Composites of intrinsically conducting polymers (ICPs) are materials that utilize conjugated polymers and at least one secondary component that can be inorganic or organic materials or biologically active species. The goal is to produce a new composite material that has distinct properties that were not observed in the individual components. This may include either new or improved chemical properties that can be exploited for chemical or biological sensing. For example, adding carbon nanotubes tends to drastically influence the electrical and thermal conductivity of ICPs. A secondary aspect concerns the stabilization of the secondary component in the polymer matrix. Enhanced optical, electrical, or mechanical properties such as stiffness and strength are common. In some cases, the physical and chemical properties of the secondary component are much different after composite formation. For the purpose of this review we will primarily focus on the ICPs such as polyaniline, polypyrrole, and polythiophene and their derivatives. The resonance-stabilized structure of ICPs allows, for example, incorporation of ions, nanoparticles, or nanowires of metals, metal oxides, carbon, or molecular species such as metallophthalocyanines or biologically active components such as enzymes, antibodies, and antigens. 1 I some cases, the ICP will simply act as a template for the incorporation of the secondary component. In that case, the secondary component will impart the chemical properties required for chemical sensing. In other cases the materials are linked through electrostatic interactions which influence the electronic and physical properties of the materials used to prepare the composite.

Composites of Intrinsically Conducting Polymers as Sensing Nanomaterials

The non-enzymatic voltammetric and amperometric detection of glucose using a gold nanowire array electrode is described. The voltammetric detection of glucose was performed by cyclic and differential-pulse voltammetry. The detection of glucose by partial and direct oxidation of glucose during the anodic and cathodic potential sweeps was shown in cyclic voltammetry. An unusual decrease in overpotential for partial oxidation of glucose on a Au NW array electrode was observed. A linear differential-pulse voltammetric response for partial oxidation of glucose was observed up to a glucose concentration of at least 20 mM with a sensitivity of 41.9 μA mM−1 cm−2 and detection limit below 30 μM (signal-to-noise ratio of 3) for glucose oxidation at low potentials, where the influence of possible intermediates can be avoided. The amperometric response was also linear up to a glucose concentration of 10 mM with a sensitivity of 309.0 μA mM−1 cm−2. The wide dynamic range and high sensitivity, selectivity and stability, as well as good biocompatibility of the Au NW electrode make it promising for the fabrication of non-enzymatic glucose sensors.

Gold nanowire array electrode for non-enzymatic voltammetric and amperometric glucose detection

Nanoporous gold as non-enzymatic sensor for hydrogen peroxide

Pt–Pb nanowire array electrode for enzyme-free glucose detection

A sensitive electroanalytical methodology for the determination of capsaicin using adsorptive stripping voltammetry (AdsSV) at a multiwalled carbon nanotube modified basal plane pyrolytic graphite electrode (MWCNT-BPPGE) is presented. This analytical method is then further developed using a multiwalled carbon nanotube screen-printed electrode (MWCNT-SPE) demonstrating the proof-of-concept that this approach can easily be incorporated into a sensing device which is both facile to use and inexpensive to produce. Capsaicin is the chemical responsible for the hot taste of chilli peppers, and measuring the concentration of capsaicin is an indicator of how hot any given chilli pepper, hot sauce and other related foodstuffs are. Standard additions plots for AdsSV of capsaicin at open circuit potential at a MWCNT-BPPGE exhibits two linear ranges, from 0.5 to 15 μM and from 15 to 60 μM. Using the first range of calibration curve, a detection limit of 0.31 μM (based on 3σ) is obtained. The plot of standard additions of capsaicin determined using the disposable MWCNT-SPE shows a linear range between 0.5 and 35 μM and a detection limit of 0.45 μM. MWCNT-BPPGE and MWCNT-SPE are successfully utilized for the determination of capsaicin in real samples, such as a few commercially available hot pepper sauces, and the determined values are in excellent agreement and correlation with the average Scoville unit values reported in the literature for these sauces. To the best of our knowledge, this is the first electroanalytical method using MWCNT-BPPGE or MWCNT-SPE reported for the determination of capsaicin. This method offers advantages such as precision and objectivity over the well-known but potentially subjective Scoville method (based on organoleptic testing by human tasting panels) and is facile and inexpensive compared to existing HPLC methods.

Carbon nanotube-based electrochemical sensors for quantifying the ‘heat’ of chilli peppers: the adsorptive stripping voltammetric determination of capsaicin

Nanoelectrode ensembles (NEEs) of gold nanodisks, prepared by electroless template deposition of gold within the pores of track-etched polycarbonate membranes, are treated with oxygen plasma or with solvent mixtures in order to achieve controlled etching of part of the polycarbonate of the template. This causes the structure of the final ensemble to change from a 2-D flat structure into a 3-D one. The cyclic voltammetric (CV) behavior of redox probes at the 3DNEEs is examined and compared with the behavior observed at 2D-NEEs. Finally, 3D-NEEs are examined in order to test possible applications for the development of mediated sensors.

/pdf/3d-ensembles-of-gold-nanowires-preparation-characterization-2x77ott72k.pdf

3D-Ensembles of Gold Nanowires: Preparation, Characterization and Electroanalytical Peculiarities

https://iris.unive.it/bitstream/10278/31754/1/Anal%20Chim%20Acta%202006%20IODIO.pdf

Gold nanoelectrode ensembles for direct trace electroanalysis of iodide

https://iris.unive.it/bitstream/10278/3693/1/2010-EA%2015320%20NEE-IL%20II.pdf

Diffusion regimes at nanoelectrode ensembles in different ionic liquids

Gold nanowires were synthesized within polycarbonate membranes according to an electroless deposition method, obtaining nanoelectrode ensembles (NEEs) with special electrochemical features. NEEs were coupled with home-produced carbon graphite screen printed electrodes and the electrochemical properties of the original nanoelectrode ensemble on screen printed substrate (NEE/SPS) assembly has been tested for sensors application. Glucose oxidase has been used as model enzyme in order to verify the feasibility of disposable gold NEE/SPS biosensors. Finally, different immobilisation and electrochemical deposition techniques based on either self assembled monolayers of cysteamine (CYS) or amino-propyl-triethoxysilane (APTES) and conductive polyaniline (PANI) molecular wires were used. Spatial patterning of the enzyme on the polycarbonate surface and of PANI wires on gold nanoelectrodes was obtained. Possible direct electron transfer between the enzyme and the PANI modified gold nanoelectrodes has been evaluated.

/pdf/biosensors-based-on-gold-nanoelectrode-ensembles-and-screen-4ymipkms79.pdf

Biosensors based on gold nanoelectrode ensembles and screen printed electrodes

The electrochemical behavior of nanoelectrode ensembles (NEEs), prepared by electroless plating of Au using microporous polycarbonate membranes as template, is tested in the ionic liquid [BMIm][BF4]. The accessible potential window is significantly wider in [BMIm][BF4] than in water, extending approximately, for 3.4 V vs. 1 V, respectively. The voltammetric behavior at NEEs of two redox probes, namely butyl viologen (BV 2þ ) and (ferrocenylmethyl) trimethylammonium (FA þ ) are examined at different scan rates. In both cases, at scan rates higher than 200 mV/s sigmoidally shaped voltammograms typical of a pure radial diffusion regime are observed. At lower scan rates the voltammograms are peak shaped, as expected for total overlap diffusion conditions. This is the first time that the pure radial regime is obtained with NEEs made using commercially available polycarbonate templates, since in water solution only the total overlap regime is typically observed. This is explained as a consequence of the high viscosity of [BMIm][BF4] which reflects in lowering of diffusion coefficients and smaller thickness of diffusion layers, for the same time scale, with respect to water solutions, but also the fact that the nanoelectrodes are slightly recessed helps in observing the pure radial regime. In order to make operative the pure radial condition it is indeed required that the thickness of diffusion layer at individual nanoelectrodes be smaller than the hemi-distance between neighboring nanoelectrodes. Examining the analytical performances achievable with NEEs in [BMIm][BF4], it is shown that a limit is given by the decreased diffusion coefficients. Detection limits at NEEs in the ionic liquid are indeed higher than those obtained in water solutions. This notwithstanding, detections limits at NEEs in [BMIm][BF4] are always improved with respect to those at conventional electrodes.

/pdf/electrochemical-behavior-of-nanoelectrode-ensembles-in-the-42q451eks4.pdf

Manuela De Leo

Papers

3D-Ensembles of Gold Nanowires: Preparation, Characterization and Electroanalytical Peculiarities

Gold nanoelectrode ensembles for direct trace electroanalysis of iodide

Diffusion regimes at nanoelectrode ensembles in different ionic liquids

Biosensors based on gold nanoelectrode ensembles and screen printed electrodes

Electrochemical Behavior of Nanoelectrode Ensembles in the Ionic Liquid [BMIm][BF4]