Abstract Among many preparation methods for the synthesis of Fe-doped ZnO nanoparticles which have been widely investigated due to versatile properties and potential applications in optoelectronics, photovoltaics, and spintronic devices, solution-based methods such as sol-gel, hydrothermal, and precipitation processes usually consume many reagents and involve numerous steps. In this study, we report a one-step synthesis of highly Fe-doped ZnO nanoparticles (NPs) by a solution plasma process (SPP) using FeCl2 and FeCl3 as precursors without any addition of chemicals. Breakdown of water bubbles caused by plasma discharge led to the formation of hydroxyl radicals, which reacted with the dissolved Zn2+ ions producing Zn(OH)2 that was indeed converted to ZnO through thermal dehydration. Meanwhile, Fe ions were incorporated into the host ZnO lattice during the synthesis process. Fe-doping levels in Zn1-xFexO NPs are easily controllable by changing the Fe precursor concentration and plasma discharging time. We achieved a high doping content (x = 0.14–0.46) within 30 min, which is difficult to achieve using traditional solution-based synthesis approaches. All the Fe-doped NPs exhibit ferromagnetic behavior, but the magnitude is strongly dependent on the Fe content and doping ratio of Fe2+ to Fe3+ ions, which are explained by the dominance and competition between the ferromagnetic and antiferromagnetic exchange interactions through the presence of mixed Fe2+ and Fe3+ ions. The observed optimal ratio of Fe2+ to Fe3+ for maximizing the magnetization is approximately 3:7. It is noteworthy that the magnetization of Fe-doped ZnO NPs can be simply controlled by manipulating the Fe content and composition of Fe2+ and Fe3+ ions achieved through the SPP. This result provides a platform for studying fundamental magnetic properties of TM-doped semiconductors for potential spintronic applications. Thus, the SPP has great potential as an alternative strategy for the synthesis of highly Fe-doped ZnO NPs, which can be expanded to the synthesis of other doped metal-oxide nanostructures for a broad range of research applications.

中文翻译：

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一步溶液等离子体法合成的高铁掺杂氧化锌纳米粒子的结构和磁性能

摘要 在许多合成 Fe 掺杂的 ZnO 纳米粒子的制备方法中，由于其在光电、光伏和自旋电子器件中的多种性质和潜在应用而被广泛研究，基于溶液的方法如溶胶-凝胶、水热和沉淀法通常消耗许多试剂并涉及许多步骤。在这项研究中，我们报告了通过溶液等离子体工艺 (SPP) 使用 FeCl2 和 FeCl3 作为前驱体，在不添加任何化学物质的情况下一步合成高度 Fe 掺杂的 ZnO 纳米粒子 (NPs)。等离子放电引起的水泡破裂导致羟基自由基的形成，羟基自由基与溶解的 Zn2+ 离子反应生成 Zn(OH)2，而 Zn(OH)2 确实通过热脱水转化为 ZnO。同时，在合成过程中，Fe 离子被结合到主体 ZnO 晶格中。通过改变 Fe 前体浓度和等离子体放电时间，可以轻松控制 Zn1-xFexO NPs 中的 Fe 掺杂水平。我们在 30 分钟内实现了高掺杂含量（x = 0.14-0.46），这是使用传统的基于溶液的合成方法难以实现的。所有 Fe 掺杂的 NPs 都表现出铁磁行为，但其大小很大程度上取决于 Fe2+ 与 Fe3+ 离子的 Fe 含量和掺杂比，这可以通过铁磁和反铁磁交换相互作用之间的优势和竞争来解释，通过混合 Fe2+ 的存在和 Fe3+ 离子。观察到的用于最大化磁化强度的 Fe2+ 与 Fe3+ 的最佳比率约为 3:7。值得注意的是，通过控制 SPP 实现的 Fe 含量和 Fe2+ 和 Fe3+ 离子的组成，可以简单地控制 Fe 掺杂的 ZnO NPs 的磁化强度。该结果为研究用于潜在自旋电子应用的 TM 掺杂半导体的基本磁特性提供了平台。因此，SPP 作为合成高 Fe 掺杂 ZnO NPs 的替代策略具有巨大的潜力，可以扩展到其他掺杂金属氧化物纳米结构的合成，用于广泛的研究应用。