Structural control of plasmon resonance in molecularly linked metal oxide nanocrystal gel assemblies

04 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Nanocrystal gels exhibit collective optical phenomena based on interactions between their constituent building blocks. However, their inherently disordered structures have made it challenging to understand, predict, or design properties like optical absorption spectra that are sensitive to the coupling between the plasmon resonances of the individual nanocrystals. Here, we bring indium tin oxide nanocrystal gels under chemical control and show that their infrared absorption can be predicted and systematically tuned by selecting the nanocrystal sizes and compositions, and molecular structures of the link-mediating surface ligands. Thermoreversible assemblies with metal-terpyridine links form reproducible gel architectures, enabling us to derive a plasmon ruler that governs the spectral shifts upon gelation predicated on the nanocrystal and ligand compositions. This empirical guide is validated using large-scale, many-bodied simulations to compute the optical spectra of gels with varied structural parameters. Based on the derived plasmon ruler, we design and demonstrate a nanocrystal mixture whose spectrum exhibits distinctive line narrowing upon assembly.


Colloidal Gel
Localized Surface Plasmon Resonance
Mutual Polarization
Plasmon Coupling
Dynamic Covalent Bonding
Plasmon Ruler

Supplementary materials

Supporting Information
Synthetic protocols of ITO nanocrystals and terpyridine-terminated ligands (TLn), descriptions on instrumentation including Scanning Transmission Electron Microscopy (STEM), UV-Vis-NIR spectroscopy, Small-Angle X-ray Scattering (SAXS), Fourier Transform Infrared Spectroscopy (FTIR), Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS), ligand functionalization procedure, nanocrystal gel preparation, and calculation of expected IR absorption spectra of gels, and supporting figures S1-S14.


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