Macromolecular bridging-enhanced holey graphene oxide-based film and its humidity deformation response

The interaction of water molecules with graphene oxide (GO) at the interface or surface will lead to the reversible deformation response of GO-based materials. However, the fabrication of structurally stable and highly sensitive GO-based humidity-responsive films remains a challenge. Since the stability and sensitivity of GO-based humidity-responsive devices are significantly limited by the deformation differences between different components. Herein, we demonstrate that polyamidoamine (PAMAM) bridge-enhanced carboxylated holey GO (hGC/PAMAM) films are sensitive to moisture and exhibit excellent stability in water. Experiments and molecular dynamics (MD) simulation show that the formation of N-C=O between PAMAM and GO sheets significantly increased the interlayer bonding force. Dynamic monitoring of the surface strain of the hGC/PAMAM films showed that the strains spread a gradient from the high-humidity to the low-humidity side, causing asymmetric expansion along the horizontal and vertical directions. This work will provide a better understanding of the mechanism of water molecule transport between layers.