Preparation Of Colloidal Crystals And Experimental Study

The three-dimensional ordered structures are formed through a self-assembly process of colloidal particles like atoms at a certain condition, named colloidal crystals. Colloidal crystals have lately been of great interest to scientists and engineers because they can serve as a model system for studying the behavior of atoms on a much larger scale and photonic crystal with special optical effect. In this paper, a series of woks in the colloidal crystals are generalized in the following aspects:1. we synthesized a series of mono-dispersed sodium polystyrene sulfonate and Silica particles used for colloidal crystals. Mono-disperse silica particles were prepared two method-tradition stober and growth of silica sol particles. The factors which particle's diameter and poly-dispersity index dependent on , such as the tetraethylorthosilicate (TEOS), ammonia, water and temperature, were investigated in stober method. It showed that stober method is sensentive to the growth environment, and have low silica content, however it is the good way of study the mechanism of growth and preparation of smaller silica particles that is less than 100nm .seeded growth of monodispered silica particles was described in this paper to shed new way for high content products. In constrast to stober method, seeded growth has the advantage that the end number of silica particles was determined by the number of silica sol and the diameter can be predicted according to the addition of TEOS. Besides, the high yields make it suitable for industry product. yet, it required that the designed diameter must be no less than 5 time of the dimeter of silica sol, that is mean that more than 100nm is more suitable. Mono-dispersed sodium polystyrene sulfonate particles was prepared by by using emulsifier emulsion polymerization, and then several factors such as initiator content, electrolyte concentration, monomer concentration etc. are discussed to discover the influences on physical chemistry properties of colloidal particles. Result demonstrates that the sodium polystyrene sulfonate particles have high surface charge density and monodispersity.2. Influence of gravity on crystallization of charged colloidal particles was studied by density-match. Understanding the structure of a material at the atomic level is essential to understanding its properties. Study of colloidal crystals holds great promise for modeling the behavior of atoms in materials because colloidal particles are more convenient to be detected and observed. However, elastic moduli of colloidal crystals are extremely low and thus even weak external fields can distort the structure of colloidal crystals. In this study, liquid mixtures of water (H2O) and deuterium oxide (D2O) as the liquid phase, was used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments under the density-matched (g=0) and unmatched (g=1) conditions are compared to examine the influence of gravity on the crystal structures formed by self-assembly of 110nm (in diameter) polystyrene microspheres. The result shows that the gravity tends to make the lattice constants of colloidal crystals smaller at lower positions, which indicates that the effect of gravity should be taken into account in the study of the colloidal crystals.3. we immobilized colloidal crystals of charged particles in a poly (acrylamide) matrix by photoinduced polymerization. A reflection spectrum and Kossel-line diffraction were employed to trace and compare changes in the colloidal crystal structure before and after immobilization processing. Our experiments showed that immobilized colloidal crystals successfully retained the structure of colloidal crystals unless the sizes and the lattice spacings of the immobilized colloidal crystals decreased slightly. By observing the structure of immobilized crystals in Milli-Q water we confirmed that the lattice spacings of the crystals varied for several days initially during immobilization because of gel swelling or de-swelling. After reaching a balance (2-5 d), the immobilized colloidal crystals are found to be stable in Milli-Q water. Our study thus explores potential applications of colloidal crystals such as their use in photonic materials.