the CdSe/CdS quantum dot that synthesized by TOPO, ODPA et al are originally dispersed in toluene or cyclohexane. they are found significantly quenched when dispersed in ethanol. what is the reason? should it be explained by the polarity of the solvent? or hydrogen bonds? I have tried to search a lot papers but failed to get an explanation for this.
Hello,
The phenomenon that you observe is primarily a result of dynamic quenching also known as collisional quenching, which occurs when excess quencher molecules (ethanol in this case) collide with the nanoparticles resulting in non-radiative energy transfer from the CdSe/CdS quantum dots to the the quencher molecules. Hence the observed decrease in the fluorescence intensity. Fluorescence quenching has been known to be greatly affected by the vibrational overtones of -OH bonds present in the immediate ligand and solvent molecules.
Cheers!!
Gouranga
A lot of speculations might take a place here. One of the proposal is that methanol as a polar solvent bounds nano-particles into clusters. As to the clusters the non-radiative relaxation can be more prominent due to the energy transfers between nearest nano-particles in a cluster (e.g. Forster resonance).
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