title: Structural color in porous, superhydrophilic, and self-cleaning SiO2/TiO2 Bragg stacks.
abstract: Thin-film Bragg stacks exhibiting structural color have been fabricated by a layer-by-layer (LbL) deposition process involving the sequential adsorption of nanoparticles and polymers. High- and low-refractive-index regions of quarter-wave stacks were generated by calcining LbL-assembled multilayers containing TiO(2) and SiO(2) nanoparticles, respectively. The physical attributes of each region were characterized by a recently developed ellipsometric method. The structural color characteristics of the resultant nanoporous Bragg stacks could be precisely tuned in the visible region by varying the number of stacks and the thickness of the high- and low-refractive-index stacks. These Bragg stacks also exhibited potentially useful superhydrophilicity and self-cleaning properties.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
authors.forename: Zhizhong
authors.initials: Z
authors.lastname: Wu
authors.forename: Daeyeon
authors.initials: D
authors.lastname: Lee
authors.forename: Michael F
authors.initials: MF
authors.lastname: Rubner
authors.forename: Robert E
authors.initials: RE
authors.lastname: Cohen
mesh_terms: D003116:Color; D003460:Crystallization / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D016062:Porosity; D012031:Refractometry / Q000379:methods*; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; C009495:titanium dioxide; D012822:Silicon Dioxide; D014025:Titanium