Self-assembled Colloidal Crystal (photons) And Its Modification

Photonic crystal (PC) is a spatial periodic dielectric structure, which is a new kind of functional materials arised from the late 1980s. With different dielectric coefficient materials periodically arrayed in the space, photonic crystals (PCs) can change the transmitting character of light in it.In this paper, monodisperse spheres of polystyrene (PS) and silica which are the PCs units have been fabricated by controlling the synthesis condition. And periodic structures were self-organized with these units by vertical deposition method (pulling and pressing method). After the periodic structures, i.e. opal PCs were fabricated, we tried to modulate the PCs by introducing functional materials, such as CdSe, PbS.The synthesized materials, structure of the bare and infiltrated opals were analyzed with XRD, TEM, SEM, UV-Vis and FTIR.Firstly, we systemically built a complete way for fabricating monodisperse PS and silica microspheres by different synthesis routines, synthesis materials and synthesis condition. In the experiments, PS spheres with the diameter range from 50nm to 2um and silica spheres with the diameter range from 10nm to 1um were fabricated with a narrow size distributed (less than 5%), respectively. Those spheres were verified to suit for the requirements of fabricating opal PCs working in the visible-light, near-infrared and infrared range.Opal PCs with fcc structure were assembled with the monodisperse PS and silica microspheres by vertical deposition method. Then the stop band gap of the fcc structure is confirmed by UV-Vis transmission spectra. Judging by the UV-Vis transmission spectra and SEM images, the mainly factors (colloid concentration, temperature and humidity) for the best quality PCs fabricated by vertical deposition method were optimized. We analyzed the PCs growth process by optical microscopy. And the variation of opal PCs after thermal treatment and the property of multilayer opal PCs were investigated.The opal PCs are modulated by some typical materials. Using wet chemistrymethod, a feasible way was found out for CdSe nanoparticles coating on the PS sphere surface. The UV-Vis spectra confirmed the effects of CdSe coating on the bandgap of opal PCs. The silica inverse opal structure was obtained by secondary vertical deposition methods. The SEM observation showed a fare good inverse opal structure and the band gap blueshifted as shown in the UV-Vis transmission spectra.Lastly, monodisperse PbS nanoparticles are successful synthesized and Co-deposited with PS miscrospheres. The PbS nanoparticles were found to infiltrate into the interspaces of spheres of the opal under the hydrostatical pressure.