Quantifying the Thermodynamics of Ligand Binding to CsPbBr₃ Quantum Dots

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, H NMR methods were used to quantify the thermodynamics of ligand exchange on CsPbBr QDs. Both oleic acid and oleylamine native ligands dynamically interact with the CsPbBr QD surface, having individual surface densities of 1.2-1.7 nm . 10-Undecenoic acid undergoes an exergonic exchange equilibrium with bound oleate (K =1.97) at 25 °C while 10-undecenylphosphonic acid undergoes irreversible ligand exchange. Undec-10-en-1-amine exergonically exchanges with oleylamine (K =2.52) at 25 °C. Exchange occurs with carboxylic acids, phosphonic acids, and amines on CsPbBr QDs without etching of the nanocrystal surface; increases in the steady-state PL intensities correlate with more strongly bound conjugate base ligands.

Surface Chemistry of Ternary Nanocrystals: Engineering the Deposition of Conductive NaBiS2 Films

“…35 In turn, CsPbX 3 (X = Cl, Br, I) nanocrystals display highly dynamic coordination chemistry, 36,37 and their native surface can be exchanged with various cationic and anionic ligands. 38,39,40,41 NaBiE 2 nanocrystals (E = S or Se) adopt a ternary rock salt structure in which mixed Na + /Bi 3+ cation sites are stuffed into the octahedral holes of an fcc arrangement of chalcogenide (E 2-) ions. NaBiS 2 can be thought of as isostructural to PbS, with mixed Na + /Bi 3+ sites replacing Pb 2+ .…”

Direct Observation of Shallow Trap States in Thermal Equilibrium with Band‐Edge Excitons in Strongly Confined CsPbBr3 Perovskite Nanoplatelets

“…[18,19] However, ligand binding to the surface is highly dynamic, which could lead to rapid desorption of the capping ligands, resulting in the formation of undercoordinated lead atoms, which act as surface traps. [20][21][22][23][24][25] Some reports have already shown that postsynthetic thiocyanate surface treatment [26,27] or inorganic passivation via the addition of ZnBr 2 [28] enables efficient trap suppression and a PLQY near unity.…”

Lead Halide Perovskite Nanocrystals: Room Temperature Syntheses toward Commercial Viability

“…The nature of the interaction between the ligand binding group and the nanocrystal surface is crucial to the efficacy and stability of surface defect passivation. [38,39] The length, bulk, and branching of the ligand tail strongly affect the colloidal stability of the nanocrystals and their conductivity when deposited as thin films for electronic devices. [40][41][42] Furthermore, the one-pot nature of the colloidal synthesis means that the impact of purification processes, which are necessary to remove reaction by-products and excesses, must also be considered.…”