| In the past decade, zinc oxide(ZnO) nanorod arrays have attracted tremendous attention in the field of nanoscience due to their high surface to volume ratio, excellent optical, electrical and chemical properties, low cost, defined alignment and good biocompatibility. Narrow band gap semiconductor nanoparticles or quantum dots(QDs) possess high fluorescence quantum yields and good optical properties. Meanwhile, the band gap of quantum dots can be controlled to match with the visible-near IR spectrum region of solar energy. They will generate multiple exciton per incident photon, so the potential energy conversion efficiency is very high. Loading of narrow band gap QDs to 1D ZnO nanomaterial can not only have both excellent properties, but also generate new synergy effect in the following:(1) ZnO nanorod arrays not only can increase the loading of QDs due to the high surface to volume ratio, but also can offer a direct channel to facilitate the electron transfer to the substrate and then obviously improve their photo-electric properties.(2) QDs has a narrow band gap matching most range of the solar spectrum, therefore, coupling QDs with ZnO nanorod arrays give rise to extension of the sensitiving of ZnO into the visible region.(3) In addition, constructing of type II heterojunction stucture with wide band-gap ZnO and narrow band-gap QDs can facilitate the electron transfer and charge seperation due to the proper band alignment.Using different coating strategies, we fabricated the QDs encapsulated ZnO nanorod arrays. The hetergeneous core-shell structures have unique optical and electrical properties which make them better untilized in the field of photocatalytic degradation of organic pollution and ECL detection of cancer cells. The main contents of this thesis are summarized as follows:ZnO nanorod arrays have been prepared by hydrothermal method and the effects of growth reaction have been investigated. It has been revealed that the high concentration of precursors and with theassist of the seed layer can facilitate the growth and get the vertical and uniform nanorod array. We further investigated the relationship of growth time and the nanorod length. In the case of no change of fresh precursors, the length of the ZnO NRs has no obvious increase even we extend the growth time. But in the case of change the fresh precursors every 2.5 h, the length of the ZnO NRs has linearly increased with the growth time.Vertically aligned QDs encapsulated ZnO nanorod composites are constructed on the indium tin oxide substrates by layer-by-layer deposition of Cd Te quantum dots on ZnO nanorod arrays and by successive ionic layer adsorption of Cd S quantum dots on ZnO nanorod arrays. Using SEM, TEM, XRD and EDX techniques, they all proved the existence of the QDs shell. The obtained QDs-ZnO nanocomposites exhibit good photo-electric properties:(1) The existence of the QD shell results the signi?cant PL quenching of ZnO and QDs, which should be attributed to separation of photo-generated charge carriers driven by the proper band alignment between ZnO and QDs.(2) The steady and prompt photocurrent generation is obtained by QDs-ZnO NRs composites. The photoelectrochemical properties of the composites are influenced by the length of the ZnO nanorod and the deposition cycles of the QDs. The results show that the composites have the best photoelectrochemical properties with 10 h growth time of ZnO NRs and 20 deposition cycles of QDs. Furthermore, we discussed the influence of two deposition strategies and the eletrolyte to the photoelectrochemical properties.(3) Cd S/ZnO nanorod composite exhibits good electrochemiluminescent property. Based on the electrochemiluminescent property of Cd S QDs encapsulated ZnO nanorod arrays, we fabricated a novel ECL immunsensor for the detection of cancer cells. Then we characterized the fabrication process, optimized the conditions and applied it to the detection of Hep G2 cancer cells. A broad detection range from 300 to 10000 cells per m L is achieved, with good selectivity and reproducibility. Furthermore, ZnO NRs and APTES effectively enhance the ECL signal of as-prepared immunosensor, and the related underlying mechanisms have been discussed. The developed ECL immunosensor has great potential for the pre-diagnosis of cancers.Cd Te/ZnO and Cd S/ZnO nanorod composites for photo-electric synergy degradation of phenols under visible light have been studied. The comparison of the direct photolysis, electrolysis, photocatalysisand photoelectrocatalysis with QDs-ZnO nanorod composites shows that the TOC removal of photoelectrocatalysis is 50-fold of photocatalysis. It highlights that there is an obvious synergetic effect between the electrochemical process and the photocatalytic process, and it results in the good mineralizing ability. We discussed the influence of visible light absorption, the change of band gap and band structure, charge separation and polymer to the photoelectrocatalytic properties. Furthermore, we systematically studied the factors such as p H value, initial concentration, oxgen environment, hole scavenger and hydroxyl radical scavenger, which have remarkable influence on the photoelectrocatalytic performance. ESR spin-trap with 5, 5-dimethyl-1-pyrroline-n-oxide(DMPO) demonstrated that hydroxide radicals were indeed generated in the reaction and disclosed that Cd Te QD/ZnO nanorod arrays have the stronger ability to produce hydroxyl radicals. Subsequently, we monitored the intermediates of photoelectrochemical degradation of phenol by UPLC and GC-MS. During the course of photoelectrochemical degradation of phenol, the common intermediates from phenol oxidation such as catechol, benzoquinone, aromatic carboxylic ac ids and fumaric acid could not be detected in this process, and only very trace amounts of intermediates occurred, which reveals that the mineralization rate via the photoelectrochemical treatment is very high. At last, on the base of the above research results, a possible charge transfer diagram is proposed to elucidate the routes of charge carrier transfer and phenol degradation. |
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