Posted: Oct 09, 2019
1. The overview of silica particles
Nanomaterials are ultrafine materials whose particle size reaches nanometer level (1-100nm). When the size of the particle is nanometer-scale, it has quantum size effect and macroscopic quantum tunneling effect, and thus exhibits many unique properties and has a broad application prospect. Silica particle is a kind of nanometer material with great industrial application prospect. It is widely used in almost all industries that use silica powder. Silica particles not only have special light, electrical properties and high magnetoresistive phenomena, but also have the singularity such as high strength, high toughness and good stability at high temperature. Silica particles can be widely used in various fields, and has a broad application prospect and great commercial value. Silica particles are the one of the early applications of nano-materials. There have been many reports on the application of nano-silica in rubber modification, engineering plastics, ceramics, biomedicine, optics, building materials and resin-based composites.
2. The properties of silica particles
Silica particles is an inorganic chemical material, commonly known as white carbon black. Due to its ultrafine nano-scale with its size ranges from 1 to 100 nm, it has many unique properties, such as optical properties against ultraviolet rays to improve the aging resistance, strength and chemical resistance of other materials. It has a wide range of uses. Nano-scale silica is amorphous white powder, which is non-toxic, tasteless, pollution-free, spherical in microstructure, and has flocculent and reticular quasi-granular structure. The molecular formula and structural formula of silica are SiO2, insoluble in water.
3. The preparation of silica particles
The preparation method of silica particles is divided into physical method and chemical method.
1. Physical methods
Physical methods generally refer to mechanical pulverization. The aggregate of SiO2 is pulverized by a super jet mill or a high-energy ball mill to obtain an ultrafine product with a particle diameter of 1 to 5?m. The process is simple but easy to introduce impurities. The properties of silica powder are difficult to control, the preparation efficiency is low and the distribution of particle size is wide.
2. Chemical method
The chemical method can produce ultrafine silica particles which are pure and have a uniform particle size distribution. Chemical methods include chemical vapor deposition (CVD), liquid phase, ion exchange, precipitation, and sol-gel methods. The main production method is sol-gel ways that is a gas phase method using silicon tetrachloride as a raw material, a precipitation method using sodium silicate and an inorganic acid as a raw material and a sol-gel method using silicate or the like as a raw material.
4. Biomedical applications of silica particles
Silica is one of the most widely used materials in industrial production. In recent years, silica particles have been widely used as a biological carrier in cancer treatment, medical imaging, DNA transfection, drug delivery and enzyme immobilization because of its special optical and electrical properties, good stability, superparamagnetic and targeted localization. For example, the mesoporous silica nanoparticles have uniform mesoporous pore size, regular pore channels and stable skeleton structure which can be continuously adjusted in the 2~50nm range. So it is easy to modify the internal and external surface to be suitable for drug carrier. Based on the unique structure and high biocompatibility of mesoporous silica (MSNs), it can be used in drug controlled release system, gene carrier, biosensor system, intracellular labeling and other biological molecules such as the controllable sustained-release proteins.
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