Hot-pressing Fabrication And Properties Of Two-dimensional Material

Free-standing two-dimensional?2D?metals have been demonstrated with many excellent physical and chemical properties as a result of their unique ultrathin structure,compared to the bulk metal.Such materials would attract dramatically increased interest in the applications of optoelectronic devices,catalyst,flexible display,and so on.For instance,Sn-based stanene could support topological superconductivity and enable the dissipationless electric conduction at room temperature,according to calculation prediction of Zhang.However,it is still challenging to grow high-quality 2D metals with large size,ultrathin structure,single crystal,and strong fibre texture.In this thesis,hot-pressing method as a facil physical strategy,in combination with typical plasticity and generable deformation at high temperature of metals,was designed to achieve 2D metals via shaping metal expanded during a very narrow 2D gap under a certain temperature and pressure.Based on hot-pressing strategy,free-standing ultrathin 2D Ag was obtained under0.7 GPa at 200^oC for 20 min.Such 2D Ag was characterized with single crystal,thickness of 2 nm,large size of 10¹?m.Optical analysis indicated that two sharp PL peaks?570 nm?578 nm?were firstly observed in ultrathin 2D Ag,and the quantum yield?QY?of these two emission peaks was estimated to be 10^-5,which is larger than previous result of Ag nanostructure.Meanwhile,2D Ag shows unanticipated mechanical behavior on account of ultralow friction(almost reach as zero,10^-1 nN)compared with silicon substrate,which can be comparable to the lubricity of the graphene.Ultrathin 2D PVDF film was successfully fabricated via hot-pressing method under0.5 GPa at 140^oC for 20 min.The PVDF film features?phase mainly,7 nm thickness,large size of 10²?m,and exhibits excellent piezoelectric property.A superior d₃₃?50pm/V?was observed in the 2D PVDF film,which is much higher than previous result of bulk or other structured PVDF.Further experimental results demonstrated that d₃₃ is sensitive to the thickness of PVDF film,and piezoelectric constant could reach as optimum sensitivity of piezoelectric performance when the thickness of PVDF film is nearly 20 nm.To further demonstrate the extensive and potential application of hot-pressing strategy during 2D material fabricating technique field,additional experiments were carried out to achieve other 2D materials.Consequently,metal nanosheets like Au,Pt,Nb,compound nanosheet Bi₂Te₃,and metallic oxide nanosheet TiO₂ and SnO₂,such nanosheets featured with thickness under 10 nm,were achieved by the hot-pressing method.And these as-prepared nanosheets exhibit high quality in the surface integrity,uniform thickness,and large size.Significantly,it is estimated that the new hot-pressing strategy and as-synthsised 2D materials could open the opportunities for the researches to study low-dimensional materials from the respective of technique and materials,and thus motivates a broad range of science researchers and readers being interested in the fundamental sicence and application of 2D materials.