If the size of the nanoparticles decreases, then surface to volume ratio increases and a greater number of non-radiative transitions takes place. Will we get an intense UV emission peak?
Sorry the surface to volume ratio is increases when the nano particle size is decreased
From basic knowledge of Chemistry, I would think that it is very difficult to infer anything about the non-radiative transitions from the emission spectra. Emission spectra records only the radiative transitions from LUMO to HOMO and shows intensity of these transitions as a function of wavelength or energy of the radiation. However, if you know the quantum yield of your fluorophore, you can comment on the non-radiative decay process. Theoretically however, as the size of the nanoparticle decreases, volume to surface area increases and therefore intensity of non radiative transitions should increase. A UV emission peak would only suggest that particle size is small. It doesn't say anything about relative radiative and non radiative decay process just by looking at emission spectra.
On what basis are you saying "As particle size decreases, greater number of non-radiative transitions takes place" ?
Here is some info which can assist you.
As particle size decreases surface area/volume increases, i.e., the ratio of the number of atoms residing on the surface to the number of atoms residing in the bulk increases, as particle size decreases. But the actual number of atoms residing on the surface increases, as particle size increases.
Further the atoms on the surface are not bonded from all directions, as a result they have unsatisfied valencies, hence the energy states contributed by these surface atoms will lie in the middle of the band gap (for semiconductor nanoparticles). These are the surface states. These surface states quench emission.
Ravi,
I believe you meant to say that unbonded atoms at the surface are at a higher energy state. Surfaces always have a higher energy than within the bulk. If they didn't bonding wouldn't occur.
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