Electrical Mobility as an Indicator for Flexibly Deducing the Kinetics of Nanoparticle Evaporation

Abstract

Condensation and evaporation of vapor species on nanoparticle surfaces drive the aerosol evolution in various industrial/atmospheric systems, but probing these transient processes is challenging due to related time and length scales. Herein, we present a novel methodology for deducing nanoparticle evaporation kinetics using electrical mobility as a natural size indicator. Monodispersed nanoparticles are fed to a differential mobility analyzer which serves simultaneously as an evaporation flowtube and an instrument for measuring the electrical mobility, realizing measurements of evaporation processes with time scales comparable to the instrument response time. A theoretical framework is derived for deducing the evaporation kinetics from instrument responses through analyzing the nanoparticle trajectory and size–mobility relationship, which considers the coupled mass and heat transfer effect and is applicable to the whole Knudsen number range. The methodology is demonstrated against evaporation but can potentially be extended to condensation and other industrial/atmospheric processes involving rapid size change of nanoparticles.

Surface equilibrium vapor pressure of organic nanoparticles measured from the Dynamic-aerosol-size Electrical Mobility Spectrometer

“…As an extension of conventional EMSs, we have recently introduced an alternative approach known as the Dynamic-aerosolsize Electrical Mobility Spectrometer (DEMS) (Yang et al, 2022(Yang et al, , 2023a. DEMS is designed to conduct in-situ measurements of rapidly evolving aerosol systems, occurring at a timescale close to that of one EMS voltage scanning cycle.…”

“…In our previous works, we presented a complete theoretical framework describing particle transmissions within the classification region of the DEMS. Additionally, we demonstrated the methodology's capability to recover the historical changes in particle size profiles, exemplified through the aerosol evaporation process (Yang et al, 2022(Yang et al, , 2023a. Traditionally, aerosol evaporation processes are characterized using a tandem differential mobility analyzer (TDMA) (Rader and McMurry, 1986;Tao and McMurry, 1989).…”