Electrodeposited Silver Nanoparticles on Carbon Ionic Liquid Electrode for Electrocatalytic Sensing of Hydrogen Peroxide

Silver nanoparticles (narrowly dispersed in diameter) were electrodeposited on carbon ionic liquid electrode (CILE) surface using a two‐step potentiostatic method. Potentiostatic double pulse technique was used as a suitable and simple method for controlling the size and morphologies of silver nanoparticles electrodeposited on CILE. The obtained silver nanoparticles deposited on CILE surface showed excellent electrocatalytic activity (low overpotential of ?0.35 V vs. Ag/AgCl) towards reduction of hydrogen peroxide. A linear dynamic range of 2–200 μM with an experimental detection limit of 0.7 μM (S/N=3) and reproducibility of 4.1% (n=5) make the constructed sensor suitable for peroxide determination in aqueous solutions.     

基于新型二氧化锰-碳纳米管复合材料的高灵敏过氧化氢传感器

本文以多壁碳纳米管(MWCNTs)和KMnO4为原料,通过直接氧化还原反应合成了一种新型MnO2-C纳米复合材料,将其滴涂在玻碳(GC)电极表面,成功制备出一种非酶型H2O2传感器。采用循环伏安法和计时电流法研究了该传感器对H2O2的电催化氧化行为。实验结果表明,与GC电极和MWCNTs修饰电极相比,该电极对H2O2氧化显示出更好的催化活性。实验对影响电极性能的各种参数,包括pH值、工作电位及MnO2-C修饰量进行了探讨。在最佳实验条件下,传感器对H2O2响应的线性范围为5.0×10-7～0.2mol·L-1,检测限(S/N=3)为1.4×10-7 mol·L-1。该传感器选材新颖,制备方法简单,重现性好,稳定性和抗干扰能力强。     

Co2SnO4/Carbon Nanotubes Composites: A Novel Approach for Electrochemical Sensing of Hydrogen Peroxide

For the first time Co₂SnO₄ (CTO)/Carbon nanotubes (CNT) composites were prepared and used to modify glassy carbon electrodes for the amperometric determination of hydrogen peroxide. The catalytic activity of composites towards the oxidation of hydrogen peroxide was dependent on the quantity of CNT present in the composite and to the pH of the medium. The pure cobalt stannate phase with a ratio of 3 : 1 (CTO:CNT) exhibited the best catalytic activity towards hydrogen peroxide oxidation at low potentials (0.200 and 0.500 V). A linear relationship between current and hydrogen peroxide concentration was obtained with a sensitivity of 95 and 258 μA mM⁻¹ and a detection limit of 0.130 and 0.08 μM respectively.     

Monodisperse MFe2O4 (M = Fe, Co, Mn) nanoparticles

High-temperature solution phase reaction of iron(III) acetylacetonate, Fe(acac)(3), with 1,2-hexadecanediol in the presence of oleic acid and oleylamine leads to monodisperse magnetite (Fe(3)O(4)) nanoparticles. Similarly, reaction of Fe(acac)(3) and Co(acac)(2) or Mn(acac)(2) with the same diol results in monodisperse CoFe(2)O(4) or MnFe(2)O(4) nanoparticles. Particle diameter can be tuned from 3 to 20 nm by varying reaction conditions or by seed-mediated growth. The as-synthesized iron oxide nanoparticles have a cubic spinel structure as characterized by HRTEM, SAED, and XRD. Further, Fe(3)O(4) can be oxidized to Fe(2)O(3), as evidenced by XRD, NEXAFS spectroscopy, and SQUID magnetometry. The hydrophobic nanoparticles can be transformed into hydrophilic ones by adding bipolar surfactants, and aqueous nanoparticle dispersion is readily made. These iron oxide nanoparticles and their dispersions in various media have great potential in magnetic nanodevice and biomagnetic applications.     

Electrochemical CO2 and Proton Reduction by a Co(dithiacyclam) Complex

While [Ni(cyclam)]²⁺ and [Ni(dithiacyclam)]²⁺ complexes were shown to be potent electrocatalysts for the CO₂ conversion, their respective Co complexes hitherto received only little attention. Herein, we report on the Co^II complexes of the cyclam and dithiacyclam platform, describe their synthesis and reveal their rich solvent dependent coordination chemistry. We show that sulfur implementation into the cyclam moiety leads to a switch from a low spin Co^II complex in [Co(cyclam)]²⁺ to a high spin form in [Co(dithiacyclam)]²⁺. Notably, while both complexes are capable to perform the reduction of CO₂ to CO, H₂ formation is generally preferred. Along this line, the complexes were shown to enable proton reduction from acetic acid. However, in comparison to [Co(cyclam)]²⁺, the altered electronics make [Co(dithiacyclam)]²⁺ complexes prone to deposit on the glassy carbon working electrode over time leading to an overall low faradaic efficiency for the reduction of protons or CO₂.     

Enhanced Hydrogen Peroxide Sensing Based on Tetraruthenated Porphyrins/Nafion/Glassy Carbon‐modified Electrodes via Incorporating of Carbon Nanotubes

The incorporation of carbon nanotubes to a Nafion/tetraruthenated cobalt porphyrin/ glassy carbon electrode (GC/Nf/CoTRP vs GC/Nf/CNTCoTRP) enhanced the amperometric determination of hydrogen peroxide. Both electrodes produced a decrease in the overpotential required for the hydrogen peroxide oxidation in about 100 mV compared to glassy carbon under the same experimental conditions. Nevertheless, for GC/Nf/CNT/CoTRP, the increase in the current is remarkable. The GC/Nf/CoTRP modified electrode gave no significant analitycal signal for hydrogen peroxide reduction. Moreover, a great increase in current is observed with GC/Nf/CNT/CoTRP at ?150mV which suggests a significant increase in the sensitivity of the modified electrode. Scanning electrochemical microscopy (SECM) revealed an enhancement in the electroactivity of the GC/Nf/CNT/CoTRP modified electrode. This fact has been explained in terms of enhanced homogeneity of the electrodic surface as a consecuence of better dispersibility of CNT‐CoTRP produced by a Nafion polyelectrolyte.     

Electrodeposition of TiO2 Nanoparticles on Multiwalled Carbon Nanotube Arrays for Hydrogen Peroxide Sensing

In this work, an amperometric H₂O₂ sensor based on TiO₂/MWCNTs electrode is reported. TiO₂ nanoparticles were synthesized on vertically aligned multiwalled carbon nanotube (MWCNT) arrays by electrodeposition. The morphology of the TiO₂/MWCNTs was characterized by scanning electron microscopy (SEM). The electrochemical performance of the TiO₂/MWCNTs electrode for detection of H₂O₂ was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry. The TiO₂/MWCNTs electrode displays high electrocatalytic activity towards oxidation of H₂O₂ in 0.1 M phosphate buffer solution (PBS, pH 7.4). At an applied potential of +0.40 V, the TiO₂/MWCNTs electrode exhibits a linear dependence (R=0.998) in the H₂O₂ concentration up to 15.0×10^?3 M with a sensitivity of 13.4 μA mM^?1 and detection limit of 4.0×10^?7 M with signal/noise=3. The optimal response time is less than 5 s with addition of 1 mM H₂O₂. The TiO₂/MWCNTs electrode presents stable, high sensitivity and also exhibits fast amperometric response to the detection of H₂O₂, which is promising for the development of H₂O₂ sensor.     

Electrocatalytic Performances of Pure and Mixed Hexacyanoferrates of Cu and Pd for the Reduction of Hydrogen Peroxide

A study on the performances of mixed hexacyanoferrates of Cu and Pd (CuPdHCFs), potentiodynamically grown on glassy carbon surfaces, was carried out. Morphological (SEM‐EDX analysis) and electrochemical characterizations were performed, and the electrocatalytic ability of films with various compositions was tested by chronoamperometry. CuPdHCFs were found to display good electrocatalytic performances, with a maximum sensitivity of 45.3 mA M^?1 cm^?2 at 0.0 V vs. SCE (depending on the Cu and Pd ratio), against the value of 9.1 mA M^?1 cm^?2 obtained with pure copper hexacyanoferrate (CuHCF). Additionally, mixed hexacyanoferrates showed a higher pH and operational stability. The key role of Cu in Cu‐based hexacyanoferrates was investigated and highlighted.     

Isomorphous Catena Transition Metal Squarates [MII(C4O4)(dmso)2(OH2)2] (M = Co,Mn) and Magnetic Investigation into their Solid Solution M = CoxMn1–x

The crystal structures of two new isomorphous transition metal squarato complexes [M^II(C₄O₄)(dmso)₂(OH₂)₂] [M^II = Co^II (3d⁷), Mn^II (3d⁵); dmso = dimethylsulfoxide] and their magnetic properties are reported. The compounds feature two symmetrically independent chains, in which 1,3‐bridging squarato ligands connect cations in distorted octahedral surroundings of pseudo‐symmetry D_4h. From an equimolar solution of CoCl₂ · 6H₂O and MnCl₂ · 2H₂O a mixed‐metal coordination polymer crystallizes; it represents a solid solution and adopts the same structure as the corresponding monometallic compounds. The results of the diffraction experiment unambiguously proof the presence of both Co^II and Mn^II cations in either independent site albeit no precise ratio between the metal cations involved may be deduced from these findings. The difference in the magnetic properties between Co^II and Mn^II cations in the given ligand field has allowed us to establish their ratio in the solid solution more reliably than by X‐ray diffraction: Accounting for ligand field potential and spin‐orbit coupling of Co^II and regarding Mn^II as a pure spin system, the calculations yielded a fraction of 73 % Co^II in the mixed‐metal polymer. With respect to superexchange effects only weak antiferromagnetic interactions have been detected for the three coordination polymers.     

生物基碳包覆纳米材料(Mn,Co)的制备

提出了一种制备碳包覆纳米材料的新方法.以生物蛋白为前驱体材料，蛋白质肽链构成的空心结构作为合成碳包覆纳米材料的模板反应器;在热处理时，蛋白肽链发生分解,残留的碳作为碳源形成富勒烯类空心纳米材料的壳体，并将填充在蛋白质空心结构内部的金属材料包覆起来.以此技术制备了铁磁性金属锰和钴的碳包覆纳米级材料，初步验证是可行的.讨论了蛋白的矿化组装和蛋白的炭化反应机理.     

Effect of the Incorporation of Proteins on the Performance of Carbon Paste Electrodes Modified with Electrogenerated Magnetite Nanoparticles towards the Reduction of Hydrogen Peroxide

This work reports the effect of the incorporation of different proteins within carbon paste electrodes (CPE) modified with electrochemically synthesized magnetite nanoparticles (20 nm) on the electrochemical response towards hydrogen peroxide. Scanning electron microscopy images reveal that the proteins produce a more efficient dispersion of the nanoparticles within the composite. When CPE is modified with 5.0 % w/w magnetite and 5.0 % w/w albumin the sensitivity for hydrogen peroxide at ?0.100 V is enhanced 40 times and the charge transfer resistance significantly decreases. The increase in sensitivity and the decrease in R_ct was dependent on the nature of the protein.     

Simple Electrodeposition of Dendritic Pd Without Supporting Electrolyte and Its Electrocatalytic Activity Toward Oxygen Reduction and H2O2 Sensing

Metallic palladium (Pd) electrocatalysts for oxygen reduction and hydrogen peroxide (H₂O₂) oxidation/reduction are prepared via electroplating on a gold metal substrate from dilute (5 to 50 mM) aqueous K₂PdCl₄ solution. The best Pd catalyst layer possessing dendritic nanostructures is formed on the Au substrate surface from 50 mM Pd precursor solution (denoted as Pd‐50) without any additional salt, acid or Pd templating chemical species. The Pd‐50 consisted of nanostructured dendrites of polycrystalline Pd metal and micropores within the dendrites which provide high catalyst surface area and further facilitate reactant mass transport to the catalyst surface. The electrocatalytic activity of Pd‐50 proved to be better than that of a commercial Pt (Pt/C) in terms of lower overpotential for the onset and half‐wave potentials and a greater number of electrons (n) transferred. Furthermore, amperometric i–t curves of Pd‐50 for H₂O₂ electrochemical reaction show high sensitivities (822.2 and ?851.9 µA mM^?1 cm^?2) and low detection limits (1.1 and 7.91 µM) based on H₂O₂ oxidation H₂O₂ reduction, respectively, along with a fast response (<1 s).     

DNA-functionalized MFe2O4 (M = Fe, Co, or Mn) nanoparticles and their hybridization to DNA-functionalized surfaces

Magnetic MFe2O4 (M = Fe, Co, or Mn) nanoparticles with uniform diameters in the 4-20 nm range and with excellent material properties, reported previously, can be rendered soluble in water or aqueous buffers using a combination of alkylphosphonate surfactants and other surfactants such as ethoxylated fatty alcohols or phospholipids. Surfactant-modified oligonucleotides can be incorporated into the particles' organic shell. The particles can withstand salt concentrations up to 0.3 M, temperatures up to 90 degrees C, and various operations such as concentration to dryness, column or membrane separations, and electrophoresis. The particles can be selectively hybridized to DNA-functionalized gold surfaces with high coverages using a two-story monolayer structure. These particles may find valuable applications involving the magnetic detection of small numbers of biomolecules using spin valves, magnetic tunnel junctions, or other sensors.     

M(H2O)2(4,4′‐bipy)[C6H4(COO)2]·2H2O (M = Mn2+, Co2+) – Zwei isotype Koordinationspolymere mit Schichtstruktur

M(H₂O)₂(4,4′‐bipy)[C₆H₄(COO)₂]·2H₂O (M = Mn²⁺, Co²⁺) – Two Isotypic Coordination Polymers with Layered Structure Monoclinic single crystals of Mn(H₂O)₂(4,4′‐bipy)[C₆H₄(COO)₂]·2H₂O ( 1 ) and Co(H₂O)₂(4,4′‐bipy)[C₆H₄(COO)₂]· 2H₂O ( 2 ) have been prepared in aqueous solution at 80 °C. Space group P2/n (no. 13), Z = 2; 1 : a = 769.20(10), b = 1158.80(10), c = 1075.00(10) pm, β = 92.67(2)°, V = 0.9572(2) nm³; 2 : a = 761.18(9), b = 1135.69(9), c = 1080.89(9) pm, β = 92.276(7)°, V = 0.9337(2) nm³. M²⁺ (M = Mn, Co), which is situated on a twofold crystallographic axis, is coordinated in a moderately distorted octahedral fashion by two water molecules, two oxygen atoms of the phthalate anions and two nitrogen atoms of 4,4′‐biypyridine ( 1 : M–O 219.5(2), 220.1(2) pm, M–N 225.3(2), 227.2(2) pm; 2 : Co–O 212.7(2), 213.7(2) pm, Co–N 213.5(3), 214.9(3) pm). M²⁺ and [C₆H₄(COO)₂)]^2? build up chains, which are linked by 4,4′‐biyridine molecules to yield a two‐dimensional coordination polymer with layers parallel to (001).Thermogravimetric analysis in air of 1 indicated a loss of water of crystallization between 154 and 212 °C and in 2 between 169 and 222 °C.     

Preparation and Characterization of Electrodes Modified with Pyrrole Surfactant,Multiwalled Carbon Nanotubes and Metallophthalocyanines for the Electrochemical Detection of Thiols

Our aim was to prepare hybrid electrodes active towards the electrooxidation of thiols by the co‐immobilization of native carbon nanotubes (CNTs) and cobalt phthalocyanine (CoPc) from aqueous solutions. This strategy was adopted to avoid the oxidation of CNTs that can induce a modification of their exceptional properties. To do so, a hydrosoluble pyrrole surfactant was used to get homogeneous aqueous dispersions of CNTs and CoPc and to trap both materials on the electrode via the electropolymerization of the pyrrole surfactant. The hybrid electrodes exhibit a good electrocatalytic activity towards the oxidation of L ‐cysteine and glutathione. Their performances in terms of limit of detection (0.01 mM) are compatible with the detection of these thiols in biological samples.     

Microperoxidase-11 Modified Electrode and Its Electrocatalytic Activity on the Reduction of O2 and H2O2

Microperoxidase-11(MP-11) was immobilized on the surface of a silanized glass carbon electrode by means of the covalent bond with glutaraldehyde.The measurements of cyclic voltammetry demonstrated that the formal redox potential of immobilized MP-11 was -170mV.which is significantly more positive than that of MP-11 in a solution or immobilized on the surface of electrodes prepared with other methods.This MP-11 modified electrode showed a good electrocatalytic activity and stability for the reduction of oxygen and hydrogen peroxide.     

过氧化氢氧化桑色素动力学荧光法测定痕量钴(Ⅱ)

建立了以Co(Ⅱ)为催化剂,催化过氧化氢氧化桑色素,使其荧光减弱的催化动力学荧光法。在pH 10.70的Na2B4O7?10H2O - NaOH缓冲溶液中,痕量钴(Ⅱ)离子对0.24%的H2O2溶液氧化 4.0×10-7 mol/L的桑色素溶液有明显的催化作用。在最大波长处( λex/λem = 416.5 nm / 556.4 nm),体系的荧光强度在一定的浓度范围内与Co(Ⅱ)的浓度呈线性相关,线性范围为0.8～8.0 μg/L,检出限为0.14 μg/L。优化了体系的最佳条件,考察了体系的离子干扰情况,对灰钙土和分子筛样品进行了分析检测,回收率分别为95.0～110.0%和98.9%～101.9%。     

Electrochemical Sensing of Ascorbic Acid,Hydrogen Peroxide and Glucose by Bimetallic (Fe,Ni)−CNTs Composite Modified Electrode

In this research, bimetallic supported CNT modified electrode ( Fe,Ni/CNTs/GCE) has been developed for sensitive, stable and highly elctroactive sensing of glucose, ascorbic acid and hydrogen peroxide. Transition metals such as Iron (Fe) and Nickel (Ni) offer high electrical and thermal conductance, high active surface‐to‐volume ratio and presence of d‐band electrons gives enhanced electrocatalytic behavior. While, CNTs provide high surface area, stability and excellent conductivity. Synthesized material is characterized by SEM, EDS, XRD and FTIR to access morphology, elemental composition and structure. This unique combination is employed for the electrochemical sensing of ascorbic acid, glucose and hydrogen peroxide and different experimental parameters are optimized. Fe,Ni/CNTs/GCE shows good sensing efficiency at pH 7.4 which is ideally suitable for variety of analytes. The modified electrode also show good reproducibility and sensitivity under optimized conditions and can be reused upto 30 cycles without compromising the efficiency. With good linearity, reproducibility and limit of detection, this material possess significant potential as non‐enzymatic biosensor for variety of analytes.     

Oxidation of o‐phenylenediamine to 2,3‐diaminophenazine in the presence of cubic ferrites MFe2O4 (M = Mn,Co, Ni,Zn) and the application in colorimetric detection of H2O2

Metal ferrites nanocrystallites, MFe₂O₄ (M = Mn, Co, Ni, Zn) were prepared by coprecipitation method and characterized by a combination of physico‐chemical and spectroscopic techniques. MFe₂O₄ nanoparticles having particle size in the range 10–35 nm were tested as catalysts in the oxidation of o‐phenylenediamine (OPD) to 2,3–diaminophenazine (DAP) using hydrogen peroxide as oxidant at room temperature. Kinetic data was collected for the catalytic oxidation of OPD to DAP by monitoring the UV–vis absorbance at 415 nm and fit well to the Michaelis–Menten model yielding kinetic parameters K_m (Michaelis–Menten constant) and V_max (maximum rate of reaction). MnFe₂O₄ nanoparticles provide the highest catalytic activity in the oxidation of OPD to DAP at room temperature. A colorimetric method was developed based on the MnFe₂O₄/OPD system for the detection of H₂O₂ in reaction solution. The method has a detection limit of 30 μM for H₂O₂ and wide linear range.