Characterization of three new condensation particle counters for sub-3 nm particle detection: ADI versatile water CPC, TSI 3777 nano enhancer and boosted TSI 3010

The scientific need to understand nanoparticle dynamics at sizes below 3 nm has pushed companies to develop commercial solutions to measure particles down to 1 nm. In this study we characterize the performance of three new particle counters able to detect particles smaller than 3 nm: Aerosol Dynamics Inc versatile water condensation particle counter (v-WCPC, ADI, Berkeley, USA), TSI 3777 nano enhancer (TSI Inc., Shoreview, USA) and modified and boosted 3010 type CPC from Clermont Ferrand University called as B3010. The 3777 and v-WCPC were characterized using tungsten oxide test particles with all charging states: negative, positive and neutral, and with positively charged tetradodecylammonium bromide. The detection efficiencies of the particle counters were measured with two different temperature settings: low temperature difference settings so that the CPCs did not detect any ions from a radioactive source; and high temperature difference settings so that the supersaturation was at the onset of homogeneous nucleation for the 3777, or confined within the range of liquid water for the ADI v-WCPC. The measured 50 % detection diameters (d50) were in the range of 1.3–2.4 nm for the tungsten oxide particles depending on the particle charging state and CPC temperature settings, and between 2.5 and 3.3 nm for the organic test aerosol for the 3777 and v-WCPC. The d50s were measured for the B3010 with negatively charged tungsten oxide particles with four different inlet flow rates. The v-WCPC and 3777 were also compared side by side by measuring atmospheric aerosol, exhibiting an excellent agreement.