Nanofluidic injection and heterogeneous kinetics of organomercaptan surface displacement reactions on colloidal gold in a microfluidic stream

John S. Kirk, Jonathan V. Sweedler, Paul W. Bohn

Research output: Contribution to journalArticle

Abstract

Colloidal gold is developed as a molecular capture reagent in hybrid nanofluidic-microfluidic devices for mass-limited sample analysis. Two fluorescent organomercaptans are injected through a nanocapillary array membrane and subsequently captured at the surface of 19-nm-diameter colloidal Au nanoparticles. The surface displacement kinetics are monitored via quenching of the organomercaptan fluorescence by the metallic particles coupled to a distance-time conversion based on fluid velocity in the microfluidic channel using the point of mixing as the zero of time. The adsorbate concentration, colloid concentration, and fluid velocity are varied to determine the surface displacement rate constants for these heterogeneous reactions in the microfluidic device. Surface displacement rate constants are ∼104 M-1 s-1 for a small organic molecule and for an octapeptide. These values are similar to values determined in macroscale measurements made with a traditional fluorometer and are 1 order of magnitude larger than values reported for adsorption of organomercaptans on planar Au, indicating faster kinetics in the colloid-adsorbate system. These results highlight the utility of colloidal Au nanoparticles as molecular carriers for the sequestration of analytes, allowing the manipulation of mass-limited samples and ultimately the capture and delivery of selected analytes from a microfabricated device to an off-line detector.

Original languageEnglish (US)
Pages (from-to)2335-2341
Number of pages7
JournalAnalytical chemistry
Volume78
Issue number7
DOIs
StatePublished - Apr 1 2006

ASJC Scopus subject areas

  • Analytical Chemistry

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