Nanografting technology The nanografting reaction changes the surface structure and state of the nanoparticle by combining nanoparticles and modifiers through chemical reaction. It plays in an important role in altering the surface of nanoparticles. Since the nanoparticles have a large specific surface area, the bonding and electron state on the surface are different from those at the core of the nanoparticle. In addition, there are many bonding sites due to incomplete electron structure, and this provides favorable conditions for nanoparticle surface modification. The classification of surface chemical modification can be generalized as follows.
1. Coupling agent: The inorganic nanoparticle usually demonstrates poor compatibility with the organic substance used for surface modification, and thus requiring the use of a coupling agent. Coupling agent usually requires two functional groups to react with both the nanoparticle surface and organic modifier. Organo-silane (X-R-Si(OR)3), where X is an organic functional group, is one of the most typical coupling agents.
2. Esterification: The reaction of the nanoparticle with alcohol is an esterification reaction which can be used to alter the hydrophilicity of the nanoparticle surface.
3. Polymer grafting modification: Polymerization is used to graft polymers onto the nanoparticle surface to alter the surface properties. Polymer grafting method can be classified as follows.
(1) Use initiator to allow polymerization of monomers on the nanoparticle surface directly, forming a polymer chain.
(2) Use chemical reaction to graft polymer chain onto the nanoparticle surface.
The surface modification methods can effectively improve or alter the dispersibility, weather resistance, durability and surface activity of nanoparticles, thereby giving nanoparticles new physical, chemical and optical properties for different applications.