Fabrication And Properties Of Two-dimensional Carbon-based Ultrathin Films And Their Polymer Hybrids

Carbon nanomaterials,including fullerene,carbon nanotube and graphene,have aroused intense interests due to their unique physical,chemical and electrical properties,which have exhibited potential applications in field effect transistors(FET),lithium battery,supercapacitors,sensors and actuators.To realize the specific functionality,it is necessary to assemble these carbon nanomaterials into well-controlled morphology.Compared with the assembled materials in one or three dimension,the two-dimensional films represent better performance for their superior specific area,transmittance and mechanical flexibility.However,it is still challenging for scalable fabrication of large-scale carbon-based films,well-controlled microarrays and adjustable functionality in high-efficiency and low-cost.This thesis has developed a capillary force driving compression technique for fabrication of close-packed carbon-based films with well-controlled thickness,distribution density and conductivity at air/water interface.This method can be further extended to nanoparticles and graphene sheets to acquire close-packed films.Through a modified spray-coating and compression strategies,scalable production of free-standing carbon nanotubes(CNTs)films could be successfully achieved in high uniformity and efficiency.The resulted films can be further asymmetrically grafted with stimuli-responsive polymer brushes via self-initiated photografting and photopolymerization(SIPGP),resulting in final hybrids with both good conductivity and functionality.When exposed to external stimuli,the achieved Janus hybrids can have a prominent current change.Additionally,the CNTs films can be further integrated into the adhesive tape to exhibit stable conductivity in bending/unbending states for applications in flexible electronics.Papers,as a flexible,low-cost,recyclable and environmentally friendly material,is considered as an ideal substrate in flexible electronics and energy storage,which are guaranteed by well-controlled thickness and conductivity of the conductive layers.Other than the conventional solution-based deposition techniques,a capillary force assisted interfacial transfer technique is developed to transfer large-area carbon-based thin films at air/water interface onto the Xerox paper surface without demolishing the original network structures.This method thus provides easy control of the thickness,distribution density and conductivity of the conductive paper,demonstrating excellent stability under the mechanical folding.As a proof of concept,this achieved conductive paper can be further integrated into strain and humid sensors.Furthermore,through an unidirectional modification of hydrophobic polyvinylidene fluoride(PVDF),a Janus composite can be successfully acquired to have quick respond to the humidity,demonstrating significant potentials in actuators.Precisely designed conductive carbon-based microarrays have play a significant role in high-efficient and high-performance devices.In this thesis,top-down and bottom-up methods are introduced to fabricate microstructured patterns.For the as-prepared carbon nanotubes films at air/water interface,one-step lift-up lithography is employed to transform the homogenous microstructures into a patterned one.In addition,microcontact printing(?CP)technique is also used to construct micropatterns on single layer graphene and silicon substrates by carbon-based inks.Through a facile SIPGP,the resulted patterned microstructures could be asymmetrically grafted with hydrophilic/hydrophobic polymer brushes to achieve specific multifunctionality.To achieve a more complex functionality,graphene oxide film with three-dimensional(3D)topological embossment is realized by a roller-assisted microcontact printing(RA?CP)technique.With the adjustment of the feature size of PDMS and graphene oxide concentration,a variety of 3D microarchitectures can be easily acquired in high-efficiency.Through a facile SIPGP method,stimuli-responsive polymer brushes can be asymmetrically grafted onto the carbon-based films,resulting in a Janus hybrid with both good conductivity and functionality,which demonstrate potential applications in sensors and actuators.In summary,we have developed a capillary force driving compression method to achieve scalable production of large-area CNTs films at air/water interface in low-cost and high-efficiency.Through a simple capillary force assisted transfer technique,the free-standing CNTs films could be further transferred onto the paper surface for flexible electronics without demolishing the original network structures within several minutes.Through typical soft lithography,including lift-up,microcontact printing and roller-assisted microcontact printing techniques,a variety of 2D and 3D microstructures are successfully achieved.