Study On Porphyrin Based Electrochemiluminescent Signal Amplification For Biosensing Zinc And Calcium

Electrochemiluminescence（ECL）is an analytical method that converts externally applied electrical signal into optical signal.It is widely used because of its high sensitivity,low detection limit and easy operation.The construction of efficient ECL sensors is the main driving force for continuous development of this field,and the fundamental problem is to find suitable luminescent materials.1.In this work,a reasonable emitter-enhancer system in ECL can greatly improve detection result.It is our goal to find porphyrins that can exist stably in the electrolyte and have good luminescence properties.Herein,zinc（II）meso-5,10,15,20-tetra（4-sulfonatophenyl）porphine（Zn TSPP）was reported in this work.It was found that the Zn TSPP was trapped into pyridine-bridgedβ-cyclodextrin dimer（Py（CD）₂）,and the luminescence intensity and light stability of Zn TSPP were significantly improved.NMR was applied to confirm that Zn TSPP was bound by Py（CD）₂ and form a clam-like biocompatible container by pinning and pinching forces of Py（CD）₂.The ECL brightness of Zn TSPP was increased up to three-fold after the formation of this biocompatible container.The absorption and emission spectroscopies showed that the improvement of signal transduction in the host molecule was due to the extended excitation lifetime and the restricted mobility of the guest.By studying enhancement effect of coreactant on illuminant,we found that hollow black TSPP@Py（CD）₂can be a highly sensitive detection of Zn²⁺with the help of coreactant H₂O₂.With the development of ECL and photophysics,this compact supramolecular assembly has become a new and feasible method in ECL analysis applications.2.Metal organic framework materials（MOFs）are materials formed by combining metal ion clusters or different inorganic ions with carboxyl groups and amino groups in organic ligands.MOFs have advantages of adsorption,hydrogen storage,and catalysis due to its large specific surface area and porous characteristic.Nowadays MOFs has been applied to many fields such as battery materials,drug loading,and fluorescent materials.Zirconium-based MOFs are tolerant in water,acid and alkaline solutions due to the strong coordination between zirconium and carboxy group,and this material is able to maintain good stability in aqueous solution.In addition to Zn TSPP,we have also discovered a zinc（II）meso-tetra（4-carboxyphenyl）porphine（Zn TCPP）.The four substituents in the porphyrin structure are carboxyphenyl groups,which can be used as a guest to synthesize metal organic framework materials.Zn TCPP is used to catalyze dissolved oxygen in water to induce ECL signal,thus the concentration of dissolved oxygen can determine the intensity of ECL.In this work,Zn TCPP was synthesized to enhance the ECL intensity due to the advantage of hydrogen storage of MOFs.In addition,we found that some metal cations had quenching effect on the ECL luminescence of MOFs.In order to explore the cause of quenching,we examined the effects of different cations on their ECL and used this principle to detect Ca²⁺in practical samples.