Metal/oxide nanoparticles exhibit superior performance in catalysis, electronics, and biomedicine due to their unique size effect, and dispersibility is a core prerequisite for their functionality. These particles have three-dimensional scales ranging from 1 to 100 nanometers. Their high specific surface area leads to a significant increase in surface free energy, making them prone to agglomeration through van der Waals forces and chemical bonding, thus losing their nanoscale properties. Therefore, efficient dispersion technology has become a research focus.
Agglomeration is driven by both thermodynamics and interfacial interactions. Unsaturated atoms on the particle surface cause the system to tend to reduce surface area and lower free energy through agglomeration, forming reversible soft agglomerations or hard agglomerations linked by chemical bonds. Simultaneously, factors such as electrical double-layer compression and insufficient solvent affinity weaken the repulsive forces between particles, accelerating the agglomeration process. For example, hydroxyl groups on the surface of oxide particles easily form hydrogen bonds, while metal particles may undergo covalent cross-linking due to oxidation, both increasing the difficulty of dispersion.
Existing dispersion technologies are divided into physical and chemical methods, which are often used in combination in practical applications. Physical dispersion uses external energy to break up agglomerates. Ultrasonic dispersion, leveraging the instantaneous high temperature and pressure generated by cavitation, efficiently dissociates soft agglomerates and is the mainstream method in both laboratory and industrial production. High-shear stirring achieves large-scale dispersion through mechanical force, suitable for batch preparation. Freeze-drying and solvent displacement methods can avoid secondary agglomeration caused by capillary forces during drying, further optimizing the dispersion effect.
Chemical modification is key to maintaining long-term stable dispersion. Adjusting the pH value creates electrostatic repulsion, causing the particle surface to carry the same charge, forming a potential barrier to inhibit aggregation. Surface grafting with polymers or adding surfactants can create a physical protective layer through steric hindrance, particularly suitable for high ionic strength systems. The amphiphilic structure of dispersants can improve the compatibility between particles and solvents, forming a stable solvation shell and weakening the driving force of agglomeration at its source.
Dispersion effectiveness needs to be verified through multi-dimensional characterization. Dynamic light scattering can detect particle size distribution and polydispersity index, Zeta potential measurement assesses electrostatic stability, and transmission electron microscopy provides direct observation of particle morphology. Precise control of dispersion allows metal/oxide nanoparticles to fully realize their potential across various fields: enhancing the exposure of reactive sites in catalysis, optimizing drug delivery efficiency in biomedicine, and ensuring the uniformity of conductive pastes in electronics.
In the future, metal/oxide nanoparticle dispersion technology will develop towards greener and more precise directions. The development of novel environmentally friendly dispersants and the optimization of intelligent processes will effectively solve the challenges of dispersion stability and system compatibility, promoting the large-scale application of these nanomaterials in high-end manufacturing, environmental governance, and other fields, unleashing their unique technological value and market potential.
