Graphene-based hierarchical sandwich-type hybrid nanostructures for optical limiters

Graphene-based multi-layer ordered nanostructures have drawn considerable research interest and revealed great potential for various applications. Here, we constructed silver nanoparticle (NP)/graphene-oxide (GO) hierarchical sandwich-type hybrid nanostructures with the use of a highly efficient and convenient chemical self-assembly method, which might be further extended to fabricate other hierarchical graphene-metal NPs hybrid nanostructures. We characterized the morphology, structure, surface chemical states, and linear optical properties of the materials. A hierarchical sandwich-type hybrid nanostructure was obtained through interactions between silver NPs and amino groups on the GO surface. Owing to the protective effect of the multilayer GO, metallic silver was preserved in the sandwich-type nanostructures. Features in the UV/Vis spectrum of the sandwich-type nanostructure were considerably red-shifted and broadened compared with those of silver NPs on a single sheet of GO. We attribute these changes to enhanced coupling of the collective electron excitation within the silver NPs to the graphene oxide. We investigated the nonlinear optical and optical limiting (OL) properties by a nanosecond open-aperture Z-scan technique at 532 nm. These results showed that the hierarchical sandwich-type hybrid nanostructure underwent an intensity-dependent transformation from saturable absorption to reverse saturable absorption. The OL effect of the hierarchical sandwich-type hybrid nanostructure was greater than that of monolayer graphene oxide with silver NPs at the same linear transmittance. We attribute this enhanced OL performance to the unique sandwich structure, which increased interfacial interactions between graphene oxide and the silver NPs and facilitated charge transfer between the two components. The excellent OL performance of hierarchical sandwich-type hybrid nanostructures arises from a combination of photoinduced electron and/or energy transfer, nonlinear absorption, and nonlinear scattering mechanisms. Together, our results indicate that hierarchical sandwich-type hybrid nanostructures might have extensive applications in optoelectronic fields.