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. 2022 Jan 26;27(3):807.
doi: 10.3390/molecules27030807.

Plasmonic Enhancement of Two-Photon Excited Luminescence of Gold Nanoclusters

Anna Pniakowska  1 , Joanna Olesiak-Banska  1
Affiliations

Plasmonic Enhancement of Two-Photon Excited Luminescence of Gold Nanoclusters

Anna Pniakowska et al. Molecules. .

Abstract

Plasmonic-enhanced luminescence of single molecules enables imaging and detection of low quantities of fluorophores, down to individual molecules. In this work, we present two-photon excited luminescence of single gold nanoclusters, Au18(SG)14, in close proximity to bare gold nanorods (AuNRs). We observed 25-times enhanced emission of gold nanoclusters (AuNCs) in near infrared region, which was mainly attributed to the resonant excitation of localized surface plasmon resonance (LSPR) of AuNRs and spectral overlap of LSPR band with photoluminescence of AuNCs. This work is an initial step in application of combined nanoparticles: gold nanorods and ultrasmall nanoclusters in a wide range of multiphoton imaging and biosensing applications.

Keywords: gold nanoclusters; gold nanorods; plasmonic enhancement; single molecule detection; two-photon excited luminescence.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Extinction spectra of Au18(SG)14 with marked bands at 465, 515, and 590 nm. Upper right corner presents TEM image of NCs. (b) Au18(SG)14 emission spectra with maximum peak position at 750 nm. Photographs in the inset present Au18(SG)14 cluster solution in visible (left) and UV light (right).
Figure 2
Figure 2
AFM images of (a) CTAB-coated and (b) bare gold nanorods. (c) Spectral overlap of longitudinal surface plasmon resonance band of nanorods (orange) and emission band of Au18 nanoclusters emission (red). One-photon absorption of nanoclusters (blue solid line) with expected two-photon absorption spectrum (blue dotted line), plotted as one-photon absorption at the double wavelength. Vertical black dotted line represents the laser wavelength used in two-photon excitation (λexc = 850 nm). (d) A scheme of the experimental setup (NA = numerical aperture, APD = avalanche photodiode, DM = dichroic mirror, and M = mirror). Above the objective and on the top of the piezoelectric stage, glass sample is placed with immobilised gold nanorods and a droplet of nanoclusters diffusing in a glycerol solution.
Figure 3
Figure 3
(a,b) TPL intensity map of well-separated AuNRs before (a) and after (b) covering with glycerine solution of AuNCs. (c,d) luminescence time traces of samples: AuNRs with local emission enhancement of floating AuNCs (red), solutions of AuNRs only (orange), AuNCs only (blue), and background noise (grey), monitored under prolonged irradiation of 70 μW in 10 ms photon counting window. AuNCs emission enhancement was determined in two concentration dependent conditions: (c) 10 μM and (d) 30 μM.
Figure 4
Figure 4
Distribution of number of occurring events of gold nanoclusters TPEL with gold nanorods (red) and gold nanorods itself (yellow).
See this image and copyright information in PMC

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