Excited-State Imaging of Single Particles on the Subnanometer Scale

• Published in: Annual review of physical chemistry Vol. 71; no. 1; pp. 415 - 433
• Main Authors: Wallum, Alison, Nguyen, Huy A, Gruebele, Martin
• Format: Journal Article
• Language: English
• Published: United States Annual Reviews 20.04.2020; Annual Reviews, Inc
• Subjects: Electron beams; Electron energy; Electron energy loss spectroscopy; electron microscopy; Energy harvesting; Excitation; excited state; Imaging; Imaging techniques; Macromolecules; Microscopy; Nanoparticles; Optical measurement; Raman spectroscopy; scanning tunneling microscopy; Spatial data; Spectroscopy; Spectrum analysis; super-resolution microscopy; Switching; electron microscopy; Raman spectroscopy; scanning tunneling microscopy; excited state; super-resolution microscopy
• ISSN: 0066-426X; 1545-1593
• DOI: 10.1146/annurev-physchem-071119-040108

At the intersection of spectroscopy and microscopy lie techniques that are capable of providing subnanometer imaging of excited states of individual molecules or nanoparticles. Such approaches are particularly important for imaging macromolecules or nanoparticles large enough to have a high probability of containing a defect. These inevitable defects often control properties and function despite an otherwise ideal structure. We discuss real-space imaging techniques such as using scanning tunneling microscopy tips to enhance optical measurements and electron energy-loss spectroscopy in a scanning transmission electron microscope, which is based on focused electron beams to obtain high-resolution spatial information on excited states. The outlook for these methods is bright, as they will provide critical information for the characterization and improvement of energy-switching, electron-switching, and energy-harvesting materials.