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Exploiting charge-transfer complexation for selective measurement of gas-phase olefins with nanoparticle-coated chemiresistors.

Authors
Rowe-MP; Steinecker-WH; Zellers-ET
Source
Anal Chem 2007 Feb; 79(3):1164-1172
NIOSHTIC No.
20031780
Abstract
Charge-transfer-mediated olefin-selective sensing by use of chemiresistors (CR) coated with composite films of n-octanethiolate-monolayer-protected gold nanoparticles (C8-MPN) and each of several square-planar PtCl2(olefin)(pyridine) coordination complexes is described. Where the gas-phase olefin analyte differs from that initially coordinated to Pt, olefin substitution occurs and is accompanied by a persistent shift in the composite film resistance. Commensurate changes in film mass are also observed with a similarly coated thickness shear mode resonator. Regeneration is possible by exposure to the initially complexed olefin gas or vapor. If the olefin analyte is the same as that initially coordinated to Pt, then a reversible charge-transfer interaction occurs that is accompanied by a decrease in film resistance (increase in film mass), which recovers spontaneously after removal of the olefin from the atmosphere above the sensor. This behavior differs from that of MPN-coated CRs lacking such Pt complexes, which invariably yield resistance increases upon exposure to nonpolar vapors. Red shifts in the UV-vis absorbance spectra of the PtCl2(olefin)(pyridine) complexes in solution upon addition of free olefin support the hypothesis that Pt-olefin coordination in the composite films creates temporary low-resistance pathways that compete effectively with the concurrent increase in tunneling resistance associated with swelling-induced separation of C8-MPN cores. Structurally analogous non-olefins produce only increases in film resistance. Selective measurement of styrene, ethylene, 1-octene, and 1,3-butadiene is illustrated. Olefin detection limits are reduced as much as 23 000-fold by inclusion of the corresponding Pt complex in the CR interface film. Composite films suffer a gradual loss of selectivity from decomposition of the Pt-olefin complex, apparently facilitated by a Au-Pt charge transfer.
Keywords
Gas-chromatography; Air-quality-monitoring; Air-quality-measurement; Gases; Analytical-instruments; Analytical-processes; Sampling-equipment; Sampling-methods; Organic-compounds; Nanotechnology
Contact
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
CODEN
ANCHAM
Publication Date
20070201
Document Type
Journal Article
Funding Type
Grant
Fiscal Year
2007
NTIS Accession No.
NTIS Price
Identifying No.
Grant-Number-R01-OH-003692
Issue of Publication
3
ISSN
0003-2700
Source Name
Analytical Chemistry
State
MI
Performing Organization
University of Michigan, Ann Arbor
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