The Nonlinear Optical Properties And Photocatalytic Applications Of Two Dimensional Graphdiyne Materials

Graphdiyne(GDY),a new two-dimensional(2D)carbon allotrope,has recently evoked burgeoning research attention in the field of storage,separation,catalysis,photoelectronic and beyond,for its intrinsic bandgap along with a high carrier mobility and extended?-conjugation compared with most conventional carbon materials.In this thesis,GDY powder and film were synthesized via two different methods,and its optical property including nonlinear optical property(NLO)and photocatalysis were studied.Besides,GDY was applied in nonlinear photonic diode.The third-order nonlinear optical response of GDY dispersed in several common solvents(alcohols)were experimentally probe using a femtosecond Z-scan technique.Z-scan spectral analysis indicated that GDY can show a self-defocusing effect.The measured nonlinear optical refractive index is in the order of?10^-8 cm² W^-1,which is approximately one order of magnitude higher than that of most 2D materials.The enhancement is most likely connected to the presence of more complex delocalized?conjugation and the intrinsic bandgap of GDY.In particular,different NLO responses can be observed from GDY when dispersed in different solvents,and the NLO refractive index of 1-propanol dispersion(1.4×10^-8 cm² W^-1)greatly outperforms those of n-butanol(3.6×10^-9 cm² W^-1),methanol(1.0×10^-9 cm² W^-1)and ethanol(1.5×10^-10 cm² W^-1)dispersions.It is proposed that some intrinsic properties of solvents,including polarity and viscosity,could influence the NLO response of GDY materials.Nonlinear photonics response of 2D GDY material has been revealed by the spatial self-phase modulation(SSPM)method for the first time.The results showed that GDY could exhibit a strong light-matter interaction with high stability to achieve a broadband Kerr nonlinear optical response.Taking advantage of the unique Kerr nonlinearity of GDY and reverse saturable absorption of SnS₂,a novel nonlinear photonic diode which used the hybrid structure of the 2D GDY/SnS₂ was constructed.The performance for the proposed GDY/SnS₂-based nonlinear photonic diode at different wavelengths were checked.SSPM measurements show that this configuration could realize the unidirectional diffraction rings excitation,and this phenomenon of the nonreciprocal light propagation indicating its good advance of application in passive photonic diode.In addition,a new similarity comparison method to estimate the nonlinear refractive index of GDY and SnS₂was proposed.The results show that the GDY has a high similar contrast(?90%)by comparing to SnS,illustrating that the GDY can have a large nonlinear refractive index(?10^-5 cm² W^-1),comparing favorably to that of graphene.The photocatalytic performance of GDY in the visible range was studied.GDY-hybridized nitrogen-doped TiO₂ nanosheets with exposed(001)facets(GDY-NTNS)were prepared via a facile hydrothermal reaction and utilized as photocatalyst for the photodegradation of rhodamine B(Rh B)under visible light illumination.The resultant GDY-NTNS composites exhibit superior visible light photocatalytic activity than that of the bare TiO₂ nanosheets(TNS)and nitrogen-doped TiO₂ nanosheets(NTNS).Nearly about 90%of Rh B has been decomposed by GDY-NTNS composites within240 min under visible light irradiation,and the apparent reaction rate constant of GDY-NTNS composites is approximately 1.6 times faster than that of the NTNS and 4 times faster than that of the pure TNS.The introduced GDY can act as the electron pool to facilitate photoinduced electron separation and the nitrogen doping broadens its scope of visible light absorption.Besides,the mechanism studies suggest that h⁺and·O₂^-are responsible for the efficient degradation of Rh B,while OH^·was not the predominant active species toward Rh B decomposition.This work was of great significance for exploring novel nonlinear optical materials and photocatalysts with high performance.