An excellent one-photon and multiphoton bioimaging potential enclosed in ultra-small chiral gold nanoclusters

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Poster Session 1
Anna Pniakowska (1), Magdalena Waszkielewicz (1), Joanna Olesiak-Bańska (1)
1. Advanced Materials Engineering and Modelling Group, Wroclaw University of Science and Technology, Wroclaw, Poland

gold nanoclusters, silver-doped gold nanoclusters, nonlinear optical properties, chirality

Abstract text

Gold nanoclusters (GNCs) are classified as a new class of nanomaterials with overall particle dimensions below 2 nm. Their photophysical and optical properties, tailored by their atomically precise structure attract remarkable attention. Rigorous control of synthesis procedure and efficient functionalization enables to achieve uniform and, if needed, highly fluorescent nano-materials. Unique optical properties arising from molecule-like behaviour and discrete electronic structure of atomically defined GNCs have already been widely studied in the linear regime. Nevertheless, prominent nonlinear optical properties highlight the significance of GNCs as fluorescent markers in multiphoton microscopy. [1,2]

Two-photon fluorescence microscopy (2PFM) is found as an alternative to a conventional confocal microscopy, providing better penetration depth and lower phototoxicity. Moreover, the near-infrared wavelengths used in this technique are known as optical window for bio-materials. Gold nanoclusters meet the demands of bioimaging probes as a perfect combination of small size structure, good photostability as well as high two-photon absorption (2PA cross sections over 7000 GM) and efficient photoluminescence in near-infrared region. Their structural and functional properties can be also customized by wide range of ligands, which may be utilized in bio-conjugation with high selectivity. In addition, long fluorescence lifetime of nanocluster probes opens usability of nanoclusters for FLIM microscopy.


In this work we describe the synthesis, purification and characterisation of optical properties of gold nanoclusters. Great potential of nanoclusters was broadly studied under one-photon (1P) and two-photon (2P) excitation, revealing enhanced luminescence induced by nanoclusters aggregation or metallic core doping. We report spontaneous and polymer-induced aggregation, resulting in six times stronger photoluminescence of polymer-stabilized aggregates in comparison to gold-silver NCs itself, and an order of magnitude higher photoluminescence in respect to GNCs. [3]

Finally, we present particular case of fluorescent gold nanoclusters being stabilized with rigid, chiral ligands to induce over 75% quantum yield and strong chirality. Enhanced luminescence enables to obtain high two-photon absorption cross-section and one- and two-photon fluorescence detected circular dichroism (FDCD) parameters. Then, presented nanoclusters may serve as a promising candidates for 1P and 2P fluorescence-based microscopies, especially when chirality of the probe can serve as additional discrimination factor. 


[1] J. Olesiak-Banska, M. Waszkielewicz, P. Obstarczyk, M. Samoc, Chem. Soc. Rev., 48, 4087-4117 (2019)

[2] J. Olesiak-Bańska, M. Waszkielewicz, K. Matczyszyn, M. Samoc, RSC Adv., 6, 98748-98752 (2016)

[3] M. Waszkielewicz, J. Olesiak–Banska, M. Grzelczak, A. Sánchez–Iglesias, A. Pniakowska, M. Samoc, J. Lumin., 221, 116994 (2020)