Design, Synthesis, Structure And Nonlinear Optical Property Of Novel Charged Organic Compouds

Organic nonlinear optical (NLO) materials have attracted more and more attentionin the past few decades due to their promising applications in the areas oftelecommunications, sensors, information technology and many advantages overinorganic materials such as strong NLO effect, ultrafast response, good processbilityand low price etc. However, the NLO materials that have been studied are mainlythose with traditional organic D--A chromophores, while the study on the chargedorganic compouds has been much less. In the past few years, the research havedemonstrated that zwitterion reveal unprecedented hyperpolarizabilities (μβ) and verylarge electro-optic coefficients (r33) and the charged organic compouds have thelargest third-order nonlinear susceptibilities ((3)). Searching for new charged organiccompouds has become one of the new frontiers in the field of organic NLO materials.This thesis studies the molecular design, synthesis, structure and properties ofsome novel organic second-order, third-order NLO materials, with an emphasis on thecharged organic compouds. It is expected to explore the relationship between thestructure of charged organic compouds and the NLO properties and thus support NLOmaterials throry developmenting.The main contents of the thesis are as the following.Chapter1gives a brief introduction on nonlinear optics and organic NLOmaterials, including NLO effects, the design theory, the D--A structure, the kindsand the measurement techniques of organic NLO materials. We review the recentprogress of charged organic compouds as organic second-order and third-order NLOmaterials and the relationship between structure and NLO properties. Then, theresearch strategies and the main contents of the thesis are presented.In chapter2, three types of zwitterion were designed and a novel type of zwitterion was synthesized and characterized by IR, UV-Vis spectra,1H NMR,13CNMR and mass spectra. The thermal, linear and nonlinear optical properties of thezwitterion were analyzed and measured. The results show that the zwitterion hasstrong NLO effect, good transparency and thermal stability. We also studied themethodology of synthesis of terminal dicyanomethyl via Pd-catalyzed cross couplingof aryl halides and sodium dicyanomethanide which can apply in zwitterion synthesis.In chapter3, we have designed and synthesized a novel ionic liquid. The structurewas confirmed by NMR and the melting point was measured. By compared, we thinkthe ionic liquid has good second-order NLO properties. This ionic liquid can use as areactant to synthesize another novel zwitterion.In chapter4, a kind of cyanine was designed and synthesized. Using thepicosecond laser and Z-scan technique, cyanines’ third-order NLO properties weremeasured. The study shows that cyanines are not excellent third-order NLO materialsunder800nm wavelenghten for their strong absorption. But our research shows thatcyanines are promising laser materials and mode-locker.Graphene was synthesized from graphite by wet-chemistry techniques in Chapter5. A graphene-polyvinyl alcohol composite is fabricated. The research shows both ofgraphene solutions and the composite have saturable absorption ability and the donorand acceptor have significant infection on NLO effect.