Study the electronic responses of individual nanoparticles by electron energy loss spectroscopy in a transmission electron microscope

Plasmon coupling of dimers of Ag nanoparticles is studied by the EELS as shown in Fig 1a [1]. The spectroscopic images in the above Fig. 1a are extracted from 2.8eV, 3.4eV and 3.6eV respectively, where one can see the preferable exciting points of the features around the Ag nanoparticles. With the aid of DDA calculation(Fig. 1b), the three features are identified as the in-phase plasmon coupling, non-coupling and anti-phase coupling modes. The in-phase mode is able to conduct the light transportation due to its dipolar nature, which redshifts from the 3.4eV at large spacings to 2.7eV near touching (Fig. 1c). Such behaviour is also observed in the chain of 3 and 4 nanoparticles. The experiment provides clear evidence on the plasmon coupling of Ag nanoparticles. Extracting the dopant states in the Co-doped ZnO nanoparticles [2]. In order to assign the dopant-introduced states in the low-loss EELS, we employ both the core-loss EELS and the valence EELS on the same Co-doped ZnO nanoparticles by spatially mapping the dopant concentration distribution via the core-loss EELS (Fig 2a 2b 2c) and simultaneously by identifying the dopant features in the accumulated valence EELS via the measured dopant richness (Fig 2d). Three Coincidentally-growing Co dopant states are successfully determined in Fig. 2e. The experimental inputs feed the first-principles calculation, which generates full electronic structure of the doped ZnO nanoparticles. The experiment supports the carrier mediated room-temperature magnetism, which is a main confusion with current dilute magnetic semiconductors.