Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Dielectric constant depression of water?
  1. Dielectric constants (Replies: 5)