Solvent Effects on the Formation of Surface Nanodroplets by Solvent Exchange

详细信息    查看全文

• 作者：Ziyang Lu ; Haolan Xu ; Hongbo Zeng ; Xuehua Zhang
• 刊名：Langmuir
• 出版年：2015
• 出版时间：November 10, 2015
• 年：2015
• 卷：31
• 期：44
• 页码：12120-12125
• 全文大小：454K
• ISSN：1520-5827

文摘

Solvent exchange is a simple process to form oil nanodroplets at solid鈥搇iquid interfaces with well-defined location and morphology. In this process, a good solvent of the oil is displaced by a poor solvent, leading to the nucleation and growth of oil droplets from a transient oversaturation at the mixing front. Our recent work has shown that the final volume of the droplets is related to the flow conditions. In this work, we investigate the effects of the type and the composition of solvents on the droplet formation under the same flow conditions. Water nanodroplets were produced by ethanol/cyclohexane (solution A) and cyclohexane (solution B) on a hydrophilic substrate. We found that the droplet size increases first and then decreases with an increase of the initial ethanol concentration in solution A. This is attributed to the phase separation of ethanol鈥揷yclohexane鈥搘ater; in particular, the composition of solution A on the phase boundary above the Ouzo region. The same reason also contributes to the lower efficiency in droplet formation for a longer alkane. The important implication from this work is that the maximal droplet volume is limited by the phase separation of the solvents used in the solvent exchange.