活性炭电极材料的表面改性和性能

以硝酸、双氧水、氨水三种化学试剂分别对活性炭进行表面改性, 用N2吸附法和FTIR表征炭材料改性前后孔结构和表面官能团的变化. 制备了以改性活性炭为电极材料, KOH溶液为电解质的模拟双电层电容器. 用恒流充放电、循环伏安、交流阻抗等方法考察了双电层电容器的电化学性能. 结果表明, 改性活性炭比表面积和平均孔径有所降低, 并且在炭材料表面引入了含氧或含氮官能团, 如—OH、>CO、—NH2等, 使炭材料的润湿性增强、电阻减小、电化学性能显著提高. 用65%硝酸改性后炭材料的比容量最高达到250 F·g-1, 比原样炭提高了72.4%; 实验电容器的漏电流急剧下降, 只有3-18 μA, 为原来电容器的漏电流(371 μA)的0.8%-4.9%.     

隔膜对双电层电容器和混合型电池-超级电容器的电化学性能的影响

隔膜是双电层电容器和混合型电池-超级电容器等电化学储能器件的重要组成元件.本文采用1 mol?L-1四乙基四氟硼酸铵的丙烯碳酸酯电解液制备了基于活性炭的扣式双电层电容器,并采用1 mol?L-1六氟磷酸锂锂离子电解液制备了(LiNi0.5Co0.2Mn0.3O2+活性炭)/石墨体系的混合型电池-超级电容器.研究了不同类型隔膜的物理化学性能,以及其对双电层电容器和混合型电池-超级电容器的电化学性能的影响.四种隔膜分别是无纺布聚丙烯毡、多孔聚丙烯薄膜、Al2O3涂层的聚丙烯薄膜和纤维素纸隔膜.进行了表面形貌、差示扫描量热、电解液吸液量和表观接触角测试表征.电化学测试表明,采用纤维素隔膜的双电层电容器具有最高的比电容和更优的倍率性能,电容器的自放电性能差别不大.而对于混合型电池-超级电容器,采用聚丙烯薄膜和无纺布聚丙烯毡隔膜器件的比容量比其它器件约高20%,且采用纤维素隔膜的器件自放电率最高.     

Construction of label-free electrochemical immunosensor on mesoporous carbon nanospheres for breast cancer susceptibility gene

In this contribution, mesoporous carbon nanospheres (MCN) were used to fabricate a label-free electrochemical immunosensor for breast cancer susceptibility gene (BRCAl). The detection platform was constructed by conjugation of anti-BRCA1 on glassy carbon electrodes which were modified by mesoporous carbon nanospheres–toluidine blue nanocomposite (MCN–TB)/room temperature ionic-liquid (RTIL) composited film. TB was adsorbed onto MCN and acted as a redox probe. The electroactivity of TB was greatly enhanced in the presence of MCN. The good conductivity of MCN and BMIM·BF₄ could promote the electron transfer and thus enhance the detection sensitivity. Moreover, the large surface area of MCN and the protein-binding properties of BMIM·BF₄ could greatly increase the antibody loading. The specific antibody–antigen immunoreaction on the electrode surface resulted in a decrease of amperometric signal of the electrode. Under optimized conditions, the amperometric signal decreased linearly with BRCAl concentration in the range of 0.01–15 ng mL⁻¹ with a low detection limit of 3.97 pg mL⁻¹. The immunosensor exhibits high sensitivity, good selectivity and stability.     

Stripping voltammetric determination of Cd(II) based on multiwalled carbon nanotube functionalized with 1-(2-pyridylazo)-2-naphthol

The present work has focused on the modification of multiwalled carbon nanotube with a ligand,l-（2-pyridylazo）-2-naphthol, and its potential application for the development of a new,simple and selective modified glassy carbon electrode for stripping voltammetric determination of Cd（Ⅱ）.The analytical curve for Cd（Ⅱ） ions covered the linear range varying from 0.8 up to 220.4μgL^-1.The limit of detection was found to be 0.1μgL^-1,while the relative standard deviation（RSD） at 50.0μgL^-1 was 1.8%（n=5）.This modified electrode was successfully applied for determination of Cd（Ⅱ） in some water samples.     

Determination of citrate in tablets and of oxytetracycline in serum using europium (III) luminescence

A direct method for the determination of citrate and oxytetracycline in samples containing complex matrices like tablets or serum has been developed using the luminescence of the ternary complex formed with Eu(III) ions. The triplet-state energy level of oxytetracycline (OxTc), the excitation maximum (412 nm) and the luminescence lifetime of Eu-OxTc (58 μs) were determined. A 17-fold luminescence enhancement at 615 nm occurs upon addition of citrate within a short 5-min incubation time at neutral pH. This is accompanied by a threefold increase of the luminescence decay time. The optimal conditions for determination of OxTc are equal concentrations of Eu (III) and citrate (C = 1 · 10^− 4 mol L^− 1) and pH 7.2. For determination of citrate, the optimal concentrations of Eu(III) and OxTc are 1 : 0.5 (C_Eu = 1 · 10^− 4 mol L^− 1, C_OxTc = 5 · 10^− 5 mol L^− 1) at pH 7.2. The linear range for determination of OxTc in serum is 0.25-250 μg mL^− 1, and for citrate in tablets from 0.5 to 10.0 μg mL^− 1 (2.3 · 10^− 6- 4 · 10^− 5 mol L^− 1). The detection limit was 0.1 μg mL^− 1 for OxTc and 0.2 μg mL^− 1 (1 · 10^-6 mol L^− 1) for citrate, respectively. A comparison of the new method with other methods for determination of citrate is given.     

Heteroatom‐Doped Porous Carbon Nanosheets: General Preparation and Enhanced Capacitive Properties

High‐performance electrical double‐layer capacitors (EDLCs) require carbon electrode materials with high specific surface area, short ion‐diffusion pathways, and outstanding electrical conductivity. Herein, a general approach combing the molten‐salt method and chemical activation to prepare N‐doped carbon nanosheets with high surface area (654 m² g^?1) and adjustable porous structure is presented. Owing to their structural features, the N‐doped carbon nanosheets exhibited superior capacitive performance, demonstrated by a maximum capacitance of 243 F g^?1 (area‐normalized capacitance up to 37 μF cm^?2) at a current density of 0.5 A g^?1 in aqueous electrolyte, high rate capability (179 F g^?1 at 20 A g^?1), and excellent cycle stability. This method provides a new route to prepare porous and heteroatom‐doped carbon nanosheets for high‐performance EDLCs, which could also be extended to other polymer precursors and even waste biomass.     

Electrosorption of Os(III)-complex at single-wall carbon nanotubes immobilized on a glassy carbon electrode: application to nanomolar detection of bromate, periodate and iodate

A simple procedure was developed to prepare a glassy carbon electrode modified with single-wall carbon nanotubes (SWCNTs) and Os(III)-complex. The glassy carbon (GC) electrode modified with CNTs was immersed into Os(III)-complex solution (direct deposition) for a short period of time (60 s). 1,4,8,12-Tetraazacyclotetradecane osmium(III) chloride, (Os(III)LCl₂)·ClO₄, irreversibly and strongly adsorbed on SWCNTs immobilized on the surface of GC electrode. Cyclic voltammograms of the Os(III)-complex-incorporated-SWCNTs indicate a pair of well defined and nearly reversible redox couple with surface confined characteristic at wide pH range (1-8). The surface coverage (Γ) and charge transfer rate constant (k_s) of the immobilized Os-complex on SWCNTs were 3.07 × 10⁻⁹ mol cm⁻², 5.5 (±0.2) s⁻¹, 2.94 × 10⁻⁹ mol cm⁻², 7.3 (±0.3) s⁻¹ at buffer solution with pH 2 and 7, respectively, indicate high loading ability of SWCNTs for Os(III) complex and great facilitation of the electron transfer between electroactive redox center and carbon nanotubes immobilized on the electrode surface. Modified electrodes showed higher electrocatalytic activity toward reduction of BrO₃⁻, IO₃⁻ and IO₄⁻ in acidic solutions. The catalytic rate constants for catalytic reduction bromate, periodate and iodate were 3.79 (±0.2) × 10³, 7.32 (±0.2) × 10³ and 1.75 (±0.2) × 10³ M⁻¹ s ⁻¹, respectively. The hydrodynamic amperometry of rotating modified electrode at constant potential (0.3 V) was used for nanomolar detection of selected analytes. Excellent electrochemical reversibility of the redox couple, good reproducibility, high stability, low detection limit, long life time, fast amperometric response time, wide linear concentration range, technical simplicity and possibility of rapid preparation are great advantage of this sensor.     

Detection of Aeromonas hydrophila DNA oligonucleotide sequence using a biosensor design based on Ceria nanoparticles decorated reduced graphene oxide and Fast Fourier transform square wave voltammetry

A new strategy was introduced for ssDNA immobilization on a modified glassy carbon electrode. The electrode surface was modified using polyaniline and chemically reduced graphene oxide decorated cerium oxide nanoparticles (CeO₂NPs-RGO). A single-stranded DNA (ssDNA) probe was immobilized on the modified electrode surface. Fast Fourier transform square wave voltammetry (FFT-SWV) was applied as detection technique and [Ru(bpy)₃]^2+/3+ redox signal was used as electrochemical marker. The hybridization of ssDNA with its complementary target caused a dramatic decrease in [Ru(bpy)₃]^2+/3+ FFT-SW signal. The proposed electrochemical biosensor was able to detect Aeromonas hydrophila DNA oligonucleotide sequence encoding aerolysin protein. Under optimal conditions, the biosensor showed excellent selectivity toward complementary sequence in comparison with noncomplementary and two-base mismatch sequences. The dynamic linear range of this electrochemical DNA biosensor for detecting 20-mer oligonucleotide sequence of A. hydrophila was from 1 × 10⁻¹⁵ to 1 × 10⁻⁸ mol L⁻¹. The proposed biosensor was successfully applied for the detection of DNA extracted from A. hydrophila in fish pond water up to 0.01 μg mL⁻¹ with RSD of 5%. Besides, molecular docking was applied to consider the [Ru(bpy)₃]^2+/3+ interaction with ssDNA before and after hybridization.     

Dispersion of multi-wall carbon nanotubes in polyhistidine: Characterization and analytical applications

We report for the first time the use of polyhistidine (Polyhis) to efficiently disperse multiwall carbon nanotubes (MWCNTs). The optimum dispersion MWCNT–Polyhis was obtained by sonicating for 30 min 1.0 mg mL⁻¹ MWCNTs in 0.25 mg mL⁻¹ Polyhis solution prepared in 75:25 (v/v) ethanol/0.200 M acetate buffer solution pH 5.00. The dispersion was characterized by scanning electron microscopy, and by cyclic voltammetry and amperometry using ascorbic acid as redox marker. The modification of glassy carbon electrodes with MWCNT–Polyhis produces a drastic decrease in the overvoltage for the oxidation of ascorbic acid (580 mV) at variance with the response observed at glassy carbon electrodes modified just with Polyhis, where the charge transfer is more difficult due to the blocking effect of the polymer. The reproducibility for the sensitivities obtained after 10 successive calibration plots using the same surface was 6.3%. The MWCNT-modified glassy carbon electrode demonstrated to be highly stable since after 45 days storage at room temperature the response was 94.0% of the original. The glassy carbon electrode modified with MWCNT–Polyhis dispersion was successfully used to quantify dopamine or uric acid at nanomolar levels, even in the presence of large excess of ascorbic acid. Determinations of uric acid in human blood serum samples demonstrated a very good correlation with the value reported by Wienner laboratory.     

Synthesis and characterization of sulfate and dodecylbenzenesulfonate intercalated zinc-iron layered double hydroxides by one-step coprecipitation route

Inorganic sulfate- and organic dodecylbenzenesulfonate (DBS)-intercalated zinc-iron layered double hydroxides (LDHs) materials were prepared by one-step coprecipitation method from a mixed salt solutions containing Zn(II), Fe(II) and Fe(III) salts. The as-prepared samples have been characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), low-temperature nitrogen adsorption, scanning electron microscopy (SEM), inductively coupled plasma emission spectroscopy (ICP), and Mössbauer spectroscopy (MS). The XRD analyses demonstrate the typical LDH-like layered structural characteristics of both products. The room temperature MS results reveal the characteristics of both the Fe(II) and Fe(III) species for SO₄²⁻-containing product, while only the Fe(III) characteristic for DBS-containing one. The combination characterization results and Rietveld analysis illustrate that the SO₄²⁻-containing product possesses the Green Rust two (GR2)-like crystal structure with an approximate chemical composition of [Zn_0.435·Fe^II_0.094·Fe^III_0.470·(OH)₂]·(SO₄²⁻)_0.235·1.0H₂O, while the DBS-containing one exhibits the common LDH compound-like structure. The contact angle measurement indicates the evident hydrophobic properties of DBS-containing nanocomposite, compared with SO₄²⁻-containing product, due to the modification of the internal and external surface of LDHs by the organic hydrophobic chain of DBS.     

Influence of Hierarchical Porosity in Carbon Material on Electrocatalytic Property of Supported Pt Nanoparticles

The influence of hierarchical porosity on electrocatalytic property was investigated with Pt nanoparticles supported on three types of carbon materials, namely, commercial Vulcan XC-72, ordered mesoporous carbon CMK-5, and hierarchical carbon aerogel (HCA). The electrocatalytic activity of carbon supported Pt nanoparticles was verified by cyclic voltammetry in H₂SO₄ and CH₃OH solution. Pt/HCA presented superior performance with higher peak current (7.5 mA·cm⁻²) and electrochemical active area (128.0 m²·g⁻¹). This could be attributed to the carbon aerogel with continuous but nonperiodical mesopore structure, which facilitated dispersion of Pt nanoparticles and mass transport around reactants and products.     

Carbon Electrode Material with High Densities of Energy and Power

Activated carbon (AC) samples as electrode materials were prepared by means of simultaneous physical-chemical activation using walnut shells as precursors. The porosity and surface chemistry of the resultant AC samples were studied by the nitrogen adsorption at 77 K, and FTIR spectrum. The testing supercapacitors were assembled with resultant carbon electrode and electrolyte of 6 mol·L⁻¹ KOH solution. Their electrochemical properties were investigated by charge-discharge of constant current, cyclic voltammogram, impedance spectrum and so on. The results showed that the capacitor had low inner resistance, low leakage current, high stability, and capacitance retainability. The specific capacitance of AC increased with increasing BET specific surface area. The specific capacitance of the AC sample with a specific area of 1197 m²·g⁻¹ could be as high as 292 F·g⁻¹. At a discharge current of 80 mA, the corresponding specific energy density, power density, and maximum power of the supercapacitor are 7.3 Wh·kg⁻¹, 770 W·kg⁻¹, and 5.1 W·g⁻¹, respectively.     

Electrodeposition of the Charge-Transfer Complex Generated during Electrooxidation of o-Tolidine and the Effects of Coexisting Chondroitin Sulfate

The electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electrodeposition of the charge-transfer complex (CTC) generated during electrooxidation of o-tolidine (o-TD) in Britton-Robinson buffers and the effects of coexisting chondroitin sulfate (CS). A V-shaped frequency response to the cyclic voltammetric switching of o-TD indicated the precipitation and dissolution of the poorly soluble CTC, an oxidation intermediate, formed at the Au electrode during the redox switching of o-TD in a neutral or a weakly acidic medium (pH=4.07-6.50). The effects of potential scan rate, solution pH, and several supporting electrolytes were examined. The depth of the V-shaped frequency curves (-Δf_0V) was related to the supporting electrolyte used, with a decreasing sequence for −Δf_0V as 0.20 mol·L⁻¹ NaNO₃ > 0.20 mol·L⁻¹ NaClO₄ > 0.10 mol·L⁻¹ Na₂SO₄. The −Δf_0V response to the redox switching of the CTC/o-TD “couple” was enhanced by the introduction of CS because of the formation of the CTC-CS adduct, as also characterized and supported by UV-Vis and FTIR spectrophotometry. The molar ratio (x) of the CTC to CS in the adduct and the electrode-collection efficiency of the CTC (η) were estimated using EQCM. The values of −Δf_0V increased with the increase in CS concentration, with a linear range from 0.75 to 15.2 μmol·L⁻¹, and a detection limit down to 50 nmol·L⁻¹. The new method proposed for CS assay was characterized by a dynamically renewed surface of the detection electrode.     

Metal–Sulfur Linkages Achieved by Organic Tethering of Ruthenium Nanocrystals for Enhanced Electrochemical Nitrogen Reduction

Inspired by the metal–sulfur (M-S) linkages in the nitrogenase enzyme, here we show a surface modification strategy to modulate the electronic structure and improve the N₂ availability on a catalytic surface, which suppresses the hydrogen evolution reaction (HER) and improves the rate of NH₃ production. Ruthenium nanocrystals anchored on reduced graphene oxide (Ru/rGO) are modified with different aliphatic thiols to achieve M-S linkages. A high faradaic efficiency (11 %) with an improved NH₃ yield (50 μg h⁻¹ mg⁻¹) is achieved at −0.1 V vs. RHE in acidic conditions by using dodecanethiol. DFT calculations reveal intermediate N₂ adsorption and desorption of the product is achieved by electronic structure modification along with the suppression of the HER by surface modification. The modified catalyst shows excellent stability and recyclability for NH₃ production, as confirmed by rigorous control experiments including ¹⁵N isotope labeling experiments.     

Semi-online preconcentration of Cd, Mn and Pb on activated carbon for GFASS

This paper presents a method whereby trace elements in NH₄Cl-NH₃ medium are adsorbed on activated carbon in a micro-flow-injection (FI) semi-online sorbent extraction preconcentration system and then determined by graphite furnace atomic absorption spectrometry (GFAAS). The analytical performance of the proposed method for determining Cd, Mn and Pb was studied. A microcolumn packed with activated carbon was used as a preconcentration column (PCC). The metals to be determined were preconcentrated onto the column for 60 s and then rinsed with 0.02% (v/v) HNO₃ and eluted with 30 μl of 2 mol l⁻¹ HNO₃. Compared with the direct injection of 30 μl of aqueous sample solution, enrichment factor of 32, 26, and 21 and detection limits (3σ) of 0.4, 4.7, and 7.5 ng l⁻¹ for Cd, Mn and Pb, respectively, were obtained with 60 s sample loading at 3.0 ml min⁻¹ for sorbent extraction, 30 μl of eluate injection, and peak area measurement. The precisions (RSD, n=6) were 2.8% at the 0.05 μg l⁻¹ level for Cd, 3.0% at the 0.3 μg l⁻¹ level for Mn, and 3.1% at the 0.5 μg l⁻¹ level for Pb. The experimental results indicate that the procedure can eliminate the fundamental interferences caused by alkali and alkaline earth metals and the application of it to the determination of Cd, Mn and Pb in some water samples is successful.     

Accumulation and trace measurement of chloroquine drug at DNA-modified carbon paste electrode

The voltammetric behaviour of chloroquine was investigated at carbon paste and dsDNA-modified carbon paste electrodes in different buffer systems over a wide pH range using cyclic and differential pulse voltammetry. Chloroquine was oxidized in the pH range 2.0-11.0 yielding one irreversible main oxidation peak. A second peak was also observed only in the pH range 5.0-7.0. The modification of the carbon paste surface with dsDNA allowed a preconcentration process to take place for chloroquine such that higher sensitivity was achieved as compared with the bare surface. The response was characterized with respect to solution pH, ionic strength, accumulation time and potential, chloroquine concentration, and other variables. Stripping voltammetric response showed a linear calibration curve in the range 1.0 × 10⁻⁷ to 1.0 × 10⁻⁵ mol l⁻¹ with a detection limit of 3.0 × 10⁻⁸ mol l⁻¹ at the dsDNA-modified electrode. Application of the modified electrode to serum, without sample pretreatment, resulted in good recovery higher than 95% and the higher standard deviation was 3.0%.     

Fabrication of Glucose Biosensor Based on Encapsulation of Glucose‐Oxidase on Sol‐Gel Composite at the Surface of Glassy Carbon Electrode Modified with Carbon Nanotubes and Celestine Blue

A simple procedure was developed to prepare a glassy carbon electrode modified with multi walled carbon nanotubes (MWCNTs) and Celestin blue. Cyclic voltammograms of the modified electrode show stable and a well defined redox couple with surface confined characteristic at wide pH range (2–12). The formal potential of redox couple (E′) shifts linearly toward the negative direction with increasing solution pH. The surface coverage of Celestine blue immobilized on CNTs glassy carbon electrode was approximately 1.95×10^?10 mol cm^?2. The charge transfer coefficient (α) and heterogeneous electron transfer rate constants (k_s) for GC/MWCNTs/Celestine blue were 0.43 and 1.26 s^?1, respectively. The modified electrode show strong catalytic effect for reduction of hydrogen peroxide and oxygen at reduced overpotential. The glucose biosensor was fabricated by covering a thin film of sol‐gel composite containing glucose oxides (GOx) on the surface of Celestine blue /MWCNTs modified GC electrode. The biosensor can be used successfully for selective detection of glucose based on the decreasing of cathodic peak current of oxygen. The detection limit, sensitivity and liner calibration rang were 0.3 μM, 18.3 μA/mM and 10 μM–6.0 mM, respectively. The accuracy of the biosensor for glucose detection was evaluated by detection of glucose in a serum sample, using standard addition protocol. In addition biosensor can reach 90% of steady currents in about 3.0 sec and interference effect of the electroactive existing species (ascorbic acid–uric acid and acetaminophen) was eliminated. Furthermore, the apparent Michaelis–Menten constant 2.4 mM, of GOx on the nano composite exhibits excellent bioelectrocatalytic activity of immobilized enzyme toward glucose oxidation. Excellent electrochemical reversibility of redox couple, high stability, technically simple and possibility of preparation at short period of time are of great advantages of this procedure for modification of glucose biosensor.     

基于碳纳米管修饰电极的胆碱电化学发光生物传感器研制

在碳纳米管(CNTs)和K3Fe(CN)6修饰的铂电极上吸附固定胆碱氧化酶,以鲁米诺为发光试剂,研制了胆碱电化学发光(ECL)生物传感器.CNTs可有效提高电极表面的电荷传输能力、提高电极表面的生物相容性和对酶分子的固载能力;K3Fe(CN)6对酶活性具有激活作用,同时对H2O2增敏的鲁米诺ECL有增强作用,均有利于提...     

Voltammetric determination of mercury (II) in aqueous media using glassy carbon electrodes modified with novel calix[4]arene

A novel calix[4]arene derivative containing benzothiazole group was coated on glassy carbon electrode (GCE) and then applied to the recognition of mercury ion. Cyclic and square wave voltammetric results showed that the modified electrode selectively recognizes Hg²⁺ ion in aqueous media. A new anodic stripping peak at −0.3 V (vs. Ag/Ag⁺) can be obtained by scanning the potential from −0.6 to 0.6 V, and the peak currents are proportional to the Hg²⁺ concentration. The modified electrode in a 0.1 M H₂SO₄+0.01 M NaCl solution shows linear voltammetric response in the range of 25-300 μg l⁻¹ and detection limit of 5 μg l⁻¹ (ca. 2.5×10⁻⁸ M). This modified GCE does not present any significant interference from alkali, alkaline and transition metal ions except for Pb²⁺, Ag⁺ and Cu²⁺ ions. Only 500, 50 and 100-fold molar excess of Pb²⁺, Ag⁺ and Cu²⁺ ions, respectively, can lead to voltammetric response comparable with that of Hg²⁺. The proposed method was successfully applied to determine mercury in natural water.