进行测定, 线性范围分别为过氧化氢2×10^－6～5×10^－3 mol/L, 水合肼7.2×10^－7～3.6×10^－4 mol/L. 利用磁性普鲁士蓝纳米颗粒制得的修饰电极具有催化性能高、稳定性好、表面易更新等优点.     

A Uric Acid Biosensor Based on Langmuir-Blodgett Film as an Enzyme-Immobilizing Matrix

A uric acid biosensor was fabricated by the Langmuir–Blodgett (LB) technique to immobilize the uricase on chitosan/Prussian blue (CS/PB) prefunctionalized indium-tin oxide (ITO) electrode. The effects of ionic strengths, acidity of subphase, and uricase amount on the film were studied. The electrochemical properties of the uricase/n-nonadecanoic acid (UOx/NA) LB film proved that CS/PB was a good electro-catalyst for the reduction of hydrogen peroxide produced by enzymatic reaction of UOx, and protein molecules retained their natural electro-catalytic activity. The linear range of uric acid detection was from 5 × 10^?6 mol/L to 1.15 × 10^?3 mol/L with a detection limit of 1.8 × 10^?7 mol/L.     

Effect of various additives on the performance of a newly developed PVC based potentiometric sensor for anionic surfactants

A new poly(vinyl chloride) PVC membrane electrode to determine monomer concentrations of dodecylbenzenesulphonate ions (DBS⁻) based on a neutral ion-pair carrier complex of dodecyltrimethylammonium–dodecylbenzenesulphonate (DTA⁺–DBS⁻), is reported here. The electrode exhibits a slope of 51.25 mV per decade for DBS⁻ ions. The DBS⁻ ion selective electrode (ISE) can determine monomer units down to concentrations as low as 3.32 × 10⁻⁴ M. The effect of three kinds of additives, i.e. alcohols, glycols and triblock polymers on the performance of the surfactant selective electrode is studied systematically. The effect of foreign anions along with primary ions on the performance of ion-selective electrode is investigated in terms of potentiometric selectivity coefficients, which were determined using the fixed interference method (FIM) at 1.0 × 10⁻² M concentration of foreign anions. The sensor responds well to the surfactant ions in the presence of additives at lower concentration. The Gibbs free energy of micelle formation (ΔG_m) of sodium dodecylbenzenesulphonate (SDBS) in the presence of various additives is calculated and found to vary differently with respect to the increase in the amount of additives. The sensor worked in the acidic pH range with a short response time of 30 s. The lifetime of the sensor is more than three months. The sensor was further used to determine the amount of DBS⁻ in local detergents. This method of determining anionic surfactants was found to be quite accurate when compared with classical methods.     

Functionalization of graphene with electrodeposited Prussian blue towards amperometric sensing application

Prussian blue (PB) was grown compactly on graphene matrix by electrochemical deposition. The as-prepared PB-graphene modified glassy carbon electrode (PB-graphene/GCE) showed excellent electrocatalytic activity towards both the reduction of hydrogen peroxide and the oxidation of hydrazine, which could be attributed to the remarkable synergistic effect of graphene and PB. The PB-graphene/GCE showed sensitive response to H₂O₂ with a wide linear range of 10-1440 μM at 0.0 V, and to hydrazine with a wide linear range of 10-3000 μM at 0.35 V. The detection limit was 3 μM and 7 μM, respectively, and both of them had rapid response within 5 s to reach 95% steady state response. The wide linear range, good selectivity and long-time stability of the PB-graphene/GCE make it possible for the practical amperometric detection of hydrogen peroxide and hydrazine.     

Deposition of U(VI) at polypyrrole film electrodes modified with chlorophosphon azoIII

A modified Gr/ppy, chlorophosphon azoIII electrode was produced by the electrochemical polymerization of pyrrole and utilized for the deposition of uranyl ions. The polymerization rate of 1.43×10⁻¹ s⁻¹ was observed with the use of NBR, a precoating agent, which was 1.3 times faster than that without NBR. The amount of deposited uranyl ions determined by QCM was 1.12×10¹⁸ molecule cm⁻² when the polymerized ppy was 1.70 C cm⁻². The value for deposited uranyl ion was 2.68 times larger than that determined by the area of oxidation wave in CV, meaning that QCM might be the method of the choice for the investigation of uranyl ion deposition of a polymer modified electrode. The impedance of the ppy modified electrode increased with the consecutive modification of Gr/ppy,AzoIII,UO⁺ and the resistance for the electron transfer was 1.32 kΩ for the ppy-only electrode, 9.43 kΩ for AsoIII modification, and 11.82 kΩ for the deposition of the uranyl ion. The conductive process for Gr/ppy was diffusion controlled, however, for Gr/ppy,azoIII,UO⁺, it was thought to be the combination of ion doping process (low frequency region) and the electron transfer of the ppy film (high frequency region).     

Fabrication of a template-synthesized gold nanorod-modified electrode for the detection of dopamine in the presence of ascorbic acid

Gold nanorods (GNRs) with suitable aspect ratio were synthesized with a template technique and then dispersed in a saturated sodium citrate solution by ultrasonication to form a GNR suspension. A GNR-modified electrode was fabricated using the GNR suspension. The oxidation of dopamine at the GNR/GC electrode exhibited surprisingly high electrocatalytic activity and adsorption-controlled characteristics. Square-wave voltammetry was used to detect dopamine. At the GNR/GC electrode, the linear concentration range of DA is from 1 × 10⁻⁸ M to 1 × 10⁻⁷ M and the detection limit (s/n = 3) is as low as 5.5 × 10⁻⁹ M. The current sensitivity is 3.280 μA/μM, and 1000-fold ascorbic acid (AA) cannot interfere with the determination of DA. All these performances are greatly superior to those of the bare GC electrode.