Aldo J. G. Zarbin

Reduced graphene oxide/copper nanowire hybrid films as high-performance transparent electrodes.

Hybrid films composed of reduced graphene oxide (RG-O) and Cu nanowires (NWs) were prepared. Compared to Cu NW films, the RG-O/Cu NW hybrid films have improved electrical conductivity, oxidation resistance, substrate adhesion, and stability in harsh environments. The RG-O/Cu NW films were used as transparent electrodes in Prussian blue (PB)-based electrochromic devices where they performed significantly better than pure Cu NW films.

Organic/inorganic hybrid materials formed from TiO2 nanoparticles and polyaniline

This paper describes the synthesis and characterization of organic/inorganic hybrid materials formed from TiO2 nanoparticles and polyaniline (PANI). The preparation method is based on a sol-gel technique using titanium tetra-isopropoxide as oxide precursor, and two synthetic routes to the hybrids formation were employed, based on the addition of aniline after or before the sol formation. Different amounts of aniline were used to verify this effect on the characteristics of the formed materials. Samples were characterized by electronic spectroscopy, Raman spectroscopy, Fourier transformed infrared spectroscopy, thermal analysis, X-ray diffractometry and cyclic voltammetry. Results show that the different experimental routes are successful to produce hybrids formed by oxides nanoparticles and polyaniline in its conducting form, the emeraldine salt. There are no strong differences between the samples obtained by the two synthetic routes employed, except by the amount of polymer in the final material.

Construction and evaluation of an optical pH sensor based on polyaniline-porous Vycor glass nanocomposite

This work describes the preparation of a polyaniline (Pani)‐porous Vycor glass (PVG) nanocomposite and its use as sensing phase in an optical fibre pH sensor. Nanocomposites of Pani‐PVG were prepared by in situ polymerisation of aniline absorbed inside the pores of a PVG (Corning 7930) with an average porous size of 8 nm. The optical sensor was constructed by fixing a PVG slide onto a distal end of bifurcated optical fibre bundle, with a cyanoacrylic resin. The sensor response was found to be reversible in the pH range from 5 to 12 and linear from pH 7.4 to 9.5. Response times of 4, 8 and >16 min were obtained for slide thickness’ of 0.5, 1 and 1.5 mm, respectively. Changes of temperature, ranging from 20 to 408C, showed minor effect on the dynamic range. Similarly, the ionic strength (0.15, 0.30 and 0.50 mol l ˇ1 ) and the nature of the ions (NaCl, KCl and NaClO4) showed minor influence on the sensor response. Leaching of Pani was not observed and the sensor lifetime was determined as being at least 5 months. These results indicate that a Pani‐PVG nanocomposite is suitable for the construction of optical pH sensors, with good analytical performance, since the glass slides can be prepared with good reproducibility and durability. # 2001 Elsevier Science B.V. All rights reserved.

Voltammetric Determination of the Antioxidant Capacity in Wine Samples Using a Carbon Nanotube Modified Electrode

A direct determination of gallic acid was achieved at a carbon paste electrode modified with carbon nanotubes under differential pulse voltammetry conditions. The values obtained for gallic acid were used to estimate the antioxidant properties of the wine sample based on gallic acid oxidation. The proposed method is based on the gallic acid oxidation process at a modified carbon paste electrode (MCPE) containing 30% (m/m) of carbon nanotubes monitored at 0.35 V versus Ag/AgCl (KCl 3 mol L(-1)). Using the optimized experimental conditions, the calibration curve for gallic acid was linear in the concentration range from 5.0 × 10(-7) to 1.5 × 10(-5) mol L(-1) with a detection limit of 3.0 × 10(-7) mol L(-1). The MCPE was successfully applied for the determination of the antioxidant capacity for red and white wine samples without interference of glucose and ascorbic acid, and the obtained results were compared with the standard spectrophotometric method.

Preparation, characterization and pyrolysis of poly(furfuryl alcohol)/porous silica glass nanocomposites: novel route to carbon template

In this paper we report the preparation of glassy carbon through the pyrolysis of poly(furfuryl alcohol) inside the pores of Vycor glass, which was used as a template. Different routes to the in situ polymerization of furfuryl alcohol inside the pores of Vycor glass were developed. The nanocomposites glass/polymer obtained were characterized by several techniques. Carbonization of these nanocomposites produces new silica glass/carbon nanocomposites, which were characterized and treated with HF to remove the silica fraction. It was found that the resulting carbon presents low crystallinity when compared to graphite. However, it presents more order than the glassy carbon resulting from the pyrolysis of the free poly(furfuryl alcohol) resin.

Nanocomposites glass/conductive polymers

Abstract We report on the preparation and characterization of two glass/conducting polymer nanocomposites obtained by the in situ oxidative polymerization of pyrrole and aniline inside the pores of Porous Vycor Glass (PVG). Oxidative polymerization of pyrrole was done via Cu2+ cation impregnated in the PVG pores. The polymerization of aniline was undertaken by impregnating PVG with the monomer, followed by an acid solution of (NH4)2S2O8. These nanocomposites were characterized by diffuse reflectance FT infrared spectroscopy, UV–Vis–NIR absorption spectroscopy, thermogravimetric analysis, Raman spectroscopy, solid state 13 C and 29 Si CP-MAS-NMR, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and conductivity measurements. The results showed that both polymers are formed inside the PVG pores in their oxidized conductive state, with the Si–O− groups of the glass surface acting as counter-anions. The dimensions of the pores of the glass preclude cross-linking of the polymers, allowing only formations of linear chains. The results suggest the formation of polymeric wires in the bulk of the glass substrate.

V2O5 nanoparticles obtained from a synthetic bariandite-like vanadium oxide: synthesis, characterization and electrochemical behavior in an ionic liquid.

Highly stable and crystalline V(2)O(5) nanoparticles with an average diameter of 15 nm have been easily prepared by thermal treatment of a bariandite-like vanadium oxide, V(10)O(24) x 9 H(2)O. Their characterization was carried out by powder X-ray diffractometry (XRD), Fourier transform infrared (FT-IR) and Raman spectroscopies, and transmission electron microscopy (TEM). The fibrous and nanostructured film obtained by electrophoretic deposition of the V(2)O(5) nanoparticles showed good electroactivity when submitted to cyclic voltammetry in an ionic liquid-based electrolyte. The use of this film for the preparation of a nanostructured electrode led to an improvement of about 50% in discharge capacity values when compared with similar electrodes obtained by casting of a V(2)O(5) xerogel.

Transparent films from carbon nanotubes/Prussian blue nanocomposites: preparation, characterization, and application as electrochemical sensors

The preparation of a homogeneous, transparent and electroactive film of a carbon nanotube/Prussian blue nanocomposite is described for the first time. Transparent films of iron- and iron oxide-filled multi-walled carbon nanotubes (CNTs) were prepared on top of ITO electrodes from NMP dispersions of CNTs. Prussian blue (PB) was electrosynthesized as nanocubes over the CNT walls through a heterogeneous reaction between ferricyanide ions in an aqueous solution and the iron-species encapsulated into CNTs. The resulting nanocomposites exhibited intimate contact between PB and CNTs, which improved the stability and redox properties of PB. The electrodeposition of PB and the chemical interaction between PB and CNTs were confirmed by cyclic voltammetry, X-ray diffraction, UV-Vis and Raman spectroscopies and Raman spectroelectrochemistry. The amount of PB obtained in the films was directly proportional to the amount of CNTs deposited initially. In addition, these electrodes were employed as hydrogen peroxide amperometric sensors, which demonstrated very low detection limits (4.60 × 10−9 mol L−1) and very high sensitivity (97.2 A cm−2 M−1).

Immobilization of iron porphyrins into porous vycor glass: characterization and study of catalytic activity

Abstract In this paper we report the immobilization and characterization of neutral and pentacationic iron porphyrins into the nanometric pores of an inorganic matrix (porous vycor glass, PVG) and the use of these materials as catalyst in mimetic–enzymatic processes. The concentration of iron porphyrin in the large glass pores depends on the conditions present during the incorporation process. The materials obtained were used as catalyst in the oxidation reaction of cyclohexane and cyclohexene by iodosylbenzene. The catalytic results were promising, evidencing adequate characteristics of PVG for immobilization of iron porphyrin and strong potential of these nanocomposites for heterogeneous catalytic procedures.

Química de (nano)materiais

An overview of different aspects related to Materials and Nanomaterials Chemistry is presented and discussed. The insertion of this field in Brazil is evaluated on the basis of the communications presented on the 30th Annual Meeting of the Brazilian Chemical Society (SBQ). The importance of the Materials Chemistry Division of SBQ for the growth and consolidation of Materials Chemistry in Brazil is also discussed.