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I am working with CdSe Quantum Dots suspended in hexane. I then tested the photoluminescence of my solution. Then I mixed my CdSe dots with a mixture of an organic conducting polymer which was dissolved in chloroform. I am attaching the structure of my polymer below.

My idea was to embed the dots in the polymer matrix. This would obviously quench the resultant luminescence of the dots because the excitons at the surface of the dots would be delocalized by the conducting matrix, but this should not result in a wavelength oriented shift of luminescence, but I am getting a shift. I am attaching the results of my photo-luminescence along with the structure of the polymer chain.

I suspect that the shift of the luminescence observed is due to an attempt by the S radical in the benzene ring of the polymer to displace the Se radical from my CdSe dots, or is there any other way that my dots could get chemically attacked by the polymer? And if so, is there any way to check it? Like a form of spectroscopy for instance?

polymers

The polymer to the left is PDMEET and the one to the right is PDMET. The shift in the luminescence image comes here.

luminescence .

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  • $\begingroup$ I'm curious - Is the difference in intensity due to a difference in the concentration of the microdots of CdSe? $\endgroup$
    – MaxW
    Commented Jan 19, 2016 at 21:42
  • $\begingroup$ Or it may also be due to exciton delocalization by the surrounding matrix? Is there a way to process it? Also, I am still not sure about the ligand which has been used to cap the dots, probably there is a ligand because the dots are very luminescent even under normal light. But, there is a probability that the quenching is due to lower dot concentration, because I just drop coated the dot polymer mixture from a vial to a slide (hence no uniformity) and then probed it with a 325 nm beam. But, I am more interested in the shift than the quench at present. Could you suggest something? $\endgroup$
    – Ghosal_C
    Commented Jan 19, 2016 at 21:55
  • $\begingroup$ Color variations in CdSe particles is due to a quantum effect of particle size. It would seem that the surface effects are making the effective size of the particles smaller and shifting the peak to a shorter wavelength. It would be very interesting if shift and quench were related. That is to say that a stronger quench results in a smaller effective particle size. $\endgroup$
    – MaxW
    Commented Jan 19, 2016 at 22:54
  • $\begingroup$ I'd certainly doubt any sulfur from the polymer replacing selenium in the particle. $\endgroup$
    – MaxW
    Commented Jan 19, 2016 at 22:56
  • $\begingroup$ Surface effects as in? Could you elaborate a little more? I don't think that quench and shift will be related if the shift is just related to decrements in particle size. Quench would imply either decrease in particle numbers or increase in surface defect state density and hence reduced probability of radiative recombinations, but I will try to get information about the ligands smothering my dots, maybe an attack on the ligands with these two polymers are possible. I will share the info with you, maybe you could make some predictions about their behaviour. Thank you for taking an interest. $\endgroup$
    – Ghosal_C
    Commented Jan 20, 2016 at 2:33

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