Characterization of long pathlength capillary waveguides for evanescent fluorescence sensing applications

E. D. Paprocki, B. K. Keller, C. P. Palmer, W. R. Laws, M. D. DeGrandpre

Research output: Contribution to journalArticlepeer-review


The optical properties of a novel fused silica fiber-optic capillary (FOCap) waveguide for fluorescence chemical sensing are evaluated. Evanescent fluorescence from samples contained in the FOCap is measured by coupling the FOCap to a light source and a fluorescence spectrophotometer. The FOCap has negligible excitation light loss over long lengths (tested to 20 m). Evanescent fluorescence is linear in FOCaps up to 20 m long when filled with a fluorophore solution and up to 15 m when a fluorophore is covalently attached to the inner surface. Evanescent fluorescence measurements in 50, 150, and 250 μm inner diameter FOCaps indicate that greater sensitivity is achieved with thinner-walled capillaries which have more internal reflections. The ability of the waveguide to function as an indirect chemical sensor for nitroaromatic compounds is demonstrated via fluorescence quenching of a pyrene-labeled FOCap.

Original languageEnglish
Pages (from-to)145-151
Number of pages7
JournalSensors and Actuators, B: Chemical
Issue number1
StatePublished - Dec 10 2008


  • Capillary waveguide
  • Evanescent wave fluorescence spectroscopy
  • Long pathlength


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