Sensing materials based on ionic liquids
Saheb, Amir Hossein
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The first chapter of this thesis describes the motivation behind using room temperature ionic liquids (RTILs) in gas sensor research and reviews current applications of RTILs in various sensors. The second chapter describes electrochemical polymerization of aniline in room temperature 1-butyl-3-methylimmidazolium ionic liquids without addition of any acid. It is shown that the polymerization of aniline in BMI(BF4) does require small but controlled amounts of water whereas the polymerization in BMI(PF6) and in BMI(TF2N) does not require any water addition. The third chapter describes the construction of reference electrodes for RTIL applications that have a known and reproducible potential versus the ferrocene/ ferrocenium couple. They are based on reference electrodes of the first kind, Ag/Ag+ couple type, or of the second kind, based on Ag/AgCl in M+Cl-. The stability, reproducibility, and temperature behavior of the two reference systems have been characterized. The fourth chapter describes the electrochemical preparation and spectral analysis of gold clusters by adding gold atoms one-by-one through polyaniline s ability to form a strong complex with chloroaurate at the protonated imine sites. Our results confirm that both the amount and the size of gold clusters affects the properties of the composite material. The fifth chapter describes the development and characterization of a CHEMFET sensing layer based on a composite of CSA-doped polyaniline (PANI), and the room temperature ionic liquid BMI(TF2N) for the sensing of ammonia gas. The work function responses of the cast films with and without IL are analyzed by step-wise changes of ammonia gas concentration from 0.5 to 694 ppm in air as a function of the mole fraction of IL to PANI. The PANI CSA/BMI(TF2N) layers shows enhanced sensitivities, lower detection limit and shorter response times. The final chapter describes the preparation and characterization of field-effect transistors with mixed ionic-electronic conductors that have been created by varying the ratio of room temperature ionic liquid and emeraldine salt of polyaniline. Transistor with high electronic conductivity (32mol% ES-PANI) and Au gate contact exhibited theoretical behavior of an IGFET; whereas, the purely ionic gate behaved irreproducibly, indicating that a capacitive divider has been formed in the gate.