Desenvolvimento de filmes nanoestruturados de polímeros condutores aplicados a sensores gustativos para avaliação de cafés.
Abstract
This work aimed the investigation of ultra thin, polymeric film compositions
made by the layer-by-layer deposition technique capable of coffee quality
classification accordingly to stablished standards, using electrical impedance
measurements and the statistical method Principal Component Analysis. Films
made of polyaniline, poly(o-ethoxyaniline), polypyrrole, poly(3,4-
ethylenedioxythiophene), poly(hexamethylene biguanide), poly(sodium
methacrylate), fatty acids and derivatives, and other materials were studied.
Films were grown showing the applicability of these materials to self-assembly
of sensors based on polymeric materials. It was verified that PANI and DBSA
has a great potential as materials for sensor construction by such process due
to high rates of film growing. Itl was also observed that PEDOT(PSS) alternated
with PHMB(HCl) was the better material combination for coffee evaluation.
Impedance measurements in broad spectrum and use of variance-based
ranking factors allowed selection of optimum operation frequency for each
sensor, aiming the classification of brewed coffee by Global Quality and bean
type. With this strategy, it was also possible to determine those materials that
presented the best responses. Experimentally, it was shown that coffee
deposition occurs on the electrode surface during the time of measurements,
and proved that the usual washing procedure was not efficient to remove all
adsorbed coffee compounds, being necessary the washing with detergents. The
results of this work allows the construction of a sensor array to classify
commercial coffees by Global Quality, and the optimization of a sensor array
specialized on defective beans, which previously could not be determined on
commercial samples of roasted coffees.