Zuluaga Sebastian, Manchanda Priyanka, Zhang Yu-Yang, Pantelides Sokrates T
Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, United States.
ACS Omega. 2017 Aug 11;2(8):4480-4487. doi: 10.1021/acsomega.7b00762. eCollection 2017 Aug 31.
Magnetic nanoparticles are widely used in biomedical and oil-well applications in aqueous, often harsh environments. The pursuit for high-saturation magnetization together with high stability of the molecular coating that prevents agglomeration and oxidation remains an active research area. Here, we report a detailed analysis of the criteria for the stability of molecular coatings in aqueous environments along with extensive first-principles calculations for magnetite, which has been widely used, and cementite, a promising emerging candidate. A key result is that the simple binding energies of molecules cannot be used as a definitive indicator of relative stability in a liquid environment. Instead, we find that H ions and water molecules facilitate the desorption of molecules from the surface. We further find that, because of differences in the geometry of crystal structures, molecules generally form stronger bonds on cementite surfaces than they do on magnetite surfaces. The net result is that molecular coatings of cementite nanoparticles are more stable. This feature, together with the better magnetic properties, makes cementite nanoparticles a promising candidate for biomedical and oil-well applications.
磁性纳米颗粒广泛应用于生物医学和油井领域的水性环境中，这些环境通常较为恶劣。追求高饱和磁化强度以及具有防止团聚和氧化作用的分子涂层的高稳定性，仍然是一个活跃的研究领域。在此，我们报告了对水性环境中分子涂层稳定性标准的详细分析，以及对广泛使用的磁铁矿和一种有前景的新兴候选物渗碳体进行的大量第一性原理计算。一个关键结果是，分子的简单结合能不能用作液体环境中相对稳定性的决定性指标。相反，我们发现氢离子和水分子会促进分子从表面解吸。我们进一步发现，由于晶体结构几何形状的差异，分子通常在渗碳体表面形成的键比在磁铁矿表面更强。最终结果是渗碳体纳米颗粒的分子涂层更稳定。这一特性，再加上更好的磁性，使渗碳体纳米颗粒成为生物医学和油井应用中有前景的候选物。
