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.

Poly(propylene fumarate) (PPF) is a linear unsaturated polyester which has been widely investigated for tissue engineering due to its good biocompatibility and biodegradability. In order to extend the range of possible applications and enhance its mechanical properties, current approaches consist in the incorporation of various fillers or obtaining blends with other polymers. In the current study we designed a reinforcing agent based on carboxylated graphene oxide (GO-COOH) grafted with 2-hydroxyethyl methacrylate (GO@HEMA) for poly(propylene fumarate)/poly(ethylene glycol) dimethacrylate (PPF/PEGDMA), in order to enhance the nanofiller adhesion and compatibility with the polymer matrix, and in the same time to increase the crosslinking density. The covalent modification of GO-COOH was proved by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Raman spectroscopy. The mechanical properties, water uptake capacity, morphology, biodegradability, mineralization and in vitro cytotoxicity of PPF/PEGDMA hybrid materials containing GO@HEMA were investigated. A 14-fold increase of the compressive modulus and a 2-fold improvement in compressive strength were observed after introduction of the nanofiller. Moreover, the decrease in sol fraction and solvent swelling in case of the hybrid materials containing GO@HEMA suggests an increase of the crosslinking density. SEM images illustrate an exfoliated structure at lower nanofiller content and a tendency for agglomeration at higher concentrations. Finally, the synthesized hybrid materials proved non-cytotoxic to murine pre-osteoblast cells and induced the formation of hydroxyapatite crystals under mineralization conditions.

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In this work, we combine two widely used techniques to produce modified electrodes, that is, the electroreduction of diazonium salts and the electropolymerization of conductive polymers in order to obtain polyaniline (PANI)/carbon nanotube (CNTs) composites. Thus, in a first step, a CNTs electrode was functionalized with 4-nitrophenyl group by electrochemical reduction of 4-nitrobenzenediazonium salt in nonaqueous media. Then, the nitro group was reduced electrochemically to amine functionality. Cyclic voltammetry and electrochemical impedance spectroscopy were used to trace the reactions in each step. The PANI film can easily be grafted onto the surface of such obtained aminophenyl-modified CNTs electrodes. The PANI/CNTs films generated by this strategy show electrochemical behavior similar to that of PANI simply electrodeposited on CNTs electrodes, but exhibit significantly improved stability and higher capacitance values.

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Single-walled carbon nanotubes (SWCNTs) possess a wealth of exceptional structural, mechanical and electronic properties. An interesting challenge is their functionalisation without altering their electronic properties by a route that ensures a stable and a strong grafting of the desired molecules. Aryl diazonium salts are promising candidates for introducing molecular tools by surface modifications. We report here the functionalisation of SWCNTs through the electrochemical reduction of aryl diazonium salts. Experiments were carried out first on a glassy carbon electrode, taking into account its low porosity and structural similarity with SWCNTs. The surface modification of both substrates is checked by electrochemical signals related to the different immobilised moieties obtained by voltammetric methods and the blocking action of the modified electrodes for Fe (CN) 6 3À/4À redox probe in cyclic voltammetry measurements. This procedure allowed the use of a variety of diazonium salts, including those that provide moieties favourable to further elaboration after attachment to the SWCNTs.

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In this paper we report the functionalization of conductive polypyrrole (PPY) films via electrochemical reduction of the aryl diazonium salts in a manner that is similar to the one employed for other conductive surfaces. To understand the general trends of the grafting behavior of diazonium salts and to establish the optimal conditions for the covalent functionalization of the PPY films, we have compared the grafting behavior of four p-substituted phenyldiazonium salts: p-nitrophenyl diazonium tetrafluoroborate (PNBDBF 4 − ), p-tolyl diazonium tetrafluoroborate (TDBF 4 − ), p-fluorophenyl diazonium tetrafluoroborate (FPDBF 4 − ) and 4-diazo-N,N-dimethylaniline tetrafluoroborate (DDMABF 4 − ). The selection of the molecules to be grafted was done both for their electroactivity after grafting and the contrasted electronegativityof the substituents at the benzene ring. For all investigated diazonium salts, a linear relationship between their reduction potential at the PPY electrodes and Hammett substituent constants was obtained, suggesting a similar electrochemical reaction mechanism. The functionalization of the polypyrrole films has been evaluated using electrochemical methods like EQCM, CV and EIS. The presence at the polymeric films surface of the functional groups introduced by the electrochemical reduction of diazonium salts was evidenced also by XPS. This approach enables new functionalities on PPY that could otherwise not withstand the polymerization conditions.