The Functional Films Prepared From Layered Rare-Earth Hydroxides Nanosheets

This dissertation focuses on the synthesis of layered rear earth hydroxide(LRH)crystals via controlled processing,the efficient exfoliation of LRH crystals into unilamellar nanosheets by,and the functionalization of the nanosheets via the construction of functional films of novel structural features on the substrate.The layered rare earth hydroxides(LRHs)could be exfoliated into unilamellar nanosheets efficiently via hydrothermal ion exchange,intercalation,inter-layer expansion,and mechanic disturbance in form amide.Detailed characterizations of the products were performed by the combined techniques of XRD,FTIR,FE-SEM,TEM,and PLE/PL analysis.The main conclusions are as follows:The hexagonal particles of(Y0.95Eu0.05)2(OH)5NO3·nH2O,(Y0.99xGdxCe0.01)2(OH)5NO3·nH2O(0≤x≤0.5)and(Y0.8Yb0.18Tm0.02)2(OH)5NO3·nH2O have been synthesized at 180℃ for 24 h via hydrothermal method.After hydrothermal ion-exchange at 120℃ for 24 h,the nitrate ions between the LRH layers were all replaced by dodecyl sulfonate ions,meanwhile the distance between the layers was effectively expanded from 0.9 nm to 2.54 nm.Single-layer nanosheets can be obtained by exfoliated the exchanged compounds LRH-DS in formamide solution via mechanical agitation easily.YAG transparent ceramic films can be prepared by spin-coating the colloidal suspension of exfoliated LRH nanosheets on the sapphire substrate,followed by calcinations in oxygen and reduction in hydrogen for the Ce3+ containing samples.The prepared YAG transparent ceramic films have a high transmittance.YAG:Eu3+ transparent ceramic films exhibited orange emissions at 593 nm,629 nm,659 nm,709 nm under the excitation of 220 nm with lifetime of a 1.69 ms.(Y,Gd)AG:Ce3+ transparent ceramic films exhibit typical yellow and green emissions of Ce3+centered at 550 nm under the excitation of 460 nm.More incorporation of Gd3+ ions resulted in increased lattice parameters of(Y,Gd)AG:Ce3+ films gradually.Red-shifting and enhanced fluorescence intensity were found along with the increasing of Gd3+ content,along with the CCT shifting from 5294.7 K to 4376.7 K.However,same activation energy(Ea)of 0.27 eV was obtained for different Gd3+content samples,(Y0.8Yb0.18Tm0.02)6O5F8 functional films were prepared via nano conversion process by spin-coating the colloidal suspension of exfoliated LRH nanosheets and NH4F on the substrate alternately.The transparent film with a high transmittance of 94%is composed of uniform 300 nm-sized particles,with exhibits 1G4→3H6,1G4→3F4,3H4→3H6 emissions of Tm3+at 486 nm,660 nm,811 nm under the excitation of 980 nm,indicating the energy transfer from Yb3+ to Tm3+.