Preparation And Fluorescence Properties Of Up-conversion Nanoparticles Based On Triplet Annihilation

In recent years,upconversion nanoparticles(UCNPs)based on triplet-triplet annihilation(TTA)have aroused great interest in biomedicine.In addition to the advantages of high signal-to-noise ratio in general conversion luminescence(i.e.short wavelength optical signal excited by long wavelength),the excitation intensity required on TTA is low and no coherent light is needed,so it shows a good application prospect in fluorescence detection and biological imaging.Since TTA upconversion luminescence depends on the arrangement between different fluorescent molecules.In this process,how to improve upconversion efficiency,reduce photobleaching,aggregation quenching and oxygen fluorescence quenching of fluorescent molecules is a key problem faced by the construction of high-quality UCNPs.Aiming to solve above problems,this paper prepared a TTA upconversion nanometer luminescent material with high luminous efficiency and perfect stability by using hollow silica spheres loaded with 8-ethylporphyrin Platinum(PtOEP)and 9,10-diphenanthrene(DPA),by optimizing the load mode and doping ratio.The main work is as follows:1.Hollow mesoporous silica nanoparticals(HMSNs)were prepared by reverse-phase microemulsion method,then their surfaces were bio-functionalized to target tumor cells.Based on the prepared nanomaterials,loading the sensitizer PtOEP and the acceptor DPA by the method of vacuum adsorption and solvent treatment,the upconversion nanoparticles(TTA-UCNPs)with good luminous performance were obtained.The morphology,size and surface potential of NPs were characterized.The average particle size is 69.6 nm,hydrated particle size is 258 nm,andsurface zeta potential is positive.2.The luminescence performance of TTA-UCNPs was studied.Under the excitation of 535 nm,we realize the upconversion luminescence of 440 nm.By optimizing the load concentration and proportion of PtOEP and DPA,the fluorescence intensity is positively quadratic function with the excitation power density,which proves its nonlinear optical properties.It’s found that the luminous intensity of conversion is the highest when the load concentration ratio was 5%PtOEP,20%DPA mass fraction relative to HMSNs.3.Other properties of TTA-UCNPs have been tested.The upconversion flurorescence intensity of NPs is not sensitive to oxygen and shows good stability under continuous light.