AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Evaluation and Modification of a Cost-effective DMA for Sub-5 nm Aerosol Classification
RUNLONG CAI, Da-Ren Chen, Jingkun Jiang, Tsinghua University
Abstract Number: 207 Working Group: Instrumentation and Methods
Abstract Effective classification is one of the limitations in sub-5 nm aerosol measurement. A cost-effective differential mobility analyzer (cDMA) was previously developed for nanoparticle classification which reduces manufacture and maintenance cost. In this study, we evaluated the transfer function and penetration of the cDMA in classifying 1-2 nm monodisperse molecular ions generated by an electrospray and a high resolution half-mini DMA. Tetra-alkyl ammonium ions with electrical mobility diameters of 1.16, 1.47 and 1.78 nm, respectively, were generated and tested. A data inversion routine based on an empirical diffusive transfer function was used to obtain the true transfer function of the cDMA. Comparing to theory, significant broadening in the transfer function was observed when classifying these sub-2 nm monomobile ions. Broadening is more severe at higher aerosol and sheath flowrate combinations. An effective length was estimated to account for the penetration efficiency of the cDMA. Modifications were made to this cDMA to decrease broadening in the transfer function and to increase the penetration efficiency for classifying sub-5 nm particles.