The Research On Nonlinear Optical Properties Of MoX₂?X=S,Se?nanocomposites

Because MoS₂ and MoSe₂ have narrow bandgap width?MoS₂,1.2¹.9 eV;MoSe₂,1.1¹.5 eV?,and tunable excitation photoelectric effect,they have great potentials in the fields of photoluminescence,phototransistor,solar cells,nonlinear optics and other aspects.However,pure MoS₂ and MoSe₂ have high photogenerated recombination rates,limiting their applications in some optical fields.By designing nanocomposites of MoS₂ or MoSe₂,the photogenerated recombination rate of these materials can be reduced and their application fields can be broadened.In this thesis,MoS₂ and MoSe₂ nanocomposites were prepared by simple methods.The two-dimensional layered MoS2 and MoSe2 nanosheets were combined withnanoparticles or nanorods.Integrating with the surface effect,small size effect and interfacial effect of ZnO,Fe₂O₃,CdS and CNT,the optical nonlinearity and optical limiting performance of MoS₂ and MoSe₂ composites were improved.The main contents of the thesis as following:1.Basing on strong linear absorption and photoelectric conversion of MoS₂ in visible range,and the characteristics of high band gap?3.37 eV?and high exciton binding energy?60me V?of ZnO,MoS₂/ZnO composite nanomaterials were prepared through growing ZnO nanoparticals on the surface of MoS₂ nanosheets by solvothermal methodfor the first time.MoS2/ZnO/PMMA plexiglass was prepared by mixing MoS2/ZnO composite nanomaterials with polymethyl methacrylate?PMMA?,and the nonlinear absorption,nonlinear scattering and optical limiting properties were studied by modified Z-scan technique for the first time.Experimental Results show that MoS2/ZnO/PMMA plexiglass has better optical nonlinearity,higher optical damage threshold and better performance in mechanical strength and flexibility than MoS₂/PMMA plexiglass.2.Basing on larger refractive index,higher third-order optical nonlinearity of Fe2O3,and the adjacent bandgap between Fe₂O₃ and MoS₂,MoS₂/Fe₂O₃ composite nanomaterials were prepared through growing Fe₂O₃ extra small nanoparticals on the surface of MoS₂ nanosheets by a solvothermal method for the first time.MoS2/Fe2O3/PMMA plexiglass was prepared and its optical nonlinear absorption characteristics and optical limiting properties were studied.The experimental results show that the MoS₂/Fe₂O₃/PMMA plexiglass exhibits anti-saturation absorption,and the tip of the anti-saturation absorption deepened with increasing of the input energy.Compared to Fe₂O₃/PMMA plexiglass,MoS₂/Fe₂O₃/PMMA plexiglass has enhanced optical nonlinear properties and higher optical limiting ability.3.Two kinds of metal sulfides of MoS₂ and CdS nanomaterials were composited through solvothermal method inspired by the excellent optical nonlinearity of MoS2 and CdS.MoS2/CdS nanocomposite was prepared by growing extra small CdS nanorods on the surface of MoS2 nano sheets.MoS2/CdS/PMMA plexiglass was prepared and its nonlinear absorption properties was studied for the first time.The experimental results show that MoS2/CdS/PMMA plexiglass exhibits a transition from saturation absorption to anti-saturation absorption,and the dip of anti-saturation absorption deepened with an increasing the input energy.Compared with CdS/PMMA plexiglass,MoS2/CdS/PMMA plexiglass has better optical nonlinear properties.4.CNT/MoSe₂ composite nanomaterials were first synthesized based on narrower band gap and lower light absorption coefficient of MoS2 than that of MoSe2 by growing MoSe2nanoparticles on the surface of CNT through a solvothermal method.CNT/MoSe2/PMMA plexiglass was prepared and its nonlinear absorption properties and optical limiting properties were studied.The experimental results show that CNT/MoSe2/PMMA plexiglass exhibits better anti-saturation absorption and higher optical limiting properties than MoSe2/PMMA and CNT/PMMA plexiglass.5.CNT/MoSSe composite nanomaterials were first synthesized inspired by better nonlinear optical performance of MoS,MoSe2 and CNT by growing MoSSe nanosheets doped with S and Se on the surface of CNT using a solvothermal method.The CNT/MoSSe/PMMA plexiglass was prepared and its nonlinear absorption and optical amplitude limiting performance were studied.The experimental results show that CNT/MoSSe/PMMA plexiglass exhibits better anti-saturation absorption and higher optical limiting properties than MoSSe/PMMA and CNT/MoSe₂/PMMA plexiglass.