In Situ Doping Inverse Silica Opals with Size-Controllable Gold Nanoparticles for Refractive Index Sensing

We report the fabrication of inverse SiO2 opals doped with gold (i-Au-SiO2-o) nanoparticles (NPs) via a co-self-assembly method combined with subsequent removal of polystyrene colloidal spheres by calcination. The resulting i-Au-SiO2-o films demonstrate long-range ordering with uniform distribution of ligand-free Au NPs. The size of Au NPs can be tuned from 6 to 30 tun by varying the calcination temperature. The as-prepared i-Au-SiO2-o films preserve both localized surface plasmon resonance (LSPR) and Bragg diffraction peaks simultaneously. Both LSPR and Bragg diffraction peaks are sensitive to the refractive index changes of the surrounding medium-an important feature for sensing applications. The method provides a facile and versatile way to fabricate high-quality Au NP doped photonic crystals for applications in sensing and others.