A sensitive hydrogen peroxide (H2O2) sensor was constructed based on graphene–Pt (RGO–Pt) nanocomposites and used to measure the release of H2O2 from living cells. The graphene and Pt nanoparticles (Pt NPs) were modified on glassy carbon electrode (GCE) by the physical adsorption and electrodeposition of K2PtCl6 solution, respectively. Through characterization by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), it was observed that the electrodeposited Pt NPs were densely covered and well distributed on the entire graphene surface. Electrochemical study demonstrates that the RGO–Pt nanocomposites modified glassy carbon electrode exhibited a high peak current and low overpotential toward the reduction of H2O2. The relevant detection limit of H2O2 is ∼0.2 μM with a wide linear range from 0.5 μM to 3.475 mM, displaying a much higher sensitivity (459 ± 3 mA M–1 cm–2, n = 5) than that of Pt nanoparticles or graphene modified electrode. This novel biosensor can measure the H2O2 release from living cells because of its low detection limit, wide linear range, and higher sensitivity.

Prussian blue (PB) has shown strong catalytic property for the reduction of hydrogen peroxide, but the application in biosensor fabrication is limited for its instability at neutral pH. In this work, an amperometric biosensor was fabricated based on glassy carbon electrode modified with reduced graphene oxide (RGO), PB and poly(toluidine blue O) (PTBO). The modified electrodes were characterized by scanning electron microscopy and UV-Visible absorption spectroscopy. Cyclic voltammetry and amperometric measurements were employed to investigate the electrochemical property of the modified electrodes. Experimental results showed that the GC/RGO/PB/PTBO modified electrode offered the best electrocatalytic activity toward the reduction of hydrogen peroxide when compared with electrodes modified with RGO-PB, RGO/PTBO and RGO materials, indicating the possible synergistic effects of the PB-PTBO composite material. The electrode showed high sensitivity and good stability for the analysis of hydrogen peroxide in phosphate buffer solution (pH 7.4). After codeposition of glucose oxidase (GOD) and chitosan (CHIT) coating, the resulting GC/RGO/PB/PTBO/CHIT-GOD electrode exhibited excellent response to glucose with a sensitivity of 59 mA M−1 cm−2, a low detection limit of 8.4 μM and a linear range from 20 μM to 1.09 mM at a detection potential of +0.2 V vs. Ag|AgCl reference.

Conducting polypyrrole modified electrodes incorporated with alizarin red S ligands were prepared by electropolymerization of pyrrole in mixtures of water and acetonitrile. Electroanalysis of copper(II) species was performed voltammetrically. The effects of solvent systems employed for pyrrole electrodeposition on the electroanalytical behaviors of the modified electrodes were evaluated in terms of the pyrrole polymerization charge, alizarin red S coverage, copper response, and the ligand-to-metal ratio for copper analysis. Experimental results showed that the water content in the solvent mixture had strong influence on the electroanalytical performance of the polypyrrole modified electrodes. The morphology of the polypyrrole films prepared in different acetonitrile–water mixtures was examined and it indicated that there was close correlation between the film morphology and the electroanalytical behavior for copper(II) determination.

A novel chemically modified electrode based on an osmium complex-containing redox polymer film coated on single-walled carbon nanotube (SWNT) modified glassy carbon electrode (GCE) has been described for the determination of nitric oxide. The results showed that the oxidation current increased significantly at the SWNT/redox polymer coated GCE, as compared to that observed on a bare GCE- and SWNT-modified GCE. Amperometric measurement was carried out at the potential of +0.80 V (vs. Ag|AgCl) and the current response to NO was found to be directly proportional to its concentration in the range from 2.0 × 10−7 to 4.0 × 10−5 M, and the detection limit was estimated to be 5.0 × 10−8 M.

Three phenylenediamine isomers (including ortho-, meta- and para-derivatives) were electrochemically polymerized to give polyphenylenediamine (PPD) films on platinized glassy carbon electrodes. Amperometric glucose sensors were developed by immobilizing glucose oxidase (GOx) into these polymer matrices during polymerization. Effects of the polymerization potential, polymerization charge, monomer concentration, GOx concentration and Pt deposition charge on the performance of the enzyme electrode to glucose were investigated. These resulting GC/Pt/PPD-GOx electrodes showed rapid electrochemical responses to hydrogen peroxide and glucose, and very good anti-interference ability to ascorbic acid. Correlation between the electroanalytical behaviors of the enzyme electrodes and the polymer structures was examined.

The adsorption behaviors of Cu2+ and Pb2+ species at electrochemically activated glassy carbon obtained by different activation methods have been studied. Micropore structures were developed by cyclic polarization while small void space located at the bottom of the large void space was resulted from potentiostatic activation. The adsorption of the adsorbents would depend on the relative sizes of both the adsorbents and the void space created by electrochemical pretreatment. Different quinone derivatives would adsorb to different adsorption sites at the activated electrode, and consequently, affected the uptake of metal ions at the activated electrode incorporated with different quinone derivatives. Electrostatic and hydrophobic interactions between the adsorbents and the graphite oxide film might be involved.