Iron Oxide nanoparticles possess great potential in technological as well as biomedical applications. Significant biomedical applications include drug delivery, cancer hyperthermia, bio-detection, magnetic separation of biomolecules, etc. Among most suitable entities are magnetite, i.e., FeO nanoparticles. Several synthetic approaches have been attempted to achieve size, shape as well as properties control and biofunctionalization. In this work, we focus on controlling crystal habit and magnetic properties via stirring velocity for potential bio-detection applications. Magnetite nanoparticles were synthesized by a simple co-precipitation method at temperature of 60ºC but at varying stirring velocities. Characterization was carried out via XRD, SEM-EDS, TEM-SAED, as well as magnetic properties were estimated by VSM and GMR. Saturation magnetization (), remanent magnetization () and coercive field () were determined during VSM analysis, while the measurement of the output voltage as a function of the applied field for a bare GMR sensor were estimated to check utility of FeO nanoparticles as a label bio-detection application. At different stirring velocities, nanoparticle size was estimated by XRD, SEM and TEM, and the result are complimentary to each other. FeO nanoparticles with size 10.19±0.21 nm 10.5± 0.33 nm, 12.5±0.35 nm and 12.79±0.15 nm at stirring velocities of 500, 600,700 and 800 rpm, respectively. XRD and EDS confirmed the formation and composition of FeO phase. This stirring velocity was found to be suitable for obtaining nanoparticles with an average size below 20 nm, and increasing the stirring velocity resulted in larger sizes and a more uniform distribution of shapes. Finally, GMR experiments have shown that the prepared FeO could be used as an effective magnetic label for bio-detection applications.

中文翻译：

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通过搅拌速度控制 Fe3O4 纳米颗粒的晶体习性和磁性，用于生物检测应用

氧化铁纳米粒子在技术和生物医学应用中具有巨大的潜力。重要的生物医学应用包括药物输送、癌症热疗、生物检测、生物分子的磁分离等。最合适的实体是磁铁矿，即Fe3O纳米颗粒。已经尝试了几种合成方法来实现尺寸、形状以及性能控制和生物功能化。在这项工作中，我们专注于通过搅拌速度控制晶体习性和磁性，以实现潜在的生物检测应用。磁铁矿纳米粒子是通过简单的共沉淀法在 60°C 的温度下以不同的搅拌速度合成的。通过 XRD、SEM-EDS、TEM-SAED 进行表征，并通过 VSM 和 GMR 评估磁性能。在 VSM 分析过程中确定饱和磁化强度 ()、剩磁 () 和矫顽场 ()，同时估计输出电压的测量值作为裸 GMR 传感器的外加磁场的函数，以检查 Fe3O 纳米粒子作为标签的效用生物检测应用。在不同搅拌速度下，通过 XRD、SEM 和 TEM 估算纳米颗粒尺寸，结果相互补充。Fe3O纳米粒子的尺寸分别为10.19±0.21 nm、10.5±0.33 nm、12.5±0.35 nm和12.79±0.15 nm，搅拌速度分别为500、600,700和800 rpm。XRD和EDS证实了FeO相的形成和组成。发现该搅拌速度适合获得平均尺寸低于20 nm的纳米颗粒，并且增加搅拌速度会导致更大的尺寸和更均匀的形状分布。最后，GMR实验表明所制备的Fe3O可以作为生物检测应用的有效磁性标记。