Core-Shell Nanoscale Coordination Polymers For Fluorescent Detection

Fluorescent nanoscaled coordination polymer sensor is the combination of nanomaterial, photochemical and biology. It has been the frontier and a hot issue in analytical chemistry today. In this thesis, we use various methods to synthesize coreshell nanostructured coordination polymers and to construct fluorescent sensor for sensing. Our works are as follows:1. A simple strategy to fabricate fluorescent Si O2@zeolitic imidazolate framework-8(ZIF-8) core-shell nanosensor for Cu2+detection was demonstrated in this work. The nanosensor was synthesized using carboxyl(-COOH) functionalized Si O2nanoparticles(Si O2 NPs) as a template to grow ZIF-8 on its surface. The porous Si O2@ZIF-8 showed extremely good adsorption property to accumulate copper ions and the pyridyl nitrogen sites in imidazole played vital roles in the recognition of Cu2+.The fluorescence intensity decreased linearly with the increasing of Cu2+concentration in the range of 10-500 n M and the detection limit was 3.8 n M. The nanosensor was further used to determine Cu2+ in real water samples.2. The fluorescent nanoscaled coordination polymers have been found promising potential applications in sensing. Novel fluorescent core-shell Au@Tb/denosine monophosphate disodium(AMP) nanostructures for the detection of 2, 6-pyridinedicarboxylic acid(DPA) have been synthesized by encapsulating AMPfunctionalized Au nanoparticles into the coordination polymers(Tb/AMP). The asprepared core-shell Au@Tb/AMP exhibited to be uniform and stable due to their nanoscaled sizes. The coordination of DPA with Tb3+ to form Au@Tb/AMP-DPA complex caused the intermolecular energy transfer from DPA to Tb3+, leading to the enhancement of Au@Tb/AMP fluorescence. The obtained Au@Tb/AMP nanostructures as a probe for the detection of DPA demonstrated high sensitive and selective with a good linear response range(10 n M-10 μM) and a low detection limit(2.7 n M).3. A facile and effective strategy for designing ratiometric fluorescent nanosensor has been demonstrated in this work. The abundant hydroxyl and carboxyl groups of carbon dots(CDs) served as starting points for the spontaneous self-assembling of europium ion(Eu3+) and 5’-guanosine monophosphate disodium(GMP) on the surface of CDs. The obtained nanosensor exhibitd the characteristic emission of CDs.Eu3+ excited state could couple more efficiently with the high frequency OH oscillators of water molecules, resulting in the more efficient quenching of Eu/GMP.The O in carboxylate and N in aromate ring of 2, 6-pyridinedicarboxylic acid(DPA)could strongly coordinate with Eu3+ to completely replace water molecules from Eu3+center. Thus, Eu/GMP was served as the DPA recognition sites. The fluorescence of CDs remained constant as a reference, while the fluorescence of Eu/GMP was enhanced upon binding with DPA, resulting in the ratiometric fluorescence response of the nanosensor. This ratiometric nanosensor exhibited good selectivity to DPA over other substances. The ratio of F615/F469 linearly increased with the increasing of DPA concentration in the range of 15 n M-5.0 μM with a detection limit as low as 5.1 n M.Additionally, this nanosensor was successfully applied for the determination of DPA in the real serum samples.4. We have established a new type of ratiometric fluorescence sensor polystyrene@terbium/guanine coordination polymer(PS@Tb/G) for sensing of O2。-.Guanine owes the highest molecular orbital energy level to attack O2。-, thus the oxidation products 8-hydroxy deoxyguanosine is the most commonly used biomarkers to detect DNA oxidative damage. Besides, the reaction rate of guanine and O2。-is higher than amino acids, unsaturated fatty acids in the cell, which ensure the selectivity for O2。-sensing. NCPs built by G and rare earth exhibit strong fluorescence due to the abundant carboxyl oxygen in G to avoid fluorescence qunching from water. However, when G reacted with O2。-, the triplet state of G was damaged and could not sensitize the fluorescence of rare earth. Therefore, the fluorescence of PS@Tb/G was qunenched by O2。-. The fluorescence of PS@Tb/G decreased with the increasing of the concentration of O2。-and showed a good linear range in 0-6.0 μM. The detection limit was as low as 3.4 nm when the singal to noise ratio was 3.