Research On The Preparation And Properties Of End-functionalized P3HT And P3HT/CdS Nanocomposites

Poly 3-hexyl thiophene (P3HT) is one kind of conjugated conducting polymers with good solubility, environmental stability and processing performance, and it has very special photoelectric properties. Nanocomposites composed of P3HT and semiconductor nanocrystals have perfect performances which are closely related to the interface of two phase. The organic-inorganic nanocomposites linked together by chemical bonds have been of great interest for many years on account of their good properties, because the compatibility of their interface is better, and the occurrence of charge transfer at the nanocomposites interface is evident. The major research works of this article were as the following:(1) The synthesis and characterization of end-functionalized P3HT. Regioregular P3HT was prepared from 2,5-Dibromo-3-hexylthiophene through the Grignard metathesis (GRIM) reaction, and then reacted with diethylchlorophosphate or CO2 to yield phosphonic ester end-functionalized P3HT and carboxylate end-functionalized P3HT respectively.The two as-prepared end-functionalized P3HT were characterized by proton nuclear magnetic resonance (1H NMR) spectroscopy, fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectra. The results of 1H NMR and FTIR show that the successful synthesis of P3HT, phosphonic ester end-functionalized P3HT and carboxylate end-functionalized P3HT. Compared with P3HT, the UV-Vis Spectra of the phosphonic ester end-functionalized P3HT and the carboxylate end-functionalized P3HT show low blue shifts, and the fluorescence intensity are decreased.(2) The synthesis and characterization of P3HT/CdS nanocomposites. In this article, we report a direct synthesis to prepare two kind of P3HT/CdS nanocomposites linked together by chemical bonds with cadmium acetate dehydrate (Cd(OOCCH3)2.2H2O) used as cadmium source, sulfur powder (S) as sulfur source, dichlorobenzene (DCB) and dimethyl sulfoxide (DMSO) as cosolvent, phosphonic ester end-functionalized P3HT and carboxylate end-functionalized P3HT as the conjugated polymer template respectively. The effect of the reaction temperature, the molar ratio of S to Cd as well as the DCB/DMSO volume ratio was studied. In order to explore the optimal reaction conditions of P3HT/CdS nanocomposites, the two as-prepared P3HT/CdS nanocomposites were characterized by X-ray diffraction (XRD) patterns, transmission electron microscope (TEM), FTIR spectroscopy,1H NMR spectroscopy, UV-Vis and PL spectra. The results show that the size and distribution of CdS nanocrystals are not only temperature-dependent, but also greatly influenced by the S/Cd molar ratio and the DCB/DMSO volume ratio. CdS nanocrystals are dispersed uniformly in the two P3HT/CdS nanocomposites, which indicated that end-functionalized P3HT can be used as a template to prevent CdS from aggregating effectively. Up to 69.1% of the PL intensity of phosphonic ester end-functionalized P3HT is quenched and the percentage of carboxylate end-functionalized P3HT is 71.7%, which suggested the charge transfer between CdS and the two end-functionalized P3HT. The charge transfer and photovoltaic property of carboxylate end-functionalized P3HT are better than phosphonic ester end-functionalized P3HT. The identification to different metal ions of the two as-prepared P3HT/CdS nanocomposites was studied. The results show that these two nanocomposites can detect Hg2+ only, and carboxylate end-functionalized P3HT/CdS nanocomposites have higher sensitivity than phosphonic ester end-functionalized P3HT/CdS. The carboxylate end-functionalized P3HT can detect Hg2+ with concentration of 10"5, which indicated that it has potential applications in fluorescent probe of the selectivity of Hg2+.