Fabrication And Application Of Mesoporous Colloidal Photonic Crystals

Photonic crystals (PCs) are one kind of photonic stop band material, whose dielectric constants are dependent on the structural periodicity. Photon with energy in the photonic band gaps cannot pass through PCs. Thereby people designed several PC devices in order to manipulate light. Colloidal photonic crystals (CPC) were PC materials that self-assembled by one or several kinds of monodisperse colloidal nanoparticles. Due to their simple, fast, efficient preparation processes, CPCs have caused great considerations in the past decades. Mesoporous materials are porous materials with pore sizes between 2-50 nm. Their large surface areas, ordered and controllable pore structures, narrow distribution of pore sizes, modifiable surfaces rendered them great potential in adsorption, separation, catalysis, battery, sensors, drug delivery applications. Mesoporous colloidal photonic crystals (MCPC) could combine the advantages of large surface areas, strong adsorption abilities of mesoporous materials and light manipulation capabilities of PCs. Therefore, they are potential useful in visible adsorption, separation, sensing and dynamic anti-counterfeitings. In this dissertation, monodisperse mesoporous silica nanoparticles were first synthesized. Several kinds of MCPCs were subsequently fabricated by self-assemble methods. Then we investigated the applications of these photonic crystals for vapor sensing and anti-counterfeiting. The detailed research content as follows:(1) We synthesized monodisperse solid silica spheres, and grew uniform mesoporous silica shells on their surface to obtained mesoporous silica nanoparticles (MSNs) with high surface areas and great uniformity. We investigated several synthesis conditions to see their influence on the uniformity of MSNs, and expounded the formation mechanism of MSNs. This synthesis method can control the size of MSNs and keep good monodispersity, thereby provides basis for development of advanced devices based on MCPC.(2) Based on the synthesized monodisperse MSNs, we prepared MCPC films/microspheres by vertical deposition or microfluidic method. And we also used inkjet printing method to fabricate MCPC patterns, and investigated the influence of several printing conditions on the quality of MCPC patterns. Then, we investigated the vapor responding properties of above three kinds of MCPCs prepared.(3) Based on the MCPC films, we loaded different kinds of fluorescent dyes in mesopores of MCPCs, and prepared hybrid fluorescent-MCPC vapor sensing array. The sensing array was capable of discriminating various kinds of vapors, as well as their concentrations, according to their fluorescence and reflective responses to vapor analytes.(4) Based on inkjet printing method, we developed a kind of responsive CPC pattern with multicolor shifting properties by inkjet printing MSNs inks on both rigid and soft substrates. By adjusting the size and mesopores’ proportion of nanoparticles, we can precisely control the original color and vapor-responsive color shift extent of mesoporous CPC. As a consequence, multicolor mesoporous CPCs patterns with complex vapor responsive color shifts or vapor-revealed implicit images are subsequently achieved. Then we investigated the potential of these mesoporous CPC patterns for anticounterfeiting applications.