| Combining two or more kinds of nano-materials with the similar or different functions together to make the synthetic nanocomposites possess either the enhanced synergistic effect or multiple functionalities, such as optical, electrical, magnetic and catalytic properties. Therefore, nanocomposites will have great potentials in the applications of analytical chemistry, catalytic field, chemical sensors, targeted drugs delivery and bioimaging.In this dissertation, we mainly worked on the synthesis of two types of nanocomposites and their applications in the environmental analysis:1. Metal organic frameworks (MOFs) are attractive as adsorbents for solid-phase extraction due to their abundant uniform cavities, large surface area and good chemical stability. Combination of MOFs with magnetic nanoparticles imparts magnetic separation ability to MOFs. We designed a facile strategy to fabricate the Fe3O4-MOF-5 nanocomposites via coordinating binding between MOF-5 and polyvinylpyrrolidone (PVP) functionalized Fe3O4 nanoparticles. Then these nanocomposites were successfully applied for the rapid magnetic solid-phase extraction (MSPE) and simultaneous detection of the multiple pesticide residues such as carbosulfan, chlorfenapyr, indoxacarb and coumaphos from water samples. The proposed method exhibited good linearity for the analytes in the range of 0.05-5.0 μg/mL (0.05-2.5 μg/mL for indoxacarb), with the correlation coefficients (r)> 0.9956. The limits of detection (LODs) were obtained ranging from 0.011 to 0.032 μg/mL. The enrichment factors (EFs) for carbosulfan, chlorfenapyr, indoxacarb and coumaphos were 17,36,49 and 61, respectively. Good precisions (RSDs%) were demonstrated in the range of 2.4-11.5%at 0.1 μg/mL level and 2.3-7.0% at 1.0 μg/mL level. The proposed method has been applied to detect the four pesticides from spiked (0.1 and 1.0 μg/mL) tap water samples with satisfactory average recoveries of 65.8-99.6% and 86.8-108.9%, respectively. Moreover, the magnetic Fe3O4-MOF-5 sorbent was reused for 5 cycles without noticeable decrease in extraction efficiency.2. Upconversional nanoparticles can effectively avoid the disturbance of the biological issue or other flurescent materials for their anti-stokes luminescent mechanism which make them have been widely applied in analytical detection and bioimaging. NaYF4 is considered as the most effective carrier of the rare-earth doped materials. We proposed a new strategy to adjust the fluorescence of oleic NaYF4:Yb3+/Er3+ and NaYF4:Yb3+/Tm3+nanoparticles through changing the amount of NaF for the reason that the Fluorine ions might influence the crystal structures by induding the formation of hexagonal or cubic crystalline.Afterwards, we successfully synthesized the two upconvertional nanocrystals with intense fluorescence. By untilizing of these upconvertional luminescent nanoparticles, then we designed a fluorescent probe for the detection of the trace amount of TNT in water based on the mechanism of FRET. The combination of the upconversional nanoparticles and the Au nanospheres decorated with amino groups will lead to a decrease in flurescence intensity at 546 nm. With the addition of TNT, it will compete to react with the amino groups on the surface of the Au nanospheres which will switch off the FRET and thus the fluorescence at 546 nm will recovery accordingly. |
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