Electron micrographs, analysis solid samples

Micrographs obtained by EPMA are shown in Figure 4. The sample in this case was VPO with 10% amorphous silica as the hard phase. This composition was prepared by spray drying an aqueous slurry with about 40% solids made of l-2 im particles of the VPO catalyst precursor and polysilicic acid. The back-scattered image shows all elements present in the porous microsphere. The X-ray image of silicon clearly shows this element concentrated exclusively on the periphery of the microsphere. Independent X-ray diffraction and electron diffraction analysis of the peripheral layer of the microspheres showed that the silicon is present as amorphous silica. 

The distribution of TPA molecules over the radius of the beads of PVA-PEG was measured using a Philips Model 505 scanning electron microscope with energy dispersive X-ray analysis (EDAX) system. The secondary electron micrographs of selected solid samples were obtained. 

The endproduct of a nanomaterial sample can be in the form of a solid powder or in solution/suspension. For a dried powder in solution, concentration is easily determined by dispersing a known amount of sample (in grams) into a known amount of solvent (in liters). For the best measurement of particles in solution, cryo-transmission electron microscopy should be used. Usually, a known volume of sample is used when preparing nanoparticles in suspension for cryo-TEM analysis. After images are taken from the sample, the nanoparticles in each micrograph are counted. 

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