Figures & data
FIG. 1 Schematic of collection region of thermophoretic sampler. L, W and h are the sampler's length, width, and the gap between hot and cold plates. Air inlet flow velocity is V f , the thermophoretic velocity is V th with V th1 and V th2 standing for thermophoretic velocity in the L 1 and L 2 region. T c and T h are cold-and hot-side surface temperatures with T h1 and T h2 standing for the hot side temperature in the L 1 and L 2 region. The temperature gradient in the L 1 and L 2 region are ∇ T 1 = T h1− T c /h and ∇ T 2 = T h2 − T c /h, respectively.
FIG. 2 Section view of designed thermophoretic sampler. The gap between the cold and hot side of collection area is 0.1 mm, and a bypass flow channel is introduced to reduce diffusional particle loss.
FIG. 3 Theoretical estimation of total particle collection efficiency as a function of thermophoretic flow rate at inlet flow rate, q v − tube , of 2 lpm for particle diameters of 1 and 5 nm.
FIG. 4 Number distributions of Ag particle generated by a homogeneous condensation aerosol generator. The furnace temperature and inlet flow rate are set at 850 and 900°C, and 1.5 and 2 liters, respectively. Note that particle size is shifted to less than 10 nm when furnace temperature is lowered.
FIG. 5 Ag particles deposited on the transmission electron microscope grid at two different grid locations. The sampling inlet flowrate is 2 lpm, thermophoretic flowrate is 0.015 lpm, temperature gradient is 4.7 × 105 K/m, and the sampling time is 90 minutes.
