Search

Abstract The sensing performance of a Langmuir-Blodgett monolayer was significantly improved by controlling the film organization at the air-water interface. Cellulose acetate (CA) and 4-tert-butylcalix [6]arene (calix) were co-spread and formed a Langmuir film, which was efficiently transferred onto a preoxidized gold electrode, Au ox. The modified gold electrode was applied as a fast, highly sensitive electrochemical sensing platform for the quantitative determination of a model molecule, dopamine (DA). The modified gold electrode, CA-calix/Au ox , demonstrated better recognition and sensing ability towards dopamine as compared with electrodes modified by a single component. Under the optimized conditions, the reduction peak currents at the CA-calix/Au ox increased linearly within the concentration range of dopamine from 5 to 100 and 100–7500 nM, and exhibited a very low limit of detection (LOD) of 2.54 nM (S/N = 3). These results suggest a simple, superior and efficient approach for the controllable rearrangement of Langmuir-Blodgett monolayers on a molecular level. The electroanalytical performance was optimized from the perspective of the electrode-electrolyte interface. Graphical abstract Image 1 Highlights • A mixed Langmuir layer composed of cellulose acetate, and the selectivity factor, calixarene, were co-spread at the air-water interface. • The Langmuir film was transferred onto a solid gold electrode and used as a means of electrochemically detecting dopamine. • The Langmuir-Blodgett based interface was carefully studied and exhibits superior electrochemical performance for the detection of dopamine. [ABSTRACT FROM AUTHOR]

Quercetin (QR), abundant in plants, is used to treat colitis and gastric ulcer and is also a promising anticancer agent. To quantificationally detect QR, a sensitive electrochemical sensor was fabricated by palladium nanoparticles loaded on carbon sphere @ molybdenum disulfide nanosheet core-shell composites (Cs@MoS2-Pd NPs). The Cs@MoS2-Pd NPs worked to remedy the shortcomings of MoS2 and exhibited good catalytic activity to QR. The oxidation reaction of QR on Cs@MoS2-Pd NPs/GCE involved two electrons and two protons. Furthermore, the molecular surface for electrostatic potential, Laplacian bond order, and Gibbs free energy were computationally simulated to speculate the order and site of the oxidation of QR. The results showed that the 4′ O–H and 3′ O–H broke successively during the oxidation reaction. When the concentration of QR was within 0.5 to 12 μM, the fabricated sensor could achieve linear detection, and the detection limit was 0.02 μM (S/N = 3). In addition, the sensor possessed good selectivity, repeatability, and stability, which has a broad prospect in practical application. [ABSTRACT FROM AUTHOR]

A simple and sensitive label-free electrochemical biosensor for nimodipine was fabricated by using nitrogen-doped graphene (NGE) modified electrode. The surface morphology and electron transfer behavior of the modified electrodes were studied by scanning electron microscopy and electrochemical impedance spectroscopy, respectively. The electrochemical behaviors of nimodipine at the modified electrodes were investigated by using cyclic voltammetry. On the basis of the excellent electrocatalytic activity of NGE, an obvious cathodic peak of nimodipine could be caused at the NGE modified glassy carbon electrode (GCE), moreover, the electrochemical signal was greatly enhanced compared with the undoped graphene modified GCE. Under the optimized conditions, the present sensor showed excellent performances for nimodipine detection including wide linear range of 0.02–3 μM, low detection limit (9.1 nM), good selectivity to the general coexisted interferences, etc. The proposed biosensor was also successfully applied to validate its capability for the analysis of nimodipine in tablets. The work would promote the potential application of NGE as an excellent material in fabricating electrochemical sensors for chemical or biochemical analysis. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor based on nitrogen doped graphene (NGE) and palygorskite (Pal) for the simultaneous detection of hydroquinone (HQ) and catechol (CT) has been proposed. Pal is particularly pointed out for its appreciable specific surface area and reactive-OH groups on its surface. Acid treatment Pal demonstrated better physico-chemical properties, which are propitious to electrochemical sensor construction. The introduction of NGE not only improved the poor conductivity of Pal but also served as an excellent adherent matrix. The modified electrode demonstrated the enhanced redox peak currents of HQ and CT with good discrimination. Under optimized conditions, the linear ranges for HQ and CT were 2–50 μM and 1–50 μM, with detection limit (LOD) of 0.8 μM and 0.13 μM, respectively. The result designates that the Pal/NGE composite promises to be a new eco-friendly modified material for sensor fabrication. [ABSTRACT FROM AUTHOR]

A fast, ultrasensitive electrochemical sensing platform based on graphitic carbon nitride-electrochemically deposited-poly(3,4-ethylenedioxythiophene) (g-C 3 N 4 -E-PEDOT) composite was constructed by in-situ electropolymerization and applied for the quantitative determination of acetaminophen (AP). E-PEDOT was introduced as the conducting matrix for developing g-C 3 N 4 composite to complement the poor conductivity disadvantage of g-C 3 N 4 . The strong affinity and synergetic effect between g-C 3 N 4 and E-PEDOT, which were analyzed by PM6 computational calculation, highly improved the electron transfer property and remarkably enhanced the electrochemical catalytic activity of the composite. The g-C 3 N 4 -E-PEDOT modified glassy carbon electrode (GCE) demonstrated better electrocatalytic activity towards the oxidation of AP than bare, g-C 3 N 4 and E-PEDOT modified ones. Under the optimized conditions, the oxidation peak currents at the g-C 3 N 4 -E-PEDOT/GCE increased linearly in the concentration range of AP from 0.01 to 2 μM and 2–100 μM, and an ultra-low limit of detection (LOD) of 34.28 nM was obtained (S/N = 3). In addition, the g-C 3 N 4 -E-PEDOT/GCE was successfully applied for the AP determination in the clinical human serum, and also exhibited excellent selectivity, reproducibility and stability. Except the novel AP determination approach, moreover, this work provided a new electrochemical application angle of graphitic carbon nitride theoretically as well as experimentally. [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]

Highlights: [•] PEDOT/NGE modified electrode was fabricated via CV method using nitrogen-doped graphene (NGE) coated GCE. [•] Highly reversible and well-separated redox couples of hydroquinone (HQ) and catechol (CT) were obtained at PEDOT/NGE/GCE. [•] A facile electrochemical sensor based on PEDOT/NGE/GCE was developed for simultaneous detection of HQ and CT. [Copyright &y& Elsevier]

Highlights: [•] A PEDOT/GO modified electrode was obtained via potentiostatic method using GO as a dopant. [•] The electrochemical behavior of acetaminophen (AP) showed highly reversibility. [•] An electrochemical sensor based on PEDOT/GO was developed for the detection of AP. [•] The sensor shows high sensitivity and selectivity to AP. [ABSTRACT FROM AUTHOR]

[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]

Abstract: A novel poly(3,4-ethylenedioxy-thiophene) (PEDOT)/graphene oxide (GO) hybrid film was directly electrodeposited on a glassy carbon electrode. The SEM and TEM images of the as-obtained film revealed that PEDOT grew well on the surface of GO sheets with high affinity. The chemical structure of the composite was characterized by FT-IR, and the result conformed the formation of PEDOT doped by GO, leading to the enhanced electrochemical performance of the modified electrode. The composite modified electrode was utilized as an electrochemical sensor for the simultaneous detection of hydroquinone (HQ) and catechol (CT). It showed well electrocatalytic activity toward the redox of HQ and CT. Under the optimized condition, the response peak currents of the modified electrodes were linear over ranges from 2.5 to 200μM for HQ and from 2 to 400μM for CT. The sensor also exhibited good sensitivity with the detection limit of 1.6μM for both HQ and CT, and good stability. This study provides a new kind of composite modified electrode for electrochemical sensors. [Copyright &y& Elsevier]

An electroreduction process was used to prepare electrochemically reduced graphene oxide/multi-wall carbon nanotubes for detecting 2,4-dinitroanisole (DNAN) by linear sweep stripping voltammetry (LSSV). DNAN is a less delicate explosive organic compound, it is modified by bacterial action when mixed with soil, in human body its converted to 2, 4-dinitrophenol. Reduced graphene oxide/multi-walled carbon nanotubes (ErGO/MWCNTs) nanohybrid was modified onto a glass carbon electrode (GCE) to detect DNAN. The synergistic effect makes the composite to have better electrochemical catalytic activity for DNAN. The composite materials showed the feature of high specific surface area, high conductivity and good electrocatalytic activity enhanced the electrocatalysis for DNAN. Under the optimized conditions, the reduction peak current of ErGO/MWNTs/GCE has a good linear relationship with the corresponding concentration of DNAN in the range of 0.1–5 μM and 5–30 μM. The limit of detection (LOD) is 0.084 μM (S/N = 3). The ErGO/MWCNTs sensor showed high catalytic activity, good selectivity, repeatability and stability towards DNAN. Unlabelled Image • ErGO/MWCNTs nanohybrid was fabricated via a simple electrochemical method • Electrochemical detection of DNAN by ErGO/MWCNTs. • The sensor had good linear relationship (0.1–5 and 5–30 μM) and LOD 0.084 μM for DNAN. • The ErGO/MWCNTs/GCE is promising tool for analytical applications. [ABSTRACT FROM AUTHOR]