Ratiometric Upconversion Luminescent Probes For Detection Applications

Photon upconversion can realize the conversion of low-energy light to high-energy light,and has been used in fields such as solar cells,photocatalytic devices,and biological imaging.Among them,upconversion based on the triplet-triplet annihilation（TTA）mechanism is generally composed of an electron donor（sensitizer）and an electron acceptor（annihilator）.Through multi-step energy transfer,TTA-UC takes the advantages of up and down conversion luminescence,adjustable band,low excitation energy,etc.,attractting unique interest in the field of sensor and detection.However,due to factors such as the TTA-UC itself being easily quenched by oxygen,there are still difficulties in its application.In this study,based on the perspectives of luminescent agent chemical structure,energy transfer process regulation,TTA-UC matrix,etc.,three responsive TTA-UC micelle systems were constructed,and their luminescence performance,energy transfer mechanism and sensor detection applications were further studied.The specific research content is as follows:（1）Anthracenecarboxylic acid TTA-UC ratio probe.Using9-anthracenecarboxylic acid（9-ACA）and 2-anthracenecarboxylic acid（2-ACA）as luminescent agent,platinum octaethylporphyrin（Pt OEP）as photosensitizer,and Pluronic P-123 block copolymer as carrier coating upconversion system use,a p H detection probe was prepared.The research results showed that the p H probe had the characteristics of wide range response（p H=5.8-9.8）,high sensitivity,strong anti-interference and good repeatability.Then,we explored the detection mechanism by discussing the molecular configuration and enery level matching mechanism,compared the triplet-triplet energy transfer（TTET）efficiency and TTA quantum efficiency of the two p H probes,and summarized the responsiveness of molecular symmetry and TTET efficiency to the sensitivity of probe.In addition,the 9-ACA based TTA-UC system was applied as a time-temperature probe for food quality monitoring.The progress of the enzymatic reaction was adjusted by changing the enzyme concentration to simulate the spoilage stages of different foods,and the probe was tested in the enzyme.Finally,we promoted the luminescence performance at different stages of the reaction,and established the relationship between probe ratio fluorescence and food quality.（2）TTA-UC p-nitrophenol probe.We constructed a multi-system probe containing Pd OEP/DPA upconversion dye pair and p-nitrophenol（PNP）,and utilized the energy transfer between the components to achieve p H detection.The detection interval was p H=6.65-8.04,and the probe had Good accuracy,resistance to cationic interference and repeatability.The probe can be used for p H detection of serum with good anti-interference,and the minimum detection interval can reach 0.03.The gelled probe can conveniently and quickly perform in vitro blood p H detection,which provided a useful reference for human health monitoring.（3）TTA-UC@F-127 probe.The Pt OEP/DPA upconversion temperature ratio probe was constructed using the temperature-sensitive F-127 micelles as the carrier.The volume of F-127 micelles decreased with the increase of temperature,which increased the collision probability of the upconversion molecules,promoted the energy transfer of TTET and TTA,and changed the luminous intensity of upconversion and downconversion.The probe can realize the color change from red to blue-violet between 30℃-60℃,and can be used for naked-eye temperature monitoring,with a sensitivity of 12.34%°C^-1.It had a good time stability and cycle stability,and was not affected by concentration factors interfere.Furthermore,DPA hydroxymethyl derivatives were used as luminescent agents to construct probes for studying the relationship between molecular structure,energy level difference and detection performance.The results showed that the higher the luminescent agent energy level difference,the higher the sensitivity of the probe.By studying the detection performance of probes based on DPA and p-DPA,it was found that the temperature sensitivity of DPA probe was closely related to the concentration of micelles,while the temperature sensitivity of p-DPA probe was basically not affected by the concentration of micelles.We studied the lifetime of fluorescent molecules and the result showed that DPA tend to enter the hydrophobic core of micelles,and its temperature-sensitive performance was greatly affected by the particle size of the micelles,while p-DPA tend to be at the oil-water interface due to the hydrophilicity of methylol,and its temperature-sensitive performance was less affected by the particle size of micelles,providing new ideas for the molecular design of responsive luminescent agents in the future.