Santos Suzilene V, Costa Cleidilane S, Paraguassu Waldeci, Silva Crystian W C, Otubo Larissa, Souza Katiusse S, Correa Bruno S, Miranda-Filho Arnaldo A, Ferreira Wanderson L, Carbonari Artur W, Cabrera-Pasca Gabriel A
Programa de Pós-Graduação em Ciência e Engenharia de Materiais - PPGCEM, Universidade Federal do Pará (UFPA), Ananindeua, Pará 67130-660, Brazil.
Faculdade de Ciências Exatas e Tecnologia, Universidade Federal do Pará (UFPA), Abaetetuba, Pará 684440-000, Brazil.
ACS Omega. 2024 Oct 10;9(42):42883-42894. doi: 10.1021/acsomega.4c05308. eCollection 2024 Oct 22.
The advancement of functional nanomaterials has become a major focus of recent research, driven by the exceptional properties these materials display compared to their macroscopic (bulk) counterparts. Cobalt oxide nanoparticles (CoO-NPs) stand out primarily for their catalytic and magnetic properties, which can enable a range of technological applications, such as advanced catalysts, drug delivery systems, implants, prosthetics, sensors. However, in addition to the dependence on factors such as size, morphology, and functionalization, the properties of CoO-NPs are significantly influenced by the crystal structure. Therefore, local investigation into the polymorphic structures of CoO at the nanometric scale may provide new insights into the local structural and magnetic characteristics of these systems. In this report, we address the synthesis and local characterization of cobalt oxide (CoO) nanoparticles in the rock-salt cubic fcc-CoO and Wurtzite hpc-CoO phases, obtained through thermal decomposition. We analyze the influence of oleylamine and oleic acid ligands on the structural and morphological control of these systems. The obtained nanoparticles were characterized using conventional techniques such as X-ray diffraction (XRD), transmission electron microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Local characterization was carried out by the perturbed angular correlation (PAC) nuclear technique using the radioactive tracer In(Cd). Measurements were conducted at 295 and 10 K to investigate possible magnetic phase transitions in these systems. XRD results confirmed the formation of fcc-CoO and hcp-CoO phases. The phase fcc was obtained with the pair of oleylamine and oleic acid ligands, while the phase hcp phase was synthesized using only oleylamine. Additionally, nanoparticles synthesized with oleylamine and oleic acid exhibited better morphological control compared to those produced with only oleylamine. Raman spectroscopy analyses suggest a phase transformation process resulting in CoO. PAC results for hyperfine interactions at the In(Cd) probe nucleus, indicate that the hcp-CoO phase shows smaller hyperfine magnetic interactions ( = 1 T) compared to the fcc-CoO phase ( = 17 T). This suggests the mechanism of superexchange interactions, which are strongly influenced by the Co-O-Co bond angle, which is 110 for the hpc-CoO phase and 180 for the fcc-CoO phase due to the geometries of the systems.
与宏观（块状）材料相比，功能纳米材料因其独特性能成为近期研究的主要焦点。氧化钴纳米颗粒（CoO-NPs）主要因其催化和磁性特性而脱颖而出，这使其能够应用于一系列技术领域，如先进催化剂、药物递送系统、植入物、假肢、传感器等。然而，除了依赖尺寸、形态和功能化等因素外，CoO-NPs的性能还受到晶体结构的显著影响。因此，在纳米尺度上对CoO多晶型结构进行局部研究，可能为这些系统的局部结构和磁性特征提供新的见解。在本报告中，我们阐述了通过热分解获得的岩盐立方fcc-CoO和纤锌矿hpc-CoO相氧化钴（CoO）纳米颗粒的合成及局部表征。我们分析了油胺和油酸配体对这些系统结构和形态控制的影响。使用常规技术如X射线衍射（XRD）、透射电子显微镜、拉曼光谱和傅里叶变换红外光谱对所得纳米颗粒进行表征。通过使用放射性示踪剂In(Cd)的扰动角关联（PAC）核技术进行局部表征。在295 K和10 K下进行测量，以研究这些系统中可能的磁相变。XRD结果证实了fcc-CoO和hcp-CoO相的形成。使用油胺和油酸配体对获得了fcc相，而仅使用油胺合成了hcp相。此外，与仅使用油胺制备的纳米颗粒相比，用 油胺和油酸合成的纳米颗粒表现出更好的形态控制。拉曼光谱分析表明存在导致CoO的相变过程。In(Cd)探针原子核处超精细相互作用的PAC结果表明，hcp-CoO相比fcc-CoO相表现出更小的超精细磁相互作用（ = 1 T），而fcc-CoO相为 = 17 T。这表明了超交换相互作用的机制，该机制受Co-O-Co键角的强烈影响，由于系统的几何结构，hpc-CoO相的键角为110°，fcc-CoO相的键角为180°。
