Preparation Of ZnO Nanomaterials And Its Applications In The Environmental Analysis

With the rapid development of modern agricultural and industrial, the problem of environmental pollution is growing serious. Because Persistent Organic Pollutants(POPs) possess the properties of chronicity, cumulative, semi-volatile and highly toxic,so there are serious harm on human health and environment. And POPs are small toxic molecules, it is not easy to preparate their antibodies. Nanomaterials have unique properties associated with its surface effects, volume effects and quantum size effects,making it a center of research interests both in fundamental science and applied research. We select 2,3’,4,5’,6-pentabromodiphenylether(BDE-121) of polybrominated diphenyl ether(PBDEs) as the target molecule by preparing the corresponding antibody for immuneanalysis. From the aspects of ZnO nanomaterial structure and modified, we systematically studied the performance of the ZnO composites and the applications in photocatalytic degradation, the field of biological sensors. In this thesis,with the rapid analysising and remove the organic pollutants as goal, to improve the photoelectrical activity of the ZnO nanomaterial, we carry out the basic research in the field of function of ZnO nano-composite materials in biosensing and removal of organic pollutants. The details are summarized as follows:(1) Preparation of ZnO nanomaterials: The three-dimensional, macroporous ZnO nanosheet(NS) is electrodeposited on conductive glass substrates in a standard three electrode system; The 1D ZnO nanowire is synthesized via a simple low-temperature hydrothermal method; The hierarchical ZnO nanorod-nanosheet derives from electrodeposited ZnO NS arrays were synthesized by combining a low-temperature electrodeposition process and subsequent aqueous chemical growth. We preliminary discuss on the growth of the ZnO mechanism and the effects of hydrothermal parameters for the structure and morphology(in chapter 2).(2) Modification and photoelectrochemical properties based on ZnO NS:Zn S/Cd Te/Mn-Cd S/Zn S sensitized three-dimensional macroporous ZnO NS photoelectrode has been prepared by electrodeposition and successive ion layer adsorption and reaction method(SILAR). The photoelectrode performances were significantly improved through the coupling the core/shell Cd Te/Mn-Cd S quantum dots(QDs) with ZnO NS, and the introduction of the Zn S layer as a potential barrier.The photocurrent density systematically increases from ZnO NS to Zn S/Cd Te/Mn-Cd S/Zn S/ZnO(6.23 m A/cm2). More important, theZn S/Cd Te/Mn-Cd S/Zn S /ZnO NS photoelectrode provides a remarkable photoelectrochemical cell efficiency of 4.20 %. Meanwhile, photocatalytic performance of the prepared photoelectrode was investigated by photodegradation of organic pollutants(in chapter 3).(3) Label-free photoelectrochemical immunoassay for BDE-121 detection: A novel photoelectrochemical(PEC) immunosensor for the rapid detection of2,3’,4,5’,6-pentabromodiphenylether(BDE-121) was developed by coating a core-shell Zn S/Cd Te/Mn-Cd S/Zn S sensitized macroporous ZnO NS photoelectrode with anti-BDE-121 polyclonal antibody; The macroporous ZnO NS contributes a high loading of sensitizer and high capacity of the target analytes for use in PEC immunoassay, leading to high responses; After introducing core-shell Cd Te/Mn-Cd S quantum dots(QDs) and the Zn S buffer layers between different interfaces, the photoresponse was enhanced, which benefits the signal amplification. The BDE-121 was detected by monitoring the changes of the photocurrent signals of the immunosensor resulting from the immunoreaction. The immunosensor is sensitive,stable and high specific toward BDE-121, displaying a linear range of 5.0×10-12 M to1.0×10-7 M with a limit of detection of 3.98 p M. BDE-121 in paint samples was analyzed with the proposed sensor and gas chromatography-mass spectrometry(GC/MS). The analysis of BDE-121 in paint sample illustrated the applicability of the immunosensor(in chapter 4).(4) Labeling photoelectrochemical immunoassay for BDE-121 detection: Dual co-sensitized structure of Cd Te/Mn-Cd S/ZnO nanorod-nanosheet was designed to develop a novel lable photoelectrochemical immunoassay for highly sensitive detection of BDE-121. Then was employed as matrix for immobilization of anti-BDE-121 antibody, whereas water-soluble TGA-capped Cd Te QDs linked to BSA-BDE-121 were used for signal amplification via the specific antibody-antigen immunoreaction. Greatly enhanced sensitivity for BDE-121 detection was derived from the new co-sensitization signal amplification strategy. First, the Cd Te/Mn-Cd S/ZnO co-sensitized structure extended the absorption range to long wavelength, which adequately utilized the light energy. Second, the co-sensitized structure possessed stepwise band-edge levels favoring ultrafast transfer of photogenerated electrons and significantly prompted the photoelectrochemical performance. Because BDE-121 is a small molecule, so a novel immunoassay based on the competitive binding of anti-BDE-121 antibody with BDE-121 antigen and Cd Te QDs-BDE-121 bioconjugate was developed, and it exhibited a wide linear range from1.0×10-12 M to 5.0×10-8 with a low detection limit of 0.25 p M for BDE-121 detection.And also opened up a new promising platform for detection of other small molecule(in chapter 5).(5) Fluorescence immunoassay for BDE-121 detection: Because the BDE-121 itself has not fluorescent properties, so it is of great significance for BDE-121 to construct the fluorescence immunoassay. Fluorescent dye(FITC) and quantum dots(CQDs) usually used as fluorescent probe in biological labeling. We combine both FITC and CQDs by linking BSA, which become complex fluorescent probe, based on the F?rster resonance energy transfer(FRET) for BDE-121. Selective and sensitive responses to BDE-121 are achieved with a linear range of 5.0×10-10 M to1.0×10-7 M and a LOD of 0.5 p M. Because BDE-121 is quantified based on the fluorescence ratio,the sensor-to-sensor difference is greatly eliminated. And the experimental illustrated that the result of detection BDE-121 is better than separate labeling with FITC or CQDs(in chapter 6).