Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 107, Issue 23, Pages 10354-10359Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1000954107
Keywords
coassembly; colloidal assembly; crack-free films; inverse opals; nanoporous
Categories
Funding
- Office of Naval Research [N00014-07-1-0690-DOD35CAP]
- Air Force Office of Scientific Research [FA9550-09-1-0669-DOD35CAP]
- Center for Nanoscale Systems (CNS)
- National Nanotechnology Infrastructure Network (NNIN)
- National Science Foundation [ECS-0335765]
- US Department of Homeland Security (DHS)
- DOE [DE-AC05-06OR23100]
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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 coassembly 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 discuss the underlying mechanisms that may account for the formation of large-area defect-free films, their unique preferential growth along the < 110 > direction and unusual fracture behavior. We demonstrate that this coassembly approach allows the fabrication of hierarchical structures not achievable by conventional methods, such as multilayered films and deposition onto patterned or curved surfaces. These robust SiO2 inverse opals can be transformed into various materials that retain the morphology and order of the original films, as exemplified by the reactive conversion into Si or TiO2 replicas. We show that colloidal coassembly is available for a range of organometallic sol-gel and polymer matrix precursors, and represents a simple, low- cost, scalable method for generating high-quality, chemically tailorable inverse opal films for a variety of applications.
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