Fluorescence Microscopy: Bridging the Phase Gap in Catalysis

Abstract

While many operando techniques focus on gas phase reactions, there is a growing need to look at working catalysts in the liquid phase. Fluorescence microscopy is a promising technique for bridging this phase gap. Like cellular biology, catalytic science may take advantage from the high spatiotemporal resolution and sensitivity of fluorescence microscopy. Earlier applications of fluorescence techniques in the study of diffusion or chemical transformation on inorganic solids are reviewed. The potential of fluorescence microscopy in catalysis is illustrated by data on acidcatalyzed transformation of fluorogenic organics on a mordenite zeolite. #

Rationalizing Inter- and Intracrystal Heterogeneities in Dealuminated Acid Mordenite Zeolites by Stimulated Raman Scattering Microscopy Correlated with Super-resolution Fluorescence Microscopy

“…To investigate the effect of the dealumination process on the catalytic performance at the individual crystal level, NASCA microscopy with furfuryl alcohol (FFA) as a fluorogenic reactant was chosen ( Figure 1 A ); based on the crystal structure of mordenite, FFA fits inside the micropores. 13 , 32 − 34 Figure 2 A reveals that the catalytic activity of nondealuminated SP-MOR is limited to the outer surface of the crystal. This is visual evidence of the so-called small-port behavior hindering access of FFA to the microporous network, which was already demonstrated at the bulk level for many synthetic and natural mordenites.…”

“…To investigate the effect of the dealumination process on the catalytic performance at the individual crystal level, NASCA microscopy with furfuryl alcohol (FFA) as a fluorogenic reactant was chosen (Figure A); based on the crystal structure of mordenite, FFA fits inside the micropores. ,− Figure A reveals that the catalytic activity of nondealuminated SP-MOR is limited to the outer surface of the crystal. This is visual evidence of the so-called small-port behavior hindering access of FFA to the microporous network, which was already demonstrated at the bulk level for many synthetic and natural mordenites. , In addition to this direct visual observation, quantitative analysis of the local reaction rate determined for 500 × 500 × 800 nm 3 voxels (see Supporting Information) reveals a clear bimodal distribution for the presented SP-MOR crystal with active regions at the crystal periphery that have an activity of 2.6 ± 0.1 × 10 –10 M·s –1 , whereas parts of the crystal away from the surface have no measurable catalytic activity (Figure F).…”

Approaches to Single-Nanoparticle Catalysis

“…The number of fluorescent bursts accumulated over time indicates hot spots of transesterification activity at the edges of the crystal (Figure 3a). They further used diffraction-limited imaging of single turnovers to demonstrate the spatially inhomogeneous product formation and local orientation of molecules within single zeolite crystals (54,67,68).…”

Morphology of Large ZSM-5 Crystals Unraveled by Fluorescence Microscopy

“…While these techniques give valuable information, e.g ., regarding diffusion barriers inside the crystallites or on the location and orientation of adsorbed organics in the pore system, they do not allow for unambiguous decision between the 2- and 3-component models. Fluorescence microscopy is a recent addition to the toolbox of the physical chemist studying zeolites. – We have introduced this technique to follow the catalytic oligomerization of furfuryl alcohol inside individual ZSM-5 crystals, and we have demonstrated the existence of internal diffusion barriers . Shortly after, Weckhuysen and co-workers adopted a similar approach in which the local activity was probed via the formation of colored styrene oligomers.…”

“…Fluorescence microscopy is a recent addition to the toolbox of the physical chemist studying zeolites. [10][11][12][13][14][15][16][17][18][19][20][21] We have introduced this technique to follow the catalytic oligomerization of furfuryl alcohol inside individual ZSM-5 crystals, and we have demonstrated the existence of internal diffusion barriers. 22 Shortly after, Weckhuysen and co-workers adopted a similar approach in which the local activity was probed via the formation of colored styrene oligomers.…”