Jorge Ginja Teixeira

Development of easy made low cost bindless monolithic electrodes from biomass with controlled properties to be used as electrochemical capacitors

The aim of the work now reported is the development of low cost electrodes in the monolithic shape without the need for a pos-production step with potential to be used in supercapacitors. The tested materials were activated carbon fibres prepared and activated carbons made from coffee endocarp. The main functional groups identified were quinone, lactone, Si-H, phenol, hydroxyl, carbonyl and ether for activated carbon samples and amine, amide, pyrone, lactone, carbonyl and hydroxyl for activated carbon fibres samples. The nanostructure of the materials is predominantly microporous but with a significant variety of porosity development with BET surface area and pore volume given by α(s) method range from 89 to 1050 m(2) g(-1) and 0.04 to 0.50 cm(3) g(-1), respectively. The electrochemical properties of the materials were investigated using classic cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy. The higher specific capacitance achieved was 176 F g(-1).

Ultra-sensitive voltammetric sensor for trace analysis of carbamazepine

A multi-walled carbon nanotubes (MWCNTs) film-coated glassy carbon electrode (GCE) was used for the voltammetric determination of carbamazepine (CBZ). The results showed that this simple modified electrode exhibited excellent electrocatalytic activity towards the oxidation of CBZ. The voltammetric response of CBZ at this film-modified electrode increased significantly when compared with that at a bare glassy carbon electrode and the sensor response was reproducible. The proposed method was applied to the quantification of CBZ in wastewater samples, collected in a municipal wastewater treatment plant, and in pharmaceutical formulations. The developed methodology yields results in accord with those obtained by chromatographic techniques commonly used in the quantification of pharmaceutical compounds in real samples. Good recoveries have been obtained and the limits of detection and quantification (40 and 140 nM, respectively) are among the lowest that have been reported to date for this pharmaceutical compound using voltammetric techniques.

HPLC-DAD Quantification of Phenolic Compounds Contributing to the Antioxidant Activity of Maclura pomifera, Ficus carica and Ficus elastica Extracts

Abstract The concentration and antioxidant activity of the known phenolics macluraxanthone, rutin, chlorogenic acid, and psoralen present in M. pomifera, F. carica, and F. elastica extracts were determined to evaluate the plant extracts potency as new antioxidant suppliers. The quantification of the compounds was obtained by HPLC-DAD. The antioxidant activity of plant extracts and compounds was evaluated using DPPH and ABTS methods. The results seem to indicate that these extracts can be promising as new antioxidant suppliers, particularly F. carica and F. elastica leaves because only about 30% and about 50%, respectively, of the total activity was due to the phenolics determined.

On the Chemical Signature and Origin of Dicoppertrihydroxyformate (Cu2(OH)3HCOO) Formed on Copper Miniatures of 17th and 18th centuries.

A corrosion product rarely reported in the literature has been found on the copper support of three miniature paintings of the 17th and 18th centuries. This product, which has been identified as dicoppertrihydroxyformate (Cu2(OH)3HCOO), is an unusual basic copper formate found on copper artifacts. The identification and characterization of dicoppertrihydroxyformate was carried out directly over the corroded surface of the objects, using a nondestructive approach, which combines the integrated use of various microanalytical techniques. Using this approach, it was possible to obtain a set of new reference data about the natural form of Cu2(OH)3HCOO, that will enable its unambiguous identification in other similar objects. In this work, the probable causes that may have contributed to its formation are also discussed.