Single-Particle Fluorescence Spectrometer for Ambient Aerosols

Abstract

A fluorescence particle spectrometer (FPS) for real-time measurement of the fluorescence spectra of aerosol particles in the size range 1-10 µm diameter is reported. The prototype FPS has a sufficiently high sample rate (from 5 to 28 l/min for 3.5 µm to 11 µm diameter particles) to measure aerosol within buildings at practical rates (from 1 up to 600 particle fluorescence spectra per minute). Previously reported bioaerosol prototype detectors for measurement of single particle spectra (Pan et al., Opt. Lett., 24, 116-118 (1999); Hill et al., Field Anal. Chem. Tech., 3, 221-239 (1999)) were unable to sample the ambient environment; air containing particles had to be forced under pressure into a sample cell. In addition, sample rates were so small (less than 0.01 l/min) as to be impractical for most applications. The present design overcomes these deficiencies by the use of an airtight cell that highly concentrates micrometer-sized particles. A virtual impactor first concentrates aerosol particles, which are then drawn under negative pressure through an aerodynamic focusing nozzle in the inlet of the instrument, through the sample region, providing further concentration. The rate of particle spectra measured by the FPS increases significantly when the particle inlet is within a few meters of some common sources of indoor biological particles, e.g., a person coughing, sneezing, or rubbing his skin, or the presence of a dog. The spectra obtained have a variety of spectral shapes. The FPS may be useful in a variety of areas, e.g., in studying and monitoring airborne particles that cause diseases or allergies.

ZnO UV photodetector with controllable quality factor and photosensitivity

“…We believe that the realization of photodetectors with improved quality factors has strategic importance and may ignite new applications such as the development of suitable detectors of hazardous airborne elements that have very sharp luminescence. 25,26 …”

Photophoretic trapping-Raman spectroscopy for single pollens and fungal spores trapped in air

“…Some of these instruments measure single particle elastic scattering, and/or single particle fluorescence, and/or laser-or spark-induced breakdown spectroscopy (LIBS/SIBS) and some are commercially available [3]. Laser induced fluorescence (LIF), especially dual-wavelength UV-LIF has been demonstrated for near-real time detection and partial classification of bioaerosols particles [4][5][6][7][8][9]. The technique was shown to be capable of differentiating pollens from various plant species [9,10].…”

Continuous bioaerosol monitoring in a tropical environment using a UV fluorescence particle spectrometer

“…In virtually all cases, the UV has been provided by one or more pulsed solid-state lasers (normally frequency tripled or quadrupled Nd-YAG lasers at 355 and 266 nm, respectively). However, these lasers are often too expensive for routine use in detector systems and also rarely emit at optimal wavelengths for exciting key biofluorophores such as the amino acid tryptophan and nicotinamide adenine dinucleotide (NADH), which are present in many bioaerosols and are utilised for their fluorescent properties to assist in this form of bioaerosol detection and characterisation (Hill et al, 1999;Pan et al, 2003).…”