Bottom-up colloidal synthesis of PMMA@Au core–shell based metallodielectric photonic crystals as substrates for surface-enhanced Raman spectroscopy

The bottom-up colloidal synthesis of photonic band gap (PBG) materials or photonic crystals (PCs) has attracted considerable interest in comparison to top-down approaches due to the relatively simple processing steps involved, the potential for large area sample production and the relatively low-costs associated with this approach for the fabrication of complex 3-dimensional (3D) structures. This research focuses on the colloidal synthesis of poly(methyl methacrylate) (PMMA)@Au core–shell (CS) structures, their bottom-up assembly into 3D metallodielectric PCs (MDPCs) and the demonstration of their potential to be used as surface enhanced Raman substrates (SERS) using the commonly deployed SERS reporter molecule, 4- aminothiolphenol. Here, monodispersed spherical PMMA particles were used both as a host material for Au nanoparticles (NPs) and as a crystal template to produce the MDPC structures. The materials engineering employed which involved combining the synthesis of monodispersed CS particles and the fabrication of their corresponding MDPCs enabled us to control the distribution of Au NPs in the PC structure and thereby investigate their light scattering, reflection and transmission properties including Raman scattering.