Particle Segregation at Contact Lines of Evaporating Colloidal Drops: Influence of the Substrate Wettability and Particle Charge鈥揗ass Ratio
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- 作者：Diego Noguera-Mar铆n ; Carmen L. Moraila-Mart铆nez ; Miguel A. Cabrerizo-V铆lchez ; Miguel A. Rodr铆guez-Valverde
- 刊名：Langmuir
- 出版年：2015
- 出版时间：June 23, 2015
- 年：2015
- 卷：31
- 期：24
- 页码：6632-6638
- 全文大小：469K
- ISSN：1520-5827
文摘
Segregation of particles during capillary/convective self-assembly is interesting for self-stratification in colloidal deposits. In evaporating drops containing colloidal particles, the wettability properties of substrate and the sedimentation of particles can affect their accumulation at contact lines. In this work we studied the size segregation and discrimination of charged particles with different densities. We performed in-plane particle counting at evaporating triple lines by using fluorescence confocal microscopy. We studied separately substrates with very different wettability properties and particles with different charge鈥搈ass ratios at low ionic strength. We used binary colloidal suspensions to compare simultaneously the deposition of two different particles. The particle deposition rate strongly depends on the receding contact angle of the substrate. We further observed a singular behavior of charged polystyrene particles in binary mixtures under 鈥渟alt-free鈥?conditions explained by the 鈥渃olloidal Brazil nut鈥?effect.