Graphene Based Multi-dimensional Assembly And Their Applications In Actuators And Energy Related Fields

Graphene has attracted much attention because of the unique two-dimensional monolayer sp2-bonded carbon atoms stucture and the excellent physical and chemical related properties. In this thesis, various graphene based miti-dementional assembles have been fabricated through many simple methods, and their applications in actuators, energy strorage and conversion and so on have been explored.1. Graphene based assembly of one-dimensional fiber structure1) The positioned laser reduction of freshly spun GO fibers has been explored to achieve the rational design and fabrication of graphene/graphene oxide(G/GO) fibers which are region asymmetric. Remarkably, the G/GO fibers display complex, well-confined, predetermined motion and deformation once exposed to moisture. Apart from their application as a single-fiber walking robot, shape-memory G/GO fibers will play a vital role for the construction of the woven devices and smart textiles.2) The intrinsic configuration of graphenes within the fiber body has been reconstructed and a new type of moisture-driven rotational motor by rationally designing the rotary processing of the freshly spun GO fiber hydrogel has achieved. Remarkably, the twisted GO fiber(TGF) with rearranged graphene sheets within the fibers presents superb performance as a reversible rotary motor, with a rotary speed of up to 5190 revolutions per minute and a tensile expansion of 4.7% under humidity alternation. More importantly, this moisture-responsive actuation behavior of TGF also builds the basis for development of humidity switches and promising moisture-triggered electric generators.3) A new type of unique graphene fiber spring(GFS) has been demonstrated. It possesses a large elongation of up to 480% while sustaining a small tensile strength of only 0.12 mN. Remarkably, the GFS presents a stable coefficient of elasticity even for one hundred thousand times of stretch with a strain of 300%. Particularly important, the GFS can behave elastically in an electrically or magnetically controllable fashion. Under electrostatic effects, the graphene spring exhibits outstanding performance as a reversibly stretchable actuator with 210% expansion. Functionalized with magnetic nanocomponents, the graphene spring can be actuated in response to an applied magnetic field, allowing the development of novel magnetostriction switches and actuators.4) A flexible electrochemical capacitor with textile electrodes made from CNT/G hybrid fibers of large surface area and high flexibility has been developed. The CNT/G hybrid fibers were fabricated by directly growing CNTs along graphene fibers with embedded Fe3O4 nanoparticles as catalysts for chemical vapor deposition(CVD) of the nanotubes.2. Graphene based assembly of two-dimensional film structureA sole GO film responsor with integrated graphene sensor has been developed. The responsor is composed of only one active GO layer and is integrated with the embedded laser reduced graphene oxide(LRG) sensor. By controlling the two sides’ surface roughness of GO film through the water natural evaporation from GO solution simply, the novel GO film exhibits excellent reversible bending/unbending deformation in response to multi stimulus and the embedded LRG sensor can perceive external stimulate signal in the real time of deformation. And remarkably, the obtained monolayer responsor can be cut into arbitrary shapes. Apart from their applications as triangular, rectangular-shaped, and even four-legged walking robot, the responsor will play a vital role for the construction of the smart perceptual fingers.3. Graphene based assembly of three-dimensional bulk structureAn alternative, solvent- and reagent-free, solid-state route for an extremely simple and fast preparation of graphene bulks and their multifunctional composites has been explored. This method specifically uses the GO aerogel as the starting material. On exposure to a remote laser spot or focused sun light irradiation, the reduction reaction occurs spontaneously and keeps going to convert the whole GO bulk to reduced sample in only tens of millisecond at ambient conditions. This powerful and efficient light irradiation method allows the preparation of not only pure graphene bulks in any macroscopic size, but also their doped structures with heteroatoms(e.g., N, P, S) and functional composites with metals and metal oxides. These as-prepared materials present high performance in energy conversion and storage devices such as fuel cells, supercapacitors and lithium ion batteries.4. Graphene based nano-assemblyHierarchically porous graphene quntam dot assembled nanotubes(GQD-NTs) has been prepared by electrophoresis deposition within a nanoporous AAO template. The electrodeposited GQD-NTs have much less O-related groups than those of the initial graphene quntam dots(GQDs), and the abundant hydrogen atoms are terminated on the surface of GQDs with GQD-NTs. Plus the unique porous nanotube architecture of GQDs, the GQD-NTs could ensure the more efficient charge transfer between target molecules and GQDs than that occurred on the flat graphene sheets, which thus produces the stronger surface enhanced Raman scattering(SERS) effect.