A dispersant is a chemical substance used to disperse
nanoparticles in solution or solid. Its basic principle is to interact with the surface of nanoparticles, change surface characteristics, reduce the attraction between particles, and achieve the dispersion of nanoparticles.
Dispersants can achieve the dispersion of nanoparticles through the following mechanisms:
1. Charge similarity: Many dispersants have the properties of surfactants and can form charge barriers on the surface of nanoparticles. If the nanoparticles have Surface charge (positive or negative), the dispersant interacts with them through functional groups with the same charge to form an electrostatic barrier and prevent the aggregation of nanoparticles.
2. Charge Anisotropy: If the surface of the nanoparticle is imbalanced with positive and negative charges, the dispersant can neutralize these charge imbalances by adsorbing to the surface. The functional groups of dispersants can form Chemical bond or mutual adsorption with the surface of nanoparticles, and change the interaction between nanoparticles to prevent aggregation.
3. Isolation effect: The dispersant forms an isolation layer by covering the surface of the nanoparticles, blocking the contact between the nanoparticles. This isolation layer can reduce the attraction between nanoparticles, prevent aggregation, and keep nanoparticles in a dispersed state in the solution.
4. Van der Waals force and capillarity: some dispersants disperse nanoparticles by introducing mutually exclusive Van der Waals force or increasing the capillarity between dispersants and solvents. These interactions can reduce the attraction between nanoparticles and stabilize their dispersion state in solution.
The selection of dispersants depends on the properties of nanoparticles, the properties of solvents, and the specific needs of applications. Common dispersants include surfactants, polymers, colloidal particles, etc. By selecting and adjusting the type, concentration, and usage conditions of dispersants reasonably, uniform dispersion and stability of nanoparticles can be achieved.
