Articles | Volume 9, issue 8
Research article
23 Aug 2016
Research article |  | 23 Aug 2016

A wavelength-dispersive instrument for characterizing fluorescence and scattering spectra of individual aerosol particles on a substrate

Donald R. Huffman, Benjamin E. Swanson, and J. Alex Huffman

Abstract. We describe a novel, low-cost instrument to acquire both elastic and inelastic (fluorescent) scattering spectra from individual supermicron-size particles in a multi-particle collection on a microscope slide. The principle of the device is based on a slitless spectroscope that is often employed in astronomy to determine the spectra of individual stars in a star cluster but had not been applied to atmospheric particles. Under excitation, most commonly by either a 405 nm diode laser or a UV light-emitting diode (LED), fluorescence emission spectra of many individual particles can be determined simultaneously. The instrument can also acquire elastic scattering spectra from particles illuminated by a white-light source. The technique also provides the ability to detect and rapidly estimate the number fraction of fluorescent particles that could contaminate a collection of non-fluorescent material, even without analyzing full spectra. Advantages and disadvantages of using black-and-white cameras compared to color cameras are given. The primary motivation for this work has been to develop an inexpensive technique to characterize fluorescent biological aerosol particles, especially particles such as pollen and mold spores that can cause allergies. An example of an iPhone-enabled device is also shown as a means for collecting data on biological aerosols at lower cost or by utilizing citizen scientists for expanded data collection.

Short summary
We describe a low-cost instrument to characterize fluorescence and spectral properties of single particles collected onto a substrate. The instrument combines relatively old astronomy concepts with a new platform applied especially toward the analysis of bioaerosols. We discuss a laboratory-based instrument as well as an iPhone-enabled device that could encourage collaborations with citizen scientists for expanded data collection and at a cost orders of magnitude less than existing instruments.