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

Abstract

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 established. But despite the growing availability of tools that enable detailed in situ characterization, 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 surfaces, 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 nanospectroscopy 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.

Flexible NO2‐Functionalized N‐Heterocyclic Carbene Monolayers on Au (111) Surface

“…Nitrophenyl‐functionalized NHCs were prepared, activated and deposited on the surface of a clean Au (111) single crystal (Scheme ) . The NHC‐coated Au sample was transferred to a ultra‐high vacuum (UHV) chamber for X‐ray photoelectron spectroscopy (XPS) and near‐edge X‐ray absorption fine structures (NEXAFS) measurements at the ALOISA beamline of the ELETTRA synchrotron (Trieste, Italy) …”

Mechanistic Insights into Growth of Surface‐Mounted Metal‐Organic Framework Films Resolved by Infrared (Nano‐) Spectroscopy

“…Apart from providing topological information of AFM as a powerful method to study mechanisms of crystal growth,32, 33 AFM‐IR can further provide local spectroscopic information with spatial resolution around 10 nm. Various versions of AFM‐based IR microscopy have been recently employed, including synchrotron‐based IR mapping of metal nanoparticle catalysis,34 structural analysis of μm‐sized MOF crystals35 and zeolite thin film investigations,31b but its application to study the initial stages of the SURMOF growth process with a monolayer chemical sensitivity has, to the best of our knowledge, never been demonstrated. In this paper, two emerging tip‐sensed AFM‐IR technologies have been used, namely, photothermal AFM‐nano‐IR and photo‐induced force microscopy (PiFM), which complement each other in their technical abilities.…”

Far Infrared Synchrotron Near-Field Nanoimaging and Nanospectroscopy

“…It provides for nano-imaging and -spectroscopy down to few nanometer length scales, gaining insight into molecular orientation [5] and coupling [6], catalytic activity [7], heterogeneity in electron and lattice dynamics [8,9], and plasmonic and polaritonic effects in quantum matter [10][11][12][13] with recent extension to the low temperature [9,14] and ultrafast regimes [15][16][17][18]. Despite these significant developments, s-SNOM has largely been limited to a narrow range of the electromagnetic spectrum of the near-to mid-IR at high frequencies, and the RF [19] and low THz [20] regime at low frequencies.…”