1C.01 "Labeling Single Particles On-the-Fly: A Novel Method for Rapid Identification of Aerosols." Matthew B. Hart, Horn-Bond Lin, Casey Jacobson, Jay D Eversole, Charles D. Merritt , Naval Research Laboratory, Washington, DC "We are developing a method to label specific chemical or biological aerosols on-the-fly with fluorescent markers using an electrospray. Labeling molecules, with affinities to specific surface epitopes and produce a detectable change in emission characteristics upon binding, will be used to coat aerosols in an air stream. Specifically targeted aerosols could be labeled in this manner, allowing single particle identification in near real-time using a simple laser-induced fluorescence technique. This method would permit the use of solutions containing mixtures of different markers to simultaneously detect/ identify multiple types of chemical or biological particles. In effect we would perform an immunoassay on the surface of individual particles as they flow, eliminating the need to sample into liquid or perform a washing process. The specifically labeled particles would then easily contrast among the dynamic ambient background of aerosols, which continues to be a formidable issue in the pursuit of rapid detection methods. Topics that are currently being investigated include the kinetics of molecular surface binding to an aerosol in flight, modeling geometries for efficient particle coating, and the control of charged aerosols in an airflow." ------------ 1C.02 "Development of a dual-excitation-wavelength single-particle fluorescence spectrometer for monitoring atmospheric aerosol and detecting biological threats." Yong-Le Pan (1), Hermes Huang (1), Richard K. Chang(1), Steven C. Hill (2), Ronald G. Pinnick (2) , (1) Department of Applied Physics, Yale University, (2) U.S. Army Research Laboratory "We report a dual-excitation-wavelength Single-Particle Fluorescence Spectrometer (SPFS) developed to measure two fluorescence spectra (excited by two different- wavelength UV laser pulses) from individual particles on-the-fly. The two fluorescence spectra are dispersed by a single spectrograph and recorded with a single 32-anode PMT array that can be read within 11 microseconds. Once a particle is detected to be approaching the sample region: a) the 351-nm laser fires and the fluorescence spectrum from 370 nm to 700 nm (in 22 channels) is recorded, b) the 32-anode PMT is read within 11 microseconds, and then c) the 263 nm laser fires and the fluorescence spectrum from 280 nm to 600 nm (in 20 channels) is recorded. The elastic scattering (at 263nm and 351nm, respectively) is also recorded for sizing each particle. A time stamp is also recorded (typically every 10 seconds). The SPFS employs a virtual-impactor-based concentrator to concentrate particles with sizes in the 1-10 micrometer range. When measuring urban atmospheric aerosol the typical count rates with the SPFS are a few ten to a few hundred particles per second, although the SPFS is capable of measuring many times faster rates. A brief development history of the SPFS system w ill also be presented along with some measurements from pure samples and atmospheric aerosols in New Haven, CT. The two spectra for each particle, obtained with dual-wavelength excitation, provide more information for understanding and monitoring atmospheric aerosol, and for discriminating between biological threats, and background aerosol." 2008.aaar.org/includes/Abstracts/abstracts_session.pdf _______________
Posted on: Tue, 02 Jul 2013 10:04:58 +0000