Preparation And Properties Of Nitrogen Doped Carbon Nanotubes And Graphene Oxide Films

Carbon nanotubes(CNTs)are a special one-dimensional carbon material,which can be regarded as a hollow nano-tubular structure formed by rolling a graphite sheet along the center.The structure of graphene/carbon nanotube(G/CNTs)composite material determines its excellentness.The physical and chemical properties,which also attracted the attention of the majority of researchers.The nitrogen atom has a smaller atomic radius than carbon,and the electronegativity(3.04)of the nitrogen atom is higher than that of the C atom(2.55).Therefore,the nitrogen atom can be used as an electron donor to dope the CNTs and graphene oxide(GO).Miscellaneous,thereby improving the performance of CNTs and GO electrical and optical aspects.Currently,nitrogen-doped carbon nanomaterials are typically prepared by multi-step chemical vapor deposition(CVD).These nitrogen-rich graphite-thin methods generally require relatively complicated experimental procedures,and generally require higher temperatures,and it is not easy to obtain high-nitrogen N-rich graphene.Especially when studying the properties of film-like doped graphite thin film,it is easy to cause the film to become brittle and easily break at high temperature,which causes the film to be discontinuous,thus affecting its research.Therefore,exploring a simple,low-temperature,high-efficiency and suitable method for large-scale synthesis of N-doped graphene and systematic research on the properties of the sample is particularly important,and it is an urgent problem for current researchers.In this paper,we use a catalyst-free CVD method to prepare nitrogen-doped carbon nanotubes in one step.The method does not require a metal catalyst,nor does it utilize a precursor,and is simpler,faster,and has a shorter reaction time.In this experiment,the factors affecting the morphology and microstructure of carbon nanotubes in the process of preparing carbon nanotubes based on graphene quantum dots(QGDs)without catalyst were studied.The main research contents of this thesis are as follows:1.Preparation of GQDs and GOThis chapter details the specific experimental procedures for preparing graphene quantum dot samples by oxidation and the preparation of graphene oxide by Hummers method.The raw materials for the experiments,the reagents used in the experiments,and the characterization instruments are given,and the morphology of GQDs and GO samples is given,also the characterization of microstructures and other simple introductions.2.Preparation and properties of carbon nanotubes based on graphene quantum dotsThis chapter introduces a simple non-catalytic method for the preparation of bamboo-type carbon nanotubes,and systematically studies the factors affecting the morphology and microstructure of carbon nanotubes in the process of preparing carbon nanotubes based on graphene quantum dots without catalysts.Optical properties of photoluminescence,which results show that the SEM comprehensive analysis can be used to obtain the best quality of carbon nanotubes when the calcination temperature is 900 °C.The calcination time has a larger diameter for the prepared carbon nanotubes.The effect,but does not change its basic morphology;the flow rate of acetylene gas has a significant effect on the morphology of the prepared carbon nanotubes.When the flow rate of acetylene is 0.25 ml/min,the prepared carbon nanotubes have better quality.TEM shows that the prepared CNTs are bamboo-type carbon nanotubes.In a certain time range,as the calcination time increases,the flow of acetylene increases,and the diameter of CNTs increases.The PL results show that the fluorescence of GQDs and CNTs can be significantly tuned from the light yellow region to the near ultraviolet region.Therefore,the superior optical properties of CNTs should enable CNTs to be used in many applications,including multicolor light-emitting devices,bio-applications,and photovoltaic power generation.3.Preparation of nitrogen-doped carbon nanotubes by one-step CVD method based on graphene quantum dotsThis section describes a simple,catalyst-free CVD process for the preparation of nitrogen-doped carbon nanotubes in a single process and production process.The method does not require a metal catalyst,nor does it utilize a precursor,and is simpler,faster,and has a shorter reaction time.The factors affecting the morphology and microstructure of carbon nanotubes in the process of nitrogen-doped carbon nanotubes based on graphene quantum dots without catalyst were studied systematically.The results show that: SEM comprehensive analysis can be obtained,the prepared nitrogen-doped carbon nanotubes have a uniform diameter distribution of 45-60 nm.The Raman and XPS test results show that the doping of N atoms destroys the original hexagonal graphite structure of CNTs,causing defects,which leads to a decrease in the degree of crystallization and thermal stability.4.Preparation of nitrogen-doped graphene oxide film and its terahertz performanceThis chapter describes a simple spin-coating method for the preparation of graphene oxide films,photochemical nitrogen doping of GO films,and the response of NGO films in the terahertz band.The SEM characterization results show that the NGO film has a coiled-like structure and is a multi-layer graphene oxide composed of a large number of single-layer graphene oxide.The XPS characterization of the samples before and after doping showed that compared with the original GO film,the oxygen content in the NGO film samples decreased significantly,and a significant nitrogen peak appeared.At the same time,the N-type bond patterns were analyzed in detail.The results of the frequency domain map in the THz-TDS test show that the NGO film exhibits significant terahertz absorption with the change of nitrogen doping time,while the terahertz band frequency domain spectrum of the rGO film remains stable and has no absorption at the characteristic frequency.