Whereas considerable interest exists in self-assembly of well-ordered, porous "inverse opal" structures for optical,
electronic, and (bio)chemical applications, uncontrolled defect formation has limited the scale-up and practicality of
such approaches. Here we demonstrate a new method for assembling highly ordered, crack-free inverse opal films over a
centimeter scale. Multilayered composite colloidal crystal films have been generated via evaporative deposition of
polymeric colloidal spheres suspended within a hydrolyzed silicate sol-gel precursor solution. The co-assembly of a
sacrificial colloidal template with a matrix material avoids the need for liquid infiltration into the preassembled colloidal
crystal and minimizes the associated cracking and inhomogeneities of the resulting inverse opal films. We demonstrate
that this co-assembly approach allows the fabrication of hierarchical structures not achievable by conventional methods,
such as multilayered films and deposition onto patterned or curved surfaces, and can be transformed into various
materials that retain the morphology and order of the original films. We show that colloidal co-assembly represents a
simple, low-cost, scalable method for generating high-quality, chemically tailorable inverse opal films for optical
applications.
Colloidal self-assembly holds promise for photonic applications as a solution-based, low-cost alternative to top-down
photolithography, if significant control of uniformity and defects can be achieved. Herein we demonstrate a new
evaporative co-assembly method for highly-uniform inverse opal thin films that involves the self-assembly of polymer
colloids in a solution containing a silicate precursor. Nanoporous inverse opal films can be made crack-free and with
highly uniform orientation at the cm scale. The silicate between the colloids appears to increase the strength against
cracking. This control of defects makes this method well-suited for the low cost fabrication of such films as sensors and
photonic devices.
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