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Interdigital electrodes fabricated by standard lithography on silicon chips are employed to probe the dipolar molecular dynamics and electric conduction properties of thin rhodamine films grown with two different methods. The conductivity is due to electronic charge carriers, and at around room-temperature, it is higher by 1 order of magnitude in solution-deposited films than in thermally evaporated ones. The organic material exhibits two intrinsic dynamic processes, of which the one at higher temperature is due to the orientational motion of the dipole moment of the rhodamine units, while the one at lower temperature is due to the motion of a local dipole associated with the chlorine counterions and is absent in thermally evaporated films. Our results show that thin-film dielectric spectroscopy is an easily implementable and versatile tool to extract valuable information on thin organic films., Peer Reviewed, Postprint (published version)

Consultable des del TDX, Títol obtingut de la portada digitalitzada, La tecnología de biosensores ha experimentado un notable avance en los últimos años, debido fundamentalmente al desarrollo de dispositivos aplicados al área de biomedicina. Estas tecnologías, en avanzado estado de madurez, han ido transfiriéndose paulatinamente de forma horizontal a otros sectores como el medioambiental, y de forma más incipiente al agroalimentario. En el presente trabajo se describe el desarrollo y caracterización de diferentes biosensores enzimáticos miniaturizados para su aplicación en la industria vitivinícola. En la construcción de sistemas integrados cobran especial relevancia las técnicas fotolitográficas («thin film») y serigráficas («thick film»). Así, el trabajo que aqui se presenta cuenta entre sus objetivos con el diseño, la producción y la caracterización de transductores miniaturizados, para lo que se recurrirá a estas tecnologías de microfabricación que proporcionan dispositivos de reducido tamaño y una alta reproducibilidad. Una vez descrita la fase de fabricación de los sensores, en los capítulos siguientes se describe su utilización para la fabricación de biosensores enzimáticos altamente selectivos a glucosa y etanol, de gran interés en la industria vitivinícola. La inmovilización enzimática es probablemente la etapa más influyente en el desarrollo de biosensores. En este caso, los enzimas, alcohol oxidasa, glucosa oxidasa y peroxidasa fueron inmovilizadas mediante dos técnicas diferentes. La primera, atrapando los enzimas en un polimero conductor (polipirrol) y el segundo método, atrapandolos mediante entrecruzamiento («cross linking»). La caracterización de estos biosensores se llevó a cabo mediante estudios de repetibilidad, reproducibilidad, límite de detección, etc., bajo las condiciones óptimas. Los principales parámetros que influyen en la respuesta del dispositivo fueron optimizados mediante la metodología del diseño de experimentos. Finalmente, se comprobó la viabilidad estos dispositivos puestos a punto mediante su aplic, Biosensing technology has undergone a great progress in the last years, due to the application of biosensors to biomedical industry. These technologies are been applied to others industrial sectors such environmental industry and, especially, alimentary industry. The present work explains the development and characterization of different miniaturized enzymatic biosensors to the application into winery industry. The main techniques to fabricate amperometric micro-transducers are thin and thick film. One of the main objectives of this work are the design, fabrication and characterization of miniaturized transducers. These devices were fabricated by thin and thick film technology. Devices with small size and high reproducibility could be achieved thought both thin and thick film technologies. Once the fabrication and characterization of these devices have been described, in the following chapters the development of several enzymatic biosensors to determine glucose and ethanol, which are important parameters in winery industry, were detailed. The enzymatic immobilization is probably the stage more influential in the development of biosensors. In this case, the enzymes, alcohol oxidase, glucose oxidase and horse radish peroxidase, were immobilized by two different techniques, entrapment into conductor polymer (polypyrrole) and immobilized by cross-linking. The characterization of these biosensors was carried out by the studies of repeatability, reproducibility, limit of detection, etc, under the optimum conditions. The main variables were optimized by the experimental design methodology. Finally, these devices were applied to the determination in real samples, both wine and grape juice.

Interdigital electrodes fabricated by standard lithography on silicon chips are employed to probe the dipolar molecular dynamics and electric conduction properties of thin rhodamine films grown with two different methods. The conductivity is due to electronic charge carriers, and at around room-temperature, it is higher by 1 order of magnitude in solution-deposited films than in thermally evaporated ones. The organic material exhibits two intrinsic dynamic processes, of which the one at higher temperature is due to the orientational motion of the dipole moment of the rhodamine units, while the one at lower temperature is due to the motion of a local dipole associated with the chlorine counterions and is absent in thermally evaporated films. Our results show that thin-film dielectric spectroscopy is an easily implementable and versatile tool to extract valuable information on thin organic films., Peer Reviewed, Postprint (published version)