A Study On Preparation Of Colloidal Silica Articles And Complex Core-shell Structures Of Magnetic Iron Oxide

In the past few decades,the level of nanotechnology has been highly improved.Due to their narrow size distribution,monodispersed can install a special crystal colloidal crystals.Sillica, a kind of inorganic materals, is common used in this area. Monodisperse sillca can be prepared by the Stober method,which is a classical method and is usually used up till now. Because of its high physical and chemical stability,sillica is highly used in the area of surface coating, photographic emulsions, chemical polishes and so on.Besides the physical chemistry characteristics of quantum size effect, macroscopical quanta size effect, surface effect,the nanomagnetic iron oxide has a special characteristics of super paramagnetic.Because of its special characteristics,nanomagnetic has a wide application in biological medicine, biological magnetic separation, photocatalytic.However,because of its large surface area,high surface energy and a special characteristics of super paramagnetic,nanomagnetic iron oxide can easily sedimentate or agrregate in the solvent. On the basis of a large number of documents,the writer has found that the nanomagnetic iron oxide coated of some inorganic inert material (such as silica, gold, etc.) or organic polymers (chitosan, polystyrene, etc.) can be easily dispersed in the solvent, or the dispersion stability can be improved.The aim of the writer is to make out a kind of composite particles. The following main aspects consists of:1. Prepared by the classical Stober method, silica nanoparticles dispersion and surface modification. Monodispersed silica can be prepared by the pure precursor (TEOS), mainly characterized by scanning electron microscopy. While other experimental conditions remain unchanged, using different alcohol (methanol, ethanol, isopropyl alcohol respectively,), can get sillica of different size.Characterized by scanning electron microscopy,it is fount that the average diameter of microspheres becomes longer with the increasing of the molecular weight of alcohol. On this basis, the writer modified the silica microspheres with carboxyl or amino groups.The modification were determined mainly by the surface potential modification of those nanoparticles.2. Use two different modifiers:sodium citrate and the silane coupling agent KH560 to the nanomagnetic iron oxide. Characterized by TEM, micro-electrophoresis, respectively,two magnetic fluid was prepared. The appropriate modifier can prepare the water-based magnetic fluid and the oil-based magnetic fluid, and writer also tried to explain the reaction mechanism of different modifiers on the nano-magnetic iron oxide.3. Using those two kind of fulid above,the silica coated magnetic iron oxide can be prepared.Using the unmodified fluid,the magnetic nanoparticles tend to adhere to the surface of sillica.Though the experiment,a kind of core-shell materials,magnetic iron oxide coated sillca has been prepared.