Model of vapor-induced resistivity changes in gold-thiolate monolayer-protected nanoparticle sensor films.
Steinecker WH; Rowe MP; Zellers ET
Anal Chem 2007 Jul; 79(13):4977-4986
An investigation of the modulation of charge transport through thin films of n-octanethiolate monolayer-protected gold nanoparticles (MPN) induced by the sorption of organic vapors is presented. A model is derived that allows predictions of MPN-coated chemiresistor (CR) responses from vapor-film partition coefficients, and analyte densities and dielectric constants. Calibrations with vapors of 28 compounds collected from an array of CRs and a parallel thickness-shear-mode resonator are used to verify assumptions inherent in the model and to assess its performance. Results afford insights into the nature of the vapor-MPN interactions, including systematic variations in apparent film swelling efficiencies, and show that the model can predict CR responses typically to within 24%. Using CRs of different dimensions, vapor sensitivities are found to be virtually independent of the MPN film volume over a range of 104 (device-area × MPN layer thickness). Sensitivities vary inversely with analyte vapor pressure similarly for the two sensor types, but the CR sensor affords significantly greater signal-to-noise ratios, yielding calculated detection limits in the low-part-per-billion concentration range for several of the analytes tested. The implications of these results for implementing MPN-coated CR arrays as detectors in microanalytical systems are considered.
Air-quality-monitoring; Air-quality-measurement; Analytical-instruments; Analytical-processes; Sampling-equipment; Sampling-methods; Organic-compounds; Vapors; Vapor-volume; Volumetric-analysis; Nanotechnology
Center for Wireless Integrated MicroSystems, Department of Chemistry, and Department of Environmental Health Sciences, University of Michigan, 109 South Observatory Street, Ann Arbor, Michigan 48109
University of Michigan, Ann Arbor