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Proceedings Paper

A dual-wavelength single particle aerosol fluorescence monitor
Author(s): Paul H. Kaye; Warren R. Stanley; Virginia Foot; Karen Baxter; Stephen J. Barrington
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Paper Abstract

Laser diodes and light-emitting diodes capable of continuous sub-300 nm radiation emission will ultimately represent optimal excitation sources for compact and fieldable bio-aerosol monitors. However, until such devices are routinely available and whilst solid-state UV lasers remain relatively expensive, other low-cost sources of UV can offer advantages. This paper describes one such prototype that employs compact xenon discharge UV sources to excite intrinsic fluorescence from individual particles within an ambient aerosol sample. The prototype monitor samples ambient air via a laminar sheathed-flow arrangement such that particles within the sample flow column are rendered in single file as they intersect the beam from a continuous-wave 660nm diode laser. Each individual particle produces a scattered light signal from which an estimate of particle size (down to ~1 um) may be derived. This same signal also initiates the sequential firing (~10 us apart) of two xenon sources which irradiate the particle with UV pulses centred upon ~280 nm and ~370 nm wavelength, optimal for excitation of bio-fluorophores tryptophan and NADH respectively. For each excitation wavelength, fluorescence is detected across two bands embracing the peak emissions of the same bio-fluorophores. Thus, for each particle, a 2-dimensional fluorescence excitation-emission matrix is recorded together with an estimate of particle size. Current measurement rates are up to ~125 particles/s (limited by the xenon recharge time), corresponding to all particles for concentrations up to ~2 x 104 particles/l. Developments to increase this to ~500 particles/s are in hand. Analysis of results from aerosols of E.coli, BG spores, and a variety of non-biological materials are given.

Paper Details

Date Published: 28 October 2005
PDF: 12 pages
Proc. SPIE 5990, Optically Based Materials and Optically Based Biological and Chemical Sensing for Defence II, 59900N (28 October 2005); doi: 10.1117/12.629868
Show Author Affiliations
Paul H. Kaye, Univ. of Hertfordshire (United Kingdom)
Warren R. Stanley, Univ. of Hertfordshire (United Kingdom)
Virginia Foot, Defence Science and Technology Lab. (United Kingdom)
Karen Baxter, Defence Science and Technology Lab. (United Kingdom)
Stephen J. Barrington, Defence Science and Technology Lab. (United Kingdom)


Published in SPIE Proceedings Vol. 5990:
Optically Based Materials and Optically Based Biological and Chemical Sensing for Defence II
Anthony W. Vere; John C. Carrano; Arturas Zukauskas; James G. Grote; Francois Kajzar, Editor(s)

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