A platform for electrochemical sensing of biomolecules based on Europia/reduced graphene oxide nanocomposite

This study aimed at preparing and evaluating the europium oxide–reduced graphene oxide (rGO) composites. Inorganic nanoparticles anchored onto rGO sheets through a facile sonochemical method. The resultant products were characterized by FT-IR, XRD, SEM. Their activity in biomolecules’ analysis were examined by cyclic voltammetry. The rectified electrodes revealed an incredibly electroactive manner. The obtained progress provided excellent materials for scrutiny of biomolecules. The linear relationship was used in the region of 100–1500 µM ascorbic acid (AA), 50–600 µM dopamine (DA), and 10–700 µM uric acid (UA), between current intensities and concentrations. The detection restrictions (LOD) (S/N?=?3) decreased to 8 µM, 1.1 µM and 0.085 µM for AA, DA and UA respectively by differential pulse voltammetry (DPV).     

酶-二维MXene复合材料的制备及其电化学检测H2O2的应用

本研究合成了具有垂直栅栏结构的二维MXene材料, 与辣根过氧化物酶进行固定, 构筑了过氧化氢电化学酶传感器。合成的MXene纳米栅栏具有大的比表面积, 优良的电子传导特性和在水溶液中的良好分散特性; 固定化在酶电极上的辣根过氧化物酶分子表现出了优良的过氧化氢催化效果。结果表明HRP@MXene/chitosan/GCE酶电化学传感器在过氧化氢浓度为5~1650 μmol/L范围内表现出很好的线性关系, 最低检测限为0.74 μmol/L, 且具有很好的操作稳定性, 该生物传感器被成功地应用于固态与液态食品中过氧化氢残留检测。     

Polyeugenol-modified platinum electrode for selective detection of dopamine in the presence of ascorbic Acid

A platinum electrode was modified with electropolymerized films of 4-allyl-2-methoxyphenol (eugenol) by its oxidative polymerization from an alkaline solution by cyclic voltammetry. The modified electrode was than used to determine dopamine (DA) in an excess of ascorbic acid (AA) by differential pulse voltammetry. The peak positions as well as relative sensitivity DA/AA were affected by the potential window applied for the polymerization. For polymerization between 0 and 2.2 V, the peak potentials recorded in a phosphate buffer solution (pH 7.4) were -61 and +152 mV vs Ag/AgCl for AA and DA, respectively. After a 5-min equilibration, relative sensitivity DA/AA was 164 and the current sensitivity for DA was 7.9 nA μM(-)(1). The detection limit for S/N = 3 is 0.1 μM. The high selectivity and sensitivity for DA was found to be due to charge discrimination/analyte accumulation and an effect of catalytic mediation of redox sites. Chronocoulometric data reveal that DA is accumulated on the electrode as a monolayer. The electrode is stable, reversible, and free of fouling problems.     

Simultaneous determination of serotonin and dopamine at the PEDOP/MWCNTs-Pd nanoparticle modified glassy carbon electrode

Electrochemical determination of dopamine (DA) and serotonin (5-HT) have been studied at a modified glassy carbon electrode (GCE) in 0.1 M phosphate buffer solution (PBS) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at pH 7.4, all over the interfering biomolecule ascorbic acid (AA). The GCE was modified by palladium-functionalized, multi-walled carbon nanotubes (MWCNTs-Pd) with electrochemical deposition of poly 3,4-ethylenedioxy pyrrole (PEDOP), denoted as PEDOP/MWCNTs-Pd/GCE, and investigated by SEM and EIS experiments. The highly electrocatalytic activity of the modified electrode toward 5-HT and DA was demonstrated from the sensitive and well-separated voltammetric experiment. The oxidation peaks found were 0.165 and 0.355 mV for DA and 5-HT, respectively. The composite film shows a significant accumulation effects on two species, as well as the mutual interference among the analytes. This biosensor was best in response compared to other modified electrodes made in the same lab. The lowest detection limits were found to be 5.0 x 10(-9) and 1.0 x 10(-8) for 5-HT and DA, respectively. The respective linear ranges were determined as 1.0 x 10(-7) to 2.0 x 10(-4) and 1.0 x 10(-7) to 2.0 x 10(-4) for 5-HT and DA.     

Hydrothermal synthesis of ZnO flower-reduced graphene oxide composite for electrochemical determination of ascorbic acid

In this work, reduced graphene oxide coated zinc oxide flower (ZnO–RGO) nanocomposite has been prepared via a simple one-pot hydrothermal synthesis method. The morphology and properties of the proposed ZnO–RGO were characterized using SEM, Raman and UV–VIS spectroscopy. Then, an ascorbic acid (AA) electrochemical sensor was prepared based on a glassy carbon electrode (GCE) modified with the ZnO–RGO nanocomposite. An advanced performance was recorded on the ZnO–RGO/GCE compared with that of the bare GCE, ZnO/GCE, and RGO/GCE. The proposed electrochemical sensor exhibited a wide linear detection from 5 μM to 2 mM with a low detection limit of 1.2 μM. Further, the proposed AA electrochemical sensor showed a good repeatability, reproducibility and stability.     

Facile deposition of polyvinylpyrrolidone-grafted multi-walled carbon nanotube on glassy carbon electrode and its application in the sensing of biomolecules

Polyvinylpyrrolidone-grafted multi-walled carbon nanotube (PVP/MWCNT) was deposited on carboxylated glassy carbon electrode (GCE) from acidic water via the electrostatic force between the positively charged PVP/MWCNTs and negatively charged GCE. It was found out that PVP/MWCNT-modified GCE (PVP/MWCNT/GCE) exhibited great catalytic capability for the oxidation of dopamine (DA), uric acid (UA), tyrosine (Tyr) and nitrite) by enhancing their oxidation currents and lowering their overpotentials. For PVP/MWCNT/GCE, the linear calibration plots for DA, UA, Tyr and nitrite were obtained over the range of 0.1–50 μM, 1–500 μM, 1–200 μM and 1–500 μM with detection limits of 0.04 μM, 0.17 μM, 0.26 μM and 0.30 μM, respectively. In addition, satisfactory results were obtained by applying PVP/MWCNT/GCE in the determination of DA, UA, Tyr and nitrite in human serum samples with standard addition method.     

Simultaneous determination of 3,4-dihydroxyphenylacetic acid, uric acid and ascorbic acid by poly(L-arginine)/multi-walled carbon nanotubes composite film

The poly(L-Arginine)(PArg)-multiwalled carbon nanotubes (MWCNTs) composite film was used to modify glassy carbon electrode (GCE) to fabricate PArg/MWCNTs/GCE through electropolymerization of L-Arginine on MWCNTs/GCE. The PArg/MWCNTs/GCE exhibited high electro-catalytic activities towards the oxidation of 3,4-dihydroxyphenylacetic acid (DOPAC), uric acid (UA), and ascorbic acid (AA), and could be sensitively used for simultaneous determination of DOPAC, AA, and UA in pH 7.4 phosphate-buffered solution (PBS).The linear ranges were 7 microM to 2.7 mM for DOPAC, 3 microM to 1.2 mM for UA, and 70 microM to 1.4 mM for AA. The detection limits were 1.3 microM for DOPAC, 0.7 microM for UA and 20 microM for AA.     

Copper germanate nanowire electrode for the electrochemical detection of glyoxalic acid using cyclic voltammetry method

Glyoxalic acid was determined by electrochemical cyclic voltammetry method using copper germanate (CuGeO₃) nanowires as the modified glassy carbon electrode (GCE) materials. The CuGeO₃ nanowire modified GCE exhibited good detection performance for glyoxalic acid in neutral solution. The intensities of two anodic peaks vary linearly with the increase of the scan rate from 25 to 200 mVs^?1 and glyoxalic acid concentration from 0.001 to 2 mM. The detection limit was 8.5 μM and 0.78 μM for cvp1 and cvp2 with the correlation coefficient of 0.991 and 0.998, respectively. The CuGeO₃ nanowire modified GCE exhibited good reproducibility and stability.     

Sensitive determination of uric acid by using graphene quantum dots as a new substrate for immobilisation of uric oxidase

A novel strategy for highly sensitive electrochemical detection of uric acid (UA) was proposed based on graphene quantum dots (GQDs), GQDs were introduced as a suitable substrate for enzyme immobilisation. Uric oxidase (UOx) was immobilised on GQDs modified glassy carbon electrode (GCE). Transmission electron microscope, scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy techniques were used for characterising the electrochemical biosensor. The developed biosensor responds efficiently to UA presence over the concentration linear range 1–800 μM with the detection limit 0.3 μM. This novel biosensing platform based on UOx/GQDs electrode responded even more sensitively than that based on GCE modified by UOx alone. The inexpensive, reliable and sensitive sensing platform based on UOx/GQDs electrode provides wide potential applications in clinical.Inspec keywords: organic compounds, graphene devices, quantum dots, enzymes, biosensors, biochemistry, electrochemical electrodes, electrochemical sensors, transmission electron microscopy, scanning electron microscopy, voltammetry (chemical analysis), electrochemical impedance spectroscopy, nanomedicine, molecular biophysicsOther keywords: sensitive uric acid determination, graphene quantum dots, uric oxidase immobilisation, electrochemical detection, GQD, enzyme immobilisation, glassy carbon electrode, GCE, transmission electron microscope, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, electrochemical biosensor, C     

碱化插层二维过渡金属碳化物的制备及其对铀酰离子的电化学检测

二维过渡金属碳化物(MXenes)具有良好的电化学性能与辐照稳定性, 其在放射性核素电化学检测领域有潜在应用价值。本研究通过碱活化的方式处理碳化钛型MXene(Ti₃C₂T_x), 随后将钾插层的Ti₃C₂T_x(K-Ti₃C₂T_x)负载到玻碳电极(GCE)上得到K-Ti₃C₂T_x/GCE修饰电极。采用XRD、SEM、XPS等手段分别对Ti₃C₂T_x和K-Ti₃C₂T_x进行分析表征, 并进一步研究了K-Ti₃C₂T_x/GCE对痕量铀酰离子(UO₂²⁺)的电化学检测性能。循环伏安(CV)实验结果表明, 相比于GCE电极, K-Ti₃C₂T_x/GCE修饰电极对UO₂²⁺的电化学响应显著增强。进一步使用差分脉冲伏安法(DPV)扫描, 发现pH=4.0时, K-Ti₃C₂T_x/GCE修饰电极对UO₂²⁺在铀浓度0.5~10 mg/L范围内呈现良好的线性检测关系, 本方法的检测限为0.083 mg/L(S/N=3), 稳定性和重复性好。     

Selective voltammetric and amperometric detection of uric acid with oxidized diamond film electrodes

Electrochemically anodized diamond film electrodes were used for selective detection of uric acid (UA) in the presence of high concentrations of ascorbic acid (AA) by differential pulse voltammetry and chronoamperometry. Because the oxidation peak potential for AA is approximately 450 mV more positive than that for UA at anodized diamond electrodes, UA can be determined with very good selectivity. By use of chronoamperometry, linear calibration curves were obtained for UA over the concentration range up to 1 x 10(-6) M in 0.1 M HClO4 solution, with the lowest experimental value measured being 5 x 10(-8) M. This is consistent with the fact that a statistical analysis of the calibration curve yielded a detection limit of 1.5 x 10(-8) M (S/N = 3). AA in less than 20-fold excess does not interfere. The practical analytical utility of the method is demonstrated by the measurement of UA in human urine and serum without any preliminary treatment.     

Determination of pentachlorophenol at carbon nanotubes modified electrode incorporated with beta-cyclodextrin

A facile and reliable electrochemical technique at beta-cyclodextrin incorporated carbon nanotubes modified glassy carbon electrode (beta-CD/CNTs/GCE) was proposed for determination of pentachlorophenol (PCP). The electrochemical behavior of PCP at the beta-CD/CNTs/GCE was investigated by cyclic voltammetry and linear sweep voltammetry. The beta-CD/CNTs/GCE showed good analytical performance characteristics in electrocatalytic oxidation of PCP, compared with the simple carbon nanotube modified electrode (CNTs/GCE) and bare glassy carbon electrode (GCE). After accumulation for 5 min on beta-CD/CNTs/GCE, the peak current increased linearly with the concentration of PCP in the range from 8.0 x 10(-7) to 1.04 x 10(-5) mol/L. The detection limit was 4.0 x 10(-8) mol/L at 3 sigma level. The proposed electrode presented good repeatability for the determination of PCP in artificial wastewater, and the recovery was 97%-103%. This modified electrode combined the advantages of carbon nanotubes and supramolecular cyclodextrin, leading to new capabilities for electrochemical detection of PCP.     

Selective detection of a catecholamine against electroactive interferents using an interdigitated heteroarray electrode consisting of a metal oxide electrode and a metal band electrode

We developed an interdigitated array electrode (IDAE) consisting of a metal oxide electrode and a metal band heteroelectrode and employed it for the selective detection of catecholamines. We used an indium-tin oxide (ITO) film as the oxidation electrode of the IDAE because the ITO was able to suppress response currents from L-ascorbic acid (AA) and uric acid (UA), which are major electroactive interferents in biological fluids. However, the ITO film also suppresses the reduction of quinones including oxidized catecholamines. We developed a simple technique for fabricating our hetero IDAE, which also preserves the electrochemical properties of the ITO. When we compared hetero ITO-gold, homo ITO-ITO, and carbon-carbon IDAEs, we found that the hetero IDAE provided both high sensitivity and selectivity for DA detection. We achieved high selectivities for DA against AA and UA. The ratios of the response currents of AA and UA to DA were calculated as 6 and 5%, respectively.     

Synthesis and characterization of α-Fe2O3/polyaniline nanotube composite as electrochemical sensor for uric acid detection

We report the synthesis of α-Fe₂O₃/polyaniline nanotube (PAn NTs) composite as an electrochemical sensor for uric acid (UA) detection. Field emission scanning electron microscopy (FESEM) indicates a hexagonal shape of the α-Fe₂O₃ while a nanotube morphology of the PAn. Impedance spectroscopy results confirm a significant decrease in the charge transfer resistance of the glassy carbon electrode (GCE) modified with α-Fe₂O₃/PAn NTs due to the presence of PAn NTs. The results show that the increase in the conductivity of α-Fe₂O₃ in the presence of PAnNTs could improve the catalytic performance of α-Fe₂O₃/PAn NTs composite, compared to the pure α-Fe₂O₃ nanoparticles. From differential pulse voltammetry, a linear working range for the concentration of UA between 0.01?µM and 5?µM, with a LOD of 0.038?µM (S/N?=?3) was obtained. The sensitivity of the linear segment is 0.433?μA?µM^?1. The reliability of the modified electrode towards the detection of UA was investigated in the presence of interfering acids such as ascorbic acid, citric acid and succinic acid.     

Carbon fiber nanoelectrodes modified by single-walled carbon nanotubes

Microelectrode voltammetry has been considered to be a powerful technique for single biological cell analysis and brain research. In this paper, we have developed a simple method to get highly sensitive carbon fiber nanoelectrodes (CFNE) modified by single-walled carbon nanotubes (SWNTs) on the basis of our previous work. The electrochemical behavior of SWNTs/CFNE was characterized by potassium ferricyanide, dopamine (DA), epinephrine (E), and norepinephrine (NE) using cyclic voltammetry (CV). Compared with CFNE, SWNTs/CFNE has a much larger available internal surface area per external geometric area, which is supported by SEM images. The modified electrodes show very high sensitivity and favorable electrochemical behavior toward these neurotransmitters. The peak current increases linearly with the concentration of DA, E, and NE in the range of 1.0 x 10(-)(7)-1.0 x 10(-)(4), 3.0 x 10(-)(7)-1.0 x 10(-)(4), and 5.0 x 10(-)(7)-1.0 x 10(-)(4) M, respectively. The CV detection limit (S/N = 3) of DA, E, and NE is 7.7 x 10(-)(9), 3.8 x 10(-)(8), and 4.2 x 10(-)(8) M, respectively. The modified electrode exhibited almost the same electrochemical behavior after 15 days, indicating that SWNTs/CFNE is pretty stable and has good reproducibility.     

A reduced graphene oxide based electrochemical biosensor for tyrosine detection

In this paper, a 'green' and safe hydrothermal method has been used to reduce graphene oxide and produce hemin modified graphene nanosheet (HGN) based electrochemical biosensors for the determination of l-tyrosine levels. The as-fabricated HGN biosensors were characterized by UV-visible absorption spectra, fluorescence spectra, Fourier transform infrared spectroscopy (FTIR) spectra and thermogravimetric analysis (TGA). The experimental results indicated that hemin was successfully immobilized on the reduced graphene oxide nanosheet (rGO) through π-π interaction. TEM images and EDX results further confirmed the attachment of hemin on the rGO nanosheet. Cyclic voltammetry tests were carried out for the bare glass carbon electrode (GCE), the rGO electrode (rGO/GCE), and the hemin-rGO electrode (HGN/GCE). The HGN/GCE based biosensor exhibits a tyrosine detection linear range from 5?×?10(-7)?M to 2?×?10(-5)?M with a detection limitation of 7.5?×?10(-8)?M at a signal-to-noise ratio of 3. The sensitivity of this biosensor is 133 times higher than that of the bare GCE. In comparison with other works, electroactive biosensors are easily fabricated, easily controlled and cost-effective. Moreover, the hemin-rGO based biosensors demonstrate higher stability, a broader detection linear range and better detection sensitivity. Study of the oxidation scheme reveals that the rGO enhances the electron transfer between the electrode and the hemin, and the existence of hemin groups effectively electrocatalyzes the oxidation of tyrosine. This study contributes to a widespread clinical application of nanomaterial based biosensor devices with a broader detection linear range, improved stability, enhanced sensitivity and reduced costs.     

导电分子印迹膜化学修饰电极的制备及其对胭脂红的电化学检测

报道了一种聚丙烯酰胺(PAAM)-植酸(PA)-聚多巴胺(PDA)导电分子印迹膜(PAAM-PA-PDA MIP)化学修饰电极的制备、表征及其在电化学定量检测食品添加剂胭脂红(P4R)中的应用。即通过原位电聚合和碱液洗脱的方法在玻碳电极(GCE)表面制得具有分子识别作用的导电分子印迹膜(PAAM-PA-PDA MIP)化学修饰电极,并利用SEM、循环伏安法(CV)及交流阻抗法(EIS)对该导电分子印迹膜化学修饰电极的表面形貌和电化学性能进行表征。研究结果表明该方法所制备的导电分子印迹膜化学修饰电极具有良好的电化学检测性能和应用前景,其对P4R的线性检测区间为10~200 μmol/L,灵敏度为0.085 A/mol/L,检测限可达23.6 nmol/L,并可有效地应用于P4R实际样品的分析检测。      

Simultaneous measurement of dopamine and ascorbate at their physiological levels using voltammetric microprobe based on overoxidized poly(1,2-phenylenediamine)-coated carbon fiber

Overoxidized poly-(1,2-phenylenediamine) (OPPD)-coated carbon fiber microelectrodes (CFMEs) exhibit, in combination with square-wave voltammetry (SWV) detection mode, the attractive ability to simultaneously measure low nM dopamine (DA) and mM ascorbate (AA) in a pH 7.4 medium. The PPD polymer film is electrodeposited onto a carbon fiber at a constant potential of 0.8 V versus Ag/AgCl using a solution containing sodium dodecylsulfate as the dopant. After overoxidation using cyclic voltammetry (CV) in the potential range from 0 to 2.2 V at a scan rate of 10 V/s, the resulting OPPD-CFME displays a high SWV current response to cationic DA at approximately 0.2 V and has a favorably low response to anionic AA at approximately 0.0 V vs Ag/AgCl. The preparation of the new OPPD-sensing film has been carefully studied and optimized. The OPPD properties and behavior were characterized using CV and SWV under various conditions and are discussed with respect to DA and AA detection. The linear calibration range for DA in the presence of 0.3 mM AA is 50 nM to 10 microM, with a correlation coefficient of 0.998 and a detection limit of 10 nM using 45-s accumulation. The detection limit for DA in the absence of AA was estimated to be 2 nM (S/N = 3). The linear range for AA in the presence of 100 nM DA is 0.2-2 mM, with a correlation coefficient of 0.999 and a detection limit of 80 microM. The reproducibilities of SWV measurements at OPPD-CFCMEs are 1.6% and 2.5% for 100 nM DA and 0.3 mM AA, respectively. Potential interfering agents, such as 3,4-dihydroxyphenylacetic acid, uric acid, oxalate, human serum proteins, and glucose, at their physiologically relevant or higher concentrations did not have any effect. These favorable features offer great promise for in vitro and in vivo application of the proposed OPPD-coated microprobe.     

Carbon nanotube nanoweb-bioelectrode for highly selective dopamine sensing

A highly sensitive and selective dopamine sensor was fabricated with the unique 3D carbon nanotube nanoweb (CNT-N) electrode. The as-synthesised CNT-N was modified by oxygen plasma to graft functional groups in order to increase selective electroactive sites at the CNT sidewalls. This electrode was characterized physically and electrochemically using HRSEM, Raman, FT-IR, and cyclic voltammetry (CV). Our investigations indicated that the O(2)-plasma treated CNT-N electrode could serve as a highly sensitive biosensor for the selective sensing of dopamine (DA, 1 μM to 20 μM) in the presence of ascorbic acid (AA, 1000 μM).     

Synthesis,characterization, and voltammetric hydrogen peroxide sensing on novel monometallic (Ag,Co/MWCNT) and bimetallic (AgCo/MWCNT) alloy nanoparticles

Multiwall carbon nanotube supported (MWCNT) Ag, Co, and Ag-Co alloy nanocatalysts were synthesized at varying metal loadings by borohydride reduction methods without stabilizers to obtain enhanced hydrogen peroxide sensitivity. The resulting materials were characterized employing Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). For electrochemical measurements carried out cyclic voltammetry (CV) and differential pulse voltammetry (DPV), glassy carbon electrode (GCE) was modified with Ag/MWCNT, Co/MWCNT, and Ag-Co/MWCNT alloy nanoparticles. Ag-Co/MWCNT/GCE exhibited the highest performance toward electrochemical oxidation of H₂O₂ in 0.1 M phosphate buffered solution (PBS). Furthermore, the sensitivity and the limit of detection values for Ag-Co/MWCNT/GCE were obtained as 57.14 µA cm^?2 mM^?1and 0.74 µM, respectively. However, the sensitivity values for Ag/MWCNT/GCE, and Co/MWCNT/GCE are 41.66 and 13.88 µA cm^?2 mM^?1, respectively. The LOD values were predicted as 1.84 µM for Ag/MWCNT/GCE and 3.3 µM for Co/MWCNT/GCE.

In addition, the interference experiment indicated that the Ag-Co/MWCNT alloy nanoparticles have good selectivity toward H₂O₂.