Study And Application Of Triplet-Triplet Annihilation Upconversion System With High Doping Concentration

Comparing with routine fluorescence luminescence,triplet-triplet annihilation upconversion luminescence is a new technique which can convert long-wavelength photons into short-wavelength photons.Annihilator is a vital component in the upconversion system and plays an important role in upconversion luminescence intensity and upconversion luminescence quantum yield.Annihilator has poor solubility in solution due to its good planarity that will resultπ-πstacking.The concentration of annihilator affects the number of triplet-state exciting produced by annihilator.In order to solve the problem of low doping concentration of annihilator and enhance the intensity of upconversion luminescence,the novel annihilators with high solubility were prepared by introducing branched chain.The upconversion properties of the annihilators were measured and analyzed,as follows:（1）The luminescence quantum yield is an important parameter for evaluating upconversion performance.The relative and absolute methods usually operated complicatedly,and cannot measure the in-situ luminescence quantum yield of specific samples.Since the down-conversion luminescence is a single-molecule process in triplet-triplet annihilation upconversion system,the down-conversion luminescence quantum yield of photosensitizer is independent of excitation power density.Thus,the down-conversion luminescence can be used as an internal standard to calculate the in-situ upconversion luminescence quantum yield of the same sample.The method is more flexible then the absolute method,and is successfully used to measure the upconversion luminescence quantum yield of desecrated solution immediately.Comparing with the relative method,internal standard method can measure the upconversion luminescence quantum yield of solid samples.The method would be used to measure the luminescence quantum yields of various upconversion materials conveniently.（2）A new annihilator（DPA1）which has highly solubility was synthesized by introducing branched chain to DPA.With Pt OEP as a photosensitizer and the prepared DPA1 as an annihilator,the obtained TTA solution converted the green light to blue light.The emission intensity of TTA upconversion systems that included DPA1increased with the concentrations of DPA1 and emitted brighter which compared with unmodified DPA.A high upconversion efficiency(Φ_UC=12.8%)and long fluorescence lifetime（τ=130.8μs）of Pt OEP/DPA1 were obtained under the excitation of a solid-state laser（532 nm）.Under combining Pt OEP/DPA1 with WO₃,the production of·OH was verified by using the coumarin solution.In the experiment of organic pollutant degradation,the degradation rate of tetracycline is 25.1%and that of methylene blue is 19.6%.A new annihilator was designed and an effective method was provided to increase the performance of TTA upconversion system in this study.（3）A new perylene derivative（Py）was designed and synthesized by introducing an alkoxy chain.Comparing with undecorated perylene,long alkoxy chain was introduced to increase the solubility of the annihilator.The upconversion system of Py/Pd TPTBP converted red light into blue-green light.The luminescence intensity of the upconversion systems enhanced with the concentration of Py in the upconversion systems.The upconversion luminescence quantum yields of 10 m M and 5 m M Py were 5.4%and 4.7%.The upconversion system of 10 m M Py exhibited luminescence lifetime more than 50μs under the excitation pulse width more than 0.8μs.