Surface Ligand Dynamics-Guided Preparation of Quantum Dots–Cellulose Composites for Light-Emitting Diodes

Surface ligand dynamics of colloidal quantum dots (QDs) has been revealed as an important issue for determining QDs performance in their synthesis and postsynthesis treatment, such as ligand-related photoluminescence, colloidal stability, and so forth. However, this issue is less associated with the preparation of highly luminescent nanocomposites, which usually leads to poor performance and repeatability. In this work, on the basis of the studies about surface ligand dynamics of aqueous QDs, highly luminescent QDs-cellulose composites are prepared and employed to fabricate high color purity light-emitting diodes (LEDs). Detailed investigations indicate that the species of QD capping ligands and in particular the temperature are the key for controlling the ligand dynamics. The preparation of nanocomposites using less dynamic ligand-modified QDs at low temperature overcomes the conventional problems of QD aggregation, low QD content, luminescence quenching and shift, thus producing highly luminescent QDs-cellulose composites. This protocol is available for a variety of aqueous QDs, such as CdS, CdSe, CdTe, and CdSe(x)Te(1-x), which permits the design and fabrication of QD-based LEDs using the nanocomposites as color conversion layer on a blue emitting InGaN chip.