Electrogenerated Radicals Boosting Chemiluminescence of CdSe/CdS/ZnS Quantum Dots

We report in this work highly efficient, temporally stable, and multicolor chemiluminescence of CdSe/CdS/ZnS quantum dots (QDs) boosted by radicals that are in situ electrogenerated near the electrode surface. Typically, electrochemical oxidation of tri-n-propylamine (TPrA), a tertiary amine, generates radical cation (TPrA•+) and radical (TPrA•). Then, TPrA• and TPrA•+ sequentially inject an electron and a hole to the valence and conduction bands of a QD to populate the excited state (QD*). In this pathway, a negatively charged QD (QD⁻) is formed as the key intermediate, instead of fragile positively charged QD⁺, thus producing highly stable and efficient luminescence. Moreover, this pathway is also identical to the so-called low-oxidation-potential electrochemiluminescence route of the gold standard luminophore, tris(2,2'-bipyridyl)ruthenium (Ru(bpy)₃ ²⁺), and therefore fully fit for microbead-based bioassays. Considering their high emission efficiency (∼5 times higher than Ru(bpy)₃ ²⁺ under same condition), narrow emission bands and tunable wavelengths, these QDs hold great promise as luminophores in ultrasensitive and multiplexed microbead-based bioassays.