Discovery of new plasmonic behaviors from nanostructured materials can be greatly accelerated by the ability to prepare and characterize their near-field behaviors with high resolution in a rapid manner. Here, an efficient and cost-effective way is reported to make 2D periodic nanostructures on electron-transparent substrates for rapid characterization by transmission electron microscopy. By combining nanosphere lithography with a substrate float-off technique, large areas of electron-transparent periodic nanostructures can be achieved. For this study, the synthesis of plasmonic nanostructures of Ag, magnetic nanostructures of Co, and bimetallic nanostructures of Ag-Co are investigated. Characterization of the materials by a combination of transmission electron microscopy, far-field optical spectroscopy, and magnetization measurements reveals that this new approach can yield useful nanostructures on transparent, flexible, and transferable substrates with desirable plasmonic and/or magnetic properties.