Nanoscale silver particles, due to their unique antibacterial, conductive, and catalytic properties, have broad application prospects in biomedicine, electronic information, and environmental protection. However, due to their large specific surface area and high surface energy at the nanoscale, nanoscale silver particles are highly prone to agglomeration. This not only results in the loss of nanoscale effects but also affects their dispersion uniformity and stability in the application system, severely restricting their functionality.
The agglomeration of nanoscale silver particles is essentially caused by intermolecular van der Waals forces and electrostatic attraction, leading to particle attraction and aggregation. Agglomerated nanoscale silver particles form larger secondary particles, drastically reducing their specific surface area and significantly weakening their original excellent nanoscale effects. For example, in the antibacterial field, agglomerated nanoscale silver particles have difficulty making sufficient contact with bacteria, resulting in a significant decrease in antibacterial efficiency; in conductive materials, agglomeration may lead to discontinuous conductive pathways, affecting conductivity. Therefore, targeted dispersion techniques to break the intermolecular forces are the core approach to preventing agglomeration.
Surface modification technology is one of the commonly used methods to achieve dispersion and anti-agglomeration of nanoscale silver particles. By grafting or coating specific modifiers onto the surface of silver nanoparticles, the chemical properties of the particle surface can be altered, increasing the repulsive force between particles. For example, surfactants such as organosilanes and fatty acids can be used; their hydrophilic groups can bind to the hydroxyl groups on the surface of silver nanoparticles, while the hydrophobic groups extend outwards, creating a steric hindrance effect that prevents particles from approaching each other. Furthermore, surface coating with polymers can not only effectively prevent aggregation but also improve the compatibility and stability of silver nanoparticles, making them better suited for different application systems.
The optimized selection of the dispersion medium also has a significant impact on controlling the aggregation of silver nanoparticles. Different dispersion media affect the surface charge state and solvation layer thickness of silver nanoparticles, thus affecting the interactions between particles. In aqueous systems, adjusting the solution pH can change the charge density on the surface of silver nanoparticles, achieving dispersion through electrostatic repulsion. In organic systems, selecting solvents with good compatibility with the surface modifiers of silver nanoparticles can reduce hydrophobic interactions between particles, preventing aggregation. Simultaneously, appropriately controlling the viscosity and temperature of the dispersion medium can also effectively inhibit particle sedimentation and aggregation.
Precise control of the preparation process is key to reducing the agglomeration of silver nanoparticles at the source. In the chemical reduction method for preparing silver nanoparticles, controlling parameters such as reaction temperature, reducing agent concentration, and silver ion concentration can regulate the particle growth rate and size distribution, reducing collisions and aggregation between particles. Furthermore, physical dispersion methods such as ultrasonic dispersion and high-pressure homogenization can break up existing micro-agglomerates during the preparation process, further improving the dispersion effect. For example, ultrasonic dispersion utilizes the cavitation effect of ultrasound to generate strong shock waves and shear forces, effectively dispersing agglomerated silver nanoparticles, and is simple to operate and produces no chemical pollution.
The technology for controlling the agglomeration of dispersed silver nanoparticles not only promotes the performance optimization of silver nanoparticle materials but also expands their application scenarios. In the biomedical field, uniformly dispersed silver nanoparticles can be used to make antibacterial dressings, drug carriers, etc., improving therapeutic effects; in the electronics field, highly dispersible silver nanoparticle pastes can be used to prepare high-performance conductive films and flexible electronic devices.
In the future, with continuous innovation in dispersion technology, the agglomeration problem of silver nanoparticles will be better solved, and their application potential in more high-end fields will be further explored, injecting new impetus into the development of the new materials industry.
