Unveiling the unprecedented optical properties of citrate-stabilized hollow AgAu nanoshells under photothermal irradiation

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Wallace, Gregory Q. and Gracie, Jennifer and Singh, Amritpal and Clark, Benjamin and Jenkinson, Kellie and Bals, Sara and Smith, W. Ewen and Tuttle, Tell and Faulds, Karen and Graham, Duncan (2026) Unveiling the unprecedented optical properties of citrate-stabilized hollow AgAu nanoshells under photothermal irradiation. Small Science, 6 (1). e202500494. (https://doi.org/10.1002/smsc.202500494)

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Abstract

Metallic nanoshells heat efficiently on excitation of the localized surface plasmon resonance (LSPR). Whilst investigating the photothermal properties of citrate-stabilized hollow gold nanoshells (HGNs) synthesized using a sacrificial silver nanoparticle (AgNPs), the LSPR undergoes a distinct blueshift (70 ± 20 nm (0.20 ± 0.06 eV)) when photothermally irradiated. Notably, when functionalized with a Raman reporter, the surface-enhanced Raman scattering (SERS) signal unexpectedly and dramatically increases 8 ± 2-fold upon plasmonic heating, despite the LSPR shifting away from the excitation wavelength. This unprecedented enhancement of the SERS signal is absent in samples lacking citrate or prepared using a cobalt nanoparticle template, underscoring the importance of citrate, heat, and AgNPs in eliciting these effects. It is hypothesized that aqueous silver ions near the surface of the HGNs react with the citrate and form a complex that is both light and temperature sensitive. The formation of silver deposits, observed by electron microscopy, alters the core-to-shell thickness ratio, resulting in a blueshift in the LSPR, and change the scattering to absorption properties, enabling an improved SERS performance. This new optical phenomenon has now been understood and will be of significant interest to future studies in harnessing the properties of HGNs.

ORCID iDs

Wallace, Gregory Q. ORCID logoORCID: https://orcid.org/0000-0003-0702-3734, Gracie, Jennifer ORCID logoORCID: https://orcid.org/0000-0002-9830-9932, Singh, Amritpal, Clark, Benjamin, Jenkinson, Kellie, Bals, Sara, Smith, W. Ewen, Tuttle, Tell ORCID logoORCID: https://orcid.org/0000-0003-2300-8921, Faulds, Karen ORCID logoORCID: https://orcid.org/0000-0002-5567-7399 and Graham, Duncan ORCID logoORCID: https://orcid.org/0000-0002-6079-2105;
  • Item type:Article
    ID code:94796
    Dates:
    Date
    Event
    12 January 2026
    Published
    4 December 2025
    Published Online
    24 November 2025
    Accepted
    Subjects:Science > Chemistry
    Department:Faculty of Science > Pure and Applied Chemistry
    Depositing user: Pure Administrator
    Date deposited:24 Nov 2025 11:58
    Last modified:05 Feb 2026 08:40
    URI:https://strathprints.strath.ac.uk/id/eprint/94796
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