Photonic crystals from core-shell colloids with incorporated highly fluorescent quantum dots

We report the preparation of nanoscaled PS/PMMA core-shell spheres with highly fluorescent CdS/ ZnS coated CdSe quantum dots (QDs) integrated in the core. Core-shell spheres of different diameters have been self-assembled to colloidal photonic crystals (PCs) with photonic stop bands located in the visible range of the electromagnetic spectrum. For the synthesis of the core, a modified miniemulsion polymerization has been used; the shell was prepared by a newly developed core-shell polymerization. The CdSe QDs embedded in the core were coated with the higher band gap semiconductor materials CdS and ZnS in a successive ion layer adsorption reaction (SILAR) keeping up the light-emitting properties of the QDs during the integration process. A modifying influence of the photonic band structure of the PC on the photoluminescence (PL) of the embedded QDs was observed by angular-dependent fluorescence measurements. The controlled combination of electronic confinement, originating from the QDs, and photon confinement, due to the periodic dielectric structure of the colloidal crystal, as it has been realized in this work presents a huge platform for the design and construction of novel optoelectronic devices based on PCs.