Figure 4.

(a) Au-loaded inverse opals combine the angle-dependent Bragg peak of inverse opals (~700 nm at normal incidence) with the angle-independent absorption peak of gold nanoparticles (~520 nm); (b) The gold absorbance peak can be tuned prior to opal assembly by adding higher amounts of gold nanoparticles to the colloidal solution. The optical images and plots correspond to three different concentrations of gold nanoparticles added to the colloidal suspension: 0 Np/mL (1); 1.2 × 10¹⁵ NPs/mL (2); and 7.2 × 10¹⁵ NPs/mL (3); (c) TEM images correspond to inverse opals assembled with 6.0 × 10¹⁴ NPs/mL (bottom) and 1.2 × 10¹⁵ NPs/mL (top) [17].