46
METHODS OF MEASURING PROPERTIES
LaC82
I
35
40
45
Time of Flight / ~ s
Figure 3.9. Time-of-flight mass spectra from soot produced by laser vaporization of a
lanthanumarbon target, showing the presence of the fullerene molecules CeO, C70, c7,, C78,
Ce2, Ce4, and Lac, , .
The spectra correspond, successively, to (a) the initial crude soot extract,
(b) a fraction after passage through a chromatographic column, and (c) a second fraction after
passage of the first fraction through another column to isolate and concentrate the endohedral
compound Lac,,.
[From K. Kikuchi, S. Suzuki, Y. Nakao, N. Yakahara, T. Wakabayashi, I.
Ikemoto, and Y Achiba, Cbem. Phys. Lett. 216, 67 (1993).]
3.3. MICROSCOPY
3.3.1. Transmission Electron Microscopy
Electron beams not only are capable of providing crystallographic information about
nanoparticle surfaces but also can be used to produce images of the surface, and they
play this role in electron microscopes. We will discuss several ways to use electron
beams for the purpose of imaging, using several types of electron microscopes.
In a transmission electron microscope (TEM) the electrons from a source such as
an electron gun enter the sample, are scattered as they pass through it, are focused by