Review: Biofunctionalized Quantum Dots in Biology and Medicine

Figure 3

Scheme of the polymer coating procedure. Several reports suggest that the surfactant chains for hydrophobically capped nanocrystals are pointing away from the nanocrystal surface, in a brush-like arrangement. The following plausible configuration is then assumed for the polymer (Poly(maleic anhydride-alt-1-octadecene)) coating process: the hydrophobic alkyl chains of the polymer intercalate with the surfactant coating. The anhydride rings are located on the surface of the polymer-coated nanocrystal. The amino end groups of the cross-linker molecule open the rings and link the individual polymer chains. The surface of the polymer shell becomes negatively charged, stabilizing the particles in water by electrostatic repulsion.