A new analytical expression for the size-dependent bandgap of colloidalsemiconductor nanocrystals is proposed within the framework of the finite-depthsquare-well effective mass approximation in order to provide a quantitativedescription of the quantum confinement effect. This allows one to convertoptical spectroscopic data (photoluminescence spectrum and absorbance edge)into accurate estimates for the particle size distributions of colloidalsystems even if the traditional effective mass model is expected to fail, whichoccurs typically for very small particles belonging to the so-called strongconfinement limit. By applying the reported theoretical methodologies to CdTenanocrystals synthesized through wet chemical routes, size distributions areinferred and compared directly to those obtained from atomic force microscopyand transmission electron microscopy. This analysis can be used as acomplementary tool for the characterization of nanocrystal samples of manyother systems such as the II-VI and III-V semiconductor materials.
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