Bright and Compact Alloyed Quantum Dots with Broadly Tunable Near-Infrared Absorption and Fluorescence Spectra through Mercury Cation Exchange

摘要

We report a new strategy based on mercury cation exchange in nonpolar solvents to prepare bright and compact alloyed quantum dots (QDs) (HgxCd1-xE, where E = Te, Se, or S) with equalized particle size and broadly tunable absorption and fluorescence emission in the near infrared. In particular, we focus on HgxCd1-xTe nanocrystals because cubic CdTe and HgTe have nearly identical lattice constants, but very different bandgap energies and electron/hole masses. Thus, replacement of Cd²⁺ by Hg²⁺ in CdTe nanocrystals does not change the particle size, but it greatly alters the bandgap energy. After capping with a multilayer shell and solubilization with a multidentate ligand, this class of cation-exchanged QDs are compact (6.5 nm nanocrystal size and 10 nm hydrodynamic diameter) and very bright (60–80% quantum yield), with narrow and symmetric fluorescence spectra tunable across the wavelength range from 700 nm to 1150 nm.