Investigation Of Preparation Methods For Graphene Nanosheets And Typical Two-dimensional Materials Nanosheets

Due to its excellent combination of optical,mechanical and electrical properties,graphene exhibits great promise in many application fields,such as optoelectronic,catalysis,energy storage,microelectronic devices,etc.The property of graphene is heavily dependent upon its layer-number.However,based on the Top-down method,how to prepare the layer-tunable graphene from natural graphite by chemical exfoliation is still facing great challenge.In addition,many chemical exfoliation methods have developed to acquire graphene and other two-dimensional materials by using high-boiling solvents and corrosive acids,but the generated hazardous wastes may cause the environmentally detrimental impact due to the use of high-boiling solvents and corrosive acids.Therefore,it is necessary to explore an eco-friendly and green strategy for exfoliating graphene and other two-dimensional materials.Based on these,this dissertation has performed the following researches:?1?We have probed systematically into the effect of the exfoliating temperature on the chemical exfoliation of graphite to graphene in the H₂SO₄ and?NH₄?₂S₂O₈ binary system.We have found that the exfoliating temperature of natural graphite has a markedly impact on the layer-number of the resultant graphene.Therefore,we have developed a technical strategy for tuning the layer-number of graphene by controlling the exfoliating temperature.?2?For the purpose of developing the green exfoliation strategy of graphene,we have investigated the feasibility of graphene exfoliation from the pre-treated graphite?graphite was treated via using CH₄N₂O₃ and H₂O₂ followed by microwave irradiation?by using H₂O₂ under assistance of microwave?MW?irradiation.The results demonstrated the pre-treated graphite was successfully exfoliated to graphene nanosheets by using H₂O₂under assistance of MW irradiation.?3?For the purpose of developing the green exfoliation strategy of graphene,we have investigated the feasibility of graphene exfoliation by using C₂H₄O₃ under assistance of MW irradiation.The results showed graphite was successfully exfoliated to graphene nanosheets by using C₂H₄O₃ under assistance of MW irradiation.A?100%yield of graphene has obtained after another chemical agent-H₂O₂ was introduced in the C₂H₄O₃exfoliation system.?4?In order to investigate the effectiveness of C₂H₄O₃-based green chemical exfoliation system on the exfoliation of other layered materials,we also has attempted to exfoliate two other typical layered materials-hexagonal boron nitride?bulk h-BN?and molybdenum disulfide?bulk MoS₂?in this exfoliation system.Similarly,the results showed that the C₂H₄O₃-based chemical exfoliation system can effectively exfoliate bulk hBN and bulk MoS₂ under the assistance of MW irradiation.This method provides a new technical strategy in preparing other two dimensional nanosheets due to its universality.