Getting the Most Out of Fluorogenic Probes: Challenges and Opportunities in Using Single-Molecule Fluorescence to Image Electro- and Photocatalysis

Abstract

Single-molecule fluorescence microscopy enables the direct observation of individual reaction events at the surface of a catalyst. It has become a powerful tool to image in real time both intraand interparticle heterogeneity among different nanoscale catalyst particles. Single-molecule fluorescence microscopy of heterogeneous catalysts relies on the detection of chemically activated fluorogenic probes that are converted from a nonfluorescent state into a highly fluorescent state through a reaction mediated at the catalyst surface. This review article describes challenges and opportunities in using such fluorogenic probes as proxies to develop structure−activity relationships in nanoscale electrocatalysts and photocatalysts. We compare single-molecule fluorescence microscopy to other microscopies for imaging catalysis in situ to highlight the distinct advantages and limitations of this technique. We describe correlative imaging between super-resolution activity maps obtained from multiple fluorogenic probes to understand the chemical origins behind spatial variations in activity that are frequently observed for nanoscale catalysts. Fluorogenic probes, originally developed for biological imaging, are introduced that can detect products such as carbon monoxide, nitrite, and ammonia, which are generated by electro-and photocatalysts for fuel production and environmental remediation. We conclude by describing how single-molecule imaging can provide mechanistic insights for a broader scope of catalytic systems, such as single-atom catalysts.

Single-molecule fluorescence imaging of photocatalytic nanomaterials

“…137 For direct oxidation, holes are transported from the semiconductor interior to the semiconductor–electrolyte interface. 138,139 However, for indirect oxidation, holes are consumed by water oxidation and generate ROSs such as hydroxyl radical and superoxide anion, which further degrade the micropollutants (Fig. 9d).…”

Nanoscale Luminescence Imaging/Detection of Single Particles: State-of-the-Art and Future Prospects

“…Single molecule FLM can reveal structure–property relationship of single particles by imaging reactants/products and surface reaction hot spots of catalytic reactions at the level of an individual molecule/particle with nanometer precision. , Such information could be utilized for designing and developing high performance catalysts. For example, Xu and colleagues revealed facet-/shape-dependent catalytic activities of single Pd NPs using single FLM .…”

A turn-off fluorescent sensor for metal ions quantifies corrosion in an organic solvent

“…[57][58][59][60] Besides corrosion detection in coatings and bulk solutions, fluorescent sensors have been applied in single-molecule fluorescence microscopy to image and quantify noncorrosive electrochemical reactions, such as electro-and photocatalysis. 61,62 However, to the best of our knowledge, most studies regarding fluorescence-based corrosion sensors primarily provide a binary "yes" or "no" assessment of corrosion, rather than a quantitative evaluation.…”