Determining size of nanosized specimens

1.XRD: Take X-ray diffraction spectrum of the specimen material. Using De bye-Schrrer formula, You can easily fix the exact size of the nano grains.
2.TEM: Take transmission electron micrograph to get an accurate grain size value. TEM equipment far expensive than XRD.
3. SEM: Rough idea can be inferred from scanning electron micrograph.