Design,Construction And Properties Of Optical Function Low-dimensional Nanomaterials Possessing With Special Structures

Electrospinning is a common technique for preparing low-dimensional nanomaterials,especially for fabricating the low-dimensional nanomaterials with special structure,such as coaxial structure,Janus structure,hollow structure nanofibers or nanoribbons.These special structured nanomaterials often afford better performance and expansibility than homogeneous structured nanomaterials and thus have greater development potential.The optical functional materials developed based on rare earth luminescence have important applications in display,illumination and detection.In this dissertation,several types of low-dimensional nanomaterials with special structure are constructed by modified electrospinning technique in order to enhance or extend fluorescence property of materials.It lays a foundation for further understanding the relationship between structure and properties of nanomaterials.1.Rare earth ions grafted polyacrylonitrile coaxial nanofibers with the diameters of ca.450 nm are prepared by electrospinning,in which the rare earth ions disperse on the surface of the nanofibers.In addition to acting as the fiber skeleton,polyacrylonitrile also acts as a ligand that can transfer energy to rare earth ions for emitting light.In order to further improve the fluorescence intensity of the product,the outermost layer of the product is modified with benzoic acid as the assistant ligand.The coaxial nanofibers have higher fluorescence intensity and mechanical strength than the homogeneous nanofibers.2.White fluorescent Janus structured nanofibers,where Dy³⁺and Eu³⁺ions are separated in their two sides,are prepared by parallel electrospinning.Each Janus nanofiber consists of two side-by-side arranged nanofibers with the diameters of about 100 nm,and Dy³⁺and Eu³⁺ions are respectively located in the two nanofibers.The unique Janus structure can effectively suppress the non-radiative energy transfer from Dy³⁺to Eu³⁺,which plays a predominant role in the total energy transfer,so that the energy of Dy³⁺with low intrinsic fluorescence intensity cannot be notably transferred to Eu³⁺with high intrinsic fluorescence intensity,thus ensuring the high fluorescence emission intensity of Dy³⁺.Compared with the nanofibers with uniform distribution of Dy³⁺and Eu³⁺ions,the Janus structured nanofibers have higher blue light emission,leading to stronger white fluorescence.3.Parallel gradient electrospinning technique is proposed to construct the nanofibers with gradient distribution of Dy³⁺and Eu³⁺.That is,in a single nanofiber,the concentration of Dy³⁺gradually decreases from one side to the other,whereas the concentration of Eu³⁺increases gradually.The distribution of Dy³⁺and Eu³⁺ions can be regulated by the controllable preparation process to achieve complete blending,partial blending or complete separation,so as to change the energy transfer degree from Dy³⁺to Eu³⁺and achieve adjustable fluorescence color of the product.4.A Janus structured anisotropic conductive flexible nanoribbons array membrane containing fluorescent materials on one side and conductive material on the other side of a nanoribbon is prepared by parallel electrospinning.On the film surface,the conduction in the conductive direction is 8 orders of magnitude higher than that in the insulating direction.After the membrane is stretched along the conductive direction,the conduction of the conductive direction decreases,and the fluorescence intensity of the membrane simultaneously decreases as well.Based on this property,the conductivity of the membrane can be monitored in real time by the change of the fluorescence intensity of the membrane.5.A fluorescent nanofiber with nested structure is constructed by electrospinning combined with double-crucible fluorination technology.The nanofiber with special structure is composed of fluorescent nanowire inside and silica nanotube outside,and there is a gap between the nanowire and nanotube.Using the nested fluorescent nanofibers as the substrate,WO₃ with gaschromic property is modified onto the nested fluorescent nanofibers to obtain the gaschromic nanofibers detectable by fluorescence,which can detect hydrogen concentration through the change of fluorescence intensity.In the range of hydrogen concentrations from 1%to 4%,the fluorescence intensity decreases linearly.