Fabrication Of Composite Nanostructured Coatings On Nickel-titanium Substrates And Their Applications In Solid-phase Microextraction

Solid phase microextraction?SPME?,which combines sampling,extraction,concentration and injection into one step,is a rapid,convenient,time-saving,solvent-free and environment-friendly sample pretreatment technology.Commercially available fused-silica fibers are usually prepared with polymeric coatings.However,these commercial fused-silica fibers have some shortcomings such as fragility,relatively low thermal stability,poor organic solvent-resistance and limited lifetime.Therefore,in this study,the nanostructures with different morphologies were developed on the nickel titanium alloy?NiTi?fibers and further used to evaluate their potential adsorption performance in SPME.Finally,the lab-made fibers were applied to the enrichment and determination for some representative PAHs in real water samples.In Chapter 1,the principles and modes of SPME,the types of commercial fibers,the advantages and drawbacks of SPME as well as the development and application of lab-made fibers were discussed.In Chapter 2,nickel-titanium oxide nanotubes?NiTiONTs?,nanoparticles and nanopores were in situ grown on the NiTi fibers by anodization.The anodized NiTi fibers were characterized by scanning electron microscopy?SEM?and energy dispersive X-ray spectroscopy?EDS?.Thereafter,the adsorption performance of different NiTiO nanostructures was evaluated using typical aromatic compounds as model analytes coupled to high-performance liquid chromatography with UV detection?HPLC-UV?.Compared to the NiTi fibers with NiTiO nanoparticles and nanopores,the NiTi fiber with NiTiONTs?NiTi@NiTiONTs fiber?exhibited good extraction selectivity and efficiency for polycyclic aromatic hydrocarbons?PAHs?.For this purpose,extraction parameters of the NiTi@NiTiONTs fiber were investigated in order to obtain high extraction efficiency of PAHs.Under the optimized conditions,the proposed method with the NiTi@NiTiONTs fiber for PAHs were linear in the ranges of 0.05-200?g·L^-1 with correlation coefficients more than 0.999.Limits of detection?LODs?were between 0.008?g·L^-1 and 0.124?g·L^-1.Relative standard deviations?RSDs?of the intra-day and the inter-day analyses with the single fiber varied from 4.09%to 5.87%and from 4.31%to6.33%,respectively.Moreover,RSDs for fiber-to-fiber reproducibility of the proposed method with five fibers prepared in different batches were between 5.75%and 7.43%.Finally,its applicability was investigated by the determination of PAHs in environmental water samples and the relative recoveries of 84.50%-116.0%were achieved with the RSDs values of 4.56%-8.01%.In Chapter 3,the bimetallic oxide nanopores were in situ rapidly grown on NiTi fibers by anodization.The anodic parameters were investigated to obtain the preferable nanopores morphology.The NiTi fiber with NiTiO nanopores was coupled with HPLC-UV to investigate the extraction performance of representative aromatic analytes.The TiO₂-rich NiTi@NiTiO nanopores fiber showed higher extraction efficiency for PAHs.In this case,the experimental conditions for the extraction of PAHs were optimized.The proposed method with the nanoporous NiTi@NiTiO fiber was linear in the ranges of 0.05-200?g·L^-1 with correlation coefficients between 0.9987 and 0.9996.LODs were from0.012?g·L^-1 to 0.258?g·L^-1.RSDs were below 5.63%and 6.21%for intra-day and inter-day analyses of PAHs at the spiking level of 50?g·L^-1 with the single fiber,respectively.Furthermore,RSDs for five fibers prepared in different batches were between 4.98%and6.74%.The proposed method was successfully applied to the enrichment and determination of target PAHs in environmental water samples with the recoveries between 85.00%and 115.8%.In Chapter 4,the composite carbon nanoparticles were prepared on the NiTiO nanoparticles?NiTiONPs?by hydrothermal method and subsequent annealing.The extraction performance of the NiTi@NiTiONPs@C-0.8 fibers was evaluated.Compared to the NiTi@NiTiONPs fiber,the extraction efficiency and selectivity of the NiTi@NiTiONPs@C-0.8 fiber were significantly improved.The results demonstrate that the NiTi@NiTiONPs@C-0.8 fiber exhibited good extraction selectivity and efficiency for PAHs.Moreover,the extraction efficiency for PAHs was higher than that of commercial PDMS and PA fibers.Under the optimized conditions,the linear ranges of PAHs were 0.05-200?g·L^-1 with correlation coefficients above 0.999,and LODs were between 0.006?g·L^-1 to 0.127?g·L^-1.RSDs of intra-day and inter-day analyses varied from 4.17%to 5.94%and 5.71%to 7.13%,respectively.Furthermore,RSDs for five fibers fabricated in different batches were between 6.89%and 9.03%.The developed method was able to enrich and determine target PAHs in real water samples and the relative recoveries of real water samples were from 82.60%to 113.6%.Moreover,all the fibers prepared in the above three chapters were stable at least 250extraction and desorption cycles.