Generation of ²¹²Pb Attached Ultrafine Particles for Deposition Experiments

ABSTRACT

The purpose of this study was to develop a method to produce mono-disperse silver (Ag) aerosols radiolabeled with ²¹²Pb. ²¹²Pb is the second decay product of ²¹²Rn and is in the size range of a molecular cluster. With its relatively long half-life (t_1/2 = 10.6 h) and low energy γ-emission (239 KeV), ²¹²Pb is suitable for gamma scintigraphy in respiratory tract deposition studies. As a decay product of ²¹²Rn 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.