We have developed an optical superresolution method based on electronbleaching of fluorophores in integrated light-electron microscopy. The main advantage of this novel superresolution method is that the non-fluorescent ultrastructure of the sample can be revealed by the simultaneously acquired SEM image. Furthermore, as the fluorescence superresolution image is based on an electron-beam-induced modification of the specimen, by "switching off" fluorescent probes, both the fluorescence and SEM image are recorded with perfect spatial overlap - being a great advantage for correlative imaging. The superresolution method is demonstrated with fluorescent microspheres, having a diameter of 40--50~nm. Their bleaching behaviour is studied as a function of various exposure parameters, and we show that the bleaching rate is mostly dependent on the injected electron dose and electron landing energy. The superresolution experiments are performed in an integrated light-electron microscope platform (SECOM, Delmic), with which fluorescence emission of the sample can be monitored while the electron beam scans over it. The method is successfully demonstrated with the fluorescent beads on ITO-coated glass and TEM-grid substrates. We have achieved a localization precision of approximately 100~nm of the fluorescent beads, and an image resolution of 160~nm -- well beyond the diffraction limit of light. The method may eventually provide an excellent tool for researchers doing correlative light-electron microscopy in modern life sciences, such as cell and molecular biology.
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