Boosting the Detection of Flame-formed Sub-5nm Materials by Operating the Saturator Inlet of a Water Condensation Particle Counter (WCPC) with Different Condensing Fluids
Farnaz Khosravi, Arantzazu Eiguren-Fernandez, Gregory S. Lewis, FRANCESCO CARBONE, University of Connecticut
Abstract Number: 341
Working Group: Instrumentation and Methods
Abstract
Combustion emissions are major contributors to air pollution in urban areas and advancements in instrumentation for detecting ever smaller materials are crucial for their effective monitoring and more stringent regulation. Among aerosol metrology instruments, Condensation Particle Counters (CPCs) stand out due to their ease, robustness, and affordability of operation as well as their ability to detect charged and neutral particles with extremely low number concentrations. However, the detection efficiency of any CPC is influenced by various factors such as the size, charge, and shape of the detected materials as well as their composition and wettability by the condensing fluid(s). The effects of these parameters can be substantial and elusive to estimate for materials smaller than 5nm whose detection efficiency needs, therefore, to be quantified by ad-hoc calibrations. This study characterizes the detection efficiency of flame-formed sub-5nm materials by a Water-based CPC (WCPC) prototype equipped with a saturator inlet to boost their growth and detection via condensation of a secondary fluid alongside water. The efficiency of the device in detecting naturally charged flame carbonaceous materials by operating the saturator inlet with DiEthylene Glycol (DEG) has been recently characterized in the literature. This work reports the same characterizations when operating the saturator inlet with different working fluids and also quantifies the detection efficiency of uncharged materials. In addition to DEG, the tested fluids are three alcohols including n-butanol which is the most commonly used CPC fluid. Experiments are performed to identify the device temperatures and flow rate to maximize the detection of the smallest materials with each of the considered fluids and are complemented by COMSOL modeling of such optimal operating conditions. The operation of the saturator inlet with any of the tested alcohols boosts the detection of flame-formed materials, regardless of their charge state, with performances comparable to that of DEG.