title: Model of vapor-induced resistivity changes in gold-thiolate monolayer-protected nanoparticle sensor films.
abstract: 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 x 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.
authors.affiliation: Engineering Research Center for Wireless Integrated MicroSystems, Department of Chemistry, University of Michigan, 109 South Observatory, Ann Arbor, Michigan 48109-2029, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Steinecker
authors.forename: Michael P
authors.initials: MP
authors.lastname: Rowe
authors.forename: Edward T
authors.initials: ET
authors.lastname: Zellers
mesh_terms: D000042:Absorption; D000465:Algorithms; D015374:Biosensing Techniques; D002138:Calibration; D005740:Gases; D006046:Gold / Q000737:chemistry*; D008567:Membranes, Artificial; D008962:Models, Theoretical; D053758:Nanoparticles / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D011312:Pressure; D012680:Sensitivity and Specificity; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties; D014835:Volatilization
chemical_list: D005740:Gases; D008567:Membranes, Artificial; D009930:Organic Chemicals; D013438:Sulfhydryl Compounds; C402924:n-octanethiol; D006046:Gold