Phosphomolybdic acid functionalized graphene loading copper nanoparticles modified electrodes for non-enzymatic electrochemical sensing of glucose

A sensitive non-enzymatic glucose electrochemical biosensor (Cu/PMo₁₂-GR/GCE) was developed based on the combination of copper nanoparticles (CuNPs) and phosphomolybdic acid functionalized graphene (PMo₁₂-GR). PMo₁₂-GR films were modified on the surface of glassy carbon electrode (GCE) through electrostatic self-assembly with the aid of poly diallyl dimethyl ammonium chloride (PDDA). Then CuNPs were successfully decorated onto the PMo₁₂-GR modified GCE through electrodeposition. The morphology of Cu/PMo₁₂-GR/GCE was characterized by scanning electron microscope (SEM). Cyclic voltammetry (CV) and chronoamperometry were used to investigate the electrochemical performances of the biosensor. The results indicated that the modified electrode displayed a synergistic effect of PMo₁₂-GR sheets and CuNPs towards the electro-oxidation of glucose in the alkaline solution. At the optimal detection potential of 0.50 V, the response towards glucose presented a linear response ranging from 0.10 μM to 1.0 mM with a detection limit of 3.0 × 10⁻² μM (S/N = 3). In addition, Cu/PMo₁₂-GR/GCE possessed a high selectivity, good reproducibility, excellent stability and acceptable recovery, which indicating the potential application in clinical field.     

Surface and chemical characteristics of platinum modified activated carbon electrodes and their electrochemical performance

Platinum (Pt) loaded activated carbons (ACs) were synthesized by the thermal decomposition of platinum (II) acetylacetonate (Pt(acac)₂) over chemically activated glucose-based biochar. The effect of Pt loading on surface area, pore characteristics, surface chemistry, chemical structure, and surface morphology were determined by various techniques. XPS studies proved the presence of metallic Pt⁰ on the AC surface. The graphitization degree of Pt loaded ACs were increased with the loaded Pt⁰ amount. The electrochemical performance of the Pt-loaded ACs (Pt@AC) was determined not only by the conventional three-electrode system but also by packaged supercapacitors in CR2032 casings. The capacitive performance of Pt@AC electrodes was investigated via cyclic voltammetry (CV), galvanostatic charge-discharge curves (GCD), and impedance spectroscopy (EIS). It was found that the Pt loading increased the specific capacitance from 51 F/g to 100 F/g. The ESR drop of the packaged cell decreased with the Pt loading due to the fast flow of charge through the conductive pathways. The results showed that the surface chemistry is more dominant than the surface area for determining the capacitive performance of Pt loaded AC-based packaged supercapacitors.     

Enhanced electrochemical sensitivity of PtRh electrodes coated with nitrogen-doped graphene

We report the enhancement of electron transfer properties of PtRh electrodes modified by nitrogen-doped graphene coating. The nitrogen-doped graphene coating prepared by a hydrazine-assisted ultrasonication allows for the development of new and effective graphene-based electrode materials for electrochemical sensing.     

Nickel and copper foam electrodes modified with graphene or carbon nanotubes for electrochemical identification of Chinese rice wines

Microchimica Acta - The authors describe the application of two types of metallic foams modified with either graphene (GR) or carbon nanotubes (CNTs) as voltammetric electrodes in order to...     

蒙脱石化学修饰电极的制备与电化学特性

用预交换法和掺入法将某些荷阳电物(NR, MB)与荷阴电物[IC, Fe(CN)~6^3-]吸附在蒙脱石膜中制备化学修饰电极(CME)。对不同电性的吸附物, 用预交换法制备的CME在支持电解质溶液中显示不同的伏安响应。被吸附物在蒙脱石膜内的电活性浓度(c*)和总浓度(c~t)之比值较小, 说明被吸附物中只有小部分表现有电化学特性。X衍射实验表明荷阳电的吸附物可能通过离子交换吸附而嵌入蒙脱石层间。吸收光谱实验亦表明荷阳电物与蒙脱石间有强的化学吸附作用。根据蒙脱石中各种不同的吸附位置, 讨论了被吸附物对电化学响应的不同贡献。     

High performance electrochemical sensor based on modified screen-printed electrodes with cost-effective dispersion of nanostructured carbon black

A novel sensor based on a screen-printed electrode (SPE) modified with a stable dispersion of commercially available carbon black (CB) N220 was developed. This probe showed significantly enhanced electrochemical activity relative to a bare SPE when tested with ferricyanide, epinephrine, norepinephrine, benzoquinone and NADH. When challenged in amperometric batch mode with NADH, the response was stable and revealed a linear dependence up to 2·10^?4 mol L^?1 with a detection limit of 3·10^?7 mol L^?1. The analytical performance, coupled with the low cost of the CB nanomaterial, suggests that this sensor holds promise for electrochemical applications.     

Electrochemical behavior of glassy carbon electrodes modified by electrochemical oxidation

Glassy carbon electrodes were modified electrochemically by pretreatment in sulfate, phosphate or carbonate solutions by means of cycling the potential well into the positive limit of the solvent. Electrodes treated in this manner were then used to incorporate and concentrate a variety of redox species that were either cations or aromatic containing compounds, including Ru(bpy)²⁺₃, Ru(NH₃)³⁺₆, Cu(NH₃)²⁺₄, ferrocene, methylviologen, 1,4-benzoquinone, anthraquinone-2-sulfonate, riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD). Surface-equivalent concentrations ranged from 5 × 10^?9 to 1 × 10^?7 mol cm^?2 for electrodes pretreated for 10 min in sulfuric acid. An E_1/2 vs. pH study of 1,4-benzoquinone, riboflavin, FMN and FAD in modified electrodes shows that the pK_a values shift toward higher pH (nearly 2 pH units). Results concerning the incorporation of redox compounds detected only by mediation with other electroactive complexes and the study of the modified electrodes in electrocatalysis are also discussed.     

聚合物修饰电极对多巴胺的电化学测定进展

多巴胺是哺乳动物中枢神经系统中的一种非常重要的信息传递物质,建立对多巴胺快速简单测定的分析方法非常重要。本文就05年以来聚合物修饰电极对多巴胺电化学检测的研究进展进行了综述。     

Derivatized humic acids modified gold electrode: electrochemical characterization and analytical applications

The preparation and application of a humic acids modified gold electrode (HA-CME) have been described. Derivatization of HAs as β-thioesters caused their partial fragmentation and, thus, a consequent separation by size exclusion chromatography (SEC) was necessary.The CME prepared with functionalized HAs having an average MW of 52000 demonstrated to be effective for trace As(III) determination (LOQ = 0.3 μg L⁻¹). This CME has been characterized both by electrochemical techniques and atomic force microscopy (AFM). The HA-CME provided reliable measurements in natural waters at different salinity with no need of desalting the sample. Total inorganic arsenic could be determined after reduction of As(V) with SO₂. Under these conditions, organic arsenic species were not mineralized and did not interfere.     

Bio-electrocatalysis of NADH and ethanol based on graphene sheets modified electrodes

Characterization and application of graphene sheets modified glassy carbon electrodes (graphene/GC) have been presented for the electrochemical bio-sensing. A probe molecule, potassium ferricyanide is employed to study the electrochemical response at the graphene/GC electrode, which shows better electron transfer than graphite modified (graphite/GC) and bare glassy carbon (GC) electrodes. Based on the highly enhanced electrochemical activity of NADH, alcohol dehydrogenase (ADH) is immobilized on the graphene modified electrode and displays a more desirable analytical performance in the detection of ethanol, compared with graphite/GC or GC based bio-electrodes. It also exhibits good performance of ethanol detection in the real samples. From the results of electrochemical investigation, graphene sheets with a favorable electrochemical activity could be an advanced carbon electrode materials for the design of electrochemical sensors and biosensors.     

Extending the dynamic range of electrochemical sensors using multiple modified electrodes

Multiple electrodes, combined with a chemometric strategy to calibrate the measurement response, have been used for the determination of an analyte across a broader dynamic range than is possible with a single electrode. The model system used for the detection of copper comprised electrodes modified with a self-assembled monolayer. The electrodes were modified with the copper-complexing species (3-mercaptopropionic acid, thioctic acid, and the peptides cysteine and Gly-Gly-His) and copper was determined over concentrations ranging from nanomolar to millimolar using voltammetric analysis. We have demonstrated that by combining the calibration functions from the four electrodes a better estimate (i.e. with smaller variance) of the concentration of the analyte is obtained. Measurement uncertainty is expressed for independently prepared electrodes, which allows the possibility of commercial production and factory calibration. The principles of using multiple electrodes modified with recognition elements with different affinities for the target analyte to extend the dynamic range of sensors is a general one that could be applied to other analytes.     

Ionic liquid-functionalized graphene as modifier for electrochemical and electrocatalytic improvement: comparison of different carbon electrodes

Electrochemical activities of typically electrochemical targets at three kinds of modified carbon electrodes, i.e. carbon ionic liquid electrode (CILE), graphene/carbon paste electrode (CPE), and ionic liquid-functionalized graphene (IL-graphene)/CPE, were compared in detail. The redox processes of the probes at IL-graphene/CPE were faster than those at CILE and graphene/CPE from cyclic voltammetry. An electrochemical method for the simultaneous determination of guanine and adenine was described with detection limits of 6.5 × 10⁻⁸ mol L⁻¹ (guanine) and 3.2 × 10⁻⁸ mol L⁻¹ (adenine). Single A → G mutation of sequence-specific DNA could be discriminated by the IL-graphene/CPE.     

Electrochemical reduction of graphene oxide and its electrochemical capacitive performance

A convenient method for the production of graphene is developed using the electrochemical reduction of graphite oxide (GO) in solution without assembling it onto the electrode. The samples were examined by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The results show that the number of oxygen functional groups can be significantly decreased. The electrochemical capacitance of the prepared graphene after 8 h of reduction is 158.5 F g^?1 at 0.5 A g^?1, much higher than that of GO and carbon nanotubes. The mechanism for this reaction is also proposed in this paper.     

Methylene blue and neutral red electropolymerisation on AuQCM and on modified AuQCM electrodes: an electrochemical and gravimetric study

The phenazine monomers neutral red (NR) and methylene blue (MB) have been electropolymerised on different quartz crystal microbalance (QCM) substrates: MB at AuQCM and nanostructured ultrathin sputtered carbon AuQCM (AuQCM/C), and NR on AuQCM and on layer-by-layer films of hyaluronic acid with myoglobin deposited on AuQCM (AuQCM-{HA/Mb}(6)). The surface of the electrode substrates was characterised by atomic force microscopy (AFM), and the frequency changes during potential cycling electropolymerisation of the monomer were monitored by the QCM. The study investigates how the monomer chemical structure together with the electrode morphology and surface structure can influence the electropolymerisation process and the electrochemical properties of the phenazine-modified electrodes. Differences between MB and NR polymerisation, as well as between the different substrates were found. The electrochemical properties of the PNR-modified electrodes were analysed by cyclic voltammetry and electrochemical impedance spectroscopy and compared with the unmodified AuQCM. The results are valuable for future applications of modified AuQCM as substrates for electroactive polymer film deposition and applications in redox-mediated electrochemical sensors and biosensors.     

An overview of the electrochemical reduction of oxygen at carbon-based modified electrodes

We present an overview of the electrochemical reduction of oxygen in water, focussing on carbon-based and modified carbon electrodes. This process is of importance for gas sensing, in fuel cells and in the electrosynthesis of hydrogen peroxide.     

Electrochromatographic performance of graphene and graphene oxide modified silica particles packed capillary columns

Graphene oxide functionalized silica microspheres (GO@SiO₂) were synthesized based on condensation reaction between amino from aminosilica particles and carboxyl groups from GO. Reduction of GO@SiO₂ with hydrazinium hydroxide generated graphene modified silica particles (G@SiO₂). GO@SiO₂ and G@SiO₂ packed capillary columns for capillary electrochromatography were thereafter fabricated by pressure slurry packing with single‐particle frits. GO of 0.3 mg/mL in dispersion solution for GO@SiO₂ synthesis was considered as a compromise between retaining and column efficiency whereas GO@SiO₂ of 20 mg/mL in slurries for column packing was chosen for a homogenous and tight bed. Optimum mobile phases were acquired considering both electroosmotic flow and resolution at an applied voltage of −6 kV as the following: acetonitrile/phosphate buffer (10 mM, pH 7.0), 75:25 (v/v) for polycyclic aromatic hydrocarbons and 50:50 (v/v) for aromatic compounds. A comparison was made between electrochromatographic performances for three PAHs (naphthalene, fluorene and phenanthrene) and three aromatic compounds of various polarities (toluene, aniline and phenol) on bare aminosilica, GO@SiO₂ and G@SiO₂ packed columns, which proved the contribution of alone or combinational actions of solvophobic effect and π‐π electron stacking as well as hydrogen bonds to retaining behaviors by GO@SiO₂ and G@SiO₂. Well over‐run, over‐day and over‐column precisions (retention time: 0.3–1.4, 1.1–3.8 and 2.8–5.2%, respectively; peak area: 2.6–6.5, 4.8–8.3 and 6.5–12.6%, respectively) of GO@SiO₂ packed columns were a powerful proof for good reproducibility. Analytical characteristics of GO@SiO₂ packed capillary columns in CEC analysis of fresh water were evaluated with respect to linearity (R² = 0.9961–0.9989) over the range 0.1 to 100 mg/L and detection limits of 9.5 for naphthalene, 12.6 for fluorene and 16.2 μg/L for phenanthrene. Further application to fresh water increased the visibility of the proposed material, where good spike recoveries in the range 89–96% were offered.     

High-performance supercapacitor electrodes based on graphene hydrogels modified with 2-aminoanthraquinone moieties

2-Aminoanthraquinone (AAQ) molecules were covalently grafted onto chemically modified graphene (CMG), and the AAQ functionalized CMG sheets were self-assembled into macroporous hydrogels for supercapacitor electrodes. The electrode based on the AAQ modified self-assembled graphene hydrogel (AQSGH) showed a high specific capacitance of 258 F g(-1) at a discharge current density of 0.3 A g(-1), which is much larger than that of a pure graphene hydrogel (193 F g(-1)). Furthermore, the AQSGH electrode exhibited excellent rate capability and a long cycle life. This is mainly due to the covalently bonded AAQ moieties contributing additional redox capacitance. Furthermore, the highly conductive graphene hydrogel scaffold provided a large specific surface area for forming electric double layers and convenient routes for charge transfer and electrolyte diffusion.     

Manufacture and evaluation of carbon nanotube modified screen-printed electrodes as electrochemical tools

Carboxylated multiwalled carbon nanotubes (MWCNT-COOH) dissolved in a mixture of DMF:water were used to modify the surfaces of commercially available screen-printed electrodes (SPEs). The morphology of the MWCNT-COOH and the modified SPEs was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. SEM analysis showed a porous structure formed by a film of disordered nanotubes on the surface of the working electrode.The modification procedure with MWCNT-COOH was optimised and it was applied to unify the electrochemical behaviour of different gold and carbon SPEs by using p-aminophenol as the benchmark redox system. The analytical advantages of the MWCNT-COOH-modified SPEs as voltammetric and amperometric detectors as well as their catalytic properties were discussed through the analysis, for instance, of dopamine and hydrogen peroxide. Experimental results show that the electrochemical active area of the nanotube-modified electrode increased around 50%. The repeatability of the modification methodology is around 6% (R.S.D.) and the stability of MWCNT-COOH-modified SPEs is ensured for, at least, 2 months.     

Electrolyte effects on electrochemical properties of osmium complex polymer modified electrodes.

The electrolyte effects on the electrochemical behaviors of osmium complex polymer modified electrodes were investigated by a comparison between two osmium complexes, [Os(bpy)2(PVI)10Cl]Cl (Os-PVI10) and [Os(bpy)2(PVP)10Cl]Cl (Os-PVP10). The electrode process at Os-PVI10 modified electrodes is reaction-controlled, while a diffusion-controlled electrode process exists at Os-PVP10 modified electrodes. Both the cation and anion in supporting electrolytes strongly affect their electrochemical behaviors, such as the redox potential, wave shape and peak current. These phenomena are attributed to a change in the film structure and polymer swelling in various supporting electrolytes. The influence of electrolyte anions on the electrochemical behaviors is related to their hydrophobicity. The electrode process of Os-PVP10 depends on the pH value of solutions, exhibiting different electron transfer mechanisms.