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An electrochemical sensor based on a glassy carbon electrode (GCE) modified by three-dimensional graphene (3D-GE) and polyglutamic acid (PGA) was developed to quantitatively detect Amoxicillin (AMX), a worldwide used antibiotic. AMX response at PGA/3D-GE/GCE involving the transfer of one electron and an equal number of protons were determined using electrochemical approaches. Density functional theory simulations were performed to give insights on the reaction mechanism of AMX on the surface of the modified electrode. When the optimization of the experimental conditions was completed, the linear range of AMX was 2–60 μM. Besides, the detection limit was calculated as 0.118 μM (S/N = 3). And the modified electrode could detect the concentration of the AMX in human urine samples. Overall, the developed PGA/3D-GE/GCE for determination of AMX shows great potentials in practice. Image 1 • A friendly and sensitive method for the determination of amoxicillin was developed. • Polyglutamic acid/three-dimensional porous graphene (PGA/3D-GE) was used for the modification of electrode. • A new reaction mechanism of amoxicillin was proposed by combining computational simulation with electrochemical methods. [ABSTRACT FROM AUTHOR]

A fast and sensitive electrochemical sensor for simultaneous determination of ascorbic acid (AA) and acetaminophen (AP) was proposed based on g-C 3 N 4 nanofibers (h-CN) doped poly(3,4-ethylenedioxy-thiophene) (PEDOT) composite. PEDOT/h-CN hybrid film was directly deposited on glass carbon electrode (GCE) by in-situ electropolymerization. The incorporation of h-CN and PEDOT brought out enhanced electro-catalytic activity and additional binding sites for AA and AP, which could be ascribed to the synergetic effect between h-CN and PEDOT. Under the optimal experimental condition, the oxidation peak currents of AA and AP give linear response over the range of 4–20 μM, 20–1800 μM and 1–10 μM, 10–50 μM, respectively. The detection limit of the modified electrode was calculated to be 1.51 μM for AA and 0.49 μM for AP (S/N = 3). The electrochemical experiments also suggested that PEDOT/h-CN modified electrode was feasible practice for quantitative detection of AA and AP. [ABSTRACT FROM AUTHOR]

The authors describe a nonenzymatic glucose sensor that was obtained by electrochemical deposition and oxidization of metallic nickel on the surface of nitrogen-doped reduced graphene oxide (N-RGO) placed on a glassy carbon electrode (GCE). An analysis of the morphology and chemical structure indicated the composite to possess a well-defined vermicular Ni(OH) nanorods combined with N-RGO. The electrochemical performance of the modified GCE with respect to the detection of glucose in 0.1 M NaOH was investigated by cyclic voltammetry and amperometry. The wrinkle and protuberance of N-RGO for loading of nanostructured Ni(OH) are found to increase electrical conductivity, surface area, electrocatalytical activity and stability. The modified GCE displays a high electrocatalytic activity towards the oxidation of glucose in 0.1 M NaOH solution. The lower detection limit is 0.12 μM at an applied potential of +0.45 V (vs Ag/AgCl) (S/N=3), and the sensitivity is 3214 μA mM cm. The modified GCE possesses long-term stability, good reproducibility and high selectivity over fructose, sucrose and lactose. [ABSTRACT FROM AUTHOR]

Ultrasensitive explosive sensors are significant in anti-terrorism and related environment issues. Herein, we proposed a novel boron-doped graphene (B-GE) modified glassy carbon electrode (GCE) applied as a simple, sensitive electrochemical high melting explosive (HMX) sensor. The morphology and structure features of B-GE were characterized. The electrochemical behaviors of HMX on the B-GE modified GCE were investigated by cyclic voltammetry (CV). Under the optimized conditions, CV was used for the quantitative detection of HMX, and the reduction peak current exhibited good linear dependence with the concentration of HMX in the ranges of 2 ∼ 20 μM and 20 ∼ 100 μM. The low detection limit (LOD) was calculated as 0.83 μM (245.81 ppb). Furthermore, the B-GE/GCE showed satisfactory repeatability, high selectivity and stability. The reduction reaction mechanism of HMX on B-GE modified electrode was explored by computational theoretical analysis. Additionally, the differences of the reduction mechanisms from nitroaromatic explosives were discussed. [ABSTRACT FROM AUTHOR]

Poly(3-methylthiophene)/nitrogen doped graphene modified glassy carbon electrode (P3MT/NGE/GCE) was prepared through simple drop-casting of NGE, followed by the electrodeposition of P3MT film for sensitive electrochemical determination of trace amounts of pesticide phoxim. The morphology and structure of P3MT/NGE/GCE were characterized by scanning electron microscopy; the electrochemical behavior of P3MT/NGE/GCE was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and chronocoulometry. The preparation conditions of modified electrode, the dropping amount of NGE and polymerization laps of P3MT, were optimized. Under the optimized conditions, the reduction peak current of cyclic voltammetric curve varied linearly with the concentration of phoxim over the two linear ranges of 0.02–0.2 μM and 0.2–2.0 μM, and the low detection limit was 6.4 nM according to lower linear range (S/N = 3). The sensor also exhibited excellent selectivity to phoxim over a wide range of possible interferents including ions, biomolecules, common environment pollutants and widely-used organophosphate pesticides. Moreover, the satisfactory practical feasibility of the sensor was evaluated by the environmental phoxim measurements. [ABSTRACT FROM AUTHOR]

Polycarbazole (PCZ)/nitrogen-doped graphene (N-GE) composite was prepared by electropolymerization of carbazole on the N-GE modified glass carbon electrode (N-GE/GCE) for fabricating a novel electrochemical sensor for 4-nitrophenol (4-NP). The PCZ/N-GE shows high conductivity and well-distributed nanostructure. The redox behavior of 4-NP at a PCZ/N-GE/GCE was investigated in acetate buffer solution by cyclic voltammetry (CV), compared with the bare GCE, reduced graphene oxide (RGO), N-GE and PCZ modified GCEs. The results indicate that all modified electrodes show the enhanced reduction peak currents. However, the PCZ/N-GE/GCE exhibits the highest peak current and most positive reduction potential of 4-NP, which reflects the PCZ/N-GE composite has the best electrocatalytic activity towards 4-NP. The enhanced electrochemical performance of PCZ/N-GE and the electrocatalytic activity to 4-NP are contributed to the synergic effect of PCZ and N-GE with highly conductivity and large surface area, which can greatly facilitate the electron-transfer processes between the electrolyte and electrode. An electrochemical sensor for 4-NP was developed based on the PCZ/N-GE modified electrode under the optimized conditions. The reduction peak current was linear with the concentration of 4-NP in the range of 8 × 10 -7 ∼2 × 10 -5 M. The low detection limit of the sensor was estimated to be 0.062 μM (S/N = 3). The sensor based on PCZ/N-GE/GCE was also applied to the detection of 4-NP in real water samples. [ABSTRACT FROM AUTHOR]

Abstract: Novel three dimensional (3D) Co3O4/C flower-like nanostructures are synthesized via a facile solvothermal strategy. The samples are characterized by XRD, XPS, FT-IR, Raman, TG, SEM and HRTEM. The results show that the 3D flower-like nanostructures are consisted of numerous 2D nanosheets with the thickness of about 20 nm. The pseudocapacitive behaviors of Co3O4/C and bare Co3O4 flower-like nanostructures are investigated by cyclic voltammograms, galvanostatic charge–discharge and electrochemical impedance spectroscopy test. The results reveal that the Co3O4/C delivers a large specific capacitance of as high as 865 F g−1 and 330 F g−1 at 1 mV s−1 and 0.5 A g−1, according to CV and galvanostatic test, respectively; while the bare Co3O4 has a poor electrochemical performance, which exhibits specific capacitance of 131.7 F g−1 and 46.1 F g−1 at the same condition. The excellent electrochemical performance is attributed to the carbon present on the Co3O4 and the morphology, which possesses large surface area, unique flower-like nanostructures and low equivalent series resistance. [Copyright &y& Elsevier]

[Display omitted] • The highly active crystal rod like Bi 2 O 3 /ZnO nanocomposite synthesized through a low cost coprecipitation method. • The modified electrode exhibits outstanding electrochemical performance towards the IP oxidation. • Bi 2 O 3 /ZnO/GCE exhibits good selectivity, stability, and reproducibility and good recovery for real sample analysis. With an increased understanding of human health in recent years, rapid and reliable methods for identifying prescription drugs have become progressively essential. In this concern, here we have demonstrated the nano crystal rod like Bi 2 O 3 /ZnO were first synthesized through a coprecipitation approach using sodium hydroxide as a precipitating agent. The prepared material was employed as an effective catalyst and then used to detect β adrenoceptor agonist isoprenaline (IP). Taking full advantage of about their improved properties, a novel electrochemical IP sensor was constructed by drop-coasting Bi 2 O 3 /ZnO on glassy carbon electrode. Various analytical and electrochemical methods were used to characterize the physical and chemical properties of prepared material. Under optimal conditions, the present sensor showed a dynamic linear range (0.04 µM to 258.4 µM) with a detection limit of 0.06 µM (n = 3). The sensitivity was calculated to be 11.45 μA μM−1 cm−2. Finally, the proposed electrode was successfully applied to the determination of IP in practical samples such as pharmaceutical and urine using standard addition method with satisfactory recovery result. [ABSTRACT FROM AUTHOR]

Metal oxides decorated carbon nanomaterials, as an electrode material have been well explored in the field of electrochemical sensor. However, instead of using the high concentration of graphene oxide (GO), we try to explore the influence of minimum quantity of GO in material synthesis. Here we demonstrate the hydrothermal synthesis of low-cost cerium (Ce)-doped tungsten oxide/graphene oxide (CeW/GO) composite for the precise electrochemical detection of antibiotic drug furazolidone (FUZ). For the synthesis of composite, 40 μg/mL concentration of GO has been utilized. Then, several physicochemical and electrochemical techniques were used to examine the morphological, structural, and electrochemical characteristics of the CeW/GO composite. Interestingly, the composite material has a porous-coral-like structure, which is being described here for the first time. The GO nanosheets cover the CeW and make the smooth surface and lead to the porous structure. Then we looked into the analytical behavior of CeW/GO composite modified glassy carbon electrode for the application towards the electrochemical detection of the FUZ using the voltammetric technique. The effect of experimental conditions, including loading concentration of active material, pH, scan rate, accumulation time, and concentration of FUZ, were analyzed with respect to the reduction peak current response of FUZ. At the optimum conditions, the fabricated sensor has a low detection limit (0.054 μM), appreciable sensitivity (2.5 μA μM−1 cm−2) with a wide linear range (1–260 μM), and the decent anti-interference ability for FUZ detection. Furthermore, the developed sensor was successfully used to assess the FUZ concentration in the human urine samples, yielding satisfactory results. [Display omitted] • porous-coral-like CeW/GO micro balls composite material was designed for the first time. • The CeW/GO composite was employed as a novel electrocatalyst to detect the furazolidone (antibiotic drug). • A detailed study was made on electrochemical performance of the developed sensor. • The performance of CeW/GO/GCE was comparable with the noble metals (Pt, Re, and Au) based modified electrodes. [ABSTRACT FROM AUTHOR]

Abstract: Polycarbazole (PCz) and PCz/chemically reduced graphene oxide (PCz/CRGO) modified glassy carbon electrodes (GCEs) were fabricated by a simple procedure and characterized. The modified electrodes based on PCz or PCz/CRGO were used as sensing electrodes for the voltammetric investigation of imidacloprid (IMI) insecticides. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as sensing techniques. Both of modified electrodes have good electrocatalytic activity toward the reduction of IMI. The presence of CRGO enhanced the electrochemical signal of the modified glassy carbon electrode (GCE), which increased the sensitivity of the sensor. The limit of detection (LOD) and the limit of quantitation (LOQ) values for CV are 0.22μM and 0.74μM, respectively; while those values for DPV are 0.44μM and 1.52μM, respectively. [Copyright &y& Elsevier]

Herein, a sensitive sensing platform for acetaminophen based on palladium and multi-walled carbon nanotube nanocomposites and its electrochemical detection mechanism were presented in the first time. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy were utilized to characterize the morphology and structure of Pd-MWCNTs composite. Through the computer simulation, the Gaussian 09 and Multiwfn methods were used to study the redox mechanism of AP. Further electrochemical performance of AP was carried out by cyclic voltammetry (CV). The experimental results illustrated that Pd-MWCNTs modified electrode amplified the redox current of AP. Quantitative detection of AP by the DPV method revealed that the oxidation peak current of AP showed an acceptable linear response of 0.5 μM–100 μM with a detection limit of 0.13 μM (S/N = 3). The modified electrode also exhibited a good recovery in real sample detection. Image 1028 • An original and sensitive method for the determination of acetaminophen was developed. • Palladium/multi-walled carbon nanotubes composite (Pd/MWCNTs) was utilized to modify electrode. • A new type of sensor was obtained by a facile process with dropping Pd/MWCNTs on a glassy carbon electrode. • A novel reaction mechanism of acetaminophen was proposed by introducing computer calculation. [ABSTRACT FROM AUTHOR]