Lanthanide-doped Ultrasmall Sc₂O₃:Controllable Synthesis,Optical Properties And Application

This thesis primarily focus on size-controlled synthesis of trivalent lanthanide(Ln3+)ions doped ultra-small Sc2O3 luminescent nanocrystals(NCs),photoluminescence(PL)properties and applications.In this thesis,we demonstrate for the first time the fine control of the nanocrystal size of Eu3+-doped Sc2O3(Sc2O3:Eu)NCs within an extremely small nanometer scale from 2.6 to 10 nm.By utilizing the red-emitting Eu3+ ion as a spectra probe,the size-dependent S/V ratios in these ultrasmall NCs are thoroughly investigated based on the site-selective spectroscopy.Benefiting from their ultrasmall nanocrystal size,these ultrasmall Sc2O3:Eu NCs work very well as an efficient light-harvesting platform for highly amplified red PL of Eu3+ by virtue of the distance-dependent luminescence resonance energy transfer from 2-naphthoyltrifluoroacetone to Eu3+ ions at surface area.More importantly,efficient interparticle energy transfer can be also achieved in these ultrasmall Sc2O3:Eu NCs,which unambiguously opens up a new avenue for the exploration of ultrasmall luminescent NCs that usually suffer from severe surface luminescence quenching for diverse applications.Some contents and results are as followed:(1)Monodisperse Ln3+ ions doped Sc2O3 NCs be prepared via a modified thermal decomposition method through tunning reaction temperature,reactant and reactant concentration.Size-controlled synthesis of Ln3+ ions doped Sc2O3 NCs range from 2 nm to 10 nm was achieved.(2)Two different Eu3+ ions sites doped in the Sc2O3 NCs which including at surface area and inner lattice site were unambiguous identified by ultilizing Eu3+ ions as luminenscent structure probe.Based on the imparity of Eu3+ ions luminescence properties at surface area and inner lattice,ue demonstrated that the size-dependence of Eu3+ ions luminescence properties,tha is surface atoms may hold majority in whole NCs below 4.6 nm,while inner atoms hold majority in whole NCs greater than 4.6 nm.(3)Nitrilotriacetic acid(β-NTA)was loaded into DSPE-PEG2000-coated ultrasmall Sc2O3:Eu NCs as an efficient light-harvesting platform by virtue of the distance-dependent LRET from β-NTA to surface Eu3+ ions for highly amplified red PL of Eu3+ ions.the conventional problem of week luminescence in ultrasmall NCs would be settle with～100 times higher than OA-coated Sc2O3 NCs.(4)Build avidin-biotin system by virtue of the specific interaction between avidin and biotin,where the sensitizer of β-NTA was loaded on the pure Biotin-DSPE-PEG2000-Sc2O3 NCs(denoted as Biotin-DSPE-PEG2000-Sc2O3@β-NTA)and the acceptor of Eu3+ ions were doped into another one type of Sc2O3 NCs with avidin coupling(denoted as Avidin-Sc2O3:Eu),respectively,to trigger the energy transfers from β-NTA to Eu3+ ion at different NCs.intense red PL emission of Eu3+ ion can be readily detected at a concentration as low as 0.1 mg/mL upon 360-nm UV lamp irradiation.In particular,the integrated red PL emission intensity of Eu3+ for the mixed solution of Biotin-DSPE-PEG2000-Sc2O3@β-NTA and Avidin-Sc2O3:Eu NCs was observed to decrease stepwise with the gradually increased nanocrystal size,thereby clearly demonstrating the overwhelming advantages of ultrasmall NCs possessing rich surface atoms over the larger ones for efficient energy transfer.The avidin-biotin system between water-solution ultrasmall NCs would promote the application of Sc2O3 in biomedicine.