Hi, I graft the cy5 to the Polymer, then dialysis the polymer-cy5 to remove the free cy5. then make the nanoparticles as before, but the nanopartcile is unable to detect the size. Do you know why?
There is no reason why it it is not detectable after removal of cy5. If the particles are not in the nanoscale then it may happen.
Dear Xiangxiang, this is due the fluorescence signal of the Cy5 dye, that adds a strong background light to the scattered light signal of your DLS setup (usually near 633 nm, depending on the laser. There is the same issue for luminescent NPs like quantum dots. The way to solve it is to use an another wavelength (like green or near infrared): you can contact your DLS provided (for instance I would advice you to contact David or Renata from https://www.cordouan-tech.com/fr/).
Good luck in your research,
Olivier
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