Complementary Lock‐and‐Key Ligand Binding of a Triplet Transmitter to a Nanocrystal Photosensitizer

Abstract

Owing to the difficulty in comprehensively characterizing nanocrystal (NC) surfaces,c lear guidance for ligand design is lacking. In this work, as eries of bidentate bis-(pyridine) anthracene isomers (2,3-PyAn, 3,3-PyAn, 2,2-PyAn) that differ in their binding geometries were designed to find the best complementary fit to the NC surface.T he efficiency of triplet energy transfer (TET) from the CdSe NC donor to ad iphenylanthracene (DPA) acceptor mediated by these isomers was used as ap roxy for the efficacy of orbital overlap and therefore ligand binding. 2,3-PyAn, with an intramolecular N-N distance of 8.2 ,p rovided the best matcht ot he surface of CdSe NCs.W hen serving as at ransmitter for photon upconversion, 2,3-PyAn yielded the highest upconversion quantum yield (QY) of 12.1 AE 1.3 %, followed by 3,3-PyAn and 2,2-PyAn. The TET quantum efficiencies determined by ultrafast transient absorption measurements showed the same trend.