Catalytic processes monitored at the nanoscale with tip-enhanced Raman spectroscopy

Abstract

Heterogeneous catalysts play a pivotal role in the chemical industry, but acquiring molecular insights into functioning catalysts remains a significant challenge1,2,3,4. Recent advances in micro-spectroscopic approaches have allowed spatiotemporal information to be obtained on the dynamics of single active sites and the diffusion of single molecules5,6. However, these methods lack nanometre-scale spatial resolution and/or require the use of fluorescent labels. Here, we show that time-resolved tip-enhanced Raman spectroscopy can monitor photocatalytic reactions at the nanoscale. We use a silver-coated atomic force microscope tip to both enhance the Raman signal and to act as the catalyst. The tip is placed in contact with a self-assembled monolayer of p-nitrothiophenol molecules adsorbed on gold nanoplates. A photocatalytic reduction process is induced at the apex of the tip with green laser light, while red laser light is used to monitor the transformation process during the reaction. This dual-wavelength approach can also be used to observe other molecular effects such as monolayer diffusion.

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Figure 1: Schematic overview of the experimental set-up.
Figure 2: Monitoring the photocatalytic reaction with SERS.
Figure 3: Time-dependent TERS measurements on a gold nanoplate substrate.
Figure 4: Time-dependent TERS measurement before and after reaction.

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Acknowledgements

This work was supported by NanoNextNL of the Dutch ministry EL&I and 130 partners. The authors also thank the Netherlands Research School Combination–Catalysis (NRSC-C) and Dutch National Science Foundation (NWO-CW Top research grant) for financial support.

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E.M.v.S.L., T.D.-G. and A.J.G.M. carried out the experiments and E.M.v.S.L. performed data processing. V.D. and T.D.-G. developed the experimental set-up. E.M.v.S.L., A.J.G.M. and B.M.W. designed the experiments. All authors contributed to the discussion of the results as well as to the preparation and writing of the manuscript. The research was directed by B.M.W.

Corresponding authors

Correspondence to Volker Deckert or Bert M. Weckhuysen.

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The authors declare no competing financial interests.

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van Schrojenstein Lantman, E., Deckert-Gaudig, T., Mank, A. et al. Catalytic processes monitored at the nanoscale with tip-enhanced Raman spectroscopy. Nature Nanotech 7, 583–586 (2012). https://doi.org/10.1038/nnano.2012.131

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