Single particle multichannel bio-aerosol fluorescence sensor

We describe a prototype low-cost multi-channel aerosol fluorescence sensor designed for unattended deployment in medium to large area bio-aerosol detection networks. Individual airborne particles down to similar to 1 mu m in size are detected and sized by measurement of light scattered from a continuous- wave diode laser (660nm). This scatter signal is then used to trigger the sequential firing of two xenon sources which irradiate the particle with UV pulses at similar to 280 nm and similar to 370 nm, optimal for excitation of biofluorophores tryptophan and NADH ( nicotinamide adenine dinucleotide) respectively. For each excitation wavelength, fluorescence is detected across two bands embracing the peak emissions of the same bio-fluorophores. Current measurement rates are up to similar to 125 particles/s, corresponding to all particles for concentrations up to 1.3 x 10(4) particles/l. Developments to increase this to similar to 500 particles/s are in hand. Device sensitivity is illustrated in preliminary data recorded from aerosols of E. coli, BG spores, and a variety of non-biological materials. (C) 2005 Optical Society of America.