García-Berríos, Edgardo and Gao, Ting and Woodka, Marc D. and Maldonado, Stephen and Brunschwig, Bruce S. and Ellsworth, Mark W. and Lewis, Nathan S. (2010) Response versus Chain Length of Alkanethiol-Capped Au Nanoparticle Chemiresistive Chemical Vapor Sensors. Journal of Physical Chemistry C, 114 (50). pp. 21914-21920. ISSN 1932-7447 http://resolver.caltech.edu/CaltechAUTHORS:20110118-092448027
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Au nanoparticles capped with a homologous series of straight chain alkanethiols (containing 4−11 carbons in length) have been investigated as chemiresistive organic vapor sensors. The series of alkanethiols was used to elucidate the mechanisms of vapor detection by such capped nanoparticle chemiresistive films and to highlight the molecular design principles that govern enhanced detection. The thiolated Au nanoparticle chemiresistors demonstrated rapid and reversible responses to a set of test vapors (n-hexane, n-heptane, n-octane, iso-octane, cyclohexane, toluene, ethyl acetate, methanol, ethanol, isopropanol, and 1-butanol) that possessed a variety of analyte physicochemical properties. The resistance sensitivity to nonpolar and aprotic polar vapors systematically increased as the chain length of the capping reagent increased. Decreases in the nanoparticle film resistances, which produced negative values of the differential resistance response, were observed upon exposure of the sensor films to alcohol vapors. The response signals became more negative with higher alcohol vapor concentrations, producing negative values of the sensor sensitivity. Sorption data measured on Au nanoparticle chemiresistor films using a quartz crystal microbalance allowed for the measurement of the partition coefficients of test vapors in the Au nanoparticle films. This measurement assumed that analyte sorption only occurred at the organic interface and not the surface of the Au core. Such an assumption produced partition coefficient values that were independent of the length of the ligand. Furthermore, the value of the partition coefficient was used to obtain the particle-to-particle interfacial effective dielectric constant of films upon exposure to analyte vapors. The values of the dielectric constant upon exposure to alcohol vapors suggested that the observed resistance response changes observed were not significantly influenced by this dielectric change, but rather were primarily influenced by morphological changes and by changes in the interparticle spacing.
|Additional Information:||© 2010 American Chemical Society. Received: February 11, 2010; Revised Manuscript Received: August 12, 2010. Publication Date (Web): August 25, 2010. The authors thank Carol M. Garland for the TEM measurements. E.G.-B. acknowledges support from the NSF for a graduate fellowship. T.G. and M.E. acknowledge support from Tyco Electronics Corporation. Research was carried out in the Molecular Materials Research Center of the Beckman Institute at Caltech. This work was supported by the NSF, Grant CHE-0604894.|
|Official Citation:||Response versus Chain Length of Alkanethiol-Capped Au Nanoparticle Chemiresistive Chemical Vapor Sensors Edgardo Garca-Berros, Ting Gao, Marc D. Woodka, Stephen Maldonado, Bruce S. Brunschwig, Mark W. Ellsworth, Nathan S. Lewis The Journal of Physical Chemistry C 2010 114 (50), 21914-21920|
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|Deposited By:||Tony Diaz|
|Deposited On:||31 Jan 2011 23:37|
|Last Modified:||26 Dec 2012 12:51|
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