Optical Resolution of the Morphological Change of Single Nanoparticles at Native Conditions: A Nonsuper-Resolution Approach

Label-free optical imaging of the morphology of single nanoparticles under native conditions remains a challenging task despite its importance in the synthesis, properties, and applications of nanomaterials. Here, we developed an angular scanning dark-field scattering microscopy (ASDFSM) that can identify the particle morphologies by the features of their angle-dependent scattering intensities without increasing spatial resolution. ASDFSM can unambiguously resolve the morphology of single nanoparticles with sizes down to 1/5 wavelength of the incident light in a large field of view, facilitating the simultaneous imaging of a large number of nanoparticles with statistical significance. Coupling with a random forest machine learning algorithm, their morphologies can be well-identified with an average accuracy of 96%, facilitating in situ monitoring of the corrosion and growth kinetics of single nanoparticles in a high-temperature solution. The ASDFSM possesses the advantages of high-throughput, noninvasiveness, dynamic traceability, and simplicity over the present methods, promising its wide applications in nanoscience.