Spectral Analysis Based On Metal-Organic Frameworks

Metal–organic frameworks materials are the combination of nanomaterial, photochemical and biology. They have been the frontier and a hot issue in analytical chemistry today. In this thesis, we use various methods to synthesize metal–organic frameworks materials and to construct spectral sensors for sensing. Our works are as follows:1. In the first work, a facile strategy to synthesize Cu-hemin metal–organic frameworks(MOFs) with peroxidase-like activity was reported. The prepared Cu-hemin MOFs were characterized by various techniques such as scanning electron microscopy, transmission electron microscopy, X–ray powder diffraction, Fourier transform infrared spectroscopy, UV-visible absorbance spectra and so on. The results showed that the prepared Cu-hemin MOFs looked like a ball-flower with an average diameter of 10 ?m and provided a large specific surface area. The Cu-hemin MOFs possessing peroxidase-like activity could be used to catalyze the peroxidase substrate of 3,3,5,5-tetramethylbenzidine in the presence of H2O2, which was employed to detect H2O2 quantitatively with the linear range from 1.0 ?M to 1.0 mM and the detection limit was 0.42 ?M. Furthermore, with the additional help of glucose oxidase, a sensitive and selective method to detect glucose was developed by using the Cu-hemin MOFs as catalyst and the linear range was from 10.0 ?M to 3.0 mM and the detection limit was 6.9 ?M. This work informs researchers of the advantages of MOFs for preparing biomimetic catalysts and extends the functionality of MOFs for biosensor application.2. The fluorescent nanoscaled MOFs have been found promising potential applications in sensing. The abundant hydroxyl and carboxyl groups of carbon dots(CDs) served as starting points for the spontaneous self-assembling of Eu3+ and 2,6-Pyridinedicarboxylic acid(DPA) on the surface of CDs. Novel fluorescent CDs@Eu-DPA nanostructures for the detection of Cu2+ have been synthesized by encapsulating CDs into the Eu-DPA MOFs. The as-prepared CDs@Eu-DPA MOFs exhibited to be uniform and stable due to their nanoscaled sizes. The as-prepared CDs@Eu-DPA MOFs looks like flower ball. The obtained CDs@Eu-DPA as a probe for the detection of Cu2+ demonstrated high sensitive and selective with a good linear response range(50 nM-10 ?M) and a low detection limit(26.3 nM).3. A facile and effective strategy for designing ratiometric fluorescent nanosensor has been demonstrated in this work. Novel fluorescent BSA-Au@Tb-AMP(BSA= bovine serum albumin,AMP=adenosine 5'-monophosphate)nanostructures for the detection of DPA and Hg2+ have been synthesized by encapsulating BSA-Au into the Tb-AMP MOFs. The O in carboxylate and N in aromate ring of 2, 6-pyridinedicarboxylic acid(DPA) could strongly coordinate with Tb3+ to replace AMP from Tb3+ center. Thus, Tb-AMP was served as the DPA recognition sites. The fluorescence of BSA-Au at 405 nm remain as a reference, while the fluorescence of Tb-AMP at 545 nm was enhanced upon binding with DPA and the fluorescence of BSA-Au at 635 nm was quenched when the Hg2+ was added, resulting in the ratiometric fluorescence response of the nanosensor. This ratiometric nanosensor exhibited good selectivity to DPA over other substances. The ratio of F545/F405 linearly increased with the increasing of DPA concentration in the range of 50 nM-10 ?M with a detection limit as low as 17.4 nM. The ratio of F635/F405 linearly increased with the decreasing of Hg2+ concentration in the range of 50 nM-1 ?M with a detection limit as low as 20.9 nM. Additionally, this nanosensor was successfully applied for the determination of DPA and Hg2+ in the running water.