The Synthesis Of Two-dimensional Organic/Inorganic Nanohybrids And Their Nonlinear Optical Properties

With the development of laser science,nonlinear optics as an independent discipline has also experienced a rapid development.In recent years,the third-order nonlinear optical materials have received increasing attention.The nonlinear optical materials,which present saturated absorption,reversed saturation absorption,nonlinear refraction,can be applied in mode-locked laser,laser protection and light switches etc.Graphene and two-dimensional materials have attracted much attentions in recent years,while very limited investigation on their nonlinear optical properties have been conducted.As electrons in the 2D nanomaterials are confined to a plane of single atomic layer,these materials exhibit different optical and electrical properties compared with the bulk material.This work focuses on the nonlinear optical properties of organic-inorganic hybrids consists of graphene,transition-metal dichalcogenides?MoS₂,WS₂ etc.?and organic semiconductors.We have studied the third-order nonlinear optical properties of the materials in solutions and polymer films using the Z-scan technique and transient absorption spectroscopy.The main works include the following parts:1.We prepared a new nanohybrid consisting of uniform PbS quantum dots?QDs?attached on the reduced graphene oxide,named rGO-PbS,via a phosphine-free method.We also studied the nonlinear optical properties by open aperture Z-scan technique.The rGO-PbS nanohybrid exhibited superior optical limiting properties to either graphene oxide or PbS QDs upon both 532nm and 1064 nm excitation in the nanosecond laser pulse regime.Meanwhile,the thin films containing the rGO–PbS nanohybrid dispersed in polymethylmethacrylate?PMMA?also showed excellent optical limiting properties with high transparency.2.We have developed a facile method for the exfoliation and dispersion of MoS₂ in organic solvents with the assistance of P3HT for the first time,which significantly improves the solubility and dispersion of the MoS₂ in organic solvents.Furthermore,unusually efficient optical limiting response of the nanohybrid was discovered by Z-scan technique,which is in contrast to the saturated absorption behavior shown by the individual compartments.3.We have prepared the nonlinear optical devices based on WS₂ and TiC nanomaterials.WS₂and TiC based saturable absorber were preapred by depositing these nanomaterials on gold mirror.Using these saturable absorber in linear Tm³⁺fiber laser cavity,we obtained stable third-order harmonically mode-locked dissipative solitons at²?m.4.We report that pentacene derivatives exhibit giant nonlinear optical response at 532 nm.The superior optical limiting behaviors can be attributed to an excited state absorption mechanism associated with large absorption cross sections due to singlet fission process.We obtained a new benchmark of optical limiting onset of 2 mJ cm^-2 which is lower than that of C₆₀ with a concentrated solution.We also doped these molecules in the polystyrene polymer film matrices which show good optical limiting performance too.