采用高温热解法制备两种形貌不同（准方形和球形）、尺寸及分布基本相同（约10nm）的油溶性Fe3O4纳米颗粒，并以配体交换的表面修饰方法将其替换到水相，在此过程中，研究了配体替换时间对颗粒形貌和尺寸的影响，之后以VSM测量、MRI造影效果、交变磁场下升温效果作为评价手段，研究了纳米颗粒形貌对其磁学性质的影响，为改善纳米颗粒性能、优化应用效果提供了一个思路。研究表明，延长替换时间，所得样品单分散性不变，但样品形貌受到破坏，进而导致磁学性质变弱。此外，准方形纳米颗粒具有较球形颗粒高的磁学性质，表现为相同条件下准方形纳米颗粒具有高的饱和磁化强度、MRI弛豫率、SAR值等。
Mengjie Song, Yu Zhang, Sunling Hu, Lina Song, Jinlai Dong, Zhongping Chen, Ning Gu. Influence of morphology and surface exchange reaction on magnetic properties of monodisperse magnetite nanoparticles. Colloids and Surf. A. 2012. 5(39):1-8
Figure 1. TEM images of (a) quasi-cubical and (b) spherical Fe3O4@OA samples and their relevant size distribution histograms. Their average diameters were 9.5nm and 9.6nm, respectively
Figure 2. TEM images (a-d) of Fe3O4@DMSA samples and their respective size distribution histograms (A-D): (a) q-cubical-30min; (b) spherical-30min; (c) q-cubical-4h; (d) spherical-4h; (e, f) HRTEM images of sample a and b.
Figure 3. Hysteresis loops of Fe3O4@DMSA samples
Samples tested were of identical concentration of 0.6mg [Fe]/ml, and the results were obtained through converting the unit to emu/g. (a) quasi-cubical-30min; (b) spherical-30min; (c) quasi-cubical-4h; (d) spherical-4h;
Figure 4. T2-weighted images of Fe3O4@DMSA samples in MR experiment and their relaxivities obtained with linear fitting (inverse of the relaxation times as a function of the iron concentration)
Figure 5. Time-temperature curves for Fe3O4@DMSA samples under alternating magnetic field (samples were measured in aqueous phase with the concentration of 0.5mg [Fe]/ml)
