Two-dimensional nanosheet-based solvent-free nanofluids: A systematic review from synthetic strategies and structural engineering to frontier applications

Abstract

Solvent-free nanofluids (SFNs) transform inorganic nanomaterials into liquid-like hybrid systems through surface-engineered core-corona-canopy architectures, offering a promising route to overcome aggregation, poor processability, and solvent-related instability. While previous studies and reviews have mainly focused on conventional zero-dimensional nanoparticles or one-dimensional nanostructures, two-dimensional nanosheet-based SFNs (2D SFNs) represent a distinct class because their high aspect ratio, anisotropic geometry, abundant surface chemistry, and interlayer interactions introduce unique opportunities and challenges in fluidization design. In particular, nanosheet restacking, non-uniform grafting, and interface-controlled rheology make 2D SFNs fundamentally different from traditional SFNs. This review therefore provides a focused and systematic overview of 2D SFNs, emphasizing their core selection, surface chemistry, modification routes, canopy regulation, and structure-property relationships. Representative systems based on graphene oxide, clay nanosheets, MXenes, MoS 2 , and other layered materials are discussed to clarify how interfacial engineering converts rigid nanosheets into stable liquid-like materials. Their emerging applications in gas separation, lubrication, polymer composites, and energy storage are further summarized from the perspective of mechanism rather than simple performance comparison. Finally, the review identifies key challenges, including long-term dispersion stability, controllable grafting density, scalable synthesis, and quantitative correlation between microscopic interface structures and macroscopic properties. Overall, 2D SFNs are highlighted as an important platform for integrating nanosheet functionality with liquid-state processability, offering new directions for advanced soft-hard hybrid materials.