The Synthesis And Photorefractive Performance Of Inorganic-organic Hybridized Nanocomposite Sensitized By CdS Nanoparticles

Fiber optic sensing technology is a new technology of monitor supervision withthe development of optical fiber communication. The basic of fiber optic sensingtechnology is the high performance photosensitive materials.Financially supported by the Key Project of National Natural Science Fund ofChina (NO. 60537050) and Open Fund of Key Laboratory of Nonferrous Materialsand Processing Technology (No.kfjj200507), in this thesis, a new photorefractive(PR)polymeric nanocomposite photosensitized with inorganic semiconductornanoparticles was designed and synthesized from the basic theories, materials design,structure and performances. These novel inorganic-organic hybridizednanocomposites sensitized with CdS nanoparticles presented PR effect withoutexternal field, which was significant for the development of PR polymer's theoriesand applications, as well as for the manufacture and applications of new type fibersensors. The main contents include:1. The effect of photovoltaic field on the space charge field was discussed inorder to provide the theoretic base of overcoming the external field in PR polymer.2. The inorganic-organic hybridized nanocomposites sensitized with CdSnanoparticles were synthesized by physical blend and chemical hybridization,respectively. The charge transport between polymer and CdS was studied, as well asits photoconductive performance.3. A new nonlinear optical (NLO) chromophore 1-n-butoxy-2-methyl-(4-p-nitropheylazo) benzene (BMNPAB) was synthesized by azo-coincidence reaction andcharacterized by ¹H-NMR, IR, UV-Vis, DSC etc. The HOMO level and NLOperformance of BMNPAB was studied.4. New PR systems of PVK/BMNPAB/CdS and PVK-10-CdS/BMNPAB wereprepared by the guest-host approach. The PVK-CdS nanocomposites prepared bychemical hybridization exhibit the significant enhancement of photoconductivity ascompared to CdS/PVK nanoblends owing to the improved interface quality betweenCdS and PVK, and it can overcome the phase separation between polymers andsemiconductor nanoparticles. Two-beam coupling (TBC) experiment clearly indicated an asymmetric optical energy exchange between two beams on the PR samplePVK-CdS/BMNPAB at zero electrical field, and the two-beam coupling gain (Γ) of50.0cm^-1 and diffraction efficiency (η) of 4.2% were obtained at 647.1nm wavelength.Comparing withΓ=31.7cm^-1 of PVK/BMNPAB/CdS system, the PR performance ofPVK-CdS/BMNPAB system is enhanced because CdS nanocomposites prepared bychemical hybridization can increase the generation speed and electric field intensityof the internal space electric field.5. A novel bi-functional PR poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl(PVNPAK) with carbazolyl fragments and chromophoric azophenyl was synthesizedby a post azo coupling reaction and characterized by ¹H-NMR, elemental analysis,UV-Vis absorption and IR spectroscopy. The calculated SHG coefficient of 4.7 pm/Vis obtained at 1064nm in the unpoled PVNPAK film. Two-beam coupling gain (Γ) of11.89cm^-1 and diffraction efficiency (η) of 3.2% were obtained in PVNPAK/CdS/ECZsample at room temperature without external electrical field or prepoling in TBCexperiment. At an applied electric filed of 6V/μm, PVNPAK/CdS/ECZ sampleexhibited better PR performance withΓ=19.66cm^-1 andη=5.1%. The possibleforming process of all-optical PR effect was suggested based the "self alignment"effect of azo chromophore in PVNPAK.6. The PVNPAK-CdS nanocomposites were successfully obtained by chemicalhybridization. Photoelectrical properties were revealed by the generation ofphotocurrents on illumination. It was shown that the use of CdS nanoparticles as asensitizing agent resulted in a considerable enhancement of the photoconductivity inthe nanocomposites. TBC measurement was carried out to determine the PRperformance in the optically transparent films formed by adding 25% ECZ toPVNPAK-CdS nanocomposites.Γ=14.26cm^-1,η=3.4% in PR samplePVNPAK-5-CdS/ECZ andΓ=16.43cm^-1,η=4.44% of PVNPAK-15-CdS/ECZ wereobtained in TBC experiment at zero electrical field, respectively. These phenomenarevealed that the all-optical PR materials might have many potential advantages indevice fabrication application and further development of PR properties.