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Dielectric constant depression of water?

  1. Jan 4, 2008 #1
    Hey Everyone. I am doing a project proposal where I am calculating the coupling efficiency between a quantum dot and a wire and I need to enter in values for the dielectric constant of the wire and the surrounding medium. I am working off a paper (doi:10.1103/PhysRevB.76.035420) where he uses the dielectric constant for the surrounding medium to be 2. I would like to do this in water (well actually the cytoplasm of a cell which I think is ~50) which has a much higher dielectric constant and unfortunately it seems to kill off the really efficient coupling that I was getting. Does anyone know of a way to suppress the dielectric constant and to somehow quantify how low I can get it? I know salt will depress it, but how much would I expect? I read that if I get water at a supercritical phase I can get it pretty low, but does anyone know of any other way? Thanks a lot for your help!
  2. jcsd
  3. Jan 5, 2008 #2
    Freezing will help, if you also drop the temperature below 0. Maybe that is what you mean by supercritical phase. Also, the dielectric constant is a function of the frequency of the EM radiation in question, and drops with increasing frequency.

    Here is a quote off of the web: "The dielectric constant of ice at 0°C is virtually the same as that of water (88.0), but decreases rapidly with decreasing temperatures below 0°C, and with increasing frequency; by 0.1 MHz, kice ~ 2-4 with little influence of temperature." Source - http://www.nanomedicine.com/NMI/10.5.5.htm
  4. Jan 6, 2008 #3
    I don;t think freezing is a good idea. It would solidify the medium and render the cells immobile
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