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[摘要]：The authors report on the spontaneous covalent growth of monomol. adlayers on mixed nickel-zinc nanoferrite colloidal suspensions (ferrofluids). Synthesized nanoparticles were subjected to surface modification by acid chloride chem., giving covalent bonds between the hydroxy groups at the nanoparticle surface and the acid chloride mols. This procedure can be easily tailored to allow for the formation of adlayers contg. both hydrophobic and hydrophilic regions stacked at predetd. distances from the magnetic core, and also providing the nanoferrites with functional carboxy groups capable of further modifications with, for example, drug mols. Here, fluorophore aminopyrene mols. were bound to such modified nanoferrites through amide bonds. The same chem. was used to modify the surface with covalently bound long-chain palmitoyl moieties, and for comparison the authors also modified the nanoferrite surface by simple adsorption of oleic acid. Both procedures made the surface highly hydrophobic. These hydrophobic colloids were subsequently spread on an aq. surface to form Langmuir monolayers with different characteristics. Also, since uniformity of size is crucial in a no. of applications, the authors propose an efficient way of sorting the magnetic nanoparticles by size in their colloidal suspension. The suspension is centrifuged at increasing rotational speed and the fractions are collected after each run. The mean size of nanoferrite in each fraction was measured by the powder x-ray diffraction (PXRD) technique. |
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