Investigation On The Electrochemiluminescence Properties Of Novel Organic Optoelectronic Molecules

Electrogenerated chemiluminescence(ECL)refers to the process of electrically activating the ECL active material,allowing it to undergo a redox reaction on the electrode surface,thereby generating free radical ions.The free radical ions form excited state molecules through electron transfer reactions,and then radiate light when they transition back to the ground state.After decades of development,ECL has now become a widely used detection technology.Throughout the developed ECL system,the most classic commercial ECL probe is the bipyridine ruthenium metal complex Ru(bpy)₃²⁺.However,such probes noble metal-rich material,facing the high cost,Potential physiological toxicity problems.In order to further develop the ECL research,the development of a new,efficient and inexpensive ECL probe system has now become a hot research topic.In this paper,organic thermally activated delayed fluorescence(TADF)and organic neutral free radical molecules were the research objects,and their photophysical,electrochemical,electrochemiluminescence properties were characterized.After investigation,it was found that these two systems have the potential to be used as new stable and efficient ECL luminescent materials.And based on the TADF polymer PCz APT10,we also tried to carry out a study of the TADF-ECL sensing detection of L-cysteine,with satisfactory results.The specific research results are as follows:1.In this work,the photophysical,electrochemical and electrochemiluminescence properties of classic TADF small molecules 4Cz IPN and BPAPTC were studied.In the study of4Cz IPN,it showed a reversible reduction peak,and could carry out annihilation ECL emission.In addition,when tripropylamine was used as co-reactant,4Cz IPN showed efficient and stable oxidation-reducing ECL,and when benzoyl peroxide was used as co-reactant,4Cz IPN showed efficient and stable reduction-oxidizing ECL.And the efficiency of reduction-oxidation ECL was significantly higher than that of oxidation-reduction ECL,which might be attributed to the more stable anion radical.In the study of BPAPTC,it showed a reversible oxidation peak,and could also carry out annihilation ECL emission.With tripropylamine as co-reactant,BPAPTC showed efficient and stable oxidation-reduction ECL performance.The ECL spectra of the two TADF small molecules were characterized,and it was found that the ECL emission pathway was consistent with the photoluminescence pathway,and two TADF molecules realized the efficient and stable ECL emission of green to yellow.Compared with commercial ECL system of bipyridine ruthenium compound(Ru(bpy)₃²⁺),the ECL efficiencies of both TADF small molecules were higher than that of Ru(bpy)₃²⁺.This study laid a theoretical foundation for the application of TADF small molecule in ECL field.2.A solid-state ECL sensing platform based on TADF polymer was constructed.TADF molecules have the characteristic of full exciton capture under electric excitation,which can theoretically achieve?100%ECL efficiency.In addition,compared with the fact that it is difficult to stably immobilize small molecules on the electrode,the structure of the polymer immobilized electrode has good stability.Therefore,TADF polymer has become our key research object to develop new efficient organic polymer ECL system.Electrochemical studies showed that TADF polymer PCz APT10 had good electrochemical oxidation performance.The annihilation ECL results showed that the ECL properties of PCz APT10 were related to the stability of free radical ions.The oxidation-reduction ECL and reduction-oxidation ECL of PCZAPT10 were achieved by using classical TPr A or S₂O₈^2-as co-reactants,respectively.And due to the excellent stability of cationic radicals,PCZAPT10 exhibited highly efficient and stable oxidation-reduction ECL property.By comparing the TADF polymer PCz APT10 with the traditional fluorescent polymer F8BT,it was found that the ECL efficiency of TADF polymer was nearly four times higher than that of F8BT.This indicated that TADF mechanism can effectively improve the efficiency of ECL,and determined the ECL emission mode of TADF polymer which was different from the traditional fluorescent polymer ECL emission.Finally,using TADF polymer as the ECL emitter,solid-state ECL sensing detection was performed on L-cysteine(an important marker of disease).This detection method had low detection limit,high sensitivity,good specificity,and excellent stability.It is foreseeable that TADF polymers will play a huge role in the field of ECL sensing.3.The photophysical,electrochemical and electrochemiluminescence properties of organic neutral radical molecule TTM-3PCz were studied.The study found that TTM-3PCz had excellent photostability,reversible redox property and good electrochemical stability.During the annihilation ECL measurement,TTM-3PCz showed strong ECL emission.And the anode ECL signal was significantly higher than the cathode ECL signal,which was attributed to the more stable anion radical of TTM-3PCz.When using tripropylamine or benzoyl peroxide as the co-reactant,TTM-3PCz exhibited highly efficient and stable oxidation-reduction ECL and reduction-oxidation ECL,respectively.The ECL spectral characterization showed that TTM-3PCz was doublet exciton transition mechanism.And the ECL efficiency of TTM-3PCz was significantly higher than that of commercial ECL system bipyridine ruthenium Ru(bpy)₃²⁺.This study proved that the organic neutral radical molecule is a new type of organic ECL system with important potential.