ascorbic-acid and silver-chloride

Silver chloride@polyaniline (PANI) core-shell (AgCl@PANI) nanocomposites were synthesized in the presence of polyvinylpyrrolidone (PVP). The obtained AgCl@PANI nanocomposites could be easily dispersed in aqueous media, which overcame the processible issues of PANI. Moreover, the nanocomposites showed excellent electrochemical behavior at pH neutral environment, and had inhibitive effect on oxidation of ascorbic acid. Fourier transform infrared spectrophotometry (FTIR) confirmed the existence of PVP in the nanocomposites. The C=O group of PVP is easy to form hydrogen bonding with the hydroxyl group of ascorbic acid, which can prevent ascorbic acid from oxidization. A selective dopamine biosensor was constructed based on the particular characteristic of the AgCl@PANI nanocomposites by the simple drop-coating. The biosensor could detect dopamine at its very low concentration in the presence of 5000 time concentration of ascorbic acid at neutral environment.

Topics: Aniline Compounds; Ascorbic Acid; Biosensing Techniques; Carbon; Dopamine; Electrochemistry; Electrodes; Fluorocarbon Polymers; Nanocomposites; Sensitivity and Specificity; Silver Compounds

We have developed a chip-based nanofluidic device to amplify the electrochemical signal of catechols by orders of magnitude. The amplification is based on rapid redox cycling between plane parallel electrodes inside a nanochannel. We show that it is possible to monitor the signal of only a few hundred molecules residing in the active area of the nanofluidic sensor. Furthermore, due to the nanochannel design, the sensor is immune to interference by molecules undergoing irreversible redox reactions. We demonstrate the selectivity of the device by detecting catechol in the presence of ascorbic acid, whose oxidized form is only stable for a short time. The interference of ascorbic acid is usually a challenge in the detection of catecholamines in biological samples.

Topics: Ascorbic Acid; Biosensing Techniques; Catecholamines; Catechols; Electrochemistry; Electrodes; Microfluidic Analytical Techniques; Oxidation-Reduction; Sensitivity and Specificity; Silver; Silver Compounds

Here, we report on a novel nonenzymatic amperometric glucose sensor based on three-dimensional PtPb networks directly grown on Ti substrates using a reproducible one-step hydrothermal method. The surface morphology and bimetallic composition of the synthesized nanoporous PtPb materials were characterized using scanning electron microscopy and energy-dispersive X-ray spectrometry, respectively. Voltammetry and amperometric methods were used to evaluate the electrocatalytic activities of the synthesized electrodes toward nonenzymatic glucose oxidation in neutral media in the absence and in the presence of chloride ions. The synthesized nanoporous PtPb electrodes have strong and sensitive current responses to glucose. Their amperometric sensitivities increase in the order of Pt-Pb (0%) < Pt-Pb (30%) < Pt-Pb (70%) < Pt-Pb (50%). These nanoporous PtPb electrodes are also highly resistant toward poisoning by chloride ions and capable of sensing glucose amperometrically at a very low potential, -80 mV (Ag/AgCl), where the interference from the oxidation of common interfering species such as ascorbic acid, acetamidophenol, and uric acid is effectively avoided.

Topics: Acetaminophen; Ascorbic Acid; Biosensing Techniques; Electrochemistry; Electrodes; Glucose; Hydrogen-Ion Concentration; Lead; Microscopy, Electron, Transmission; Platinum; Reproducibility of Results; Sensitivity and Specificity; Silver; Silver Compounds; Uric Acid

Electropolymerization regime of meso-tetrakis(3-methoxy-4-hydroxyphenyl) porphyrin is optimized to yield films possessing both electrocatalytical and permselective properties towards nitric oxide oxidation. The sensor composed of electrochemically oxidized carbon fiber, covered solely with nickel porphyrin derivative layer electropolymerized using our method, is characterized by high selectivity towards nitrite (1:600), ascorbate (1:8000) and dopamine (>1:80), determined by constant potential amperometry at 830 mV (vs. Ag/AgCl). Selectivity for ascorbate and dopamine as well as detection limit for NO (1.5 nM at S/N=3) is 5-10 times better than parameters usually reported for Nafion coated porphyrinic sensors. Nafion coating can further enhance selectivity properties as well as aids to the stability of the sensors' responses.

Topics: Ascorbic Acid; Biosensing Techniques; Carbon; Carbon Fiber; Catalysis; Dopamine; Electrochemistry; Electrodes; Fluorocarbon Polymers; Metalloporphyrins; Nickel; Nitric Oxide; Nitrites; Oxidation-Reduction; Sensitivity and Specificity; Silver; Silver Compounds; Time Factors