(Digital Presentation) Synthesis of Multisize Layered Silica Inverse Opal Photonic Crystals

Today, human beings have found an increasing need for energy. The ever-increasing effort to shrink information systems at higher speeds has led to the common idea that photons are used as carriers of information instead of electrons. Photonic crystals have a structure whose dielectric constants and refractive indices change alternately in one, two, or three dimensions, which are called one-dimensional, two-dimensional, and three-dimensional photon crystals. Periodicity in the refractive index of the crystal structure causes a photonic bandgap that includes a range of frequencies in which light with a frequency of this range is not allowed to pass the crystal structure and is reflected or absorbed. In this work, Poly(methyl methacrylate) (PMMA) microspheres of different sizes were first synthesized using the suspension polymerization method. Concentrations of used materials including initializer, monomer, reaction temperature, reaction time, and rotation speed play important roles in determining the final diameter of PMMA microspheres. Then, the vertical deposition method is used for the growth of multi-layered opals of different sizes, one on top of another. On the other hand, inverse opals have porous and organized structures that are made using opals as the template. The method used in this study to make multisize layered inverse opal made of silica is as follows: 1- Fabrication of a uniform layer of polymer microspheres on a glass substrate with a specified size as a colloidal crystal template 2- Infiltration of void space between the microspheres of the opal template 3- Creating the next layer with different size on the first layer 4- Reinjection of the silica precursor. 5- Repeating the coating layer and injection of the precursor. 6- Finally, selective removal of the opal template by calcination or etching with an organic solvent to create the porous structure of the multisize layered Silica inverse opal photonic crystals. The silica precursor contains a mixture of ethanol, TEOS tetraethyl orthosilicate, and hydrochloric acid. The results show that the fabricated inverse opals are organized, crack-free, and uniform. It is possible to make the desired number of layers by changing the concentration of the PMMA microspheres' colloidal suspension. By changing the characteristics of photonic crystals, such as their constituent materials and refractive indices, lattice constants, and the number of layers, it is possible to control their photonic properties which are beneficial for different applications.