Covalent Functionalization Of VA Group Two-Dimensional Materials And Their Optoelectronic Properties Study

After the boom of graphene,VA group 2D materials received an ever-grown attention due to their fantastic physical and chemical properties.As a direct semiconductor,black phosphorus exhibits an impressive high carrier mobility,anisotropy,excellent photo-catalytic and photothermal therapy behavior.Atimonene demonstrates a high electrochemical capacity,outstanding electrocatalytic and photoelectronic response,and impressive activity in catalyzing organic reactions.However,the poor stability of black phosphorus nanosheets hinders its further practical applications.Moreover,as another member of VA group 2D materials,antimonene also suffers from the low efficiency in preparation,lack of scale-up production and size controllable method due to its ultrashort layer distance.This thesis aims to develop high-efficient covalent functionalization method for black phosphorus nanosheets in order to improve its stability.Meanwhile,the intercalation method to prepare other 2D materials is used to produce Sb nanosheets with high efficiency,in a large scale and size controllable manner.The optoelectronic properties of both covalent functionalized black phosphorus nanomaterials and Sb nanosheets were explored.We have also developed three different 2D materials with the reverse saturable absorption behavior for the optical limiting application.The main works of this thesis are listed below:1.An efficient surface functionalization strategy for BP taking advantage of the high reactivity of diazonium salts on the negatively charged ultrathin BP nanosheets was developed for the first time.Based on this covalent functional method,not only the ambient stability of black phosphorus nanosheets is improved,but also the saturable absorption behavior is enhanced.Moreover,the surface bonded organic groups also provide a versatile platform for further surface functionalization to fabricate more complicated BP-based nanomaterials.Surface nitro groups were reduced into amine groups and gold nanoparticles were introduced to the surface of functionalized black phosphorus nanosheets through assembling.The hybrid material was applied in the catalytic reduction of 4-nitrophenol as catalyst and the catalytic behavior was investigated.2.We have synthesized a hybrid material based on the black phosphorus nanosheets covalently bonded with conjugated porous polymer via our negative charge strategy.The structure of this hybrid material was characterized in detail through scanning electron microscopy,X-ray photoelectron spectroscopy,etc.We proved the surface functional molecules can be further converted into anchor groups to construct more complicated structure.As a proof of concept,the electrochemical property of the hybrid material is investigated,providing a new way to extend the electrochemical application of this 2D material.3.We reported the covalent functionalization of liquid-phase exfoliated black phosphorus nanosheets with carbene for the first time.Apart from traditional conditions involving phase-transfer catalyst for the heterogeneous catalysis reaction,we developed the homogeneous catalysis for the carbene functionalization of black phosphorus nanosheets utilizing organic base with high efficiency.The reaction conditions were optimized and the plausible mechanism was discussed.Moreover,the third-order nonlinear optical property of the prepared material was studied.4.We have developed an ion intercalation method to fabricate Sb nanosheets for the first time.Due to the relative short layer distance of antimony,most of the reported preparation method based on liquid-phase sonication cannot meet the requirements of large scale,high efficiency and size controllable preparation.Based on a lithium ion intercalation method,an efficient fabrication of Sb nanosheets with scale-up and size-controllable manner is achieved.Using this method,we have systematically studied the solubility and stability of the prepared Sb nanosheets.The oxidation of Sb nanosheets in aqueous solution was studied,which is important for the high-quality production of Sb nanosheets.The third-order nonlinear optical behavior of Sb nanosheets was investigated systematically.Intensity-dependent and size-dependent behaviors of Sb nanosheets were observed.Transient absorption spectra on nanosecond and femtosecond scale were employed to study their carrier dynamics.5.We have prepared three different 2D materials through electron irradiation and chemical vapor deposition.The nonlinear optical behaviors of the prepared samples were investigated.The results showed that all of the three materials displayed reverse saturable absorption behavior and the nonlinear absorption coefficient is up to10^-9 m/W,which indicates these samples could be used in future laser protection applications.These results pave new ways to efficiently control and adjustment on the nonlinear optical response of 2D materials.