Surface-Enhanced Raman Spectroscopy-Based Spatial Temperature Profiling in Space-Confined Hollow Carbon Nanospheres for a Reaction Mechanism Study

Accurately sensing the spatial distribution of temperature, one of the most fundamental parameters, is crucial for understanding the mechanism of the physicochemical process in confined space. However, traditional methods for temperature measurement often show a very limited spatial resolution and sensitivity. Herein, we develop a surface-enhanced Raman spectroscopy (SERS) nanosensor to measure the spatial distribution of temperature within the hollow carbon nanospheres (HCNSs) and study the light-promoted Fenton-like process catalyzed by a Fe single-atom anchored on the HCNSs. Based on the temperature-dependent SERS spectra of phenyl isocyanide adsorbed on Au nanoparticles, the spatial distribution of the temperature gradient in the nanocavity and on the surface of the HCNSs, induced by light-irradiation, is sensed with a sensitivity of 0.8 °C. Furthermore, by combining the local temperature measurement and reaction kinetics-temperature relationship, we clarify that the Fe single-atom catalyzed oxidation of phenol by peroxymonosulfate occurs at the surface of the HCNSs, thus providing sound evidence on the homogeneous mechanism. Besides providing a new strategy for local temperature measurement with submicrometer resolution, this work also shows the feasibility of the reaction mechanism study through locating the reactive site.