Electronic devices based on organic thin-film transistors (OTFT) have the potential to supply the demand for portable and low-cost gadgets, mainly as sensors for in situ disease diagnosis and environment monitoring. For that reason, poly(3-hexylthiophene) (P3HT) as the active layer in the widely-used bottom-gate/bottom-contact OTFT structure was deposited over highly-doped silicon substrates covered with thermally-grown oxide to detect vapor-phase compounds. A ten-fold organochloride and ammonia sensitivity compared to bare sensors corroborated the application of this semiconducting polymer in sensors. Furthermore, P3HT TFTs presented approximately three-order higher normalized sensitivity than any chemical sensor addressed herein. The results demonstrate that while TFTs respond linearly at the lowest concentration values herein, chemical sensors present such an operating regime mostly above 2000 ppm. Simultaneous alteration of charge carrier mobility and threshold voltage is responsible for pushing the detection limit down to units of ppm of ammonia, as well as tens of ppm of alcohol or ketones. Nevertheless, P3HT transistors and chemical sensors could compose an electronic nose operated at room temperature for a wide range concentration evaluation (1–10,000 ppm) of gaseous analytes. Targeted analytes include not only biomarkers for diseases, such as uremia, cirrhosis, lung cancer and diabetes, but also gases for environment monitoring in food, cosmetic and microelectronics industries.

No abstract

No abstract

No abstract

No abstract

An electronic tongue (ET) system based on non-specific chemical sensors was used to detect and quantify off-flavors compounds, namely geosmin (GSM) and 2-methylisoborneol (MIB), in raw and treated water samples collected from the Guarapiranga reservoir (Sao Paulo-Brazil). Four sets of samples were evaluated with the ET system: sets 1 and 2 were composed by raw and treated waters, respectively, and measured as collected whereas sets 3 and 4 were composed by raw and treated samples plus addition of known amounts of MIB and GSM. The electrical fingerprints (capacitance) generated by the ET for the different samples were processed by principal component analysis. The ET easily performed samples` discrimination while providing distinct and well-separated clusters for each type of sample. Furthermore, scores after repeated samples` replicas were close grouped which indicates that the ET`s response is reproducible. The ET`s sensitivity is also high and the presence of both GSM and MIB could be detected at concentrations as low as 20 ng.L -1. The results confirmed the analysis performed independently by GC/MS spectrometry and by a human panel.

No abstract

No abstract