التفاصيل البيبلوغرافية
| العنوان: |
Spontaneous formation of nanopatterns in velocity-dependent dip-coated organic films : from dragonflies to stripes |
| المؤلفون: |
Corrales, Tomas P., Bai, Mengjun, Del Campo, Valeria, Homm, Pia, Ferrari, Piero, Diama, Armand, Wagner, Christian, Taub, Haskell, Knorr, Klaus, Deutsch, Moshe, Retamal, Maria Jose, Volkmann, Ulrich G., Huber, Patrick |
| بيانات النشر: |
American Chemical Society |
| سنة النشر: |
2014 |
| المجموعة: |
Hamburg University of Technology (TUHH): TUBdok |
| مصطلحات موضوعية: |
2D crystallization, atomic force microscopy, Marangoni flows, n -alkane, scanning electron microscopy, silicon, X-ray diffraction, 540: Chemie |
| الوصف: |
We present an experimental study of the micro- and mesoscopic structure of thin films of medium length n-alkane molecules on the native oxide layer of a silicon surface, prepared by dip-coating in a n-C32H66/n-heptane solution. Electron micrographs reveal two distinct adsorption morphologies depending on the substrate withdrawal speed v. For small v, dragonfly-shaped molecular islands are observed. For a large v, stripes parallel to the withdrawal direction are observed. These have lengths of a few hundred micrometers and a few micrometer lateral separation. For a constant v, the stripes quality and separation increase with the solution concentration. Grazing incidence X-ray diffraction and atomic force microscopy show that both patterns are 4.2 nm thick monolayers of fully extended, surface-normal-aligned alkane molecules. With increasing v, the surface coverage first decreases then increases for v > vcr ∼ 0.15 mm/s. The critical vcr marks a transition between the evaporation regime, where the solvents meniscus remains at the bulks surface, and the entrainment (Landau-Levich-Deryaguin) regime, where the solution is partially dragged by the substrate, covering the withdrawn substrate by a homogeneous film. The dragonflies are single crystals with habits determined by dendritic growth in prominent 2D crystalline directions of randomly seeded nuclei assumed to be quasi-hexagonal. The stripes strong crystalline texture and the well-defined separation are due to an anisotropic 2D crystallization in narrow liquid fingers, which result from a Marangoni flow driven hydrodynamic instability in the evaporating dip-coated films, akin to the tears of wine phenomenology. ; U.S. National Science Foundation ; Deutsche Forschungsgemeinschaft (DFG) |
| نوع الوثيقة: |
article in journal/newspaper |
| اللغة: |
English |
| تدمد: |
1936-086X |
| Relation: |
ACS nano; ACS Nano 8 (10): 9954-9963 (2014); http://hdl.handle.net/11420/9911; 2-s2.0-84908409362 |
| الاتاحة: |
http://hdl.handle.net/11420/9911 |
| رقم الانضمام: |
edsbas.809EC2D6 |
| قاعدة البيانات: |
BASE |