Preparation And Properties Of Two Typical Upconversion Luminescent Materials For Photodynamic Therapy

In recent years,rare-earth ion-doped up-conversion luminescence materials have great application prospects in anti-counterfeiting identification,solar cells,temperature sensors,3D display,solid-state lasers,and biological imaging due to their good stability,high resolution and unique luminescence characteristics.Especially in the area of photodynamic therapy（PDT）,which has unique advantages,such as good chemical stability,strong tissue penetration ability,small background interference,and less body damage.Up-converting luminescent materials are hot materials in PDT research,but as far as the current research status is concerned,the research of up-converting luminescent materials in the field of PDT is still in its infancy,far from meeting clinical requirements.Therefore,there is still a lot of work to be done.In this paper,NaGd（MoO₄）₂:Tm³⁺,Yb³⁺and NaGdF₄:Er³⁺,Yb³⁺@NaGdF₄:Tm³⁺,Yb³⁺are taken as the research objects.Works are carried out on their luminescence performance,reactive oxygen generation performance and PDT performance.The main contents are as follows:（1）NaGd（MoO₄）₂:Tm³⁺,Yb³⁺nanoparticles were synthesized by sol-gel method,and photosensitizer MC540 was compounded on the surface of the particles.The luminescent properties of the sample were studied by the spectral characterization,and it was found that the sample has excellent blue light emission,which could effectively activate photosensitizer MC540to generate reactive oxygen species.The results of biocompatibility experiments show that the folate modified sample has good biocompatibility.After applying the composite samples to tongue squamous cell carcinoma cells,the cells were irradiated with 980nm laser to study the cell killing ability of the sample.In the case of the sample concentration of 640μg ml^-1,the mortality rate of cancer cells was close to 80%after laser irradiation for 5 min.The results show that the composite samples of NaGd（MoO₄）₂:Tm³⁺,Yb³⁺and MC540 has good PDT performance.（2）Fluoride-based upconversion luminescent materials have the advantage of low phonon energy,which can effectively reduce the non-radiative transition process,so that the material has higher luminous efficiency than other matrix materials.The core-shell NaGdF₄:Er³⁺,Yb³⁺@NaGdF₄:Tm³⁺,Yb³⁺samples were synthesized by thermal decomposition method.The core-shell structure can effectively avoid the surface quenching effect,meanwhile,Tm³⁺in the shell transmits part of the photons in its excited state to Er³⁺in the core,which effectively enhancing the red emission of Er³⁺and improving the luminous efficiency of the sample as a whole.The sample was further coated with a layer of mesoporous silica,and the photosensitizers Ce6（red light activated）and MC540（blue-green light activated）were loaded on the mesoporous silica through covalent bonds and electrostatic forces,respectively.The sample emits red,green,and blue light under 980nm laser irradiation.Simultaneous the emitted light activates two photosensitizers to generate reactive oxygen species that can induce cancer cell death.Cells experiment results show that the composite sample can effectively produce reactive oxygen species and has excellent killing capacity for cancer cells.