Growth Of Cobalt-Manganese Oxide Nanostructured Coatings On Nickel-Titanium Alloy Substrates And Their Applications In Solid-Phase Microextraction

Sample pre-treatment techniques play an important role in environmental analysis.SPME is a powerful sample preparation technique for the extraction,enrichment,separation,purification and sample introduction.Currently commercially available fused-silica SPME fibers suffer from their fracture,poor stability and selectivity,limiting their application in the analysis of complex matrices.To address these issues,it is particularly important to develop SPME fibers with high thermal and chemical stability and high extraction efficiency.For this purpose,cobalt-manganese oxides with different nanomorphologies were prepared in situ by hydrothermal reaction on a superelastic Ni Ti substrate and successfully applied to the enrichment and analysis of PAHs in environmental water samples.Chapter 1:This chapter provides a brief introduction to an overview of SPME technology and its current research and development,with a focus on currently developed coating materials and their properties,as well as applications of the developed SPME technology.Chapter 2:In this chapter,Mn Co₂O₄ nanoneedle bundles（Ni Ti@Mn Co₂O₄NBs）were successfully prepared on Ni Ti substrates by hydrothermal reaction for the first time and characterized by SEM,EDS,XPS and XRD.Their extraction selectivity was also investigated.PAHs were used as target analytes and compared with commercial fibers including PA and PDMS.The established SPME method was evaluated and successfully applied to the enrichment of trace PAHs in real water samples.The developed method showed satisfactory linearity in the range of 0.05-500μg·L^-1 with a correlation coefficient（R²）>0.9992 and a limit of detection（LODs）of 0.014-0.150μg·L^-1.Spiked experiments were performed with recoveries of 86.95%-105.0%and 85.57%-109.4%.Its high extraction selectivity for the target analytes was attributed to the large specific surface area of the fiber surface and the synergistic effect of two metal oxides.Chapter 3:Mn Co₂O₄ microparticles（Ni Ti@Mn Co₂O₄MPs）with a diameter of 2.5μm were successfully prepared on the Ni Ti substrates by hydrothermal reactions,and their surfaces were composed of nanoparticles with smaller size,giving them a larger specific surface area that provides a larger number of adsorption sites.The effects of hydrothermal temperature and time on the morphology of the fibers and their properties were investigated.The prepared fiber was applied to SPME and an analytical method for the detection of trace PAHs in water samples was established by coupling with HPLC-UV.Under the optimised SPME conditions,the established method demonstrated excellent linearity in the range of 0.05-500μg·L^-1;R²>0.9991 and LODs in the range of0.013-0.379μg·L^-1.The relative recoveries were in the range of 83.64%-108.3%and86.20%-106.3%by spiked recovery experiments,finally,the stability of the prepared fiber coatings was investigated.The results showed that the prepared fibers had satisfactory extraction selectivity and high stability.Chapter 4:In this chapter,the Ni Ti fibers with Mn Co₂O₄NBs@Mn O₂NSs were used as the substrate and Mn O₂ nanosheets were grown in situ on Mn Co₂O₄NBs to construct a novel SPME fiber with a unique core-shell structure（Ni Ti@Mn Co₂O₄NBs@Mn O₂NSs）.The prepared fibers have a unique hierarchical structure,and the in-situ growth of Mn O₂ nanosheets on Mn Co₂O₄NBs did not destroy the nanobundle morphology.The prepared fibers were applied to SPME and the established method showed satisfactory linearity in the range of 0.05-500μg·L^-1 with a correlation coefficient（R²）>0.9990 and LODs in the range of 0.013-0.598μg·L^-1.The applicability of the developed method was investigated by spiked recovery experiments.The stability of the prepared fibers was investigated.The results showed that the prepared Ni Ti@Mn Co₂O₄NBs@Mn O₂NSs fibers exhibited superior extraction performance as well as stability.