Luxa Jan, Jankovský Ondřej, Sedmidubský David, Medlín Rostislav, Maryško Miroslav, Pumera Martin, Sofer Zdeněk
Department of Inorganic Chemistry, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague 6, Czech Republic.
New Technologies - Research Centre (NTC) at University of West Bohemia (UWB), CZ-30614 Pilsen, Czech Republic.
Nanoscale. 2016 Jan 28;8(4):1960-7. doi: 10.1039/c5nr05757d.
Bulk layered transition metal dichalcogenides (TMDs) show diamagnetic properties. When exfoliated, the materials' band gap increases and changes from an indirect band gap to a direct one. During the exfoliation, the TMDs may undergo a phase transition from 2H to 1T polymorph, which is likely electronically driven and accompanied by a metal-insulator transition. A significantly higher efficiency of the exfoliation was observed using sodium naphthalenide compared to butyllithium. Moreover we demonstrate that the exfoliation has a dramatic influence on the magnetic properties of two TMDs, MoS2 and WS2. These materials become partly ferromagnetic upon exfoliation, which is a highly unexpected behavior. Exotic ferromagnetism is generally observed on samples with a high degree of exfoliation, which indicates the association of this effect with defects formed on the edges of dichalcogenide sheets. Such an exotic ferromagnetic behavior, if properly understood and brought under material engineering control, shall open the door to new applications of these materials.
块状层状过渡金属二硫属化物（TMDs）表现出抗磁性。剥离时，材料的带隙增大，并从间接带隙转变为直接带隙。在剥离过程中，TMDs可能经历从2H到1T多晶型的相变，这可能是由电子驱动的，并伴随着金属-绝缘体转变。与丁基锂相比，使用萘钠观察到剥离效率显著提高。此外，我们证明剥离对两种TMDs（MoS2和WS2）的磁性有显著影响。这些材料在剥离后部分变为铁磁性，这是一种非常意外的行为。奇异铁磁性通常在高度剥离的样品上观察到，这表明这种效应与二硫属化物片边缘形成的缺陷有关。如果能正确理解并将这种奇异的铁磁行为置于材料工程控制之下，将为这些材料的新应用打开大门。
