An amperometric hydrogen peroxide sensor based on immobilization of hemoglobin in poly(o-aminophenol) film at iron–cobalt hexacyanoferrate-modified gold electrode

Electrochemically addressable nanofluidic devices based on PET nanochannels modified with electropolymerized poly-o-aminophenol films

Nanofluidic field-effect transistors (nFETs) have attracted attention from the scientific community due to their remarkable level of control over ionic transport. Particularly, the combination of nanofluidic systems and electroactive polymers has demonstrated to be an interesting approach to achieve an electrochemically addressable device. In this work, the development of nFETs based on the integration of electropolymerized poly-o-aminophenol (POAP) films into track-etched nanochannels is proposed. The electropolymerization of POAP on the tip side of Au-sputtered asymmetric PET nanochannels not only allowed having a programmable tip diameter but also offered a precise and very rapid control of ionic transport by switching an external bias voltage. Moreover, the system exhibited a reversible behaviour between non-selective and anion-selective states. We believe that this work provides new tools and concepts to design and build high-performance nanofluidic field-effect transistors working under electrochemically controlled conditions.

Poly(o-aminophenol) film electrodes: synthesis and characterization and formation mechanisms — A review article

This review, which is divided into three parts, concerns electrochemical synthesis, spectroscopic characterization, and formation mechanisms of poly(o-aminophenol) (POAP) film electrodes. The first part of this review is devoted to describing the electropolymerization process of o-aminophenol (o-AP) on different electrode materials and in different electrolyte media by employing both potentiodynamic and potentiostatic methods. The evolution of the voltammogram during the electrosynthesis of POAP and the assignation of the voltammetric peaks to different species, according to the formation mechanism formulated by each author, are described. The effects of some chemical substances and electrochemical pretreatments of the electrode surface, on the electropolymerization process of o-AP, are also considered in this part of the review. The synthesis of POAP in neutral media, which yields a nonconducting polymer, and its use as component of biosensors and protective layer in corrosion processes, are analyzed at the end of the first part. The second part of this review refers to spectroscopic studies carried out by different authors to both identify the products of the o-AP electro-oxidation and elucidate the chemical structure of POAP film electrodes. This second part of the review also describes the different spectroscopic methods employed to study the redox process of POAP, which allows the demonstration of the existence of transient species during the transition of the completely oxidized form of POAP to the completely reduced one. The third part of this review shows the different mechanisms formulated to interpret the POAP film formation from both acid and basic solutions of o-AP. Also, some electrochemical and spectroscopic data which allowed to propos the corresponding formation mechanisms, especially in basic media, are described.

Electrosynthesis and Spectroscopic Characterization of Poly(o-Aminophenol) Film Electrodes

This review, which is divided into three parts, concerns electrochemical synthesis, spectroscopic characterization, and formation mechanisms of poly(o-aminophenol) (POAP) film electrodes. The first part of this review is devoted to describe the electropolymerization process of o-aminophenol on different electrode materials and in different electrolyte media by employing both potentiodynamic and potentiostatic methods. The second part refers to spectroscopic studies carried out by different authors to both, identify the products of the o-aminophenol electrooxidation and elucidate the chemical structure of poly(o-aminophenol) film electrodes. The third part shows the different mechanisms formulated to interpret the POAP films formation from both acid and basic solutions of o-AP. Also, some electrochemical and spectroscopic data which allowed to propos the corresponding formation mechanisms, especially in basic media, are described.

Electrochemical Sensor for Tryptophan Determination Based on Copper-cobalt Hexacyanoferrate Film Modified Graphite Electrode

In this work, the development of a tryptophan sensor and its application to milk are described. The mixed metal (copper and cobalt) hexacynoferrates are electrodeposited on the graphite electrode, and this film exhibits an electrocatalytic activity towards for the oxidation of tryptophan. The experimental conditions, including the scan cycles, the ratio of copper(II) and cobalt(II), pH value, applied potential, are investigated in detail. At the optimal conditions, the eletctrocatalytic response is a linear relationship with the concentration of tryptophan in the range of 10 μM and 900 μM, with a detection limit of about 6 μM. This modified electrode was also successfully used to detect the tryptophan concentration in milk.

Immobilization of hemoglobin on SBA-15 applied to the electrocatalytic reduction of H2O2

The direct electron transfer between hemoglobin (Hb) and an electrode was realized by first immobilizing the protein onto SBA-15. The results of the immobilization showed that the adsorption was pH-dependent with a maximum adsorption near the isoelectric point of the protein, and SBA-15 with a larger pore diameter showed greater adsorption capacity for Hb. UV-vis spectroscopy and nitrogen adsorption analysis indicated that Hb was adsorbed within the channel of SBA-15 and no significant denaturation occurred to the protein. The Hb/SBA-15 composite obtained was used for the fabrication of a Hb biosensor to detect hydrogen peroxide. A pair of well-defined redox peaks at -0.337 and -0.370 V on the Hb/SBA-15 composite modified glassy carbon electrode was observed, and the electrode reactions showed a surface-controlled process with a single proton transfer at a scan rate range from 20 to 1,000 mV/s. The sensor showed a fast amperometric response, a low detection limit (2.3 x 10(-9) M) and good stability for the detection of H(2)O(2). The electrochemical results indicated that the immobilized Hb still retained its biological activity.