Figure 2
Comparison of imaging methods: secondary electron (SE), cathodoluminescence (CL) and confocal fluorescence.
Each row shows images of a sample of a single NP species exhibiting (from top to bottom) red, green and blue CL (and fluorescence) emission. Scale bars are 200 nm. SE images in the first column give excellent spatial resolution (<5 nm), but are monochromatic; whereas confocal images in the third column are in colour, but diffraction-limited. CL images in the middle column are in colour and provide resolution limited by NP size (~ 40–80 nm). Spatial correlations between the CL and optically-excited fluorescence images (second and third columns) and the corresponding SE image (first column) are very good for each type of NP. (See also Supplementary Figure S1.)
