General view of Using Spectroscopy with Quantum Dots - Lab Overview (Buffalo.edu)

To record the spectra, samples each with a different nanocrystal radius can be used. From these data, you can determine the average nanocrystal radius as well as its range of values.

Finally, you can record the emission spectrum for just the light source (light emitting diode LED) which you use to excite the Quantum Dot spectra

The spectrometer can be used to record the absorption spectra from CdSe nanocrystals also known as “quantum dots.” 
The QDs will be in the form of glass filters each with a different nanocrystal radius. 

"These filters aren’t just painted or colored glass, but actually quantum dots inside of the glass itself."

The spectrometer captures a transmission spectrum similar to the one shown below;

Expected result from the SEM for Quantum Dots;

http://www.physics.buffalo.edu/faculty/APetrou/QD_Intro.pdf