Pathak Saurabh, Verma Rajni, Kumar Prashant, Singh Arjun, Singhal Sakshi, Sharma Pragati, Jain Komal, Pant Rajendra Prasad, Wang Xu
Department of Mechanical Engineering, University of Melbourne, Parkville, VIC 3052, Australia.
School of Engineering, RMIT University, Melbourne, VIC 3001, Australia.
Nanomaterials (Basel). 2021 Nov 9;11(11):3009. doi: 10.3390/nano11113009.
The present work reports the synthesis of a stable aqueous magnetic fluid (AMF) by dispersing double-surfactant-coated FeO magnetic nanoparticles (MNPs) in water using a facile ambient scalable wet chemical route. MNPs do not disperse well in water, resulting in low stability. This was improved by dispersing double-surfactant (oleic acid and sodium oleate)-coated MNPs in water, where cross-linking between the surfactants improves the stability of the AMFs. The stability was probed by rheological measurements and all the AMF samples showed a good long-term stability and stability against a gradient magnetic field. Further, the microwave spin resonance behavior of AMFs was studied in detail by corroborating the experimental results obtained from the ferromagnetic resonance (FMR) technique to theoretical predictions by appropriate fittings. A broad spectrum was perceived for AMFs which indicates strong ferromagnetic characteristics. The resonance field shifted to higher magnetic field values with the decrease in particle size as larger-size MNPs magnetize and demagnetize more easily since their magnetic spins can align in the field direction more definitely. The FMR spectra was fitted to obtain various spin resonance parameters. The asymmetric shapes of the FMR spectra were observed with a decrease in particle sizes, which indicates an increase in relaxation time. The relaxation time increased with a decrease in particle sizes (sample A to D) from 37.2779 ps to 42.8301 ps. Further, a detailed investigation of the structural, morphological, and dc magnetic properties of the AMF samples was performed. Room temperature dc magnetic measurements confirmed the superparamagnetic (SPM) characteristics of the AMF and the - plot for each sample was fitted with a Langevin function to obtain the domain magnetization, permeability, and hydrodynamic diameter of the MNPs. The saturation magnetization and coercivity of the AMF samples increased with the increase in dispersed MNPs' size of the samples. The improvement in the stability and magnetic characteristics makes AMFs suitable candidates for various biomedical applications such as drug delivery, magnetic fluid hyperthermia, and biomedicines.
本工作报道了一种稳定的水性磁流体（AMF）的合成方法，该方法通过一种简便的环境可扩展湿化学路线，将双表面活性剂包覆的FeO磁性纳米颗粒（MNPs）分散在水中。MNPs在水中分散性不佳，导致稳定性较低。通过将双表面活性剂（油酸和油酸钠）包覆的MNPs分散在水中，改善了这一情况，其中表面活性剂之间的交联提高了AMF的稳定性。通过流变学测量探究了稳定性，所有AMF样品均表现出良好的长期稳定性以及抗梯度磁场稳定性。此外，通过将铁磁共振（FMR）技术获得的实验结果与通过适当拟合得到的理论预测结果相结合，详细研究了AMF的微波自旋共振行为。观察到AMF呈现出宽谱，这表明其具有强铁磁特性。随着颗粒尺寸减小，共振场向更高磁场值移动，因为较大尺寸的MNPs更容易磁化和退磁，因为它们的磁自旋能够更明确地沿磁场方向排列。对FMR光谱进行拟合以获得各种自旋共振参数。随着颗粒尺寸减小，观察到FMR光谱的不对称形状，这表明弛豫时间增加。弛豫时间随着颗粒尺寸从样品A到D的减小而从37.2779 ps增加到42.8301 ps。此外，对AMF样品的结构、形态和直流磁性进行了详细研究。室温直流磁性测量证实了AMF的超顺磁性（SPM）特性，并且对每个样品绘制的 - 图用朗之万函数进行拟合，以获得MNPs的畴磁化强度、磁导率和流体动力学直径。AMF样品的饱和磁化强度和矫顽力随着样品中分散MNPs尺寸的增加而增加。稳定性和磁性特性的改善使得AMF成为药物递送、磁流体热疗和生物医学等各种生物医学应用的合适候选材料。
