Core-Shell Upconversion Materials Of Rare Earth Fluorides/SiO₂ And Their Application In Constructing CO-Releasing System

Lanthanide-doped upconversion nanoparticles?UCNPs?are photoluminescent materials which can convert long-wavelength of low-energy radiation into short-wavelength of highenergy light.Usually,the conversion is between near-infrared light and UV-vis light.The materials have been widely applied in biolabeling,bioimaging,photodynamic therapy and drug delivery due to their low toxicity,good chemical stability,deep penetration in body tissues,weak background flourescence and high imaging sensitivity.CO-releasing molecules?CORMs?is a general designation of compounds which can release CO under certain conditions.Most CORMs are metal carbonyls.There are many approaches to promate CO-release and photo-induction is one of them.It is an attractive approach due to its good controllability.In this dissertation,our works were based on UCNPs to construct a NIR-active system for CO-release and the CO-releasing behavious of the system was investigated.It comprises three sections:?1?The ?-NaYF₄:Yb³⁺/Er³⁺UCNPs with particle size of about 25 nm and 66 nm were prepared by solvothermal method.Then,reverse micelle method was applied for constructing a core-shell upconversion nanoparticles?UCNPs@SiO₂?.The results show that UCNPs@SiO₂ maintains the same upconversion luminescence stability as UCNPs.?2?A NIR-responded system for CO-release?UCNPs@SiO₂-CORMs?was constructed based on UCNPs@SiO₂.In this system,uniform ?-NaYF₄:Yb³⁺/Er³⁺ UCNPs were coated with a SiO₂ shell which was chemically decorated thiol groups.Through ligand-exchange reaction with the thiol groups,a iron carbonyl unit,“Fe??⁵-Cp??CO?₂”,was immobilized onto the surface of UCNPs@SiO₂-CORMs.The results show that UCNPs@SiO₂-CORMs maintains good upconversion luminescence property.The CO-releasing behaviors of the system and kinetics were investigated in DMSO/D2 O media upon irradiation of a NIR laser?980 nm?at a power density of 1.0 W cm-?17??13?Its biocompatibility was also assessed using HUVEC and L929 cell lines,which showed that UCNPs@SiO₂-CORMs has good biocompatibility with no significant photo-toxicity.?3?Water-soluble iron carbonyl complex,[FeCp?CO?₂?3-O₂CC₆H₄SO₃-Na?]?2?,was synthesized by using [??⁵-Cp?Fe??-CO??CO?]2 and Sodium 3-sulfobenzoate under room temperature.The CO-releasing behaviors and kinetics of the complex were investigated in physiological saline solution?D2O?upon irradiation of visible lights?blue and green LED lights?.The results show that complex 2 has a good water-solubility and the CO-release process was a first-order reaction model.Due to these advantages of complex 2,it is possible to construct a water-dispersible and NIR-responded system for CO-release.