Park Jooneon, Porter Marc D, Granger Michael C
†Department of Chemical Engineering, University of Utah, Salt Lake City, Utah, United States.
§Nano Institute of Utah, University of Utah, Salt Lake City, Utah, United States.
Langmuir. 2015 Mar 24;31(11):3537-45. doi: 10.1021/acs.langmuir.5b00268. Epub 2015 Mar 10.
Stable suspensions of magnetic nanoparticles (MNPs) with large magnetic moment, m, per particle have tremendous utility in a wide range of biological applications. However, because of the strong magnetic coupling interactions often present in these systems, it is challenging to stabilize individual, high-moment, ferro- and ferrimagnetic nanoparticles. A novel approach to encapsulate large, that is, >100 nm, ferrimagnetic zinc ferrite nanocubes (ZFNCs) with silica after an intermediary layer-by-layer polyelectrolyte deposition step is described in this paper. The seed ZFNCs are uniform in shape and size and have high saturation mass magnetic moment (σ(s) ∼100 emu/g, m ∼ 4 × 10(-13) emu/particle at 150 Oe). For the MNP system described within, successful silica encapsulation and creation of discrete ZFNCs were realized only after depositing polyelectrolyte multilayers composed of alternating polyallylamine and polystyrenesulfonate. Without the intermediary polyelectrolyte layers, magnetic dipole-dipole interactions led to the formation of linearly chained ZFNCs embedded in a silica matrix. Characterization of particle samples was performed by electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, powder X-ray diffraction, dynamic light scattering (hydrodynamic size and ζ-potential), and vibrating sample magnetometry. The results of these characterizations, which were performed after each of the synthetic steps, and synthetic details are presented.
具有较大磁矩m的磁性纳米颗粒（MNP）稳定悬浮液在广泛的生物应用中具有巨大的实用性。然而，由于这些系统中常常存在强磁耦合相互作用，稳定单个的、高磁矩的铁磁性和亚铁磁性纳米颗粒具有挑战性。本文描述了一种新颖的方法，即在中间的逐层聚电解质沉积步骤之后，用二氧化硅封装大尺寸（即>100 nm）的亚铁磁性锌铁氧体纳米立方体（ZFNC）。种子ZFNC的形状和尺寸均匀，具有高饱和质量磁矩（σ(s) ∼100 emu/g，在150 Oe下m ∼ 4 × 10(-13) emu/颗粒）。对于本文所述的MNP系统，只有在沉积由交替的聚烯丙胺和聚苯乙烯磺酸盐组成的聚电解质多层膜之后，才实现了成功的二氧化硅封装并生成离散的ZFNC。没有中间的聚电解质层时，磁偶极-偶极相互作用导致形成嵌入二氧化硅基质中的线性链状ZFNC。通过电子显微镜、能量色散X射线光谱、红外光谱、粉末X射线衍射、动态光散射（流体动力学尺寸和ζ电位）以及振动样品磁强计对颗粒样品进行表征。给出了在每个合成步骤之后进行的这些表征的结果以及合成细节。
