Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Chemistry

Background:

• Cesium lead halide perovskite quantum dots (QDs) are promising optoelectronic materials.
• Their performance is critically dependent on surface chemistry.
• Fundamental questions about QD surface termination and ligand binding persist.

Purpose of the Study:

• To elucidate the atomic termination and ligand binding modes on CsPbBr3 QD surfaces.
• To demonstrate the utility of high-resolution solid-state NMR for nanomaterial surface analysis.

Main Methods:

• Utilized 1H, 13C, and 31P solid-state NMR for ligand assignment.
• Employed surface-selective 133Cs NMR to identify surface Cs atoms.
• Applied 1H{133Cs} RESPDOR and 1H{207Pb} S-REDOR for distance measurements.
• Compared experimental data with theoretical calculations on model QD surfaces.

Main Results:

• Unambiguously assigned organic surface ligands using multinuclear NMR.
• Identified a unique 133Cs NMR signal attributed to Cs-terminated surfaces coordinated by carboxylates.
• Determined CsBr termination (not PbBr2) with alkylammonium ligands at Cs sites via dipolar dephasing measurements.
• Validated findings through comparison with theoretical models.

Conclusions:

• Solid-state NMR spectroscopy is a powerful tool for characterizing nanomaterial surfaces.
• The study clarifies the surface termination and ligand coordination in CsPbBr3 QDs.
• Provides crucial insights into the structure-property relationships of perovskite QDs.