在大氣中因為天然及人為因素產生相當多的奈米微粒，成為大氣氣膠中重要成分，其物理及化學性質對大氣以及氣候有著巨大的影響。本研究以電噴霧法製備二氧化矽(SiO2，6nm~30nm)以及甘露糖(D-Mannose，8nm~30nm)奈米微粒並以流動型雲霧室來探討帶電或中性微粒在正壬烷蒸氣中所引起之非均勻相核凝機構。
SiO2微粒及甘露糖微粒在過飽和正壬烷蒸氣中，其臨界過飽和度值皆隨著粒徑減小而增高，此粒徑效應與理論定性描述一致，與理論模擬之定量上則有一段差距。
在電荷效應方面，SiO2微粒在實驗粒徑範圍內並無顯現電荷效應，而甘露糖微粒在小粒徑時，中性微粒之臨界過飽和度高於帶單一正電荷及單一負電荷的微粒。在電荷極性效應方面，當粒徑小至6nm時，對於SiO2帶單一負電荷的微粒而言，其臨界過飽和度稍高於帶單一正電之微粒，但對甘露糖微粒則無明顯差別，而理論預期非極性的正壬烷分子核凝時應無電荷極性效應的產生。
由比較無機與有機微粒的引起核凝所需的臨界過飽和度，可發現有機甘露糖微粒的核凝能力高於無機二氧化矽微粒，此現象推測與蒸氣在微粒表面的潤濕性有關。

Nanoparticles may have a property different from the bulk due to their small size. Recently, the subjects concerning their production, properties and applications have received extensively attention and been intensively investigated. On the other hand, nanoparticles are generated due to natural and anthropogenic activities, and become an important component of the atmospheric aerosols. In the study, an electrospray aerosol generator was used to generate organic/inorganic nanoparticles and a flow cloud chamber(FCC) was employed to examine the effects of particle size and charge on the critical supersaturation for the condensation of a supersaturated n-nonane vapor on organic/inorganic nanoparticles with a diameter from 6 to 30nm, each carrying a single positive or negative charge or no charge.
The results show that the experimental critical supersaturation(Scr) decreases with increasing particle size, at a rate in reasonable agreement with that predicted by Fletcher’s version of Volmer’s theory of heterogeneous nucleation.
There are almost no different in the experimental Scr between the neutral and charged SiO2 particles. That means there is no charge effect observed in the SiO2 particle size range we measured. But it is observed in mannose particles. In the sign preference, for 6nm SiO2 particles, the experiment results show that nonane could condense more readily on positively charged particle, while for mannose there is no such different, agreeing with the theoretical prediction.
Furthermore, nonane condense on organic mannose particles more efficiently than on inorganic SiO2 particles. This phenomenon may be caused by their difference in the wettability and contact angle.

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