Grupo de Investigación de Nanotecnología Aplicada para Biorremediación Ambiental, Energía, Biomedicina y Agricultura (NANOTECH), Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Av. Venezuela Cdra 34 S/N, Ciudad Universitaria, Lima 15081, Peru.
Centro Brasileiro de Pesquisas Físicas (CBPF), R. Xavier Sigaud, 150, Urca, Rio de Janeiro 22290-180, Brazil.
Int J Mol Sci. 2022 Jul 27;23(15):8279. doi: 10.3390/ijms23158279.
Novel magnetic nanohybrids composed of nanomaghemite covered by organic molecules were successfully synthesized at room temperature with different functionalization agents (sodium polystyrene sulfonate, oxalic acid, and cetyltrimethylammonium bromide) in low and high concentrations. Structural, vibrational, morphological, electron energy-loss spectroscopy, magnetic, and Mössbauer characterizations unraveled the presence of mainly cubic inverse spinel maghemite (γ-FeO), whilst X-ray diffraction and Fe Mössbauer spectroscopy showed that most samples contain a minor amount of goethite phase (α-FeOOH). Raman analysis at different laser power revealed a threshold value of 0.83 mW for all samples, for which the γ-FeO to α-FeO phase transition was observed. Imaging microscopy revealed controlled-size morphologies of nanoparticles, with sizes in the range from 8 to 12 nm. Organic functionalization of the magnetic nanoparticles was demonstrated by vibrational and thermogravimetric measurements. For some samples, Raman, magnetic, and Mössbauer measurements suggested an even more complex core-shell-like configuration, with a thin shell containing magnetite (FeO) covering the γ-FeO surface, thus causing an increase in the saturation magnetization of approximately 11% against nanomaghemite. Field cooling hysteresis curves at 5 K did not evidence an exchange bias effect, confirming that the goethite phase is not directly interacting magnetically with the functionalized maghemite nanoparticles. These magnetic nanohybrids may be suitable for applications in effluent remediation and biomedicine.
新型磁性纳米杂化材料由纳米磁赤铁矿覆盖有机分子组成，在室温下用不同的功能化试剂（聚苯乙烯磺酸钠、草酸和十六烷基三甲基溴化铵）在低浓度和高浓度下成功合成。结构、振动、形态、电子能量损失光谱、磁性和穆斯堡尔特征揭示了主要立方反尖晶石磁赤铁矿（γ-FeO）的存在，而 X 射线衍射和 Fe 穆斯堡尔光谱表明，大多数样品含有少量针铁矿相（α-FeOOH）。不同激光功率下的拉曼分析显示，所有样品的阈值为 0.83 mW，在此阈值下观察到γ-FeO 到α-FeO 相转变。成像显微镜揭示了纳米颗粒的可控尺寸形态，尺寸范围为 8 至 12nm。通过振动和热重测量证明了磁性纳米颗粒的有机功能化。对于一些样品，拉曼、磁性和穆斯堡尔测量表明存在更复杂的核壳样结构，薄壳中含有磁铁矿（FeO）覆盖γ-FeO 表面，从而使饱和磁化强度增加约 11%，相对于纳米磁赤铁矿。在 5K 下的磁场冷却磁滞回线没有表现出交换偏置效应，这证实了针铁矿相不会与功能化的磁赤铁矿纳米颗粒直接进行磁相互作用。这些磁性纳米杂化材料可能适用于废水处理和生物医学应用。
