Unipolar Charging of Nanosized Aerosol Particles Using Soft X-ray Photoionization |
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| Authors: | Bangwoo Han Manabu Shimada Mansoo Choi Kikuo Okuyama |
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| Affiliation: | 1. Department of Chemical Engineering, Graduate School of Engineering , Hiroshima University , Higashi-Hiroshima , Japan;2. School of Mechanical and Aerospace Engineering , Seoul National University , Seoul , South Korea;3. Department of Chemical Engineering, Graduate School of Engineering , Hiroshima University , Higashi-Hiroshima , Japan;4. School of Mechanical and Aerospace Engineering , Seoul National University , Seoul , South Korea;5. National CRI Center for Nano Particle Control, Institute of Advanced Machinery and Design , Seoul National University , Seoul , South Korea |
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| Abstract: | 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 diffusion 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 charging 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. |
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