Matei Raicopol

Functionalized single-walled carbon nanotubes/polypyrrole composites for amperometric glucose biosensors.

This article reports an amperometric glucose biosensor based on a new type of nanocomposite of polypyrrole (PPY) with p-phenyl sulfonate-functionalized single-walled carbon nanotubes (SWCNTs-PhSO3−). An environmentally friendly functionalization procedure of the SWCNTs in the presence of substituted aniline and an oxidative species was adopted. The nanocomposite-modified electrode exhibited excellent electrocatalytic activities towards the reduction or oxidation of H2O2. This feature allowed us to use it as bioplatform on which glucose oxidase (GOx) was immobilized by entrapment in an electropolymerized PPY/SWCNTs-PhSO3− film for the construction of the glucose biosensor. The amperometric detection of glucose was assayed by applying a constant electrode potential value necessary to oxidize or reduce the enzymatically produced H2O2 with minimal interference from the possible coexisting electroactive compounds. With the introduction of a thin film of Prussian blue (PB) at the substrate electrode surface, the PPY/GOx/SWCNTs-PhSO3−/PB system shows synergy between the PB and functionalized SWCNTs which amplifies greatly the electrode sensitivity when operated at low potentials. The biosensor showed good analytical performances in terms of low detection (0.01 mM), high sensitivity (approximately 6 μA mM−1 cm−2), and wide linear range (0.02 to 6 mM). In addition, the effects of applied potential, the electroactive interference, and the stability of the biosensor were discussed. The facile procedure of immobilizing GOx used in the present work can promote the development of other oxidase-based biosensors which could have a practical application in clinical, food, and environmental analysis.

Supercapacitance of Single-Walled Carbon Nanotubes-Polypyrrole Composites

The composites based on carbon nanotubes (CNTs) and conducting polymers (CPs) are promising materials for supercapacitor devices due to their unique nanostructure that combines the large pseudocapacitance of the CPs with the fast charging/discharging double-layer capacitance and excellent mechanical properties of the CNTs. Here, we report a new electrochemical method to obtain polypyrrole (PPY)/single-walled carbon nanotube (SWCNT) composites. In the first step, the SWCNTs are covalently functionalized with monomeric units of pyrrole by esterification of acyl chloride functionalized SWCNTs and N-(6-hydroxyhexyl)pyrrole. In the second step, the PPY/SWCNTs composites are obtained by copolymerizing the pyrrole monomer with the pyrrole units grafted on SWCNTs surface using controlled potential electrolysis. The composites were further characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The results showed good electrochemical charge storage properties for the synthesized composites based on PPY and SWCNTs covalently functionalized with pyrrole units making them promising electrode materials for high power supercapacitors.

Role of dopants on the electro-optic effect in nematic liquid crystals aligned with doped polypyrrole

In order to estimate electro-optical response times, measurements of the transmitted light intensity through positive uniaxial nematic thin films in planar alignment have been performed. Very fast relaxation times were experimentally found for nematic samples aligned with conductive polymers, namely, polypyrrole doped with 5 types of anions having different molecular sizes and geometries. Using undoped polypyrrole alignment layers, slower electro-optical responses were obtained. Given that the improvement in the relaxation times is induced by the presence of the anions in the polypyrrole films, the increasing of the total restoring torque of the nematic molecules to the confining surfaces—responsible for the short relaxation times—is related to the charges accumulated at the nematic-conductive polymer interface.

Fabrication of Polyaniline/Carbon Nanotubes Composites Using Carbon Nanotubes Films Obtained by Electrophoretic Deposition

In this study, we report a facile electrochemical method to obtain polyaniline/single-wall carbon nanotubes (PANI/SWCNTs) composite electrodes by combining the electroreduction of diazonium salts and electropolymerization of conductive polymers. In a first step, the SWCNTs are covalently functionalized with diphenyl amine through the electrochemical reduction of the 4-aminodiphenylamine diazonium salt in order to provide anchors for the subsequent polymer electrodepostion. The aniline oxidation remains possible on this grafted layer and PANI can easily be deposited on the diphenyl amine-modified electrodes. The electrochemically deposited PANI/SWCNTs composites exhibit excellent electrochemical charge storage properties making them promising electrode materials for high power supercapacitors.

Electrochemical Functionalization of Single-Walled Carbon Nanotubes Films Obtained by Electrophoretic Deposition

In this paper, we report an electrode coated with single-walled carbon nanotubes (SWCNTs) thin-film prepared by the electrophoretic deposition (EPD) technique. SWCNTs electrodes are fabricated on indium tin oxide (ITO) glass substrates using a mixture of CNTs and a cationic detergent tetraoctylammonium bromide (TOAB) in tetrahydrofuran (THF) by applying a negative voltage to the ITO glass plate. The functionalization of these nanotubes is then achieved via electrochemical reduction of aryl diazonium salts, in a manner similar to that employed for functionalization of other carbon surfaces. A variety of diazonium salts have been used, including those that provide moieties conducive to further elaboration after attachment to the nanotubes.