Generation of 212Pb attached ultrafine particles for deposition experiments

The purpose of this study was to develop a method to produce monodisperse silver (Ag) aerosols radiolabeled with 212Pb. 212Pb is the second decay product of 220Rn and is in the size range of a molecular cluster. With its relatively long half-life (t1/2 = 10.6 h) and low energy g-emission (239 KeV), 212Pb is suitable for gamma scintigraphy in respiratory tract deposition studies. As a decay product of 220Rn in pure air, the 212Pb particles are in the size range of 1–2 nm. An evaporation/condensation technique and electrostatic classification were used to generate the aerosol that ranged in size between 10 to 50 nm. Monodisperse radiolabeled Ag particles of 10 and 40 nm were produced by attachment of the 212Pb clusters. Wire mesh screens were used to remove the unattached 212Pb in the coagulation chamber so that the attached Ag particles with a narrow size distribution could be produced.