High-spatial-resolution mapping of catalytic reactions on single particles


The critical role in surface reactions and heterogeneous catalysis of metal atoms with low coordination numbers, such as found at atomic steps and surface defects, is firmly established1,2. But despite the growing availability of tools that enable detailed in situ characterization3, so far it has not been possible to document this role directly. Surface properties can be mapped with high spatial resolution, and catalytic conversion can be tracked with a clear chemical signature; however, the combination of the two, which would enable high-spatial-resolution detection of reactions on catalytic surfaces, has rarely been achieved. Single-molecule fluorescence spectroscopy has been used to image and characterize single turnover sites at catalytic surfaces4,5, but is restricted to reactions that generate highly fluorescing product molecules. Herein the chemical conversion of N-heterocyclic carbene molecules attached to catalytic particles is mapped using synchrotron-radiation-based infrared nanospectroscopy6,7 with a spatial resolution of 25 nanometres, which enabled particle regions that differ in reactivity to be distinguished. These observations demonstrate that, compared to the flat regions on top of the particles, the peripheries of the particles—which contain metal atoms with low coordination numbers—are more active in catalysing oxidation and reduction of chemically active groups in surface-anchored N-heterocyclic carbene molecules.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Schematic representation of the experimental set-up.
Figure 2: Comparison between near-field and far-field infrared spectroscopy.
Figure 3: AFM topography scans and infrared nanospectroscopy line scans.
Figure 4: Infrared nanospectroscopy line-scan measurements on the centre and edge of Pt particles.
Figure 5: Infrared nanospectroscopy measurements of NO2-functionlized NHCs on Au particles.


  1. 1

    Somorjai, G. A. & Li, Y. Introduction to Surface Chemistry and Catalysis 2nd edn (Wiley, 2010)

  2. 2

    Zambelli, T., Wintterlin, J., Trost, J. & Ertl, G. Identification of the “active sites” of a surface-catalyzed reaction. Science 273, 1688–1690 (1996)

    ADS  CAS  Article  Google Scholar 

  3. 3

    Buurmans, I. L. C. & Weckhuysen, B. M. Heterogeneities of individual catalyst particles in space and time as monitored by spectroscopy. Nat. Chem. 4, 873–886 (2012)

    CAS  Article  Google Scholar 

  4. 4

    Ristanović, Z. et al. Quantitative 3D fluorescence imaging of single catalytic turnovers reveals spatiotemporal gradients in reactivity of zeolite H-ZSM-5 crystals upon steaming. J. Am. Chem. Soc. 137, 6559–6568 (2015)

    Article  Google Scholar 

  5. 5

    Andoy, N. M. et al. Single-molecule catalysis mapping quantifies site-specific activity and uncovers radial activity gradient on single 2D nanocrystals. J. Am. Chem. Soc. 135, 1845–1852 (2013)

    CAS  Article  Google Scholar 

  6. 6

    Bechtel, H. A., Muller, E. A., Olmon, R. L., Martin, M. C. & Raschke, M. B. Ultrabroadband infrared nanospectroscopic imaging. Proc. Natl Acad. Sci. USA 111, 7191–7196 (2014)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Hermann, P. et al. Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy. Opt. Express 22, 17948–17958 (2014)

    ADS  Article  Google Scholar 

  8. 8

    Stavitski, E. & Weckhuysen, B. M. Infrared and Raman imaging of heterogeneous catalysts. Chem. Soc. Rev. 39, 4615–4625 (2010)

    CAS  Article  Google Scholar 

  9. 9

    Gross, E. et al. In Situ IR and X-ray high spatial-resolution microspectroscopy measurements of multistep organic transformation in flow microreactor catalyzed by Au nanoclusters. J. Am. Chem. Soc . 136, 3624–3629 (2014)

    CAS  Article  Google Scholar 

  10. 10

    Muller, E. A., Pollard, B. & Raschke, M. B. Infrared chemical nano-imaging: accessing structure, coupling, and dynamics on molecular length scales. J. Phys. Chem. Lett. 6, 1275–1284 (2015)

    CAS  Article  Google Scholar 

  11. 11

    Centrone, A. Infrared imaging and spectroscopy beyond the diffraction limit. Annu. Rev. Anal. Chem. (Palo Alto, Calif.) 8, 101–126 (2015)

    ADS  CAS  Article  Google Scholar 

  12. 12

    van Schrojenstein Lantman, E. M., Deckert-Gaudig, T., Mank, A. J. G., Deckert, V. & Weckhuysen, B. M. Catalytic processes monitored at the nanoscale with tip-enhanced Raman spectroscopy. Nat. Nanotechnol. 7, 583–586 (2012)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Huth, F. et al. Nano-FTIR absorption spectroscopy of molecular fingerprints at 20 nm spatial resolution. Nano Lett. 12, 3973–3978 (2012)

    ADS  MathSciNet  CAS  Article  Google Scholar 

  14. 14

    van Schrojenstein Lantman, E. M., de Peinder, P., Mank, A. J. G. & Weckhuysen, B. M. Separation of time-resolved phenomena in surface-enhanced Raman scattering of the photocatalytic reduction of p-nitrothiophenol. ChemPhysChem 16, 547–554 (2015)

    CAS  Article  Google Scholar 

  15. 15

    Blum, C. et al. Tip-enhanced Raman spectroscopy – an interlaboratory reproducibility and comparison study. J. Raman Spectrosc. 45, 22–31 (2014)

    ADS  CAS  Article  Google Scholar 

  16. 16

    Ayache, M., Lux, S. F. & Kostecki, R. I. R. Near-field study of the solid electrolyte interphase on a tin electrode. J. Phys. Chem. Lett. 6, 1126–1129 (2015)

    CAS  Article  Google Scholar 

  17. 17

    Mastel, S., Govyadinov, A. A., de Oliveira, T. V. A. G., Amenabar, I. & Hillenbrand, R. Nanoscale-resolved chemical identification of thin organic films using infrared near-field spectroscopy and standard Fourier transform infrared references. Appl. Phys. Lett. 106, 023113 (2015)

    ADS  Article  Google Scholar 

  18. 18

    Pollard, B., Muller, E. A., Hinrichs, K. & Raschke, M. B. Vibrational nano-spectroscopic imaging correlating structure with intermolecular coupling and dynamics. Nat. Commun. 5, 3587 (2014)

    ADS  Article  Google Scholar 

  19. 19

    Berweger, S. et al. Nano-chemical infrared imaging of membrane proteins in lipid bilayers. J. Am. Chem. Soc. 135, 18292–18295 (2013)

    CAS  Article  Google Scholar 

  20. 20

    Levratovsky, Y. & Gross, E. High spatial resolution mapping of chemically-active self-assembled N-heterocyclic carbenes on Pt nanoparticles. Faraday Discuss. 188, 345–353 (2016)

    ADS  CAS  Article  Google Scholar 

  21. 21

    Crudden, C. M. et al. Ultra stable self-assembled monolayers of N-heterocyclic carbenes on gold. Nat. Chem. 6, 409–414 (2014)

    CAS  Article  Google Scholar 

  22. 22

    Zhukhovitskiy, A. V., Mavros, M. G., Van Voorhis, T. & Johnson, J. A. Addressable carbene anchors for gold surfaces. J. Am. Chem. Soc. 135, 7418–7421 (2013)

    CAS  Article  Google Scholar 

  23. 23

    Rühling, A. et al. Modular bidentate hybrid NHC-thioether ligands for the stabilization of palladium nanoparticles in various solvents. Angew. Chem. Int. Ed. 55, 5856–5860 (2016)

    Article  Google Scholar 

  24. 24

    Arnold, R., Azzam, W., Terfort, A. & Wöll, C. Preparation, modification, and crystallinity of aliphatic and aromatic carboxylic acid terminated self-assembled monolayers. Langmuir 18, 3980–3992 (2002)

    CAS  Article  Google Scholar 

  25. 25

    García-García, F. R., Bion, N., Duprez, D., Rodríguez-Ramos, I. & Guerrero-Ruiz, A. H. 2/D2 isotopic exchange: a tool to characterize complex hydrogen interaction with carbon-supported ruthenium catalysts. Catal. Today 259, 9–18 (2016)

    Article  Google Scholar 

  26. 26

    Janssens, T. V. W. et al. Insights into the reactivity of supported Au nanoparticles: combining theory and experiments. Top. Catal. 44, 15–26 (2007)

    CAS  Article  Google Scholar 

  27. 27

    Somorjai, G. A. & Blakely, D. W. Mechanism of catalysis of hydrocarbon reactions by platinum surfaces. Nature 258, 580–583 (1975)

    ADS  CAS  Article  Google Scholar 

  28. 28

    Vang, R. T. et al. Controlling the catalytic bond-breaking selectivity of Ni surfaces by step blocking. Nat. Mater. 4, 160–162 (2005)

    ADS  CAS  Article  Google Scholar 

  29. 29

    Lopez, N. et al. On the origin of the catalytic activity of gold nanoparticles for low-temperature CO oxidation. J. Catal. 223, 232–235 (2004)

    CAS  Article  Google Scholar 

  30. 30

    Kang, L. L. et al. In situ surface-enhanced Raman spectroscopy study of plasmon-driven catalytic reactions of 4-nitrothiophenol under a controlled atmosphere. ChemCatChem 7, 1004–1010 (2015)

    CAS  Article  Google Scholar 

  31. 31

    Bowker, M. et al. Encapsulation of Au nanoparticles on a silicon wafer during thermal oxidation. J. Phys. Chem. C 117, 21577–21582 (2013)

    CAS  Article  Google Scholar 

  32. 32

    Jurčík, V., Gilani, M. & Wilhelm, R. Easily accessible chiral imidazolinium salts bearing two hydroxy-containing substituents as shift reagents and carbene precursors. Eur. J. Org. Chem. 2006, 5103–5109 (2006)

    Article  Google Scholar 

  33. 33

    Sato, T., Hirose, Y., Yoshioka, D. & Oi, S. N-heterocyclic carbenes with a N-2,4-dinitrophenyl substituent: comparison with PPh3 and IPr. Organometallics 31, 6995–7003 (2012)

    CAS  Article  Google Scholar 

Download references


F.D.T. thanks the Director, Office of Science, Office of Basic Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences of the US Department of Energy at LBNL (DE-AC02-05CH11231) for partial support of this work. We thank the M. Raschke group at the University of Colorado for collaborating on the development of the SINS endstation. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract number DE-AC02-05CH11231. W.J.W. thanks the NSF for a predoctoral fellowship (DGE 1106400), and the Arnold Group (UCB) for use of their infrared spectrometer.

Author information




E.G. and F.D.T. conceived the idea and co-wrote the paper. C.-Y.W. and W.J.W. prepared the carbene ligands and attached them to Pt and Au surfaces. Y.L. analysed the XPS measurements. H.A.B. and M.C.M. designed the SINS beamline and assisted in conducting the SINS measurements and analysing the data. E.G. performed the SINS experiments and analysed the data. All authors contributed to the overall scientific interpretation and edited the manuscript.

Corresponding authors

Correspondence to F. Dean Toste or Elad Gross.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information

Nature thanks C. Campbell, G. Rothenberg, F. Tao, B. Weckhuysen and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Extended data figures and tables

Extended Data Figure 1 Preparation schematic of functionalized NHCs.

a, b, Preparation procedure of OH-functionalized 1 (a) and NO2-functionalized (b) NHCs that were anchored to the surface of Pt and Au particles, respectively.

Extended Data Figure 2 XPS measurements of Pt particles with and without NHCs.

a, b, Pt 4f XPS data before (a) and after (b) the adsorption of NHCs on Pt particles. c, d, C 1s XPS data following exposure of the NHC-coated Pt particles to oxidizing (O2, 70 °C, 10 h; c) and reducing (H2, 70°C, 10 h; d) conditions. XPS data (black curves) and the calculated Gaussians that construct the measured XPS signal (coloured curves) are shown. CPS, counts per second; B.E., binding energy.

Extended Data Figure 3 Far-field ATR-IR spectra of NHC-coated Pt particles.

ATR-IR measurements were conducted after the following treatments: blue, exposure of the sample to mild oxidizing conditions (1 atm O2, 40 °C, 10 h); red, exposure of the sample to harsher oxidizing conditions (1 atm O2, 70 °C, 10 h); black, exposure of the sample to reducing conditions (1 atm H2, 70 °C, 10 h).

Extended Data Figure 4 HR-SEM images of Au particles.

a, b, Low-magnification (a) and high-magnification (b) HR-SEM images were taken following deposition of 20-nm Au film on Si(110) surface and surface annealing (under flow of N2) to 1,073 K for 2 h.

Extended Data Figure 5 XPS measurements of Au particles coated with NO2-functionalized NHCs.

N 1s XPS data of NO2-functionalized NHCs that were attached to the surface of Au particles. XPS measurements were conducted before (red spectrum) and after the exposure of the sample to reducing environment, using NaBH3CN (green spectrum) or NaBD3CN (blue spectrum) as a reducing agent. The black dots represent the measured XPS data points; the coloured curves are the averaged XPS signals. The XPS signals that were measured after exposure of the sample to reducing agents (blue and green spectra) have been multiplied by three.

Extended Data Figure 6 Full SINS spectrum of Au particles coated with NO2-functionalized NHCs.

NHCs were attached to the surface of Si-supported Au particles. The sample was exposed to reducing conditions with a deuterated reagent. The dip in the scattering signal around 1,250 cm−1 is induced by a high Si signal from the reference spectra.

Extended Data Figure 7 Full spectra of the SINS point measurements.

Infrared point measurements were conducted on the bare Si surface (green spectrum) and on the edge and centre of a single Pt particle (red and black spectra, respectively). High noise levels between 1,900 cm−1 and 2,600 cm−1 (indicated by the vertical dotted lines) are induced by the presence of a diamond window that separates the ultrahigh-vacuum part of the light source from the rough vacuum area and that highly absorbs the infrared light in this range.

Extended Data Figure 8 Non-biased spectra of SINS line-scan measurements.

The corresponding biased spectra are shown in Fig. 3. ad, AFM topography scans and infrared nanospectroscopy line scans were conducted following exposure of the sample to various oxidizing (a, b) and reducing (c, d) conditions. The path of the infrared line scans along the surface is marked by red arrows in the AFM images (left). The colour and size of the different pentagons represent the chemical properties and surface densities of NHCs, as detected by the infrared line scans (blue, OH functional group; purple, acid functional group). The relatively narrow O–H peaks at high wavenumbers are correlated to a deteriorated signal-to-noise ratio in this region. Because only the most dominant part of the O–H peak is highlighted in this colour scheme, the peak width of high-wavenumber (>2,700 cm−1) vibrations is about 50 wavenumbers.

Extended Data Figure 9 Non-biased spectra of SINS line-scan measurements.

The corresponding biased spectra are shown in Fig. 4. Infrared nanospectroscopy line scans were performed across the centre and edge of NHC-coated Pt particles (marked by red and green arrows, respectively, in the AFM images). a, c, Infrared nanospectroscopy measurements were conducted after the samples were exposed to mild oxidizing (a) and reducing (c) conditions. The coloured pentagons (blue, OH functional group; purple, acid functional group) represent the molecules that reside on the centre and edge of the particle as detected by infrared line-scan measurements. The relatively narrow O–H peak of the carboxylic acid was correlated to a deteriorated signal-to-noise ratio at high wavenumbers. Because only the most dominant part of the O–H peak is highlighted in this colour scheme, the peak width is about 250 wavenumbers. b, d, Schematics of Pt particles with NHCs (coloured pentagons) following their exposure to oxidizing (b) and reducing (d) conditions.

Extended Data Figure 10 Cross-sectional analysis of NHC-coated Pt particles.

a, AFM topography image of NHC-coated Pt particles that were deposited on Si surface. The white line indicates the path of the line scan along the sample. b. Cross-sectional analysis of the height of one Pt particle. The length of the profile of the particle is about 20 nm (indicated by the distance between the vertical dash-dotted lines; the positions of which are indicated by blue crosses in a). The error in the AFM height measurements is about 2%, as estimated by Si surface roughness measurements.

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Wu, CY., Wolf, W., Levartovsky, Y. et al. High-spatial-resolution mapping of catalytic reactions on single particles. Nature 541, 511–515 (2017). https://doi.org/10.1038/nature20795

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing