A Facile Fabrication of Poly-ethionine Film on Glassy Carbon Electrode for Simultaneous and Sensitive Detection of Dopamine and Paracetamol

An electrochemical sensor based on poly-ethionine (Poly-ET) film modified glassy carbon electrode was developed for sensitive and simultaneous sensing of dopamine (DA) and paracetamol (PA). The electropolymerization of ethionine monomer was carried out to modify the electrode. The modified electrode was characterized by using scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The Poly-ET/GCE exhibited excellent electrocatalysis towards the sensing of DA and PA. Poly-ET/GCE showed a linear increase of current response with increase concentration of DA and PA ranging from 0.1 μM–60 μM and 0.1 μM–180 μM, respectively. The LODs were found to be 7 nM and 18 nM (S/N=3) for DA and PA, respectively. This electrochemical sensor was successfully utilized for the detection of DA and PA in pharmaceutical samples.     

RNA Modified Electrodes for Simultaneous Determination of Dopamine and Uric Acid in the Presence of High Amounts of Ascorbic Acid

A promising electrochemical biosensor was fabricated by electrochemical grafting of ribonucleic acid (RNA) at 1.8 V (vs. SCE) on glassy carbon electrode (GCE) (denoted as RNA/GCE), for simultaneous detection of dopamine (DA) and uric acid (UA) with coexistence of excess amount of ascorbic acid (AA). The electrode was characterized by X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The RNA modified layer on GCE exhibited superior catalytic ability and anionic exclusive ability in comparison with the DNA modified electrode. Three separated anodic DPV peaks were obtained at 0.312, 0.168 and ?0.016 V for UA, DA and AA, respectively, at the RNA/GCE in pH 7.0 PBS. In the presence of 2.0 mM AA, a linear range of 0.37 to 36 μM with a detection limit of 0.2 μM for DA, and in the range of 0.74 to 73 μM with a detection limit of 0.36 μM for UA were obtained. The co‐existence of 5000 fold AA did not interfere with the detection of DA or UA. The modified electrode shows excellent selectivity, good sensitivity and good stability.     

A Simple and Renewable Nanoporous Gold‐based Electrochemical Sensor for Bisphenol A Detection

A sensitive and simple electrochemical sensor based on nanoporous gold (NPG) was developed for the detection of bisphenol A (BPA). NPG was prepared by the dealloying method. The NPG modified glassy carbon electrode (GCE) displayed excellent catalytic activity towards the electrooxidation of BPA. The mechanism of the electrooxidation of BPA on NPG/GCE sensor was inferred. The sensor showed a linear range from 0.1 μM to 50 μM with a detection limit of 12.1 nM BPA. Specially, a simple but effective approach was attempted to renew the used sensor. The application of the sensor for real sample analysis was demonstrated.     

Synthesis and Electrochemical Investigation of Tetra Amino Cobalt (II) Phthalocyanine Functionalized Polyaniline Nanofiber for the Selective Detection of Dopamine

A new electrochemical sensing platform based on tetra‐amino cobalt (II) phthalocyanine (TACoPc) ingrained polyaniline (PANI) nanofiber composite (TACoPc/PANI hybrid) has been developed for the selective detection of dopamine. The uniform fibrous network of PANI/TACoPc hybrid was synthesized by a one‐step oxidative polymerization at room temperature. The synthesized nanocomposite was characterized using field emission scanning electron microscopy (FESEM), energy dispersive X‐ray (EDX), fourier transmission infrared spectroscopy (FTIR), raman spectroscopy, X‐ray diffraction (XRD) and UV‐Visible spectroscopy. The electrochemical behavior of the TACoPc/PANI hybrid material was studied by using different electrochemical techniques, including cyclic voltammetry (CV) and chronoamperometry in 0.1 M phosphate buffer solution (PBS) of pH 7 by modifying the glassy carbon electrode (GCE). Due to the synergistic impact of PANI and TACoPc, the suggested altered electrode provided superior catalytic performance for dopamine even in the presence of ascorbic acid. It exhibited a linear reaction with a high sensitivity of 1.212 μA/μM cm^?2 and a low detection limit of 0.064 μM over the 20–200 μM concentration range in 0.1 M PBS. One of the commonly faced problems of interference of ascorbic acid and uric acid in the electrochemical detection of dopamine was completely excluded from this modified electrode which led to an increase in the catalytic activity of the material for the detection of dopamine in the presence of ascorbic acid.     

A Sensitive Electrochemical Sensor for Voltammetric Determination of Ganciclovir Based on Au‐ZnS Nanocomposite

An electrode modified with ZnS and gold nanoparticles (Au‐ZnS NPs) is introduced for highly sensitive voltammetric determination of ganciclovir (GCV). Surface structure and topography of the modified electrode was studied by SEM, EDX and XRD techniques. Electrochemical oxidation of GCV was investigated by cyclic (CV) and square wave voltammetry (SWV) in Briton‐Robinson buffer solution (pH 1.5). The results showed that electrochemical oxidation of GCV at the Au‐ZnS modified glassy carbon electrode (GCE) is irreversible and exhibited diffusion controlled electrode process over the pH range from 1.0 to 6.0. The oxidation potential peak and pH relationship showed that electrons and protons were transferred simultaneously over the electrochemical oxidation process. Using the proposed sensor, the linear calibration curves were obtained in the ranges of 0.04–1.50 μM and 1.5–70.0 μM with detection limit of 0.01 μM GCV by SWV technique. The modified electrode was successfully applied as a sensitive, reproducible and repeatable sensor for determination of the trace amount of GCV in human serum, urine and cymevene vials. Reasonable results were obtained from comparing the measurements of the real samples by the new sensor to high performance liquid chromatography (HPLC) as a standard method.     

Synthesis of graphene oxide nanosheet: A novel glucose sensor based on nickel-graphene oxide composite film

The graphene oxide (GO) nanosheets were produced by chemical conversion of graphite, and were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR). An electrochemical sensor based on Ni/graphene (GR) composite film was developed by incorporating Ni²⁺ into the graphene oxide film modified glassy carbon electrode (Ni/GO/GCE) through the electrostatic interactions with negatively charged graphene oxide. The Ni²⁺/graphene modified glassy carbon electrode (Ni/GR/GCE) was prepared by cyclic voltammetric scanning of Ni/GO/GCE in the potential range from ?1.5 to 0.2 V at 50 mV s^?1 for 5 cycles. The electrochemical activity of Ni/GR/GCE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni/GR/GCE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. The introduction of conductive graphene not only greatly facilitates the electron transfer of Ni²⁺, but also dramatically improves the long-term stability of the sensor by providing the electrostatic interactions. Ni/GR/GCE also shows good electrocatalytic activity toward the oxidation of glucose. The Ni/GR/GCE gives a good linear range over 10 to 2700 μM with a detection limit of 5 μM towards the determination of glucose by amperometry. This sensor keeps over 85% activity towards 0.1 mM glucose after being stored in air for a month, respectively. Furthermore, the modified sensor was successfully applied to the sensitive determination of glucose in blood samples.     

A Novel Sensitive Electrochemical Sensor Based on Nickel Chloride Solution Modified Glassy Carbon Electrode for Curcumin Determination

In this research, the high conductivity of nickel chloride solution as well as the ability of nickel ions in establishing particular bonds with curcumin was benefited to fabricate a new electrochemical sensor based on nickel chloride solution modified glassy carbon electrode (NiCl₂/GCE) for detection and measurement of curcumin in human blood serum. Atomic force microscope (AFM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) methods indicated that using nickel chloride solution for the modification of the glassy carbon electrode (GCE) surface had a significant effect on improvement of the electrode performance. Differential pulse voltammetry (DPV) was used for quantitative measurement of curcumin, which exhibited the linear response of NiCl₂/GCE toward curcumin within the concentration range of 10–600 μM and provided the detection limit of 0.109 μM for curcumin in human blood serum.     

盐酸普萘洛尔分子印迹电化学传感器的制备与研究

以盐酸普萘洛尔为目标模板分子,通过电聚合多巴胺,在多壁碳纳米管修饰的玻碳电极表面制备了对目标分子有特异响应的分子印迹电化学传感器.利用扫描电子显微镜、循环伏安法和差示脉冲伏安法对此传感器的表面形貌及性能进行了表征,并且优化了检测条件,研究了印迹传感器对模板分子及其结构类似物的选择性响应.结果表明:此传感器具有较好的选择性响应,而且碳纳米管的存在显著提高了传感器的灵敏度.盐酸普萘洛尔的浓度在0.20～100 μmol/L范围内与峰电流呈良好的线性关系;检出限为2.53×10-8 mol/L(S/N=3).此传感器还具有良好的稳定性和重现性.     

Electrochemical reduced graphene oxide-poly(eriochrome black T)/gold nanoparticles modified glassy carbon electrode for simultaneous determination of ascorbic acid,dopamine and uric acid

This work reports on the preparation of electrochemically reduced graphene oxide (ERGO)-poly(eriochrome black T) (pEBT) assembled gold nanoparticles for the simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA) in PBS pH 6.0. Characterisations of the composite were carried out by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. As a result of the synergistic effect, the modified glassy carbon electrode (GCE) possessed an efficient electrochemical catalytic activity with a high selectivity and sensitivity in oxidising AA-DA and DA-UA as compared to the bare GCE. The peak separations of AA and DA, DA and UA were 183 mV and 150 mV, respectively. The linear response ranges for AA, DA and UA were 10–900 μM, 0.5–20 μM and 2–70 μM with detection limits of 0.53 μM, 0.009 μM and 0.046 μM (S/N = 3), respectively. The sensitivity of ERGO-pEBT/AuNPs was measured as 0.003 µA/μM, 0.164 µA/μM and 0.034 µA/μM for AA, DA, and UA, respectively. The modified electrochemical sensor was used in the determination of AA, DA, and UA in vitamin C tablets and urine sample with good recovery.     

Sensitive and Facile Determination of Catechol and Hydroquinone Simultaneously Under Coexistence of Resorcinol with a Zn/Al Layered Double Hydroxide Film Modified Glassy Carbon Electrode

A stable dihydroxybenzene sensor was fabricated by electrochemical deposition of Zn/Al layered double hydroxide film on glassy carbon electrode (LDHf/GCE). The sensitive and facile electrochemical method for the simultaneous determination of catechol (CA) and hydroquinone (HQ) under coexistence of resorcinol (RE) has been achieved at the LDHf/GCE in phosphate buffer solution (pH 6.5). Under the optimized conditions, the differential pulse voltammetry response of the modified electrode to CA (or HQ) shows a linear concentration range of 0.6 μM to 6.0 mM (or 3.2 μM to 2.4 mM) with a correlation coefficient of 0.9987 (or 0.9992) and the calculated limit of detection is 0.1 μM (or 1.0 μM) at a signal‐to‐noise ratio of 3. In the presence of 50 μM isomer, the linear concentration ranges for CA and HQ are 3.0 μM to 1.5 mM and 12.0 μM to 0.8 mM, respectively. The detection limits are 1.2 μM and 9.0 μM. Further, the proposed method has been performed to successfully detect dihydroxybenzene isomers in analysis of real samples, such as water and tea.     

Platinum Nanoparticles/Poly(isoleucine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Hydroquinone and Catechol

A new electrochemical sensor based on Poly(Isoleucine) modified glassy carbon electrode decorated with platinum nanoparticles (Pt/Poly(Isoleucine)/GCE) was developed for sensitive individual and simultaneous determination of hydroquinone (HQ) and catechol (CC). Scanning electron microscopy (SEM), Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) were performed in order to characterize the Pt/Poly(Isoleucine)/GCE nanocomposite. For simultaneous determination of HQ and CC, Pt/Poly(Isoleucine)/GCE showed wide linear range between the 0.01–100.0 μM. The detection limits were 0.006 μM for HQ and 0.005 μM for CC. The Pt/Poly(Isoleucine)/GC electrode exhibited good sensitivity and reliability in the simultaneous electroanalysis of two isomers in PBS of pH 7.5. The modified electrode was used to detect the isomers in naturel samples.     

Electrochemical Behavior and Voltammetric Determination of Curcumin at Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode

This work presents a sensitive voltammetric method for determination of curcumin by using a electrochemically reduced graphene oxide (ERGO) modified glass carbon electrode (GCE) in 100 mM KCl‐10 mM sodium phosphate buffer solution (pH 7.40). The electrochemical behaviors of curcumin at ERGO/GCE were investigated by cyclic voltammetry, suggesting that the ERGO/GCE exhibits excellent electrocatalytic activity towards curcumin, compared with bare GCE and GO/GCE electrodes. The electrochemical reaction mechanisms of curcumin, demethoxycurcumin and bisdemethoxycurcumin at the ERGO/GCE were also investigated and discussed systematically. Under physiological condition, the modified electrode showed linear voltammetric response from 0.2 μM to 60.0 μM for curcumin, with the detection limit of 0.1 μm. This work demonstrates that the graphene‐modified electrode is a promising strategy for electrochemical determination of biological important phenolic compounds.     

Electrocatalysis of Cu−MOF/Graphene Composite and its Sensing Application for Electrochemical Simultaneous Determination of Dopamine and Paracetamol

A nanocomposite of HKUST‐1 (MOF) and electroreduction graphene oxide (ERGO) is prepared and applied as an electrochemical sensor for the simultaneous determination of paracetamol and dopamine by means of one‐step electrodeposition. The MOF/ERGO composite displays excellent electrochemical catalytic activities towards the paracetamol and dopamine, which is attributed to the synergistic effect of big surface area, porosity and high electrocataytic activity of the MOF and good conductivity of ERGO. The modified electrode could be applied to determine simultaneously paracetamol and dopamine in biochemical samples with wide linear ranges (0.2 μM to 160 μM for paracetamol and 0.2 μM to 300 μM for dopamine) and low detection limits (0.016 μM for paracetamol and 0.013 μM for dopamine). Meanwhile, the proposed sensor still displays high sensitivity, good selectivity and excellent stability.     

Carbon Quantum Dots Co‐catalyzed with ZnO Nanoflowers and Poly (CTAB) Nanosensor for Simultaneous Sensitive Detection of Paracetamol and Ciprofloxacin in Biological Samples

A novel platform based incorporation of carbon quantum dots (CQDs) and zinc oxide nanoflowers (ZnO‐NFs) decorated with poly cetyltrimethylammonium bromide (CTAB) was developed as electrochemical sensor for the sensitive and selective simultaneous detection of Paracetamol (PAR) and Ciprofloxacin (CIP) in biological samples. For this, CQDs and ZnO‐NFs were first deposited on a glassy carbon electrode (GCE) and subsequently a Poly (CTAB) layer was grown onto their surfaces through electro‐polymerization. The synthesized nanostructures and the corresponding fabricated sensor were characterized by the techniques of TEM, XRD, FE‐SEM, and EDX analysis. Moreover electrochemical characterization by CV and DPV were performed to elucidate the construction process and electron transfer abilities of the CQDs/ZnO‐NFs/Poly(CTAB)/GCE. Increased sensitivity and efficiency of this sensing system was obtained due to the synergistic effects of CQDs, ZnO‐NFs and Poly (CTAB) with multi‐signal amplification. Under the optimum conditions, the DPV response of proposed sensor to PAR and CIP was linear at 0.05–30.0 μM and 0.01–30.0 μM, with the detection limit of 2.47 nM and 1.97 nM respectively. The sensor possessed high stability, reproducibility, sensitivity, and selectivity toward PAR and CIP detection, over potential interferents and presented high recovery percentage in the real sample matrices.     

In situ Electroreduction of Graphene Oxide: Increased Sensitivity for the Determination of NADH

A novel and useful method to catalyze the electro‐oxidation of nicotinamide adenine dinucleotide (NADH) over a glassy carbon electrode (GCE) modified with graphene oxide (GO) is presented. Based on the presence of oxygen moieties in GO, which can be easily reduced, an in situ electrochemical generation of reduced graphene oxide (denoted as erGO) applying a sufficient negative potential. A potential of ?1.000 V was selected to generate the erGO/GCE as a pretreatment potential before the detection of NADH. The in situ generated erGO/GCE system produces a decrease in the overpotential of NADH oxidation from +0.720 V to +0.230 V compared with GCE. The process also produced an important increase in current signals. The modified electrode was characterized by scanning electron (SEM) and electrochemical microscopies (SECM), cyclic voltammetry and by Raman spectroscopy. Amperometric detection of NADH via this straightforward electrocatalytic method provides a wide linear range between 10 and 100 μM, a lower detection limit of 0.36 μM and an excellent sensitivity of (1.47±0.09) μA mM^?1.     

Preparation and Characterization of Bhant Leaves‐derived Nitrogen‐doped Carbon and its Use as an Electrocatalyst for Detecting Ketoconazole

In this study, the electrocatalytic characteristics of nitrogen‐doped carbon (NDC) prepared from Clerodendrum Infortunatum L leaves on a glassy carbon electrode (GCE) surface was evaluated with regards to its ability to detect the electroactive drug ketoconazole (KCZ). The NDC was prepared by carrying out a simple pyrolysis of dry powder of the leaves at 850 °C. The prepared NDC was characterized using field‐emission scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X‐ray photoelectron spectroscopy and Brunauer‐Emmett‐Teller analysis, and was then used as an electrode material. The performance of the electrochemical KCZ sensor with the NDC‐modified glassy carbon electrode (NDC/GCE) was found to be optimal when using PBS buffer at pH 3 and a concentration of 0.1 mg/ml of NDC in the conjugate with Nafion polymer. Under these conditions, the NDC/GCE displayed a KCZ detection limit of 3 μM and a linear dependence of its response on KCZ concentration over a wide range of KCZ concentrations from 47 μM to 752 μM (R²=0.9742). These results confirmed the potential of NDC as an electrocatalyst.     

Synthesis of chiral cyclodextrin metal-organic framework modified with platinum on glassy carbon electrodes: Electrochemical chiral recognition of methionine enantiomers

A platinum nanoparticle-modified chiral cross-linked cyclodextrin MOF (Pt-CLMOF) was synthesized. Then, a chiral electrochemical sensor was constructed using the Pt-CLMOF nanomaterials for the recognition of methionine (Met) enantiomers and the chiral recognition mechanism was revealed by density functional theory calculations. The recognition effect of Pt-CLMOF modified electrode (Pt-CLMOF/GCE) on Met was studied by differential pulse voltammetry. The enantioselectivity coefficient (IL/ID) was 1.98. There is an acceptable linear relationship between peak current and Met enantiomer concentration in the 2–200 μM range, the detection limits of L–Met and D-Met were 0.33 and 0.60 μM which were obtained by this electrochemical sensor, respectively. The synthesized materials were successfully applied to the analysis of Met enantiomers, indicating that Pt-CLMOF materials have good application potentiality.     

Ni0.1Co0.9Fe2O4-based electrochemical sensor for the detection of paracetamol

A novel electrochemical sensor based on nickel-doped cobalt ferrite nanoparticles (Ni_0.1Co_0.9Fe₂O₄)-modified glassy carbon electrode (NCF/GCE) was presented for the sensitive detection of paracetamol. Experimental conditions such as pH, applied potentials and concentration were investigated using cyclic voltammetric and chronoamperometric techniques. The modified electrode exhibited excellent catalytic response towards the oxidation of paracetamol with good reproducibility. The overpotential for oxidation of paracetamol is decreased, and the current response enhanced significantly on the modified electrode in comparison with that of bare electrode. Linear calibration curve is obtained over the range 2 μM to 8,000 μM having a detection limit of 11 nM. The modified electrode facilitated the simultaneous detection of paracetamol, ascorbic acid, and dopamine with good reproducibility.     

Single step modification of copper electrode for the highly sensitive and selective non-enzymatic determination of glucose

A non-enzymatic sensor was developed for the determination of glucose in alkaline medium by anodisation of copper in sodium potassium tartrate solution. The morphology of the modified copper electrode was studied by scanning electron microscopy, and its electrochemical behavior by cyclic voltammetry and electrochemical impedance spectroscopy. The electrode enables direct electrocatalytic oxidation of glucose on a CuO/Cu electrode at 0.7 V in 0.1 M sodium hydroxide. At this potential, the sensor is highly selective to glucose even in the presence of ascorbic acid, uric acid, or dopamine which are common interfering species. The sensor displays a sensitivity of 761.9 μA mM^?1 cm^?2, a linear detection range from 2 μM to 20 mM, a response time of <1 s, and a detection limit of 1 μM (S/N = 3). It was tested for determination of glucose level in blood serum.     

Highly Sensitive Electrochemical Sensor Based on Pt Doped NiO Nanoparticles/MWCNTs Nanocomposite Modified Electrode for Simultaneous Sensing of Piroxicam and Amlodipine

In this paper, a high‐sensitivity electrochemical sensor based on platinum (Pt) doped nickel oxide (NiO) nanoparticles and multi‐walled carbon nanotubes (MWCNTs) modified glassy carbon electrode (Pt?NiO/MWCNTs/GCE) has been developed to determine piroxicam (PIR) and amlodipine (AML) simultaneously. The electrochemical behavior of PIR and AML at the proposed sensor has been investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) methods. Pt doped NiO nanoparticles were synthesized by the sol‐gel procedure and were investigated using X‐ray diffraction (XRD), energy dispersive X‐ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM) techniques. DPV responses of PIR and AML increased linearly with their concentration in wide linear dynamic ranges of 0.6–320.0 μM and 1.0–250.0 μM, respectively. The limits of detection were 0.061 μM for PIR and 0.092 μM for AML. The excellent analytical figure of merits of the proposed modified electrode leads to application of it promising electrochemical sensor to determine PIR and AML in human serum and urine with satisfactory results.