Choice of electrode metal influences the chemoresistive vapor response of brominated SWCNTs

Summary A series of functionalized single walled carbon nanotubes (SWNTs) rationalized on the basis of covalent chemical modification to impart electron-donating or electron-withdrawing functionalities has been synthesized and characterized. Brominated SWNTs (SWNT-Br) were dispersed in dimethyl formamide (DMF) and cast onto the interdigit space of microlithographically fabricated interdigitated microsensor electrodes (IMEs) of gold (Au) or platinum (Pt) that were unmodified or chemically modified with octadecyltrichlorosilane (OTS). The resulting devices (receptors) were characterized by two-electrode impedance spectroscopy (EIS) with equivalent circuit modeling and by direct current (DC)-based current-voltage (IV) characterization in various gases/vapors. The chemoresistive responses to these same gases/vapors were determined under DC conditions by continuous monitoring following flow injection of gas/vapor. The EIS and I-V characterization produced similar results that averaged 40.7 ± 1.1 ohms at the Au-electrode devices and 73.9 ± 1.9 ohms at the Pt- electrode devices confirming that the choice of metal greatly influences the magnitude of DC and AC responses. Exposure to vapors via flow injection results in ethanol (EtOH) > methyl isoamyl ketone (MIAK) > octane > toluene and with higher relative and more reproducible responses at Au compared to Pt devices. Surface modification influences the reproducibility of both devices.