A unipolar charging device based on a soft X-ray (< 9.5 keV) photoionization was developed to investigate the charging efficiency of aerosol nanoparticles. Unipolar charging using a ~(241)Am charger was also evaluated as a comparison with the characteristics obtained by X-ray charging. The production rate and the concentration of ions generated by the X-ray and ~(241)Am unipolar chargers were estimated from ion current measurements. Theoretical calculations by the unipolar difusion charging theory were also carried out and the calculated data were compared with the experimental results. For acquiring a high number of standard nanoparticles, the classification of monodisperse nanoparticles from polydisperse aerosol particles using the X-ray unipolar charger and a differential mobility analyzer (DMA) was also evaluated. The ion production rate of the X-ray unipolar charger was at least 5.5 times higher than that of the ~(241)Am unipolar charger and the ion concentration was about three times higher.Therefore, the X-ray unipolar charger showed a higher capability for charing aerosol particles of 10-40 nm size in diameter than the ~(241)Am charger. The charging state of particles produced by the X-ray unipolar charger was in good agreement with theoretical calculations. The X-ray unipolar charger developed herein has potential for use in charging a high number concentration of nanoparticles for use in nanotechnology investigations.
展开▼
