Polymer-Based Fabrication of 2D Metallic and Ceramic Nanomaterials

Since the ground-breaking achievement of successfully exfoliating single-layer graphene in 2004, there has been significant and rapid development in the field of two-dimensional (2D) nanomaterials. In the field of materials science, 2D nanomaterials are defined as freestanding nanomembranes with a thickness below 100 nm and other lateral dimensions that can extend to the millimeter scale or beyond. These materials exhibit exceptional mechanical, physical, and chemical properties due to their extremely high surface area to volume ratios, surpassing those of their bulk counterparts. As a result, numerous top-down and bottom-up methods have emerged over the past decades to synthesize novel 2D nanomaterials, catering to diverse applications. In this Account, we review the existing top-down methods, such as mechanical compression and mechanical exfoliation, as well as bottom-up methods including hydrothermal induction/solvothermal synthesis, chemical vapor deposition synthesis, etc. We critically discuss the advantages and limitations of each method. Subsequently, we highlight our recently developed method known as polymer surface buckling enabled exfoliation (PSBEE). Unlike previous synthesis techniques, PSBEE is based on the chemical reaction between metals and polymers to fabricate 2D nanomaterials with unique nanostructures. This approach offers a simple, efficient, cost-effective, and environmentally friendly means of achieving large-scale production of 2D nanomaterials, featuring an extremely high lateral size to thickness ratio ranging from 10⁶ to 10⁷. Notably, PSBEE eliminates the need for chemical etching and enables precise control over the morphology of the synthesized nanomaterials, allowing for transitions from 2D nanomembranes to 1D nanotubes. Through thermal annealing, some of the PSBEE-fabricated 2D nanomaterials, such as 2D gold nanomaterials, can undergo pyrolysis and transform into 0D gold nanoparticles. Furthermore, the versatility of PSBEE extends beyond 2D metallic nanomaterials to the synthesis of 2D ceramic nanomaterials, showcasing its broad applicability across diverse material systems. The unique nanostructures of PSBEE-fabricated 2D nanomaterials, usually featuring a network of nanosized ceramics and metals, contribute to their exceptional mechanical and functional properties. These include an outstanding elastic strain limit, superb strength, remarkable plasticity, superior fracture toughness, high electrocatalytic properties, and unique triboelectric performance. Consequently, these properties lead to novel applications of the PSBEE-fabricated nanomaterials, such as triboelectric sensing and 2D electrocatalysis. At the same time, the PSBEE method also offers notable advantages in terms of scalable production, high throughput efficiency, and low energy consumption, making it highly suitable for future industrial applications. In general, polymer-based fabrication of 2D nanomaterials opens up possibilities for producing diverse and technologically significant 2D nanomaterials, leading to new avenues for various practical applications.