Laser photophoretic migration with periodic expansion-contraction motion of photo-absorbing microemulsion droplets in water.
Laser photophoretic migration with periodic expansion-contraction motion of photo-absorbing microemulsion droplets in water.
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DOI：
10.1021/la0485780
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发表时间：
2004-11
期刊：
影响因子：
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通讯作者：
Makiko Tanaka;H. Monjushiro;H. Watarai
中科院分区：
文献类型：
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作者：
Makiko Tanaka;H. Monjushiro;H. Watarai
以Co(III)-吡啶偶氮配合物为吸光剂的油包水（w/o）微乳液滴在连续波Ar（+）离子激光（514.5 nm）照射时，我们观察到水中的吸光微乳液滴在激光光致迁移过程中反复出现膨胀和突然收缩的现象。膨胀-收缩周期的周期与络合物的浓度和照射的激光功率成反比，与液滴的初始尺寸无关。通过局部温度测量和拉曼显微镜光谱研究了液滴周期运动的机理。提出双连续微乳液滴的第一步是由激光诱导的微乳内部温度梯度引起的正常w/o微乳外相和水相内相的相分离。随后，由于激光诱导的微乳液液膜内外温度梯度，外部水通过热渗透渗透，导致内部水相膨胀。当液膜变薄到临界厚度时，内部水相被释放，液滴缩小到原来的大小。所提出的机构可以解释独特的周期运动。
When the water-in-oil (w/o) microemulsion droplets including the Co(III)-pyridylazo complex as the photo-absorber were irradiated with a continuous-wave Ar(+) ion laser (514.5 nm), we have observed unexpected phenomenon that photo-absorbing microemulsion droplets in water repeated the expansion and the sudden contraction during the laser photophoretic migration. The period of the expansion-contraction cycle was inversely proportional to both the concentration of the complex and the irradiated laser power and was independent of the initial size of the droplet. The mechanism of the periodic motion of the droplet was investigated by local temperature measurement and Raman microscope spectroscopy. It was suggested that the first step was the phase separation of the bicontinuous microemulsion droplet into the normal w/o microemulsion outer phase and the aqueous inner phase in the droplet, which was caused by the laser-induced temperature gradient inside the droplet. Subsequently, an expansion of the inner aqueous phase was induced by the percolation of the external water by thermo-osmosis, which was caused by the laser-induced temperature gradient between the inside and the outside of the microemulsion liquid membrane of the droplet. When the liquid membrane became thinner to a critical thickness, the inner aqueous phase was released and the droplet shrank into the original size. The proposed mechanism can give an account of the unique cyclical motion.