“Enhancement of Sensitivity and Selectivity of Chemical Sensors Through Thin Film Coatings and Surface Modifications

Chemical sensors have become major analytical tools for how we monitorand obtain information about the chemical nature of ourselves and oursurroundings. Two characteristics of chemical sensors that are under constantdevelopment and improvement are their selectivity and their sensitivity.Selectivity is a concern of any chemical sensor, without it the signal obtained bya chemical sensor cannot be related to the target species concentration with anyconfidence. With chemical sensors the selectivity is generally created by theused of a chemical recognition layer such as a permeable membrane, or a thinchemical film. The sensitivity of a chemical sensor is a concern, as with anyquantitative analytical method, so that small differences in analyte concentrationare distinguishable and trace analysis can be performed. In this work theselectivity and sensitivity of two distinctly different devices used as chemicalsensors are investigated. The first device combines a scintillation fiber with aselective polymer coating to create a chemical sensor selective for 137Cs. Boththe selectivity and sensitivity of the scintillation fiber are improved with theaddition of the chemical recognition layer. The second device investigated is amicrocantilever sensor. Microcantilevers have been used to monitor chemicalspresent in both air and liquid environments. However, in moving frommeasurements made in air to measurements made in liquids, a great deal ofsensitivity is lost due to differences in the interfacial energies of thevmicrocantilevers in these two different environments. To overcome this limitationsurface modification of the microcantilevers was investigated to improve thesensitivity of these devices. Surfaces of the microcantilevers were modified byseveral different methods, the binding of gold nanobeads to the surface, creationof a roughened dealloyed surface, and the physical milling and chemical etchingof grooves into the surface of the microcantilevers, each of these surfacemodifications was shown to enhance the sensitivity of microcantilever chemicalsenors over microcantilever chemical sensors with smooth surfaces