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The Size Distribution of Semiconductor Quantum Dots (QDs) 
H. Weller , Chem. Phys. Lett. 124, 557 - 560 (1986)

Title: ``Photochemistry of colloidal semiconductors: Onset of light absorption as a function of size of extremely small CdS particles.''

The quality and uniformity of QDs synthesized is not clear at the outset. This work on ``spherical'' nanocrystallites of CdS set out to verify these using a gamut of techniques. Specifically

1.

It reports the absorption threshold for various sizes.

2.

It compares this experimental absorption threshold with several theoretical EMT type calculation : semiclassical, infinite barrier, finite barrier.

3.

A detailed description of the experimental size distribution is given (see Fig. (2)). The variety of techniques employed was remarkable:

(1) X-ray diffraction Internal lattice Structure is zinc-blende. with Scherrer formula Average size 2R.   (2) Fluorescence Quenching Average size 2R   (3) Pulse radiolysis : Assume spherical size with hydroxyl radicals and diffusion coefficient Gives average size 2R   (4) Electron Microscopy Gives size distribution of particles P(R) See Fig. (2).
 
 

Some other methods for determination of size and perhaps its distribution are (i) Raman, (ii) Scanning Electron Microscopy (SEM), (iii) Transmission Electron Microscopy (TEM), and (iv) Atomic Force Microscopy (AFM).

1999-01-04