No abstract

No abstract

No abstract

No abstract

The response to relative humidity (RH) and alcohol vapors of resistive-type sensors based on nanobeads of conjugated polymers, namely polyphenylacetylene (PPA) and copolymer poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)] (P(PA/HEMA)), were investigated. Sensors based on ordered arrays of these nanostructured polymeric materials showed stable and reproducible current intensity variations in the range 10-90% of relative humidity at room temperature. Both polymers also showed sensitivity to aliphatic chain primary alcohols, and a fine tuning of the sensor response was obtained by varying the chain length of the alcohol in relation to the polarity. The nanostructured feature of polymeric-based membranes seems to have an effect on the sensing response and an enhancement of the sensitivity was observed for the response to water and alcohol vapor variations with respect to previous studies based on amorphous polyphenylacetylene. High stability of the polymeric nanostructured membranes was detected with no aging after two weeks in continuum stressing measurement conditions.

Phenanthrene is a hydrophobic organic pollutant, composed of three--fused benzene rings belonging to polycyclic aromatic hydrocarbons (PAHs). PAHs are produced by incomplete combustion of organic matter due to natural events, i.e. fires, and anthropogenic actions, i.e. C--containing fuels combustion. The presence of PAHs in contaminated soils is usually detected by classical extraction techniques, such as solvent extractions through Soxhlet extractor. In this work two recently developed techniques (solid phase microextraction-SPME and electronic nose-EN) able to analyse the headspace of solid or liquid samples were used to monitor the possible degradation of phenanthrene in an artificially contaminated soil. The analysis by SPME showed a drastic decrease of phenanthrene content after 30 days of incubation (−92%) and different treatments with nutrient solutions and/or surfactant improve this rate up to 97%. Differently, the analysis of soil headspaces by EN, processed by principal component analysis (PCA), showed that contaminated and uncontaminated soil samples (controls) might be distinguished on a temporal scale. Furthermore, PCA showed that phenanthrene--contaminated soil samples produced chemical images, which were delayed relative to controls at the same period of incubation. The application of partial least square--discriminant analysis (PLS DA) to chromatograms obtained by SPME pointed out the presence, in the headspace of phenanthrene--treated soils, of a series of possible indicators involved in phenanthrene degradation, which were completely absent in relative unpolluted controls. Results suggest that the two techniques do not necessarily represent mutually exclusive alternatives, but giving different information, they may be considered as complementary.

No abstract

No abstract