| Two-dimensional (2-D) nanomaterials are thin flakes of two-dimensional layered materials (graphite, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS2), tungsten disulfide (WS2), fluorinated graphite, etc.) with thicknesses at nanoscale. They have exceptional optical, electronical, thermal, mechanical properties. Among them,2-D nanomaterials/polymer flexible layered films (polymer as substrates and2-D nanomaterials as functional layers) have great potential for applications in the areas such as flexible optoelectronics, flexible new energy materials and devices, biology science, etc., for their good flexibility.However, cunrrent approaches for fabrication of2-D nanomaterials on polymer substrates have the following shortcomings:"indirect" procedures with "transfer" steps, relatively complex processes and long cycles, a certain degree of biological or chemical contaminations, high energy consumption, poor adhesion between2-D nanomaterials and polymer substrates.In response to the above problem, the research objective of this thesis is to design new method which can make up for those shortcomings of current approaches to fabricate2-D nanomaterials/polymer flexible layered films, and realizing the goal of rapid room temperature direct fabrication of various2-D nanomaterials with different thicknesses on polymer substrates.This thesis introduced friction as complete fabrication method into fabrication of2-D nanomaterials/polymer flexible layered films for the first time. Through chosing of best rubbing track, designing and making rubbing equipment, this thesis proposed and designed prototyping technology of soft contact rubbing method, and realized the goal of "direct" fabrication of various2-D nanoplates with thicknesses between100nm and200nm (with sizes of several micrometers) on polymer substrates. And the fabricated graphite nanoplates/polymer flexible layered film has transparent and conductive function (transparency was85.7%and surface resistivity was97.7kΩ/sq).Then, in response to the limitations of prototyping technology of soft contact rubbing method (the2-D nanoflakes were thicker than100nm and the transparent and conductive properties of flexible layered film were limited), this thesis explored the exfoliation thining effect during friction processes, and conducted a technical evolution based on the effect. On this basis, this thesis developed soft contact exfoliation rubbing method and universal soft contact exfoliation rubbing method. By using graphite block and2-D material powders as raw materials, this thesis realized the breakthrough of2-D nanomaterials fabricated on polymer substrates by soft contact rubbing technologies:from hundreds of nanometers to scale of2-D nanosheets (with thickness less than100nm, and with sizes of several micrometers), and fulfilled the goal of "direct" fabrication of different kinds of2-D nanosheets with thickness less than100nm on polymer substrates. And the transparent and conductive properties of fabricated graphene nanosheets/polymer flexible transparent film were enhanced (transparency was80.3%and surface resistivity was1.19kΩ/sq). While being used as flexible transparent heater, the graphene nanosheets/polymer flexible transparent heater showed a much higher resistant to bending decay compared with commercial ITO flexible transparent heater.For the purpose of resolving the following problems of the above soft contact rubbing method:(1) the layer number of atoms were still bigger than10,(2) the transparent and conductive properties of flexible layered films were still limited,(3) the broad optoelectric properties such as semiconductor energy level changes of MoS2and WS2, this thesis explored the following technical evolution idea:treating the surface of the2-D material sheets on sandpaper surface by friction with a very smooth surface, and using the polytetrafluoroethylene (PTFE) films which have similar surface and physical properties of graphite block surfaces (low friction coefficient, smooth surface morphology). On this basis, this thesis developed soft contact specular rubbing method and universal soft contact specular rubbing method. By using graphite block and2-D material powders as raw materials, this thesis realized the breakthrough of2-D nanomaterials fabricated on polymer substrates (thickesses decreasing from tens of nanometers to atom layer scale), and fulfilled the goal of "direct" fabrication of different kinds of few-layer2-D nanoflakes (with only2to10atom layers, and with sizes of tens of micrometers) on polymer substrates. This theis further enhanced and enriched the optoelectric properties of fabricated flexible layered films:(1) the properties of flexible transparent conductive films were enhanced (transparency was87.6%and surface resistivity was1.2kΩ/sq),(2) while being used as flexible transparent heater, the few-layer graphene/polymer flexible transparent heater showed a better performance compared with graphene nanosheets/polymer flexible transparent heater (transparency increased7.3%at the same heating power),(3) the high gauge factor (50.9) and high transparency (98.3%) of transparent strain sensors based on few-layer graphene flexible transparent conductive films showed the application potential of few-layer graphene with strong adhesion with polymer substrates,(4) the fluorescence spectroscopy results of few-layer sulfur2-D nanomaterials flexible layered films demonstrated their potential to be used as flexible fluorescence materials.Unlike current "indirect" approaches needing "transfer" steps for fabrication of2-D nanomaterials/polymer flexible layerd films, soft contact rubbing technology is a "direct" fabrication method, and it has its own advantages such as:rapid room temperature processes, no chemical or biological wastes. Also, unlike2-D nanomaterials/polymer flexible layerd films fabricated by current "indirect" approaches (weak adhesion between2-D nanomaterials and polymer substrates), the2-D nanomaterials/polymer flexible layerd films fabricated by soft contact rubbing method have strong adhesion between2-D nanomaterials and polymer substrates.This thesis provides a featured method with high efficiency, room temperature progresses, low cost of raw materials,"direct" fabrication procedures for the development of2-D nanomaterials/polymer flexible layerd films in the areas of optoelectrics, new energy, and biological science. Thus this thesis has important theoretical and practical significance. |
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