Surface Chemistry of Colloidal Nanocrystals

Surface chemistry governs the stability, optical properties and functional integration of colloidal nanocrystals (NCs) by mediating the interactions between inorganic cores and their surrounding environment. Organic ligands tethered to NC surfaces control colloidal dispersibility, electronic passivation and interparticle coupling. Fine tuning of ligand binding modes and surface reconstructions offers routes to suppress trap states, adjust band-edge energies and direct assembly into ordered superstructures. Recent advances exploit both experimental and computational approaches to resolve ligand arrangements at the molecular level, engineer inorganic shells by colloidal atomic layer deposition and predict thermodynamic and kinetic factors behind ligand adsorption and desorption. Mastery of surface chemistry underpins the design of high-performance optoelectronic devices, robust catalysts and multifunctional hybrid materials.

Research from Nature Portfolio

Detailed nuclear magnetic resonance studies have quantified ligand–ligand interactions on cadmium selenide NCs, revealing that mixed alkanoate ligands segregate into partitioned domains and unlock enhanced rotational freedom. This partitioning model predicts solubility orders of magnitude higher than for single-ligand shells and provides a framework to rationalise ligand-mediated dispersion phenomena. Powder X-ray diffraction has been shown to detect ordered aliphatic ligand shells on small quantum dots, with a characteristic peak at q ≈ 1.4 Å⁻¹ serving as a sensitive probe of ligand length, geometry and thermal disorder. Observation of this ligand peak opens a powerful, nondestructive window into shell organisation and informs strategies for ligand-exchange and thermal processing. Atomistic simulations corroborate that stoichiometric cadmium selenide NCs remain inherently defective, with surface-associated dark excitonic states arising from under-coordinated chalcogen atoms. These dark states dominate low-energy spectra even in the absence of vacancies, underlining the need for tailored surface treatments to mitigate non-radiative pathways and enhance photoluminescence.

Surface Chemistry of Colloidal Nanocrystals publication trend

The graph below shows the total number of articles in surface chemistry of colloidal nanocrystals across all publications each year (not limited to Nature Index journals).

Technical terms

Ligand exchange: Replacement of native surface ligands by new molecules to modify surface properties, electronic coupling and solubility.

Passivation: Chemical treatment of surface atoms to eliminate electronic trap states and enhance photoluminescence and stability.

Colloidal atomic layer deposition (c-ALD): Sequential addition of molecular precursors to grow conformal inorganic shells on NCs at low temperature in solution.

Surface trap state: Electronic defect at the NC surface that localises charges non-radiatively, reducing luminescence yield.

Band-edge positions: Energies of the highest occupied and lowest unoccupied electronic levels, which determine optical absorption and emission.

References

1. Partitioning surface ligands on nanocrystals for maximal solubility. Nature Communications (2019).
2. Observation of ordered organic capping ligands on semiconducting quantum dots via powder X-ray diffraction. Nature Communications (2021).
3. Colloidal CdSe nanocrystals are inherently defective. Nature Communications (2021).
4. Colloidal-ALD-Grown Metal Oxide Shells Enable the Synthesis of Photoactive Ligand/Nanocrystal Composite Materials. Journal of the American Chemical Society (2023).
5. Surface Reconstructions in II–VI Quantum Dots. ACS Nano (2024).
6. Ligands as a universal molecular toolkit in synthesis and assembly of semiconductor nanocrystals. Chemical Science (2020).