Herein, we report the optical and magnetic response of magnesium oxide nanoparticles synthesized using magnesium nitrate in a citric acid host. The precursor obtained during the synthesis process was annealed at 350 °C, 400 °C, 500 °C, 700 °C, 900 °C and 1100 °C to obtain magnesium oxide nanoparticles. The rock salt phase of the synthesized nanoparticles was investigated by Rietveld analysis of their X-ray diffraction (XRD) patterns. The temperature-dependent XRD investigation revealed a stable rock salt phase at the measured temperature of 300 °C for these nanoparticles. The nanoparticles exhibited varying crystallite sizes in the range from 6.9 ± 0.2 nm to 29.7 ± 3.9 nm as the annealing temperature increased from 350 °C to 1100 °C. Furthermore, scanning electron microscopy and transmission electron microscopy revealed the formation of regular particles above 500 °C; however, below this temperature, the particles appeared to be embedded in a carbonaceous-like matrix. A variation in color with annealing temperature was visually observed for the nanoparticles, which was associated with the presence of the carbonaceous-like matrix. Near-edge X-ray absorption spectroscopy (NEXAFS) measurements carried out at the O K-edge also revealed a carbonaceous-like matrix, and these results were supported by C and N K-edge measurements. These measurements indicated the presence of C–O–, CO–, C–N–, and C–H-like bonds attached to MgO crystallites having dominant contribution at low annealing temperatures. This behavior was also reflected by the X-ray photoelectron spectroscopic measurements at O 1s, C 1s and N 1s. The Mg K-edge NEXAFS measurements exhibited slight distortion in the Mg²⁺ ion coordination at lower annealing temperatures, which may be due to the presence of Mg²⁺ ions in MgO- and MgCO₃-like co-ordinations, as investigated from Mg 1s spectra of these nanoparticles. Diffuse reflectance measurements showed almost 100% reflectance for the nanoparticles at an annealing temperature of 900 °C and wavelength of 600 nm; the reflectance of these nanoparticles reduced when the annealing temperature was lowered, and it reduced to almost 8% at an annealing temperature of 350 °C. Additionally, O K-edge X-ray magnetic circular dichroism (XMCD) measurements obtained for these materials showed the onset of magnetism in these C-rich materials.

中文翻译：

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有机模板负责MgO纳米粒子的光学和磁性响应吗？†

在本文中，我们报告了在柠檬酸基质中使用硝酸镁合成的氧化镁纳米颗粒的光学和磁响应。在合成过程中获得的前体在350℃，400℃，500℃，700℃，900℃和1100℃下退火以获得氧化镁纳米颗粒。通过Rietveld分析其X射线衍射（XRD）图案，研究了合成纳米颗粒的岩盐相。与温度相关的XRD研究表明，这些纳米颗粒在300°C的测量温度下具有稳定的岩盐相。随着退火温度从350℃增加到1100℃，纳米颗粒表现出在6.9±0.2nm至29.7±3.9nm范围内的变化的微晶尺寸。此外，扫描电子显微镜和透射电子显微镜显示高于500°C的规则颗粒的形成。然而，在该温度以下，颗粒似乎被埋在碳质基质中。在视觉上观察到纳米颗粒的颜色随退火温度的变化，这与碳质样基质的存在有关。在O K边缘进行的近边缘X射线吸收光谱（NEXAFS）测量也显示出类似碳质的基质，这些结果得到C和N K边缘测量的支持。这些测量表明存在C–O–，C 这与碳质基质的存在有关。在O K边缘进行的近边缘X射线吸收光谱（NEXAFS）测量也显示出类似碳质的基质，这些结果得到C和N K边缘测量的支持。这些测量表明存在C–O–，C 这与碳质基质的存在有关。在O K边缘进行的近边缘X射线吸收光谱（NEXAFS）测量也显示出类似碳质的基质，这些结果得到C和N K边缘测量的支持。这些测量表明存在C–O–，C与MgO晶体相连的O–，C–N–和C–H样键在较低的退火温度下起主要作用。X射线光电子能谱在O 1s，C 1s和N 1s处的测量也反映了这种行为。Mg K边缘NEXAFS测量结果显示，在较低的退火温度下Mg ²⁺离子配位会出现轻微变形，这可能是由于MgO-和MgCO _3中存在Mg ²⁺离子引起的。这些纳米粒子的Mg 1s光谱研究了类似的配位。漫反射率测量结果表明，在900°C的退火温度和600 nm的波长下，纳米颗粒的反射率几乎为100％。当降低退火温度时，这些纳米粒子的反射率降低，而在退火温度为350°C时，其反射率降低至近8％。另外，针对这些材料获得的O边缘X射线磁性圆二色性（XMCD）测量结果表明，这些富含C的材料开始出现磁性。