Graphene, currently the thinnest and strongest two-dimensional nanomaterial discovered, possesses immense application potential in energy, electronics, and medicine due to its ultra-high electrical conductivity, excellent thermal conductivity, and good mechanical properties. However, its performance is highly dependent on the quality of its fabrication. The emergence of ultrasonic exfoliation provides a crucial solution for the large-scale production of high-quality thin-layer graphene.
Traditional graphene preparation methods have long faced bottlenecks. While mechanical exfoliation can yield high-quality graphene, the yield is extremely low, making it difficult to meet industrial demands. Chemical vapor deposition requires high-temperature and high-pressure conditions, resulting in expensive equipment and a high risk of structural defects in the products. Redox methods introduce numerous oxygen-containing functional groups, disrupting the intrinsic structure of graphene and leading to performance degradation. These problems have severely limited the industrialization of graphene.
Ultrasonic exfoliation breaks this deadlock with its unique advantages. Its core principle utilizes the "cavitation effect" generated by ultrasound in liquids—tiny bubbles in the liquid periodically expand, contract, and burst under the influence of sound waves, releasing strong shock waves and shear forces.
The preparation process of this method is simple and controllable, mainly consisting of three steps. The first step is raw material pretreatment, where natural or artificial graphite is pulverized and dispersed in an organic solvent or an aqueous solution containing surfactants to form a stable suspension, preparing for subsequent exfoliation. The second step is ultrasonic treatment, where the suspension is placed in an ultrasonic reactor. By adjusting the ultrasonic power, frequency, and treatment time, the exfoliation efficiency and the number of graphene layers are controlled. Generally, higher ultrasonic power and longer treatment time result in more thorough exfoliation, but excessive ultrasonication must be avoided to prevent damage to the graphene structure. The third step is separation and purification, where centrifugation is used to remove unexfoliated graphite particles, followed by filtration or drying to obtain high-quality thin-layer graphene products.
Compared to traditional methods, the ultrasonic exfoliation method has significant advantages. First, the process is simple, requiring no complex equipment, significantly reducing production barriers and costs. Second, the preparation process is gentle, preserving the complete structure of graphene to the greatest extent, resulting in fewer defects and higher quality products. Third, the number of graphene layers can be flexibly controlled by adjusting process parameters to meet the needs of different application scenarios, and it is easy to achieve large-scale production.
Currently, high-quality thin-layer graphene prepared by ultrasonic exfoliation has been applied in multiple fields. In energy storage, it is used as an electrode material for supercapacitors, significantly increasing the specific surface area and conductivity of the electrodes, thereby greatly improving the energy density and charge/discharge efficiency of the capacitors. In thermal conductivity, it can be added to polymer materials to prepare high thermal conductivity composite materials for heat dissipation in electronic devices. In sensing, its high sensitivity makes it a core component of electrochemical biosensors, enabling precise detection of trace substances.
However, challenges remain, such as the low concentration of graphene dispersions and the tendency for aggregation due to prolonged ultrasound. In the future, by optimizing the dispersion system, developing novel ultrasonic equipment, and combining it with other auxiliary technologies, ultrasonic exfoliation is expected to further improve preparation efficiency and product quality, promoting the industrial application of graphene materials in more high-end fields and injecting stronger momentum into the development of the new materials industry.
