Airborne nanoparticle collection efficiency of a TEM grid-equipped sampling system

摘要

The recently developed aerosol sampler called mini particle sampler (MPS), which is equipped with a porous transmission electron microscopy (TEM) grid, renders nanoparticle sampling convenient. The present study aims to improve the nanoparticle sampling efficiency and to optimize the sampling technology. The sensitivity of the parameters in the whole set-up is estimated by the Taguchi method. The effects of the main parameters on the collection efficiency are compared between experiments and theories. The sampling efficiencies are determined for particles with mobility diameters ranging from 5 to 100 nm. The results show that parameters: salt concentration of the atomizer, high-voltage polarity in the differential mobility analyzer (DMA), sampling efficiency assessment method, sampling temperature, and porosity of the porous TEM grid minimally affect the collection efficiency. Small filter pore size and high flowrate promote particle capturing, but may aggravate the burden on the TEM grid. Denser particles increase the deposition possibility due to impaction, and thereby increasing the overall collection efficiency. The minimum collection efficiency is up to 40% by adjusting the parameter settings of the sampling system. The results are of immediate importance for assessing nano-exposure using the MPS sampling system.