An instrument for the simultaneous acquisition of size, shape, and spectral fluorescence data from single aerosol particles

Abstract

We describe the construction of a bio-aerosol monitor designed to capture and record intrinsic fluorescence spectra from individual aerosol particles carried in a sample airflow and to simultaneously capture data relating to the spatial distribution of elastically scattered light from each particle. The spectral fluorescence data recorded by this PFAS (Particle Fluorescence and Shape) monitor contains information relating to the particle material content and specifically to possible biological fluorophores. The spatial scattering data from PFAS yields information relating to particle size and shape. The combination of these data can provide a means of aiding the discrimination of bio-aerosols from background or interferent aerosol particles which may have similar fluorescence properties but exhibit shapes and/or sizes not normally associated with biological particles. The radiation used both to excite particle fluorescence and generate the necessary spatially scattered light flux is provided by a novel compact UV fiber laser operating at 266nm wavelength. Particles drawn from the ambient environment traverse the laser beam in single file. Intrinsic particle fluorescence in the range 300-570nm is collected via an ellipsoidal concentrator into a concave grating spectrometer, the spectral data being recorded using a 16-anode linear array photomultiplier detector. Simultaneously, the spatial radiation pattern scattered by the particle over 5°-30° scattering angle and 360° of azimuth is recorded using a custom designed 31-pixel radial hybrid photodiode array. Data from up to ~5,000 particles per second may be acquired for analysis, usually performed by artificial neural network classification.

Simulation of ultraviolet laser-induced fluorescence LIDAR for detecting bioaerosol

“…Simultaneously, the elastic scattered light is recorded by using a 31-pixel photodiode array. Data from up to 5,000 particles per second may be acquired for analysis, usually performed by artificial neural network classification [10] .…”

Optical Techniques for Detecting and Identifying Biological-Warfare Agents

“…ECBC has focused on the development of low-cost sensors, including providing the initial funding support for the Biological Agent Warning Sensor (BAWS) and, more recently, developing light-emitting diode (LED)-based sensors [48]. DSTL has extended the original work of Kaye et al and developed sensors based on particle shape and fluorescence detection [49]- [51]. In addition to the FLAPS produced by TSI Inc., other companies have also developed fluorescence-based sensors [52]- [55].…”

A dual-wavelength single particle aerosol fluorescence monitor

“…In the earliest systems, continuous wave lasers were employed, for example 1,2 , though these were usually large and fragile and operated at wavelengths which were too long for efficient excitation of some of the important bio-fluorophores such as tryptophan, for which optimal excitation occurred at wavelengths of ~260-280 nm. Hence the use of various solid-state lasers employing harmonic generation, such as frequency quadrupled Nd-YAG lasers, has gained acceptance [3][4][5][6][7][8][9][10][11] , both for the output wavelength of 266nm and because they offered a generally smaller form-factor than continuous-wave gas lasers.…”