A non-enzymatic sensor for hydrogen peroxide based on polyaniline, multiwalled carbon nanotubes and gold nanoparticles modified Au electrode

We describe the construction of a polyaniline (PANI), multiwalled carbon nanotubes (MWCNTs) and gold nanoparticles (AuNPs) modified Au electrode for determination of hydrogen peroxide without using peroxidase (HRP). The AuNPs/MWCNT/PANI composite film deposited on Au electrode was characterized by Scanning Electron Microscopy (SEM) and electrochemical methods. Cyclic voltammetric (CV) studies of the electrode at different stages of construction demonstrated that the modified electrode had enhanced electrochemical oxidation of H(2)O(2), which offers a number of attractive features to develop amperometric sensors based on split of H(2)O(2). The amperometric response to H(2)O(2) showed a linear relationship in the range from 3.0 μM to 600.0 μM with a detection limit of 0.3 μM (S/N = 3) and with high sensitivity of 3.3 mA μM(-1). The sensor gave accurate and satisfactory results, when employed for determination of H(2)O(2) in milk and urine.     

Fabrication of multiwalled carbon nanotubes/polyaniline modified Au electrode for ascorbic acid determination

An ascorbate oxidase (AsOx) (E.C.1.10.3.3) purified from Lagenaria siceraria fruit was immobilized covalently onto a carboxylated multiwalled carbon nanotubes and polyaniline (c-MWCNT/PANI) layer electrochemically deposited on the surface of an Au electrode. The diffusion coefficient of ascorbic acid was determined as 3.05 × 10(-4) cm(2) s(-1). The behavior of different electrolytes on electro-deposition was also studied. An ascorbate biosensor was fabricated using a AsOx/c-MWCNT/PANI/Au electrode as a working electrode, Ag/AgCl (3 M/saturated KCl) as standard and Pt wire as an auxiliary electrode connected through a potentiostat. Linear range, response time and detection limit were 2-206 μM, 2 s and 0.9 μM respectively. The biosensor showed optimum response at pH 5.8 and in a broader temperature range (30-45 °C), when polarized at +0.6 V. The biosensor was employed for determination of ascorbic acid level in sera, fruit juices and vitamin C tablets. The sensor was evaluated with 91% recovery of added ascorbic acid in sera and 6.5% and 11.4% within and between batch coefficients of variation respectively for five serum samples. There was a good correlation (r = 0.98) between fruit juice ascorbic acid values by the standard 2,6-dichlorophenolindophenol (DCPIP) method and the present method. The enzyme electrode was used 200 times over a period of two months, when stored at 4 °C. The biosensor has advantages over earlier enzyme sensors in that it has no leakage of enzyme, due to the covalent coupling of enzyme with the support, lower response time, wider working range, higher storage stability and no interference by serum substances.     

A novel hydrogen peroxide sensor based on Ag nanoparticles electrodeposited on DNA-networks modified glassy carbon electrode

A novel strategy to fabricate hydrogen peroxide (H₂O₂) sensor was developed by electrodepositing Ag nanoparticles (NPs) on a glassy carbon electrode modified with three-dimensional DNA networks. The result of electrochemical experiments showed that such constructed sensor had a favorable catalytic ability to reduction of H₂O₂. The well catalytic activity of the sensor was ascribed to the DNA networks that facilitated the formation and homogenous distribution of small Ag NPs. The resulted sensor achieved 95% of the steady-state current within 2 s and had a 1.7 μM detection limit of H₂O₂.     

A highly sensitive hydrogen peroxide amperometric sensor based on MnO2-modified vertically aligned multiwalled carbon nanotubes

In this report, a highly sensitive amperometric sensor based on MnO₂-modified vertically aligned multiwalled carbon nanotubes (MnO₂/VACNTs) for determination of hydrogen peroxide (H₂O₂) was fabricated by electrodeposition. The morphology of the nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer and X-ray diffraction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were applied to investigate the electrochemical properties of the MnO₂/VACNTs nanocomposite electrode. The mechanism for the electrochemical reaction of H₂O₂ at the MnO₂/VACNTs nanocomposite electrode was also discussed. In borate buffer (pH 7.8, 0.20 M), the MnO₂/VACNTs nanocomposite electrode exhibits a linear dependence (R = 0.998) on the concentration of H₂O₂ from 1.2 × 10⁻⁶ M to 1.8 × 10⁻³ M, a high sensitivity of 1.08 × 10⁶ μA M⁻¹ cm⁻² and a detection limit of 8.0 × 10⁻⁷ M (signal/noise = 3). Meanwhile, the MnO₂/VACNTs nanocomposite electrode is also highly resistant towards typical inorganic salts and some biomolecules such as acetic acid, citric acid, uric acid and d-(+)-glucose, etc. In addition, the sensor based on the MnO₂/VACNTs nanocomposite electrode was applied for the determination of trace of H₂O₂ in milk with high accuracy, demonstrating its potential for practical application.     

A novel nonenzymatic hydrogen peroxide sensor based on multi-wall carbon nanotube/silver nanoparticle nanohybrids modified gold electrode

A novel strategy to fabricate hydrogen peroxide (H₂O₂) sensor was developed based on multi-wall carbon nanotube/silver nanoparticle nanohybrids (MWCNT/Ag nanohybrids) modified gold electrode. The process to synthesize MWCNT/Ag nanohybrids was facile and efficient. In the presence of carboxyl groups functionalized multi-wall carbon nanotubes (MWCNTs), silver nanoparticles (Ag NPs) were in situ generated from AgNO₃ aqueous solution and readily attached to the MWCNTs convex surfaces at room temperature, without any additional reducing reagent or irradiation treatment. The formation of MWCNT/Ag nanohybrids product was observed by transmission electron microscope (TEM), and the electrochemical properties of MWCNT/Ag nanohybrids modified gold electrode were characterized by electrochemical measurements. The results showed that this sensor had a favorable catalytic ability for the reduction of H₂O₂. The resulted sensor could detect H₂O₂ in a linear range of 0.05-17 mM with a detection limit of 5 × 10⁻⁷ M at a signal-to-noise ratio of 3. The sensitivity was calculated as 1.42 μA/mM at a potential of −0.2 V. Additionally, it exhibited good reproducibility, long-term stability and negligible interference of ascorbic acid (AA), uric acid (UA), and acetaminophen (AP).     

A novel non-enzyme hydrogen peroxide sensor based on an electrode modified with carbon nanotube-wired CuO nanoflowers

We have prepared a novel sensor for hydrogen peroxide that is based on a glassy carbon electrode modified with a film containing multi-walled carbon nanotubes wired to CuO nanoflowers. The nanoflowers were characterized by X-ray powder diffraction, and the electrode was characterized by cyclic voltammetry (CV) and scanning electron microscopy. The response of the modified electrode towards hydrogen peroxide was investigated by CV and chronoamperometry and showed it to exhibit high electrocatalytic activity, with a linear range from 0.5?μM to 82?μM and a detection limit of 0.16?μM. The sensor also displays excellent selectivity and stability.

Hydrogen peroxide sensor based on a stainless steel electrode coated with multi-walled carbon nanotubes modified with magnetite nanoparticles

Multi-walled carbon nanotubes (MWCNTs) were decorated with magnetite (Fe₃O₄) nanoparticles and then used to modify a stainless steel electrode. The Fe₃O₄/MWCNTs composite was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray diffraction patterns. Electrochemical properties of the modified electrode revealed a substantial catalytic activity for the reduction of hydrogen peroxide. The relationship between peak current and the concentration of hydrogen peroxide was linear in the range from 0.06?mmol?L^?1 to 0.36?mmol?L^?1, and the lowest detectable concentration is 0.01?mmol·L^?1 (S/N?=?3). The modified stainless steel electrode displays excellent stability.

Nd_2O_3/多壁碳纳米管修饰电极检测亚硝酸根

制备了纳米Nd2O3/多壁碳纳米管修饰电极并用于亚硝酸盐的检测。采用原子力显微镜、X-粉末衍射仪表征制备的纳米材料。实验表明:修饰电极对亚硝酸根的氧化具有明显地电催化作用。利用示差脉冲伏安法测定亚硝酸盐,其氧化峰电流和其浓度在20μmol·L-1-20 mmol·L-1范围内呈现良好的线性关系,检测线为0.83μmol·L-1(S/N=3)。更重要的是,实验结果表明:与Nd2O3修饰电极相比,多壁碳纳米管能显著地提高电极的稳定性。此外,修饰电极具有良好的选择性,能用于样品的检测,结果令人满意。     

A hydrogen peroxide biosensor based on horseradish peroxidase/poly(L-leucine)/polydopamine modified glassy carbon electrode

A simple and practical sensor of hydrogen peroxide (H₂O₂) was designed successfully. The mixture of horseradish peroxidase (HRP) and chitosan (Chit) are effectively immobilized on the surface of poly-L-leucine/polydopamine modified glassy carbon electrode (PL-LEU/PDA/GCE). Under the optimum conditions, the biosensor based on HRP exhibits a fast amperometric response (within 3 s) to H₂O₂. The linear response range of the sensor is 0.5–952.0 μmol L^–1, with the detection limit of 0.1 μmol L^–1 (S/N = 3) and the sensitivity of 0.23 A L moL^–1 cm^–2. The apparent Michaelis–Menten constant (k _M ^app) of the biosensor is evaluated to be 0.12 mmol L^–1, which suggests that the HRP-Chit/PL-LEU/PDA/GCE shows a higher affinity for H₂O₂. The sensor exhibits good sensitivity, selectivity, stability and reproducibility. The proposed method has been successfully applied to the determination of H₂O₂ in practical samples.     

Direct electrochemistry of xanthine oxidase at a gold electrode modified with single-wall carbon nanotubes.

The direct electrochemistry of xanthine oxidase (XOD) was accomplished at a gold electrode modified with single-wall carbon nanotubes (SWNTs). A pair of well-defined redox peaks was obtained for XOD with the reduction peak potential at -0.478 V and a peak potential separation of 28 mV at pH 7.0. Both FT-IR spectra and the dependence of the reduction peak current on the scan rate revealed that XOD adsorbed onto the SWNT surfaces. The redox wave corresponds to the redox center of the flavin adenine dinucleotide (FAD) of the XOD adsorbate. Compared to other types of carbonaceous electrode materials, the electron transfer rate of XOD redox reaction was greatly enhanced at the SWNT-modified electrode. The peak potential was shown to be pH dependent. Spectral methods verified that the attachment of XOD onto SWNTs does not perturb the XOD conformations drastically.     

A hydrogen peroxide biosensor with high stability based on gelatin-multiwalled carbon nanotubes modified glassy carbon electrode

A biosensor with high stability was prepared to determine hydrogen peroxide (H₂O₂). This hydrogen peroxide biosensor was obtained by modifying glassy carbon electrode (GCE) with a composite film composed of gelatin-multiwalled carbon nanotubes. Catalase (Cat) was covalently immobilized into gelatin-multiwalled carbon nanotubes modified GCE through the well-known glutaraldehyde (GAD) chemistry in order to enhance the stability of electrodes. The enzyme sensor can achieve direct electrochemical response of hydrogen peroxide. The cyclic voltammograms at different scan rates, electrochemical impedance spectroscopy (EIS), and scanning electron microscope (SEM) tests indicate that the enzyme sensor performs positively on increasing permeability, reducing the electron transfer resistance, and improving the electrode performance. The linear response of standard curve for H₂O₂ is in the range of 0.2 to 5.0 mM with a correlation coefficient of 0.9972, and the detection limit of 0.001 mM. A high operational and storage stability is demonstrated for the biosensor. The peak potential at room temperature in two consecutive weeks stays almost consistent, and the enzyme activity is kept stable even after 30 days in further study.     

Direct electron transfer of Mb on chitosan/single-wall carbon nanotubes film modified Au electrode and its interaction with cimetidine

Three methods were used to immobilize myoglobin (Mb) on chitosan/single-wall carbon nanotubes (SWNTs) film, and direct electrochemistry of the immobilized Mb was extensively investigated. Immobilized Mb displayed a couple of stable and well-defined redox peaks with the formal potential (E’) is at about −0.27 V (vs. SCE) in 0.1 M phosphate buffer solution (pH 7.0). The E′ was shifted linearly with pH in the range of 3.0 to 9.0 with a slope of −54.1 mV pH⁻¹, denoting that one-electron accompanies with one-proton transfer in electrode reaction process. The FT-IR spectroscopy and UV-vis spectroscopy showed that Mb on the film retained its secondary structure similar to its native state. The experimental results demonstrated that the immobilized Mb exhibited excellent electrocatalytic activity to reduction of cimetidine with a significant lowering of overpotential. The electrocatalytic current was proportional to the concentration of cimetidine over the range from 9.80 × 10⁻⁶ to 1.1 × 10⁻⁴ M; the detection limit is 8.40 × 10⁻⁶ M (signal-to-noise ratio of 3). The proposed method exhibits good sensitivity, stability and reproducibility. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 2, pp. 235–243. The text was submitted by the authors in English     

A lead(II) sensor based on a glassy carbon electrode modified with Fe3O4 nanospheres and carbon nanotubes

We have developed a highly sensitive and selective sensor for lead(II) ions. A glassy carbon electrode was modified with Fe₃O₄ nanospheres and multi-walled carbon nanotubes, and this material was characterized by scanning electron microscopy and X-ray diffraction. The electrode displays good electrochemical activity toward Pb(II) and gives anodic and cathodic peaks with potentials at ?496 mV and ?638 mV (vs. Ag/AgCl) in pH?6.0 solution. The sensor exhibits a sensitive and fairly selective response to Pb(II) ion, with a linear range between 20 pM and 1.6 nM, and a detection limit as low as 6.0 pM (at a signal-to noise ratio of 3). The sensor was successfully applied to monitor Pb(II) in spiked water samples.

A novel nitrite sensor based on graphene/polypyrrole/chitosan nanocomposite modified glassy carbon electrode

A novel nitrite sensor was fabricated based on a graphene/polypyrrole/chitosan nanocomposite film modified glassy carbon electrode. The nanocomposite film was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The electron transfer behaviour of the modified electrodes was investigated in [Fe(CN)(6)](3-)/(4-) redox probe using cyclic voltammetry and electrochemical impedance spectroscopy. Differential pulse voltammetry and amperometry were used to study the electrochemical properties of the proposed sensor. Under optimum conditions, the sensor exhibited good reproducibility and stability for nitrite determination. Linear response was obtained in the range of 0.5-722 μM with a detection limit of 0.1 μM (S/N = 3) for nitrite determination.     

Hydrogen peroxide sensor based on horseradish peroxidase immobilized on a silver nanoparticles/cysteamine/gold electrode

A third-generation hydrogen peroxide biosensor was prepared by immobilizing horseradish peroxidase (HRP) on a gold electrode modified with silver nanoparticles. A freshly-cleaned gold electrode was first immersed in a cysteamine–ethanol solution, and then silver nanoparticles were immobilized on the cysteamine monolayer, and finally HRP was adsorbed onto the surfaces of the silver nanoparticles. This self-assemble process was examined via atomic force microscopy (AFM). The immobilized horseradish peroxidase exhibited an excellent electrocatalytic response toward the reduction of hydrogen peroxide. The linear range of the biosensor was 3.3 M to 9.4 mM, and the detection limit was estimated to be 0.78 M. Moreover, the biosensor exhibited a fast response, high sensitivity, good reproducibility, and long-term stability.     

Fabrication of a novel impedance cell sensor based on the polystyrene/polyaniline/Au nanocomposite

Gold nanoparticles (AuNPs) were assembled on the surface of polystyrene (PS) and polyaniline (PANI) core-shell nanocomposite (PS@PANI) for the immobilization of HL-60 leukemia cells to fabricate a cell electrochemical sensor. The immobilized cells exhibited irreversible voltammetric response and increased the electron transfer resistance with a good correlation to the logarithmic value of concentration ranging from 1.6 × 10³ to 1.6 × 10⁸ cells mL⁻¹ with a limit of detection of 7.3 × 10² cells mL⁻¹ at 10σ. This biosensor was simple, low cost and disposable, which implied that the PS@PANI/Au composites can regard as the potential applications for clinical applications.     

Direct electron transfer of hemoglobin on dihexadecyl hydrogen phosphate/single-wall carbon nanotubes film modified Au electrode and its interaction with taxol

Direct electrochemistry of hemoglobin (Hb) immobilized on the dihexadecyl hydrogen phosphate (DHP)/single-wall carbon nanotubes (SWNTs) film modified Au electrode is investigated. The immobilized Hb displays a couple of stable and well-defined redox peaks, whose formal potential (E ⁰) is −0.434 V (SCE) in a phosphate buffer solution of pH 7.0. The formal potential of the heme Fe(III)/Fe(II) couple shifts negatively linearly with increased pH with a slope of −42.3 mV/pH, denoting that one electron transfer accompanies single proton transportation. Both SWNTs and DHP can accelerate the electron transfer between Hb and the electrode. Using DHP/Hb/SWNTs-film-modified Au electrode, the interaction between Hb and taxol is investigated. The voltammetric response of Hb decreases with increasing concentration of taxol. The peak currents decreases proportionally to the taxol concentration at 1.4 × 10⁻⁵ to 1.3 × 10⁻⁴ M, the linear regression equation being Δi (A) = 2.9603 − 0.4225 c_taxol (M), with a correlation coefficient (r) 0.9985, and the detection limit 6.95 × 10⁻⁶ M (signal-to-noise ratio of three). Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 801–807. The text was submitted by the authors in English.     

Electrochemical dipyridamole sensor based on molecularly imprinted polymer on electrode modified with Fe3O4@Au/amine-multi-walled carbon nanotubes

Journal of Solid State Electrochemistry - A novel molecularly imprinted electrochemical sensor based on Fe3O4@Au nanoparticles immobilized on amine-multi-walled carbon nanotubes by the strong...     

Amperometric sensor for detection of bisphenol A using a pencil graphite electrode modified with polyaniline nanorods and multiwalled carbon nanotubes

We report on a simple and highly sensitive amperometric method for the determination of bisphenol A (BPA) using pencil graphite electrodes modified with polyaniline nanorods and multiwalled carbon nanotubes. The modified electrodes display enhanced electroactivity for the oxidation of BPA compared to the unmodified pencil graphite electrode. Under optimized conditions, the sensor has a linear response to BPA in the 1.0 and 400?μM concentration range, with a limit of detection of 10?nM (at S/N?=?3). The modified electrode also has a remarkably stable response, and up to 95 injections are possible with a relative standard deviation of 4.2% at 100?μM of BPA. Recoveries range from 86 to 102% for boiling water spiked with BPA from four brands of baby bottles.

Nonenzymatic hydrogen peroxide sensor based on a glassy carbon electrode modified with electrospun PdO-NiO composite nanofibers

A glassy carbon electrode was modified with PdO-NiO composite nanofibers (PdO-NiO-NFs) and applied to the electrocatalytic reduction of hydrogen peroxide (H₂O₂). The PdO-NiO-NFs were synthesized by electrospinning and subsequent thermal treatment, and then characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Factors such as the composition and fraction of nanofibers, and of the applied potential were also studied. The sensor exhibits high sensitivity for H₂O₂ (583.43 μA?·?mM^?1?·?cm^?2), a wide linear range (from 5.0 μM to 19 mM), a low detection limit (2.94 μM at an SNR of 3), good long term stability, and is resistant to fouling.