Dark quenchers, namely nonfluorescent quenching dyes, have been commonly applied in Förster resonance energy transfer (FRET) based fluorogenic probes for protease activity detection, nucleic acid hybridization and real-time polymerase chain reaction. In FRET-based systems, a specific quencher is normally able to quench the fluorescence only from those fluorophore donors that have significant overlap of their emission spectra with the absorption spectrum of the quencher when the donor and quencher are brought into proximity ^[1]. 

In our work, we will fabricate a FRET system choosing CuInS₂/ZnS QDs as donor while dark dyes as acceptor by using water-soluble quencher, IRDye QC-1, that efficiently quenches fluorescence from a wide range of fluorophores spanning from 500 to 800 nm. High quality CuInS₂/ZnS QDs with photoluminescence quantum yields (PLQYs) ~70% were prepared using ZnI₂ as zinc source. To make them water-soluble and preserve small hydrodynamic size, amine-terminated lipoic acid will be used to cap CuInS₂/ZnS QDs via ligand exchange. These water-soluble QDs can be easily combined with NHS ester group in IRDye QC-1. By tuning the PLQYs of donor and the degree of spectra overlap between the donor emission and the acceptor absorption, different Förster distance (R₀) and efficiency of energy transfer (E) can be obtained. These optimized results will contribute to the further investigation on the Lipoprotein biointeractions via FRET.

[1] X. Peng, et al., Anal. Biochem. 388, 220–228(2009).