Rapid preparation of paper-based plasmonic platforms for SERS applications

A simple spray method is utilized to prepare plasmonic paper loaded with gold nanoparticles (AuNPs) to serve as a signal enhancing substrate for surface enhanced Raman scattering (SERS) spectroscopy. The spray coating of plasmonic AuNPs onto hydrophilic porous paper-based materials notably improves their loading efficiency and distribution profile in much shorter time compare to typical dip- or drop-coating methods. This preparation approach involves the rapid drying of the solution to prevent the loss of the nanoparticles on the hydrophilic paper, which results in the improved packing of the plasmonic nanoparticles with local aggregations. Upon treating these spray-coated substrates with Raman reporter molecules, their sensing capability of SERS is a minimum of 2 times higher than that found with a dip-coated platform. Subsequently applying an additional layer of AuNPs onto these two substrates by dip- and spray-coating methods readily leads to greatly enhanced SERS signals over 2-5 times that are mainly caused by the plasmonic couplings and hot spots of sandwich-type structures. Without the modification of the paper substrates, the way the sandwich structure is formed on the paper materials with typical AuNPs significantly influences the packing and structural properties of the plasmonic nanoparticles, thereby highly impacting the SERS enhancement patterns.