Plasmonic-3D photonic crystals microchip for surface enhanced Raman spectroscopy.

Plasmonic-dielectic hybrid substrates of Ag-islands on three-dimensional photonic crystals are fabricated through magnetron sputtering of silver onto hydrophobized silica photonic crystals, free from etching process. Without typical "hot-spots" such as nanogaps, significant Raman enhancements can be achieved, attributed to the enhanced electromagnetic field and scattering of the plasmonic nanoparticles as well as the enhanced light-matter interaction by the slow photon effects. The detection limit for adenine by the hybrid substrates reaches nM level, with a calculated enhancement factor of 1.13 × 107, which is three orders of magnitude higher than the conventional noble metal film over nanosphere (FON) control group. Furthermore, microchips based on the hybrid substrates are facilely achieved, enabling micro-detection through super hydrophobic concentration. The facile fabrication and effective Raman enhancements make the Ag-islands on 3D photonic crystals promising candidates in the field of chemical sensors, Raman mapping and bioassays.