I have a silica solution and I want to use dip coating method to fabricate a 3D photonic crystals. i would like to know the ratio of silica to solvent (ethanol) in mL, withdrawal speed, immersion time and number of dipping cycles.
I think you should explore the literature and do some trial experiements.
www.scopups.com could be helpful to you
dip-coating is a relatively tricky thing, if you want to deposit colloidal crystals. I never heard of silica opals produced by dip coating and can only wish you good luck. Usually, polystyrene or whatever polymer microspheres are used. For your reference, you may find interesting the article of Gu, Z Z; Fujishima, A; Sato, O, "Fabrication of High-Quality Opal Films with Controllable Thickness" in Chemistry of Materials journal (vol. 14, 2002, p. 760). You should also find the PhD thesis of R.K. Čapek: "Nanoteilchen in künstlichen Opalen: Einfluss auf die optischen und photonischen Eigenschaften" defended at the University of Hamburg in 2008. They both deal with dip-coating. You can look for the papers of W. Khunsin written at the Tyndall National Institute in Cork, Ireland, such as "Optical transmission in triple-film hetero-opals", Journal of Applied Physics, vol. 104 (2008) 013527.
I assume that you are not bound to dip-coating. If you can choose the method of depostion, you could also think of something like slide-coating (S. C. Gil, Y. G. Seo, S. Kim, J. Shin, and W. Lee, “High-speed fabrication of 3-dimensional colloidal photonic crystal films by slide coating of polymer microspheres with continuous feeding of colloidal suspension,” Thin Solid Films 518 (20), 5731–5736 (2010)). Another alternative could be a so-called dip-drawing technique, which is somewhat similar to the dip-coating, but could be much faster and cheaper (A. Wang, S.-L. Chen, and P. Dong, “Rapid fabrication of a large-area 3D silica colloidal crystal thin film by a room temperature floating self-assembly method,” Mater. Lett. 63 (18-19), 1586–1589 (2009)) - it is about silica particles. If, however, the results will not be convincing or the setups too complicated, I would strongly recommend to do it in a usual way known since 15 years already - P. Jiang, J. F. Bertone, K. S. Hwang, and V. L. Colvin, “Single-Crystal Colloidal Multilayers of Controlled Thickness,” Chem. Mater. 11 (8), 2132–2140 (1999).
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