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In an effort to obtain porous scaffolds with improved mechanical properties and biocompatibility, the current study discusses nanocomposite materials based on poly(propylene fumarate)/N-vinyl pyrrolidone(PPF/NVP) networks reinforced with polymer-modified graphene oxide (GO@PPF). The GO@PPF nanofiller was synthesized through a facile and convenient surface esterification reaction, and the successful functionalization was demonstrated by complementary techniques such as FT-IR, XPS, TGA and TEM. The PPF/NVP/GO@PPF porous scaffolds obtained using NaCl as a porogen were further characterized in terms of morphology, mechanical properties, sol fraction, and in vitro degradability. SEM and nanoCT examinations of NaCl-leached samples revealed networks of interconnected pores, fairly uniform in size and shape. We show that the incorporation of GO@PPF in the polymer matrix leads to a significant enhancement in the mechanical properties, which we attribute to the formation of denser and more homogenous networks, as suggested by a decreased sol fraction for the scaffolds containing a higher amount of GO@PPF. Moreover, the surface of mineralized PPF/NVP/GO@PPG scaffolds is uniformly covered in hydroxyapatite-like crystals having a morphology and Ca/P ratio similar to bone tissue. Furthermore, the preliminary biocompatibility assessment revealed a good interaction between PPF/PVP/GO@PPF scaffolds and murine pre-osteoblasts in terms of cell viability and proliferation. [ABSTRACT FROM AUTHOR]

Nucleic-acid aptamers consisting in single-stranded DNA oligonucleotides emerged as very promising biorecognition elements for electrochemical biosensors applied in various fields such as medicine, environmental, and food safety. Despite their outstanding features, such as high-binding affinity for a broad range of targets, high stability, low cost and ease of modification, numerous challenges had to be overcome from the aptamer selection process on the design of functioning biosensing devices. Moreover, in the case of small molecules such as metabolites, toxins, drugs, etc., obtaining efficient binding aptamer sequences proved a challenging task given their small molecular surface and limited interactions between their functional groups and aptamer sequences. Thus, establishing consistent evaluation standards for aptamer affinity is crucial for the success of these aptamers in biosensing applications. In this context, this article will give an overview on the thermodynamic and structural aspects of the aptamer-target interaction, its specificity and selectivity, and will also highlight the current methods employed for determining the aptamer-binding affinity and the structural characterization of the aptamer-target complex. The critical aspects regarding the generation of aptamer-modified electrodes suitable for electrochemical sensing, such as appropriate bioreceptor immobilization strategy and experimental conditions which facilitate a convenient anchoring and stability of the aptamer, are also discussed. The review also summarizes some effective small molecule aptasensing platforms from the recent literature. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Based on environmentally friendly (bio-based) precursor materials a new class of benzoxazine derivatives was synthesized using phenolated high oleic sunflower oil as phenol component and either aniline or 1,6-diaminohexane as amine components. Hydrophobic and dense poly(benzoxazine) coatings on Zn–Mg-Al alloy coated steel were obtained after spin-coating or air-brush type spray coating by crosslinking during a heat treatment step. The poly(benzoxazine)-coated ZM-steel samples showed an anodic shift of the open circuit potential as well as the break-through potential. Using an automatic scanning droplet cell the impact of the polymer film thickness on corrosion protection was evaluated. [ABSTRACT FROM AUTHOR]

Benzoxazine derivatives were synthesized using phenolated methyl oleate and either aniline, 1,6-diaminohexane, or 4,4'-diaminodiphenylmethane, respectively, as amine components. Polymerization of the benzoxazine derivatives led to the formation of hydrophobic and dense coatings on Zn-Mg-Al alloy coated steel sheets for passive corrosion protection. The polybenzoxazine coatings which are formed by crosslinking during a heat-treatment step invoked a substantial anodic shift of the open-circuit potential as well as the breakthrough potential in potentiodynamic measurements. The proposed polybenzoxazine derivatives pave the way for a new type of passive polymer protection system based on sustainably obtained precursor components. [ABSTRACT FROM AUTHOR]

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 (PNBDBF4-), p-tolyl diazonium tetrafluoroborate (TDBF4-), p-fluorophenyl diazonium tetrafluoroborate (FPDBF4-) and 4-diazo-N,N-dimethylaniline tetrafluoroborate (DDMABF4-). 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. [ABSTRACT FROM AUTHOR]

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 excellentmechanical 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. [ABSTRACT FROM AUTHOR]

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)63−/4− 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. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Food safety monitoring assays based on synthetic recognition structures such as aptamers are receiving considerable attention due to their remarkable advantages in terms of their ability to bind to a wide range of target analytes, strong binding affinity, facile manufacturing, and cost-effectiveness. Although aptasensors for food monitoring are still in the development stage, the use of an electrochemical detection route, combined with the wide range of materials available as transducers and the proper immobilization strategy of the aptamer at the transducer surface, can lead to powerful analytical tools. In such a context, employing aryldiazonium salts for the surface derivatization of transducer electrodes serves as a simple, versatile and robust strategy to fine-tune the interface properties and to facilitate the convenient anchoring and stability of the aptamer. By summarizing the most important results disclosed in the last years, this article provides a comprehensive review that emphasizes the contribution of aryldiazonium chemistry in developing electrochemical aptasensors for food safety monitoring. [ABSTRACT FROM AUTHOR]

A new thiosemicarbazone ligand was immobilized through a Cu(I)-catalyzed click reaction on the surface of glassy carbon (GC) and electrochemically reduced graphene oxide (GC-ERGO) electrodes grafted with phenylethynyl groups. Using the accumulation at open circuit followed by anodic stripping voltammetry, the modified electrodes showed a significant selectivity and sensibility for Hg(II) ions. A detection limit of 7 nM was achieved with the GC modified electrodes. Remarkably, GC-ERGO modified electrodes showed a significantly improved detection limit (0.8 nM), sensitivity, and linear range, which we attribute to an increased number of surface binding sites and better electron transfer properties. Both GC and GC-ERGO modified electrodes proved their applicability for the analysis of real water samples. [ABSTRACT FROM AUTHOR]

Abstract: The novel 1,2-di(azulen-1-yl)cyclopent-1-ene 3 was conveniently synthesized via a two-step procedure involving Vilsmeier–Haack acylation of azulene with N,N,N′,N′-tetraethylglutaramide (TEGA) and POCl3, followed by an intramolecular McMurry coupling of the resulting diketone. In contrast with the previously reported (E)-1,2-di(azulen-1-yl)ethene that shows negligible fluorescence in the solid state, alkene 3 displays fluorescence emission from the S2 excited state of the azulene moieties. This compound easily polymerizes upon electrochemical oxidation, leading to the formation of a conducting polymer film at the electrode surface. [Copyright &y& Elsevier]