The effect of fluorophore incorporation on fluorescence enhancement in colloidal photonic crystals

The significant effect of photonic crystals (PhCs) on fluorophore emission has recently received intense interest. However, so far little attention has been paid on the influence of the fluorophore incorporation method on the performance of PhCs, particularly in practical applications. In this study, rhodamine B is immobilised on polystyrene spheres using a diffusion-swelling method, which are self-assembled into three-dimensional colloidal photonic crystal films. This immobilization method has resulted in 230-fold fluorescence enhancement compared to control films, the greatest fluorescence enhancement of RhB immobilised on monolithic colloidal photonic crystals compared to other immobilization methods such as infiltration and electrostatic charge-facilitated dye attachment on the particle surface. We further demonstrate the stability of dye attachment and the relationship between fluorescence intensity enhancement and the pseudo bandgap position relative to a fluorophore fluorescence peak.