Preparation,Optical Properties Control And Application Of Lanthanide-doped LaF₃/BaGdF₅ Multifunctional Nanomaterials

Bioimaging has become an indispensable tool in cancer research,clinical trials,and medical practice.Optical imaging has played a key role in biomedical imaging and provides a great convenience for early disease detection and treatment owing to its unique advantages of fast feedback,high sensitivity and non-radiation.Compared with the visible light?400-750 nm?and the first near-infrared biological window?NIR-I,750-1000 nm?biological imaging window,the optical imaging in the second near-infrared?NIR-II,1000-1700 nm?window with can provide deeper tissue optical imaging and is emerged as the new generation of bioimaging technology due to the advantages of reduced photon absorption,negligible tissue auto-fluorescence,remarkably reduced tissue scattering losses.In recent years,photothermal therapy?PTT?is considered as a promising adjuvant therapy route for cancer owing to its advantages of high efficiency,non-invasiveness and low side effects.Rare earth materials with simultaneous narrow-band NIR-I and NIR-II emission,long luminescence lifetime,high optical stability,and low biotoxicity are considered as ideal fluorescent nanoprobes.Therefore,it is of great significance to design a rare earth fluorescent nanoprobe with excellent NIR-II emission for bio-imaging and further integrate with photothermal therapy.The main research contents are as following:?1?The Yb³⁺/Er³⁺doped hydrophilic BaGdF₅ downconversion nanomaterials were successfully synthesized via a hydrothermal route.The effects of Yb³⁺doping concentrations on the luminescence properties of BaGdF₅ nanocrystals were studied.The results demonstrate that the BaGdF₅ nanocrystals with a doping concentration of 20%Yb³⁺present the strongest luminescence.In addition to the visible light emission,the BaGdF₅:Yb³⁺/Er³⁺nanocrystals also have excellent NIR-II emission under the excitation of 980 nm laser.The highly sensitive NIR-II bioimaging and non-invasive brain vessel imaging were successfully realized.?2?The down-conversion luminescent LaF₃:Nd nanocrystals with hexagonal phase,controllable size and high efficiency NIR-II emission were successfully prepared by hydrothermal method.The Nd doping induced NIR-II emission variation was studied.The biocompatibility of LaF₃ nanocrystals was achieved by polyacrylic acid?PAA?modification and further applied to biological optical imaging.The results of optical biological imaging demonstrated that Nd³⁺doped LaF₃ down-converted luminescent nanocrystals could be used as an ideal imaging nano-probe in NIR-II biological window.?3?The polydopamine?PDA?coated LaF₃:Nd³⁺downconversion luminescent nanocrystals were successfully prepared by microemulsion method,and the photothermal properties of the nanocrystals solution excited by 808 nm laser were systematically studied.The results showed that the designed PDA coated LaF₃:Nd³⁺nanocrystals holded excellent photothermal properties.Therefore,the prepared PDA-coated LaF₃:Nd³⁺probes have potential application in photothermal therapy of tumor.