Discussion
The following UV-vis spectra recorded on various sizes of semiconductor nanoparticles :
The blue shift in the spectra is correlated to :
Answer: A
The blue shift is correlated to decrease in size of nanoparticles.
In semiconductor nanoparticles, quantum confinement makes the effective band gap larger as the particle gets smaller. A larger gap means absorption at higher energy, that is, at shorter wavelength. So the spectra moving towards the blue, as the arrow shows, are those of progressively smaller particles.
Larger particles would shift the absorption to longer wavelength (a red shift), towards the bulk band gap. Surface plasmon resonance belongs to metal nanoparticles, not semiconductors, and the shift has everything to do with size.
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