Sensitive light-scattering detection-magnetophoretic acceleration mass analysis of single microparticles in an atmosphere

摘要

Optically detected magnetophoretic acceleration mass analysis of an individual micro-particle in an atmosphere has been remarkably improved in sensitivity by using a reflective microscope objective, by which forward scattered light from a particle could be effectively collected. From the light-scattering simulation, the detection limit for the radius of a micro-particle was estimated to be smaller than 0.4 mu m, and about 60 times intensity enhancement was observed for a polystyrene particle with a radius of 2.8 mu m. For both paramagnetic and diamagnetic micro-particles, the mass magnetic susceptibility and the relaxation time could be determined without knowing any parameters of the particles. From the relaxation time, the mass of a particle was obtained if the radius or the density of the particle was known. For a test sample silica particles were used to adsorb paramagnetic dysprosium(III), the surface concentration of dysprosium( III) on a single particle could be successfully determined by use of this method.