Probing Resonance Energy Transfer and Inner Filter Effects in Quantum Dot-Large Metal Nanoparticle Clusters using a DNA-Mediated Quench and Release Mechanism

The energy transfer between DNA-linked CdSe/ZnS quantum dots (qdots) and gold nanoparticles (AuNPs) is described. The assembly produced qdot-AuNP clusters with satellite-like morphology. Owing to the programmability of the DNA linkage, both assembly as well as disassembly were used as a tool to probe quenching efficiency. Upon assembly, resonance energy transfer between the qdot donor and AuNP acceptor was measured as photoluminescence (PL) quenching. The magnitude of the quenching was approximated upon measurement of PL recovery once the cluster was disassembled by addition of a ssDNA fuel strand, which effectively displaced the qdot-to-AuNP dsDNA linkage. This controllable assembly/disassembly behavior was then used as a morphological tool to separate PL quenching from an inner filter effect originating from the AuNP's high surface plasmon resonance (SPR) extinction. This corrected quenching value was observed from steady state PL measurements, which were then substantiated by PL decay measurements. Finally, the quenching efficiency was related to cluster spatial properties via use of the nanometal surface resonance energy transfer (NSET) method. The AuNP interface to qdot core distance was estimated at approximate to 8 nm, which was close to the distances visualized by TEM.