Synthesis And Characterization Of Photo-responsive Organic Conjugated Molecules And Carbon Nanotubes

With the increasing development of advanced optoelectronic devices, the design and synthesis of photoresponsive organic conjugated compounds and nanocomposites have received more attention due to their potential applied value. The electron interaction among the conjugated systems and the variation of steric hindrance and dipole moment in different conjugated compounds functionalized with photo-responsive chromophore were investigated. In this dissertation, photo- responsive azobenzene moiety was functionalized to perylene imide derivatives and multi-walled carbon nanotubes (MWCNT) respectively to discuss the change of microstructure, photoelectric properties and photoisomerization.1. The photo-responsive perylene diimide-azobenzene dyad (PDI-AZO) was synthesized by covalently adjoining azobenzene chromophore to N-position of perylene diimide. Larger ordered one-dimension nanobelts were observed in PDI-AZO aggregate due to the strong molecule stacking. The part electron overlap betweenÏ€-conjugation of perylene imide and azobenzene chromophore led to the red-shifts bands of perylene ring and the decline of its energy level orbit. The PL quenching of PDI-AZO was dominated by the photoinduced excitons and energy transfer between azobenzene moiety and perylene imide. The large photochromism rate constant indicated the distinct photoresponse of PDI-AZO.2. The acid modification led to the existence of carboxyl group on the surface of well-dispersed MWCNT. The photo-responsive PDI-AZO/MWCNT was prepared byÏ€-Ï€electron stacking between nanotubes and PDI-AZO. TEM showed the well-regulated ordered structure of PDI-AZO/MWCNT films. The absorption in ultraviolet and visible light regions of PDI-AZO/MWCNT was enhanced due to the effect of MWCNT. The red-shifted bands in optical spectra arose from theÏ€-stacking between MWCNT and PDI-AZO. The evident quenching in PL spectra of PDI-AZO/MWCNT was attributed to the absorption and scattering of excitons and energy transfer of MWCNT due to the electron interaction. The decreased photochromism rate was ascribed to the restricted photoisomerization of PDI-AZO/MWCNT.3. Azobenzene chromophore-modified multi-walled carbon nanotubes (AZO- MWCNT) and dodecane-attached multi-walled carbon nanotubes(MWCNT-CONH -C₁₂H₂₅)were synthesized by functionalizing azobenzene moiety and dodecane chains on the side wall of MWCNT respectively via the covalent bond. The XRD result showed the increase of microcrystalline structure in PDI-AZO films. The compact organic coated layers were both observed on the side-wall of MWCNT. The grafted efficiency of AZO-MWCNT and MWCNT-CONH-C₁₂H₂₅ was 3.76% and 5.33% respectively. The red-shifted absorption bands were attributed to the part electron overlap betweenÏ€-conjugation of azobenzene chromophore and MWCNT. The PL quenching of MWCNT-AZO was ascribed to the scattering of excitons and energy transfer of MWCNT due to the electron interaction. The results of polarized light absorption preliminarily indicated photo-induced alignment of AZO-MWCNT in the direction parallel to the electric field vector of polarized light due to the photo-orientation of azobenzene chromphore. This result offered a great promise to the further development of photo-induced ordered carbon nanotunes film.