Quantifying the Thermodynamics of Ligand Binding to CsPbBr₃ Quantum Dots

Abstract

Abstract Cesium lead halide perovskites are an emerging class of quantum dots (QDs) that have shown promise in a variety of applications; however, their properties are highly dependent on their surface chemistry. To this point, the thermodynamics of ligand binding remain unstudied. Herein, 1 H NMR methods were used to quantify the thermodynamics of ligand exchange on CsPbBr 3 QDs. Both oleic acid and oleylamine native ligands dynamically interact with the CsPbBr 3 QD surface, having individual surface densities of 1.2–1.7 nm −2 . 10‐Undecenoic acid undergoes an exergonic exchange equilibrium with bound oleate ( K eq =1.97) at 25 °C while 10‐undecenylphosphonic acid undergoes irreversible ligand exchange. Undec‐10‐en‐1‐amine exergonically exchanges with oleylamine ( K eq =2.52) at 25 °C. Exchange occurs with carboxylic acids, phosphonic acids, and amines on CsPbBr 3 QDs without etching of the nanocrystal surface; increases in the steady‐state PL intensities correlate with more strongly bound conjugate base ligands.