Visualizing Nanostructures in Supramolecular Hydrogels: A Correlative Study Using Confocal and Cryogenic Scanning Electron Microscopy

Submitting author affiliation:
ICMAB, Cerdanyola del Vallès, Spain

Beilstein Arch. 2025, 202555. https://doi.org/10.3762/bxiv.2025.55.v1

Published 12 Sep 2025

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Abstract

Solvated supramolecular hydrogels present unique challenges in nanoscale morphological characterization because of their fragile fibrous nature and low concentration of the solid component. In this study, imidazolium-based hydrogels containing either diketopyrrolopyrrole (DPP) or zinc(II) phthalocyanine (ZnPc) fluorophores were imaged using confocal laser scanning microscopy (CLSM) of fully solvated gels and cryogenic scanning electron microscopy (cryo-SEM) of the corresponding xerogels. The DPP@Gel systems exhibit strong fluorescence and are effectively imaged using CLSM, with fibre morphologies that closely correlate with those seen with cryo-SEM. In contrast, the analogous imidazolium gel system containing a sulfonated zinc phthalocyanine (ZnPc@Gel) yields poor CLSM images because of the relatively weak emission and sample disruption during compression, whereas cryo-SEM enables clear visualization of the native fibrous network. These results demonstrate the complementary nature of CLSM and cryo-SEM and highlight the value of cryo-SEM as a very useful tool for imaging soft nanomaterials with low fluorescence or limited optical contrast.

Keywords: Anion binding; colloid; fluorophore; microscopies; nanostructure; supramolecular hydrogel

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Smith, S. M.; Malagreca, F.; Hicks, J.; Mantovani, G.; Amabilino, D. B.; Parmenter, C.; Pérez-García, L. Beilstein Arch. 2025, 202555. doi:10.3762/bxiv.2025.55.v1

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