Inkjet−Printable Nanoporous Ag Disk Arrays Enabling Coffee−Ring Effect−Driven Analyte Enrichment Towards Practical SERS Applications

To make surface enhanced Raman scattering (SERS) sensors more practical, we propose nanoporous Ag disks as SERS-active plasmonic structures that can be readily inkjet-printed just before use to avoid degradation of SERS enhancement. Together with the aid of the enhanced plasmonic fields from the nanoporous Ag (confirmed by electromagnetic simulation), we utilize a coffee-ring effect to concentrate target analytes, which is demonstrated by confocal Raman measurements. By using the proposed SERS sensor, Raman signals of TiO2 nanoparticles with a concentration of ppm to sub-ppb have been successfully measured. TiO2 in commercial consumables has been also detected by distinguishing its crystalline phase.