Spatiotemporal Heterogeneity of Reactions in Solution Observed with High‐Speed Single‐Nanorod Rotational Sensing

Abstract

A high-speed darkfield microscope has been developed to monitor the rapid rotation of single gold nanorods (AuNRs) and used to study the spatiotemporal heterogeneity of chemical reactions in free solution. A wide range of viscosities from 237 cP to 0.8 cP could be detected conveniently. We studied H₂ O₂ decomposition reactions that were catalyzed by AuNRs coated with Pt nanodots (AuNR@PtNDs) and observed two different rotational states. The two states and their transitions are related to the production and the amalgamation of O₂ nanobubbles on the nanorod surface depending on H₂ O₂ concentration. In addition, the local fluidic environment of pure water was found to be non-uniform in time and space. This technique could be applied to study other chemical and biochemical reactions in solution.