Colloidal crystals

 

Inventors: Prof. Dr. Bahaa Tumaa Jiad, Assis. Prof. Dr. Muhammed Abdulaah Hameed/ Department of physics, College of science, University of Baghdad

Abstract

Cystography wide scientific field to study the attractive behavior of the materials and produced it in crystals structure in all scientific field. Colloidal crystals are the one of this crystal are characterized by wide experimental filed. It can find it in high complex scientific and practical fields because of their possible application. Photonic crystals (PhC) are periodically structured dielectric media, generally possessing photonic band gap for a range of frequency in which light cannot propagate through the structure. This periodicity, whose length scale is proportional to the wavelength of light in the band gap, is the electromagnetic analog of a crystalline atomic lattice, where the latter acts on the electron wave function to produce the familiar band gaps. Colloidal crystals and their internal structure have been the focus and characterized by small atomic clusters (50-300) nm. Same time this crystal called molecular crystals because of its dimension about the length of the wavelength of UV and IR region in the electromagnetic spectrum. There are different methods to produce this crystal namely Nano- lithography and self-assembly. This crystal has many defects and dislocations in the crystal; therefore, it is important to reduce these defects for this proposes this study closed the upper end of the capillary tube to get a long time to avoid the dislocations and defects. Another point added to the work is adding the dye molecules to study the fluorescence spectra to our knowledge that we get crystals. Silica spheres doped with lasing dyes to modify the optical properties of these spheres and making a light source inside the crystal for studying the effect of the photonic crystal on the emission spectrum, Modification of the spontaneous emission of dyes in PhC samples exhibited stop bands in the visible range was observed, whose center position, and width are analyzed and compared to stop bands from transmission measurements, the diameter of the crystal sphere about (120-140) nm.