可溶性聚噻吩甲烯包覆碳纳米管的三阶非线性光学响应

采用原位聚合的方法合成了聚(3-己基噻吩)-2,5-二(4-羟基-3-甲氧基苯甲烯)包覆的多壁碳纳米管(PHTHMOBQ/MWNTs). 荧光光谱分析表明, PHTHMOBQ/MWNTs复合体中, 碳纳米管与共轭聚合物PHTHMOBQ之间形成光致电子转移体系, 使得π电子离域程度增加, 并且导致荧光量子效率降低. 根据E_g与入射光子能量hν的关系, 拟合了PHTHMOBQ/MWNTs薄膜的光学禁带宽度. 发现随着碳纳米管含量的增加, E_g逐步减小. 采用简并四波 关键词： 共轭聚合物 碳纳米管 光致电子转移 三阶非线性光学效应

Third-order nonlinear response of conjugated polymer coated carbon nanotubes

Carbon nanotubes coated with an nonlinear optical (NLO) polymer, poly［3-hexylthiophene-2,5-diyl］-［3-methoxyl-4-hydroxyl-benzylidenequino-methane］(PHTHMOBQ/MWNTs), were synthesizedvia in-situ polymerization. The micrograph of PHTHMOBQ/MWNTs has the coaxial tubular structure, which indicated that the polymer was restricted and wrapped on the surface of carbon nanotubes while propagating during polymerization. PHTHMOBQ/MWNTs showed fluorescence quenching, which involved the inter-molecular photo-induced charge transfer process. Third-order nonlinear susceptibility χ⁽³⁾ and second-order hyperpolarizability γ of PHTHMOBQ/MWNTs were measured using degenerate four wave mixing at 532nm under nanosecond pulse excitation. The two pump beams were vertically polarized and the probe beam was horizontally polarized to avoid thermal effect. The third-order NLO responses were enhanced gradually when nanotube content increased, which was attributed to inter-molecular photo-induced electron transfer between PHTHMOBQ and MWNTs.