STEM is a type of TEM that scans electron beam across sample. Electron beam is focused to 0.05-0.2 nm spot size. Requires stable room environment for atomic resolution
Colloidal gold is a suspension of gold nanoparticles in water. Particles appear wine red for small (<100 nm) or blue-purple for larger ones. Properties depend strongly on size and shape. Particles absorb and scatter light through surface plasmon resonance
Excludes unscattered beam from image, creating dark background. Requires darkfield condenser lens with oil immersion. Objective lens NA must be less than 1.0. Works by illuminating sample with scattered light
SEM scans sample surface with focused electron beam to produce images. Secondary electrons detected using Everhart-Thornley detector. Resolution can reach resolutions better than 1 nanometer. Magnification ranges from 10 to over 500,000 times
Electron microscope uses electron beam as illumination source. Electron optics control beam for magnification and diffraction patterns. Resolution is about 0.1 nm compared to 200 nm for light microscopes
Louis de Broglie proposed electron waves in 1924. Max Knoll and Ernst Ruska developed first electron microscope in 1931. Manfred von Ardenne and Charles Oatley laid foundations for electron microscopy. Stigmator invention in 1946 accelerated development after WWII