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Introduction to Nanotechnology

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CdSe colloidal NCs<br />

a = 1.2 nrn<br />

3.4. SPECTROSCOPY 63<br />

J<br />

I I I I I I I<br />

I .8 2.0 2.2 2.4 2.6 2.8 3.0<br />

Pho<strong>to</strong>n Energy (eV)<br />

Figure 3.27. Room-temperature optical absorption spectra for CdSe colloidal nanocrystals<br />

(NCs) with mean radii in the range from 1.2 <strong>to</strong> 4.1 nm. [From V. I. Klimov, in Nalwa (2000),<br />

Vol. 4, Chapter 7, p. 464.1<br />

irradiated with ultraviolet light (UPS) or X rays (XPS) can emit electrons called<br />

pho<strong>to</strong>electrons from a<strong>to</strong>mic energy levels with a kinetic energy equal <strong>to</strong> the<br />

difference between the pho<strong>to</strong>n energy hVph and the ionization energy Eion, which<br />

is the energy required <strong>to</strong> completely remove an electron from an a<strong>to</strong>mic energy level<br />

KE hVph - Eion (3.11)

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