A fiber-optic chemical sensor (FOCS) for detection of nitrogen dioxide (NO 2 ) molecules is reported. The FOCS presents an optropode structure because of the transmission properties of the sensitive material. The NO 2 FOCS is activated by using the semiconductor polymer: regioregular head-to-tail poly(3-octylthiophene-2,5-diyl). The operation wavelength of the sensor is 543.5 nm such that a simple LED and detector can be used for the design of this device. The sensor response decreases after each exposure, demonstrating the reduction in sensitivity as well as irreversibility lower than 5%. However, its properties such as rapid response, high selectivity, high sensitivity (0.43˙0.01 muW/ppm), hygroscopic properties, and its operation at room temperature make this kind of FOCS a good alternative for NO 2 toxic gas detection.
Hemos construido un sistema integrado de sensores para la caracterización organoléptica de un licor destilado de la vis llamado pisco, analizando su fase liquida en una celda electroquímica, además se analiza la fase gaseosa en una pequeña cámara donde se encuentran los sensores de gas. Se ha diseñado una nariz electrónica con 4 sensores de gas de diferentes características (Figaro Inc.) y una lengua electrónica basada en una celda electroquímica de dos electrodos de acero inoxidable con Pt y Au, respectivamente. El sistema está compuesto principalmente por sensores de gas, actuadores válvulas, bombas de líquido y gas que están gobernadas por el microcontrolador PICI8F4523 que se encarga del envío de datos hacia el computador. El prototipo desarrollando es robusto, económico y portátil. Para el tratamiento de datos se ha desarrollado un programa en Matlab usando análisis por componentes principales. Se ha realizado pruebas con diferentes piscos, lográndose obtener la huella digital de los piscos analizados.
Chemical oxidation doping effect produced by 3000 ppm of NO 2 with N 2 balance on spin coated regioregular head-totail poly(3-octylthiophene) (P3OT) thin films is reported. Undoped and doped states mechanisms are discussed based on changes in optical absorptiometry, surface analysis and refractive index. The two midgaps created for few minutes in the P3OT under NO 2 doping effect by the polarons and bipolarons for mobility capabilities and its final doped state has been optically monitored and discussed. A significant change on the surface of undoped and doped P3OT thin films was inspected by atomic force microscopy (AFM). A P3OT refractive index transition from 1.69 (undoped) to 1.55 (doped) has been observed and discussed. Finally, the electrostatic attraction between the polaron and its counter ion (NO 2 -) has been analyzed for the possibility to diffuse the counter ion from the P3OT thin films and make possible its backward state (reversibility). The theoretical and experimental data results presented are part of a fiber optic chemical sensor (FOCS) project for NO 2 particles detection.
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