Controllable Ag-rGO heterostructure for highly thermal conductivity in layer-by-layer nanocellulose hybrid films

Many researchers have attempted to address the problem of frequency reduction or overheating damage caused by inadequate thermal conductivity of substrates. Developing advanced, green, and practical thermal interface materials (TIMs) is one of the most promising solutions to date. Herein, a facile method is proposed to achieve fascinating thermal conductivity of TIMs via constructing two-dimension (2D) reduced graphene oxide (rGO) decorated with zero-dimension (0D) silver nanoparticles (AgNPs) in hybrid nanofibrillated cellulose (NFC) film. The surface morphology and chemistry of Ag-rGO-functionalized NFC (Ag-rGO/NFC) are significantly altered by adding a small amount of Ag-rGO nanosheets (9.6 wt%), resulting in remarkable improvement in the thermal conductivity. The in-plane thermal conductivity of Ag-rGO/NFC (27.55 W m−1 K−1) showed a massive enhancement of over 1095% compared to pure NFC (2.3 W m−1 K−1), accompanied by 573% increase in through-plane conductivity. These enhancements could be attributed to the robust heterostructural Ag-rGO networks and dense layer-by-layer (LBL) structures. It is likely that these controllable structures come into being due to the intense static adsorption between graphene oxide (GO) and Ag+ as well as the hydrogen bonding interaction between GO and NFC. It is worth noting that exceptionally fast heat transport is achieved for Ag-rGO/NFC in practical application, with values as high as 0.18 °C/s, in sharp contrast to 0.16 °C/s for pure NFC films in the time range of 80–220 s. This could be due to the excellent thermal conduction networks built by Ag-bridged rGO nanosheets. This work provides valuable insights into the fabrication of highly thermal conductive composites in the promising field of electronic equipment, integrating intelligent functionality and environmental compatibility.