Monitoring the dynamic photocatalytic activity of single CdS nanoparticles by lighting up H2 nanobubbles with fluorescent dyes.

The capability of semiconductor nanomaterials to convert solar energy to chemical energy has led to many promising applications, for instance, photocatalyzed H2 generation. Studying this important photocatalytic reaction at the single nanocatalyst level provides a great opportunity to understand the microscopic reaction kinetics and mechanism by overcoming the chemical and structural heterogeneity among individuals. Here we report a fluorescence (FL) labeling strategy to visualize individual H2 nanobubbles that are generated at single CdS nanoparticles during photocatalysis. In operando imaging of nanobubble growth kinetics allows for determination of the photocatalytic activity of single nanocatalysts, which was found to randomly alternate among high activity, low activity and inactive states. In addition to H2 nanobubbles, the present labeling strategy is also suitable for other types of gas nanobubbles. Since nanomaterial-catalyzed gas generation is widely involved in many important photochemical (water splitting), electrochemical (electrolysis) and chemical (nanomotors) reactions, the present work is promising for the general applicability of single nanoparticle catalysis in broad basic and industrial fields by lighting up nanobubbles under commercial and conventional FL microscopes.