Preparation And Properties Of Porphyrin Derivatives And Molybdenum Disulfide Composites

In recent years,two-dimensional layered transition metal disulfides with nonlinear optical properties have been widely used in optical storage,optical communication,optical switching and optical limiting.Molybdenum disulfide（MoS₂）is a typical layered material that can act as an energy acceptor to initiate complex energy transfer processes.This feature also provides a variety of possibilities for electron or energy transfer based on the prepared composites.However,the reactivity of MoS₂ is poor,and it is still a great challenge to improve the nonlinear optical properties of MoS₂ by surface modification.Porphyrin is a typical organic macrocyclic molecule with strong reverse saturable absorption properties and is an excellent optical limiting material.A series of new organic-inorganic composite nonlinear optical materials can be prepared by modifying MoS₂ with porphyrin and its derivatives.The nonlinear optical properties of MoS₂ are improved by the electron or energy transfer generated in the composite material.Based on this,the main research work of this study is as follows:1.Firstly,amino-modified MoS₂-NH₂ was obtained by inserting cysteamine into pre-treated MoS₂ nanosheets with sulfur vacancies on the surface.Secondly,the synthesized5,10,15,20-tetrakis（4-carboxyphenyl）porphyrin（TCPP）was covalently connected with MoS₂-NH₂ by amide bond to obtain MoS₂-TCPP.Compared with TCPP,MoS₂-TCPP had fluorescence quenching,and the quenching degree was 95%.Moreover,MoS₂-TCPP also has better thermal stability.Finally,the nonlinear optical properties of MoS₂-TCPP composites were studied by Z-scan technique.The third-order nonlinear absorption coefficient（β）of MoS₂-TCPP composite is 4.3×10^-10 m/W,and the third-order imaginary part polarizability(Im[χ^（3）])is 1.41×10^-11 esu,which is significantly higher than that of MoS₂.This is attributed to the accumulation of nonlinear optical properties of MoS₂ and TCPP,and the electron or energy transfer between the two materials.2.The porphyrin molecules on MoS₂-TCPP were used as active growth sites to directly grow porphyrin-based metal-organic frameworks（MPF）.MoS₂-Cu MPF and MoS₂-Zr MPF composites with stable structure were prepared by combining MoS₂ with MPF.Theβvalues of MoS₂-Cu MPF and MoS₂-Zr MPF are both 6×10^-10 m/W,and the Im[χ^（3）]value are both1.97×10^-11 esu.Compared with MoS₂-TCPP,MoS₂-MPF composites have better nonlinear optical properties.This can be attributed to the charge transfer between the porphyrin ligand and the metal in the MPF material and the electron or energy transfer between the porphyrin and MoS₂.3.Using polymethyl methacrylate（PMMA）as the matrix,a certain amount of MoS₂-TCPP,MoS₂-Cu MPF and MoS₂-Zr MPF were incorporated into PMMA to prepare optical plastics MoS₂-TCPP/PMMA,MoS₂-Cu MPF/PMMA and MoS₂-Zr MPF/PMMA with good optical uniformity and transparency.Theβvalue of MoS₂-TCPP/PMMA is 8×10^-10 m/W,and the Im[χ^（3）]value is 2.63×10^-11 esu;theβvalue of MoS₂-Cu MPF/PMMA is 1.8×10^-9 m/W,and the Im[χ^（3）]value is 5.92×10^-11 esu;theβvalue of MoS₂-Zr MPF/PMMA is 1.7×10^-9 m/W,and the Im[χ^（3）]value is 5.59×10^-11 esu.These materials have certain optical limiting characteristics and can be processed into optical limiting devices for laser protection.Compared with in organic solvents,the improvement of nonlinear optical properties of optical plastics can be attributed to the inhibition of porphyrin aggregation in plastic matrix.