<\/p>\n<\/div><\/div>\n\n\n\n

There\nare a large number of hydroxyl groups and unsaturated residual bonds in\ndifferent states on the surface of the silica\nnanoparticles<\/a>, making the silica nanoparticles hydrophilic and\noleophobic and easy to agglomerate. They must be functionally modified to\nimprove performance and range of applications.<\/p>\n\n\n\n

The\npurpose of silica nanoparticle surface modification mainly includes the\nfollowing three aspects:<\/p>\n\n\n\n

One is to improve or increase the\ndispersion between silica nanoparticles and compatibility with other substances\nbecause the surface-modified nanoparticles can weaken the charging effect of\nsurface-active hydroxyl groups and the hydrophilicity of surface groups. Thus,\nit prevents particles from agglomeration or to achieve compatibility with\norganic substances;<\/li>
The second is to cover the surface of\nthe silica with active groups to improve or control its surface activity\nthrough surface modification, thereby providing the possibility of further\ngrafting or functionalization of nanoparticles;<\/li>
The third is to broaden the scope of\nthe application of silica nanoparticles. Surface-modified nanoparticles can\nproduce new functions, such as drug delivery and release, and stimulus\nresponsiveness.<\/li><\/ul>\n\n\n\n
The\nsurface modification of silica nanoparticles can be divided into two categories\nbased on whether there is a chemical reaction between the surface hydroxyl\ngroup and the modifier: physical modification and chemical modification. The\nphysical modification changes the ratio of hydroxyl groups on the surface of\nsilica, while chemical modification needs to change the chemical properties of\nnanoparticles.<\/p>\n\n\n\n
1.\nPhysical modification of silica nanoparticles<\/p>\n\n\n\n
Adsorption,\nencapsulation, and coating of silica nanoparticles by polymers or inorganic\nsubstances are the main ways of physical modification of silica nanoparticles.\nThe combination of the hydroxyl functional group on the surface of the silica\nnanoparticles and the modifier is carried out through the interaction of\nhydrogen bonds, van der Waals forces, or coordination processes, which means\nphysical modification is a kind of physical adsorption modification.<\/p>\n\n\n\n
The\nsurface deposition method is the main method for the physical modification of\nthe silica nanoparticles. The coating layer is deposited on the surface of the\nsilica nanoparticles by substances, and there is no chemical binding in this\nprocess.<\/p>\n\n\n\n
2.\nChemical modification of silica nanoparticles<\/p>\n\n\n\n
The\nsurface chemical modification of silica nanoparticles is based on the chemical\nreaction between a large number of hydroxyl groups or unsaturated bonds on the\nsurface of the particles and the modified molecules.<\/p>\n\n\n\n
Chemical\nmodification has become a major method for surface modification because of its\nsimplicity and strong firmness. Modification molecules can be divided into\norganic molecules and inorganic molecules. The commonly used chemical\nmodification methods are as follows:<\/p>\n\n\n\n
(1)\nCoupling agent method (such as silane coupling agent). One of the most common\nand basic methods.<\/p>\n\n\n\n
(2)\nEsterification method.<\/p>\n\n\n\n
(3)\nSurface graft polymerization method. This method can prepare hybrid materials\nwith complementary properties and mutual promotion effects, so it is an\nimportant research topic with application prospects in the field of materials\nscience.<\/p>\n\n\n\n
3.\nPhysicochemical modification of silica nanoparticles<\/p>\n\n\n\n
It is the ultimate goal to prepare nanomaterials with excellent properties and wide applications, so physical and chemical simultaneous modification in the modification process is also possible. In order to obtain silica nanoparticles with small particle size and extremely high surface energy, and make the nanoparticles tightly combine with the organic chain in the organic system, the synthesized silica sol can be directly added to the organic system that needs to be modified. Organic materials that are used as modified molecules can be added during the preparation of silica nanoparticles as well. <\/p>\n\n\n\n
The advantage of this method is to avoid the agglomeration of silica nanoparticles<\/a> before modification, to ensure the crystal structure and bulk composition of the nanoparticles, to improve the dispersion of the silica nanoparticles, to make the particle size smaller and more uniformly dispersed. <\/p>\n","protected":false},"excerpt":{"rendered":"
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