Probing the electronic absorption spectrum of single gold nanoparticles in the gas phase

ABSTRACT

Gold nanoparticles (Au NPs) exhibit a localised surface plasmon resonance (LSPR) which can be excited in the visible spectral range and is sensitive to the size, shape and environment of the NP. Here, we present electronic action spectra of single 38.5–52.5 nm diameter Au NPs in the gas phase measured by means of single nanoparticle action spectroscopy at cryogenic temperatures (cryo-SNAS). A single Au NP is trapped in a temperature-controllable Paul-type ion trap, thermalised by collisions with a buffer gas and coated with messenger molecules at sufficiently low temperature, while its absolute mass is non-destructively monitored. Absorption of monochromatic electromagnetic radiation (400–800 nm) is detected indirectly by monitoring the change in mass due to messenger desorption. We find that the LSPR is red-shifted by ∼ 75 nm compared to the predicted value for a bare Au NP in vacuum. Laser heating changes the intensity, but not position or width of the LSPR and can be used to ultimately quench the LSPR. The measured spectra are modelled using Mie theory and assuming the formation and annealing of a refractive surface layer.

GRAPHICAL ABSTRACT

KEYWORDS:

• Electronic spectroscopy
• nanoparticle mass spectrometry
• gold nanoparticle
• plasmon resonance
• plasmon quenching

Acknowledgements

We would like to take the opportunity of this special issue to acknowledge the invaluable advice of Dieter Gerlich during the initial planning stages of this instrument. We thank Bernd Abel for providing the supercontinuum laser, Jörg Matysik together with Patrick Kurle for measuring solution UV/Vis spectra as well as Reinhard Denecke along with Maximilian Franz for recording preliminary XPS spectra. We are grateful for helpful comments and discussions with Stephan Link and Björn Bastian and appreciate the financial support of the Deutsche Forschungsgemeinschaft (DFG). S.L. acknowledges the Hans-Böckler-Stiftung (HBS) for financial support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) under grant number 461913655 (Einzelnanopartikelcharakterisierung in der Gasphase).