The Study On Porphyrin Electrochemiluminescence System Based On Depolymerization Strategy

Electrogenerated chemiluminescence,also known as electrochemiluminescence and abbreviated ECL,is a chemiluminescence triggered by electrochemical methods.In this process,it will undergo a series of redox reactions to form a light-emitting excited state,and a high-energy excited state returns to a low-energy ground state.Energy is released in the form of light,and then a kind of light-emitting phenomenon is exhibited.Similar to chemiluminescence,but ECL does not require the introduction of an additional light source.ECL has the advantages of high sensitivity,high selectivity,wide linear detection range,small amount of luminescent reagents,strong controllability of reaction and fast analysis speed.ECL technology is increasingly used for DNA analysis,protein detection,immunoassay,and cell testing.However,in the organic phase,although the hydrophobic illuminant has good solubility and high luminous efficiency,it is not suitable for practical detection applications,while the application of illuminants in the aqueous phase has been an experimental difficulty.Porphyrins and their derivatives exist in organisms and nature,porphyrins have simple synthesis steps,paintability,high luminous efficiency,good biocompatibility,electrochemical and photochemical properties,and important applications in the ECL field.Because of the poor water-solubility of porphyrins,the stability of free radicals in the aqueous phase is poor,and porphyrins easily form aggregate,and the Q-bands absorption is weaker,the above results limit the redox reaction of porphyrin molecules and lead to the failure of ECL research.Therefore,improving the water-solubility of porphyrins and stabilizing the porphyrin radicals are the key factors for enhancing the ECL efficiency of porphyrins in the aqueous phase.So,the main research contents in this paper include solving aggregate of porphyrin,improving the ECL efficiency of porphyrin and applying it.The main research is divided into the following three parts:Part ?:Depolymerization-Induced Electrochemiluminescence of Insoluble PorphyrinIn this chapter,the ECL properties of porphyrins in aqueous phase were studied by self-assembling porphyrins.Tetra-hydroxyphenyl porphyrin?THPP?and?-cyclodextrin??-CD?synthesis a supramolecular self-assembled material?THPP@?-CD?by generating hydrogen-bond.The electrochemical and ECL properties of THPP@?-CD in aqueous phase were studied,and the ECL mechanism of THPP@?-CD self-assembled materials was further explored.THPP@?-CD self-assembled material not only avoids the aggregate of porphyrins due to the?-?stacking effect,but also enhances the water-solubility of porphyrins.Self-assembling changes the structural symmetry of THPP and enhances UV absorption of the Q band.The unique properties of?-CD have important guiding significance for enhancing the ECL study of a series of porphyrins which are easy to form hydrogen bonds with hydroxyl groups and have poor water-solubility,and broad the research of porphyrins in the field of ECL.Part ?:Double-Emission Electrochemiluminescence System of Self-Assembled Porphyrin/luminolBased on tetra-carboxyphenyl porphyrin?TCPP?and luminol,a novel self-assembled material?SA-TCPP/luminol?dual-emission ECL system was constructed without additional co-reactants in the aqueous phase.The dual-emission ECL system simplifies the complex mechanism,which requires H₂O₂ as an anode co-reactant of luminol in an alkaline environment and K₂S₂O₈ as a cathode co-reactant of TCPP,with high sensitivity and reproducibility.And then ECL system avoids the aggregate of TCPP in the aqueous phase,and improves the water-solubility of luminol.And the ECL system constructed by SA-TCPP/luminol materials can quickly and sensitively detect hydrogen peroxide?H₂O₂?.Part ?:Electrochemiluminescence Study of PVP Modified Porphyrin MOFs?PCN-224?Metal organic frameworks?PCN-224?material of porphyrin is synthesized by tetra-carboxyphenyl porphyrin?TCPP?as an organic ligand,zirconium?Zr?as a metal node.PCN-224 show excellent luminescence properties and is often used as an ideal material for fluorescent probes in aqueous solutions?uniformly dispersed in water?to construct luminescent sensors or apply it in catalysis and other fields.However,because it is insoluble and stable in water,and it cannot be well researched in the field of ECL.Thereupon,PVP and PCN-224 are self-assembled to form a water-soluble,stable PCN-224@PVP materials.Due to the framework structure of PCN-224,agglomeration of porphyrins is avoided and the first use of MOFs as illuminants for ECL studies.PVP protected the structure of PCN-224 in PBS.This strategy points out the direction for MOFs as luminophore in ECL field.