Gelation of Plasmonic Metal Oxide Nanocrystals by Polymer-Induced Depletion-Attractions

Abstract

Gelation of colloidal nanocrystals (NCs) emerged as a strategy to preserve inherent nanoscale properties in multiscale architectures. Yet available gelation methods still struggle to reliably control nanoscale optical phenomena such as photoluminescence and localized surface plasmon resonance (LSPR) across NC systems due to processing variability. Here, we report on an alternative gelation method based on physical inter-NC interactions: short-range depletion-attractions balanced by long-range electrostatic repulsions. The latter are established by removing the native organic ligands that passivate tin-doped indium oxide (ITO) NCs while the former are introduced by mixing with small polyethylene glycol (PEG) chains. As we incorporate increasing concentrations of PEG, we observe a reentrant phase behavior featuring two favorable gelation windows; the first arises from bridging effects while the second is attributed to depletion-attractions according to phase behavior predicted by our unified theoretical model. The NCs remain discrete within the gel network, based on X-ray scattering and high-resolution transmission electron microscopy. The infrared optical response of the gel is reflective of both the NC building blocks and the network architecture, being characteristic of ITO NC LSPR with coupling interactions between neighboring NCs.

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Cited by in corpus (8)

• Assembling Inorganic Nanocrystal Gels
• Structure and phase behavior of polymer-linked colloidal gels
• Effects of linker flexibility on phase behavior and structure of linked colloidal gels
• Universal Gelation of Metal Oxide Nanocrystals via Depletion Attractions
• Simple production of cellulose nanofibril microcapsules and the rheology of their suspensions
• Wertheim's thermodynamic perturbation theory with double-bond association and its application to colloid-linker mixtures
• Dynamics of equilibrium linked colloidal gels
• Effects of Ligand vs. Linker on Phase Behavior and Mechanical Properties of Nanoparticle Gels