Investigating the evaporation and decomposition of airborne nanoparticles by thermomobility analysis (TMobA)

1 Abstract Tandem DMA setups generally consist of two DMAs: the first selects particles of a specific electrical mobility, and the second measures these particles, which may be manipulated (e.g., heated or charged) or exposed to different conditions such as temperature, humidity, or electric field strength. Thermomobility analysis (TMobA) extends this concept to the direct thermal analysis of nanoparticles in the gas phase, closely representing conditions of gas-phase-synthesized nanoparticles and combustion-derived aerosols. TMobA achieves high mass sensitivity, detecting changes on the order of 10 -19 μg with a mass resolution of ∼367. In this work, we present a TMobA furnace with residence times between 20–60 ms and total measurement times below 2 h. Heat transfer simulations combined with mean wall temperature measurements provided access to furnace temperature profiles and the particle temperature. Under free molecular conditions, the evaporation of organic or inorganic nanoparticles is easily distinguishable from the decomposition of these particles. Measured data are described well by corresponding models. We demonstrate TMobA’s potential through several applications: nanoscale distillation of mixed nanoparticles, determination of vapour pressures of PEGs of different molecular weights, complete removal of CTAB from model particles, and complex decomposition of AgNO 3 to Ag nanoparticles. These results highlight TMobA as a versatile tool for the thermal analysis of airborne nanoparticles.