Many Faces of Ni<sub>3</sub>Bi<sub>2</sub>S<sub>2</sub>: Tunable Nanoparticle Morphology via Microwave-Assisted Nanocrystal Conversion
作者:Maria Roslova、Wouter Van den Broek、Anna Isaeva、Thomas Doert、Michael Ruck
DOI:10.1021/acs.cgd.7b01647
日期:2018.4.4
Several combinations of the microwave-assisted polyol route and conversion chemistry techniques were exploited to access the bimetallic sulfide Ni3Bi2S2 with a variety of morphological features. First, Bi2S3 microstructures can be converted into Ni3Bi2S2 at 240 °C; the precursor’s rod-like shape and size pertain to the final product. Second, round Ni3Bi2S2 particles can be obtained directly from a presynthesized NiBi intermetallic precursor; the resultant submicron size particles agglomerate and thus differ from the starting alloy’s shape. Third, microwave reflux of bismuth nitrate and nickel acetate solution in ethylene glycol in the presence of thiosemicarbazide can be employed to produce Ni3Bi2S2 with a peculiar flower-like morphology. The presence and the decisive role of the in situ generated NiBi intermediate are unraveled, confirming that the reaction proceeds via transformation of solid rather than via a solution–dissolution process. NiBi nanoparticles preconfigure the Ni3Bi2S2 product morphology in a wide range of pH values. In turn, the pH value is found to be a key factor that determines the type of impurities accompanying the Ni3Bi2S2 ternary phase. At pH ≈ 4 bismuth precipitates as a main side-phase, while pH ≈ 12 favors the formation of NiS impurity.
研究人员利用微波辅助多元醇路线和转化化学技术的多种组合,获得了具有多种形态特征的双金属硫化物Ni3Bi2S2。首先,Bi2S3微结构可在240°C下转化为Ni3Bi2S2;前体的棒状形状和大小与最终产品有关。其次,圆形的Ni3Bi2S2颗粒可以直接从预先合成的NiBi金属间化合物前体中获得;生成的亚微米级颗粒会聚集,因此与起始合金的形状不同。第三,在硫代氨基脲存在下,乙二醇中的硝酸铋和乙酸镍溶液的微波回流可用于生产具有特殊花朵状形态的Ni3Bi2S2。原位生成的NiBi中间体的存在和决定性作用得以揭示,证实了反应是通过固体转化而不是通过溶液-溶解过程进行的。NiBi纳米粒子在广泛的pH值范围内预先确定了Ni3Bi2S2产品的形态。反过来,pH值被认为是决定Ni3Bi2S2三元相伴随的杂质类型的关键因素。在pH≈4时,铋以主要副相的形式沉淀,而pH≈12时有利于形成NiS杂质。