Preparation And Properties Of Polymer/Rare Earth Upconversion Luminescence Nanohybrid Materials

Surface polymer functionalization of rare earth upconversion luminescence nanoparticles(UCNPs) is one of the hot research fields. Currently, freedom control the parameters ofpolymer structure, composition and content on the surface of UCNPs is difficulties in thisresearch fields. On the basis of the combination of in-situ polymerization and living/controlled polymerization techniques, a series of polymer/UCNPs nano hybrid materials havebeen prepared in this paper. The applications of the resulting UCNPs-based nanocompositeswere also explored. The detailed content is described as follows.(1) Hydroxyl-functionalized UCNPs were synthesis based on the solvothermal techniqueby using ricinoleic acid as ligand. TEM and XRD characterizations indicate that thesynthesized UCNPs possess hexagonal phase structure and spherical shape with a meandiameter of20nm. The UCNPs show strong upconversion luminescence. FT-IR and TGAanalysis indicate that UCNPs have been capped with ricinoleic acid. Moreover, the presenceof hydroxyl groups on the surface of UCNPs allows for further modification as confirmed bythe successful reaction with dodecanoyl chloride.(2) On the basis of the combination of the features of UCNPs and PNIPAM, a novelfluorescence temperature sensitive hydrogel PAAm/PNIPAM-UCNPs has been prepared.Owing to the existence of PNIPAM, the PL intensity of the hydrogels is sensitive to theexternal temperature stimuli. It found that the maximum sensitivity of the hydrogels wasobtained26.5%peroC at33oC. Five cycles of heating-cooling experiments reveal that thechanges of PL intensity due to temperature were reversible. Moreover, this approach can beextended to prepare both upconversion luminescence and downconversion luminescencemulti-functional hydrogel by simply immersing the as-synthesized hydrogel in the RBsolution. It is found that the multi-functional hydrogel show temperature sensitive both underNIR excitation and UV excitation. And the maximum fluorescence temperature sensitivitywas obtained24.3%peroC and39.1%peroC under excitation of980nm and550nm,respectively.(3) HPG was covalently grafted from the surfaces of hydroxyl-functionalized UCNPs bythe “grafting from” method based on in situ anionic ring-opening polymerization. The amountof HPG grafted from UCNPs can be adjusted by tuning the feed ratio of glycidol to UCNPs.The resulting HPG-grafted UCNPs (UCNPs-g-HPG) nanohybrids were characterized byFT-IR, TGA, NMR spectroscopy and TEM. Preliminary biological studies demonstrate that the UCNP-g-HPG shows low cytotoxicity, high luminescent contrast and light penetrationdepth, posing promising potential for bioimaging applications. On the basis of the numeroussurface hydroxyl groups, we demonstrate the post-functionalization of UCNP-g-HPG by arepresentative fluorescent dye rhodamine B to afford UCNP-g-HPG-RB that simultaneouslypresents upconversion and downconversion luminescence.(4) PCL and HPG was covalently grafted from the surfaces of hydroxyl-functionalizedUCNPs by the “grafting from” method based on in situ cationic ring-opening polymerization,respectively. The effect of the feed ratio of-caprolactone to UCNPs on the amount of PCLgrafted from UCNPs was study. In addition, the RB dye was used as a model drug molecule,and study the drug delivery properties of UCNPs-g-HPG. Drug release results revealed thatthe UCNPs-g-HPG has good drug delivery performance.