Doctor of Philosophy (PhD)



Document Type



There has been an ever-increasing demand for the development of high-performance sensing devices for detection and discrimination of volatile organic compounds (VOCs) present in different environments. Among a number of sensing devices currently available, sorption-based sensors are particularly attractive because they are simple and inexpensive, require low power, and are appropriate for fabrication of multisensor arrays. A sorption-based sensor is comprised of a chemically active coating immobilized on the surface of a physical transducer. The chemically active film interacts with analytes, and the transducer converts the binding event into an electrical signal. This dissertation is focused on a sorption-based sensor prepared by using ionic liquids (ILs) and a group of uniform materials based on organic salts (GUMBOS) as the sensing materials and the quartz crystal microbalance (QCM) as the transducer. ILs are defined as organic salts which melt below 100 °C, and similar organic salts with melting point between 25 and 250 °C are defined as GUMBOS. In this research, a series of films comprising binary blends of an IL (or GUMBOS) and polymer are deposited onto the QCM surface in order to evaluate their vapor-sensing characteristics. The QCM sensors on exposure to organic vapors displayed a change in frequency and motional resistance, and both of these parameters were simultaneously measured. Examination of the data revealed an interesting relationship between the QCM parameters and the molecular weight of the absorbed vapors. The initial findings are reported in Chapter 2 of this dissertation. Additional studies were conducted in an effort to fully understand the interesting behavior of this type of material. More elaborate studies along with the theoretical rationale for the relationship between the QCM parameters and the molecular weight of vapors are presented in Chapter 3. Another important aspect of this dissertation is the design of highly sensitive materials for vapor-sensing applications. Toward this end, two representative GUMBOS were synthesized using porphyrin and phthalocyanine derivatives. The QCM device coated with these GUMBOS exhibited a rapid response and high sensitivity toward different organic vapors. Altogether, these studies demonstrate the true potential of this type of materials for vapor-sensing applications.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Warner, Isiah M.

Included in

Chemistry Commons