Silver film over nanospheres (AgFoN) as tri-modal plasmonic sensing platform for Surface Plasmon Resonance Spectroscopy, Surface-Enhanced Raman Scattering, and Surface-Enhanced Fluorescence

•silver film over nanosphere (AgFoN) fabricated from different sized spheres.•SPRS, SERS, and SEF/MEF on the same plasmonic substrate.•SPR and SERS sensing of 11-mercaptoundecanoic acid.•observations of size-dependent SERS behaviour.•FDTD simulations of AgFoN reflectance spectra and field profiles.