We have synthesized a fluorescent conjugated polymer. The optical density (OD) of the polymer increases in presence of nano particle. We have also taken the OD of the polymer and the nano particle individually and just add two ODs. The OD of the mixture (polymer + nano particle) from the experimental data is higher than the OD obtain from the summation. We assumed, in presence of nano particle the extinction coefficient is being higher? Please provide if there is any information or article regarding this issue.
Thanks in advance !
The extinction coefficient is directly proportional to absorbance which in itself is a measure of fraction of radiation of characteristic wavelength absorbed by the material under examination. The absorption characteristics and in turn absorbance which further in turn absorptivity or extinction coefficient
and shift in it to higher (red shift) or lower (blue shift) depends upon the nature of material in question in the form of its structural features e.g.functional groups, particle size, morphology etc.
What is the polymer, and is it in the solid state?
We have previously seen in conjugated polymers in film form, loading with nanoparticles can change the optical properties based on the fact that they reduce the aggregation of the polymer in the film, and so the polymer begins to look more like it does in solution form.
In addition to Hugh's structural changes, I can offer a mere "optical" explanation. First of all, we have shown that "extinction coefficients" are no specific quantities. This becomes obvious through the derivation of the concentration dependence from electromagnetic theory. Furthermore, even dielectric nanoparticles can enhance the electric field around them, so what you see can be surface enhancement (in the language of Beer's law, the nanoparticle can "enhance" the absorption cross sections of the polymer molecules; actually, absorption and scattering cross sections are also not specific but wave properties). Have a look at the following paper and the references therein:
Article Deviations from Beer's law on the microscale - Nonadditivity...
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