Electrochemical Calcite-Assisted Localization and Kinetics (E-CLocK) Microscopy

Nanoparticle (NP) morphology is a critical factor influencing the efficiency and selectivity of electrochemical reactions. However, conventional electrochemical techniques do not provide information about the dynamic morphological changes of NPs during these reactions. Advanced methods such as atomic force microscopy (AFM) and transmission electron microscopy (TEM) offer higher resolution but are costly and may impact electrochemical measurements. Here, we introduce dark-field-based electrochemical calcite-assisted localization and kinetics (E-CLocK) microscopy, a novel multiparameter super-resolution imaging technique enabling real-time, non-invasive tracking of qualitative and quantitative morphological changes at the single-nanoparticle level during electrochemical processes. In E-CLocK microscopy, a rotating calcite crystal is integrated into the infinity space of a dark-field microscope, generating a distinctive point spread function that can be analyzed to determine the anisotropy and orientation of NPs. Using gold NP electrodeposition as a model reaction, we quantitatively assessed the morphological anisotropy of the individual NPs during their growth. Nearly all particles exhibited steady isotropic growth with only the gold precursor solution; however, the addition of cetyltrimethylammonium bromide (CTAB), a surfactant, induced oscillatory behavior and significantly promoted the growth of anisotropic NPs. E-CLocK microscopy provides a high-throughput and reliable method for tracking morphological changes during electrochemical reactions, significantly advancing single-particle structure–activity studies.