Assembly of large-area, highly ordered, crack-free inverse opal films

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Birgit Hausmann


B. Hatton et. al. "Assembly of large-area, highly ordered, crack-free inverse opal films" PNAS 107 (23) 2010


Coassembly, colloidal assembly, crack-free films, inverse opals, nanoporous


A new synthesis of crack-free inverse opal films over cm length scales is presented. The two step process consists of a) an evaporative deposition of polymeric colloids in a hydrolyzed silicate sol-gel precursor solution and b) a colloidal/matrix coassembly. The preferential grwoth direction is <110>. The synthesis of multilayered hierarchical films are also demonstrated. Furthermore, the inverse opal films were converted to inverse opal films of other materials as porous Si and <math>TiO_2</math> while maintaining their morphology during the gas/solid displacement reaction.

Results and Discussion

Fig. 1 Schematic for inverse opal synthesis: 1) Colloids assemble from a sol-gel solution 2) template removal

Herein we demonstrate the evaporative coassembly of a sacrificial colloidal template with a matrix material in a single step to yield a colloidal composite, thereby avoiding the need for liquid infiltration into a preassembled porous structure

Fig. 2 Highly ordered I-<math>siO_2</math> films formed from PMMA/sol-gel coassembly (Left scale bar is <math>10\mu m </math> and right scale bar is <math>1\mu m </math>)
Fig. 3 A) Film thickness is directly proportional to the colloidal concentration. The threshold thickness for cracking is indicated. B) A 1.5cm I-<math>siO_2</math> film. C)A cleaved film reveals the growth direction along <110>.

Cracking seems to occur along {111} planes for thin films, which is consistent with conventional evaporative deposited films, whereas thicker films seem to crack along {110} planes.

Fig. 4