Optimisation and Characterisation of Ultrabright Nanotags for Surface-Enhanced Raman Scattering

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: Optimised characterisation of SERS Nanotags, using Field-Flow Fractionation for correlated structural, optical and spectroscopic characterisation.

Abstract Text:

Surface-enhanced Raman scattering (SERS) is a powerful spectroscopic technique which harnesses the optical properties of plasmonic nanostructures to amplify Raman scattering. Indirect detection by SERS involves the preparation of a plasmonic nanostructure followed by functionalisation with a Raman reporter. Often, this is then subsequently encapsulated in an outer shell, which can support the conjugation of targeting moieties. For many applications an intense SERS signal is crucial, such as the detection of these “nanotags” in complex biological environments. Understanding the relationship between structure and SERS response therefore represents an important fundamental aspect in the preparation of ultrabright SERS nanotags.

One current strategy to increase the SERS response is to employ the use of aggregated nanoparticles. However, aggregation is an uncontrolled process that yields a wide range of structures. In this work, we discuss our recent endeavours in optimising and characterising gold nanoparticle aggregates, with the aim of better understanding the relationship between aggregate structure and optical response. Specifically, to determine a combination of structural features that will maximise the SERS response of spectroscopic tags in both dry and ‘in-situ’ conditions.

This will be achieved using two complementary approaches, asymmetrical-flow field-flow-fractionation (AF4) and correlative SERS/SEM imaging. AF4 facilitates the comprehensive characterisation of specific morphologies in their ‘in-situ colloidal state’, by subjecting polydisperse samples to a high-resolution separation under flow, prior to on-line structural and optical characterisation. Correlative SERS/SEM imaging allows for the direct comparison between structure and SERS response at a single nanotag level; these highly specific dry state characterisations can then be compared against wet-colloidal state characterisations of similar morphologies obtained by AF4 analysis.

By ascertaining the combination of structural features that maximise the SERS response of nanotags, it will become possible to rationally design and develop aggregated plasmonic structures that exhibit improved sensitivity.

 

 

 

References

(1) Fergusson, J.; Wallace, G. Q.; Sloan-Dennison, S.; Carland, R.; Shand, N. C.; Graham, D.; Faulds, K. Plasmonic and Photothermal Properties of Silica-Capped Gold Nanoparticle Aggregates. The Journal of Physical Chemistry C 2023, 127 (50), 24475-24486.