Metal Oxide Quantum Wire Synthesized By Nanoparticle-induced Graphene Oxide Rolling And Its Application In Gas Sensing

The emergence of quantum technology not only provides a new perspective for human to understand nature,but also opens a new door for the development of modern technology.Quantum technology is based on quantum materials.And among them,quantum wire(QW)is the most promising candidate for the future applications in electronics,optics and sensors.In addition,numerous researches and discussions of quantum confinement effect and plentiful designs and developments of quantum device are based on QW.Considering the potential application of semiconductor QWs in many areas,people use different techniques to fabricate semiconductor QWs,these strategies include the method based on microfabrication techniques,mediated metal catalyst,oriented attachment and template strategy.Although these methods can manufacture many semiconductor QW,they still suffer from drawbacks such as contamination of catalyst,poor universality,and harsh growth conditions.In this thesis,a novel growth method of QW based on Nanoparticle-Induced Graphene Oxide Rolling(NIGOR)procedure is proposed.The main idea of this method is using a tubular structure as a template for QW growth,and the template was formed by rolling of Graphene Oxide(GO),which was induced by nanoparticles.Thus,the QW will grow and develop inside the GO tube.Furthermore,this thesis provides a complete theoretical and experimental explanation and demonstration of this NIGOR process and its mechanism to form QWs using cuprous oxide(Cu₂O)as an example.Firstly,this thesis demonstrated the NIGOR method therotically and experimentally.The models of Cu₂O nanoparticles and GO was built with by computer,and the molecular dynamics process of systems with different number(0-3)of Cu₂O nanoparticles and GO were simulated with molecular dynamics after geometric optimization.The simulation results show the sequence chart of different GO/Cu₂O system structures from the very beginning,the structures evolution of the kinetic processes at different time and the final structures at the thermodynamic steady state.The results demonstrated that nanoparticles are an important prerequisite for the inducing of GO rolling,which verified the theoretical feasibility of the NIGOR method.Secondly,Cu₂O QWs with diameters around 3-4 nanometers was synthesized with experimental scheme designed in this thesis via NIGOR method by controlling the experimental parameters,and the product was purified and characterized.The characterization results of transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS)demonstrated the successfully synthesis of Cu₂O QW.and their formation process was observed as well.After that,the intermediate phase of the QW was observed by using TEM and the formation mechanism of QW synthesized by the NIGOR method was discussed.Thus,the unification of NIGOR method between theory and experiment was achieved.Additionally,the synthsis of the Zinc Oxide(Zn O)and Cadmium Oxide(Cd O)QWs proved the universality of this NIGOR method.After that,this thesis investigated the morphology variances of Cu₂O materials synthesized by the NIGOR method with different experimental parameters,including the Cu ion,GO,temperature,glucose,anion species,and p H factor levels of precursors.Further,this thesis summarized and explained the morphology evolution of the materials from the perspectives of crystalline growth mechanism,thermodynamic energy,and steric effect.This work was an important reference for tuning the synthesis of materials with specific structures or functions by NIGOR method.Finally,this thesis synthesized composites with/without Cu₂O QW structures by NIGOR method through controlling experimental parameters.The characterization such as field emission scanning electron microscopy(FESEM),TEM,X-ray diffraction(XRD),Raman spectroscopy,XPS,thermogravimetric analysis validated the successful synthesis of the materials.And it also revealed the differences between the Cu₂O QW components between these as-prepared materials.The gas-sensitive test results show that the device consist of Cu₂O QW possessed high sensitivity(66%response towards50 ppb NO₂),fast response and recovery time,modest repeatability(root-mean-square was 7.98×10^-3 within 3 times),stability,selectivity and humidity-resistance property,that proved it has great potential for application in gas sensing.Although this thesis proposed a new method of quantum wires synthesis and demonstrated the feasibility of this method in theory,simulation and experiment.However,there are still some shortcomings in this method,such as the universality of the method and the optimization of the process of synthesizing quantum wires.As the research continues,the NIGOR method will be optimized,and it is expected to become an alternative method for the synthesis of quantum wires,and the quantum wires synthesized by NIGOR method will show extraordinary properties in the fields of electricity,optics,catalysis,and sensing in the near future.