Surface plasmonic coupling of Au nanoparticle arrays with ultrathin hexagonal boron nitride nanosheets for Raman enhancement.

Integration of hexagonal boron nitride (h-BN) with plasmonic nanostructures that possess nanoscale field confinement will enable unusual properties; hence, the manipulation and understanding of the light interactions are highly desirable. Here, we demonstrate the surface plasmonic coupling of Au nanoparticles (ANPs) with ultrathin h-BN nanosheets (BNNS) in nonspecific nanocomposites leading to a great enhancement of the Raman signal of E2g in both experimental and theoretical manner. The nanocomposites were fabricated from liquid-exfoliated atomically thin BNNS and diblock copolymer-based ANPs with excellent dispersion through a self-assembly approach. By precisely varying the size of ANPs from 3 to 9 nm, the Raman signal of BNNS was improved from 1.7 to 71. In addition, the underlying mechanism has been explored from the aspects of electromagnetic field coupling strength between the localized surface plasmons excited from ANPs and the surrounding dielectric h-BN layers, as well as the charge transfer at the BNNS/ANPs interfaces. Moreover, we also demonstrate its capability to detect dye molecules as a surface enhanced Raman scattering (SERS) substrate. This work provides a basis for the self-assembly of BNNS hierarchical nanocomposites allowing for plasmon-mediated modulation of their optoelectronic properties, thereby showing the great potential not only in the field of SERS but also in large-scale h-BN-based plasmonic devices.