Experimental study on transverse relaxation rate of protons in aqueous suspensions of magnetite nanocrystal clusters with a SiO_2 shell

摘要

The transverse relaxation rate (1/T_2) of aqueous suspensions of magnetite nanocrystal clusters with a SiO_2 shell of different thicknesses has been studied experimentally. With the increase of the shell thickness, l/T_2 decreases slightly due to the aggregation of clusters during coating process. In T_2 measurement, the waiting time dependence decreases when the shell gets thicker, because of the decreased magnetic attractive energy, particle number concentration and diffusion coefficient of magnetite nanocrystal clusters with a thicker SiO_2 shell. These experimental results, supporting the relaxation theory and computer simulations, may promote future development of magnetic contrast agents.