Silva Ricardo S, Mikhail Hanna D, Guimarães Eder V, Gonçalves Elis R, Cano Nilo F, Dantas Noelio O
Departamento de Física, Instituto de Ciências Exatas, Naturais e Educação (ICENE), Universidade Federal do Triângulo Mineiro, Uberaba 38025-180, Minas Gerais, Brazil.
Departamento de Engenharia Mecânica, Instituto de Ciências Tecnológicas e Exatas (ICTE), Universidade Federal do Triângulo Mineiro, Uberaba 38064-200, Minas Gerais, Brazil.
Molecules. 2017 Jul 11;22(7):1142. doi: 10.3390/molecules22071142.
Iron-doped bismuth sulphide (BiFeS₃) nanocrystals have been successfully synthesized in a glass matrix using the fusion method. Transmission electron microscopy images and energy dispersive spectroscopy data clearly show that nanocrystals are formed with an average diameter of 7-9 nm, depending on the thermic treatment time, and contain Fe in their chemical composition. Magnetic force microscopy measurements show magnetic phase contrast patterns, providing further evidence of Fe incorporation in the nanocrystal structure. The electron paramagnetic resonance spectra displayed Fe typical characteristics, with spin of 5/2 in the 3d⁵ electronic state, thereby confirming the expected trivalent state of Fe ions in the Bi₂S₃ host structure. Results from the spin polarized density functional theory simulations, for the bulk Fe-doped Bi₂S₃ counterpart, corroborate the experimental fact that the volume of the unit cell decreases with Fe substitutionally doping at Bi1 and Bi2 sites. The Bader charge analysis indicated a pseudo valency charge of 1.322|| on Fe₁ and 1.306|| on Fe₂ ions, and a spin contribution for the magnetic moment of 5.0 per unit cell containing one Fe atom. Electronic band structures showed that the (indirect) band gap changes from 1.17 eV for Bi₂S₃ bulk to 0.71 eV (0.74 eV) for Bi₂S₃:Fe (Bi₂S₃:Fe). These results are compatible with the 3d⁵ high-spin state of Fe, and are in agreement with the experimental results, within the density functional theory accuracy.
采用熔融法成功地在玻璃基质中合成了铁掺杂硫化铋（BiFeS₃）纳米晶体。透射电子显微镜图像和能量色散光谱数据清楚地表明，根据热处理时间的不同，形成的纳米晶体平均直径为7 - 9纳米，并且其化学成分中含有铁。磁力显微镜测量显示出磁相衬度图案，进一步证明了铁掺入到纳米晶体结构中。电子顺磁共振光谱显示出铁的典型特征，在3d⁵电子态下自旋为5/2，从而证实了Bi₂S₃主体结构中铁离子预期的三价态。对于体相铁掺杂Bi₂S₃对应的自旋极化密度泛函理论模拟结果，证实了实验事实，即随着铁在Bi1和Bi2位点的替代掺杂，晶胞体积减小。巴德电荷分析表明，Fe₁离子上的赝价电荷为1.322||，Fe₂离子上的赝价电荷为1.306||，对于包含一个铁原子的每个晶胞，磁矩的自旋贡献为5.0。电子能带结构表明，（间接）带隙从Bi₂S₃体相的1.17 eV变为Bi₂S₃:Fe（Bi₂S₃:Fe）的0.71 eV（0.74 eV）。这些结果与铁的3d⁵高自旋态相符，并且在密度泛函理论精度范围内与实验结果一致。
