Metallic nanoparticle ensemble, with narrow inter-particle distance, is a useful element for diverse optical devices due to highly enhanced electric field intensity at the gap. Self-assembly of block copolymer (BCP) can provide the versatile solution to fabricate precise nanostructures, but this methodology has the intrinsic limitation to realize optically coupled metallic multimer geometry with narrow inter-particle distance. This is because BCP-based nanotemplate possesses a minimum size limit for interparticle distance imposed by its thermodynamic restriction. Herein, we investigate the facile formation of metallic multimer with scalability and area-selectivity through the collapse of self-assembled BCP nanopattern. The capillary-force-induced collapse phenomenon enables a spatial transformation of lateral regular ordering in metallic nanoparticle array and enhances electric field intensity. The fabrication of this metallic nanoparticle ensemble from BCP lithography is successfully utilized for surface enhanced Raman scattering (SERS). The enhancement factor of metal nanoparticle multimer is calculated as ~6.74 × 105 at 1000 cm−1, 2.04 × 106 at 1022 cm−1, and 6.11 × 106 at 1580 cm−1, respectively.
Tuning surface-enhanced Raman scattering from graphene substrates using the electric field effect and chemical doping
