The Fabrication And Upconversion Luminescence Propertie Of Oxide Inverse Opal Photonic Crystals Doped With Rare Eatrth Ions

Photonic crystal as a nanoscale material,the orderly periodic materials with holes structure is in focus since it was put foward.It has the character of photonic band gap and photon localization,the emission properties can be modulated.It has huge potential in photocatalysis,solar energy,detection,laser,sensing,display and so on.In the work,we fabricated Bi2WO6:Yb3+,Tm3+ nanopowder and BaTiO3: Yb3+,Er3+,Tm3+ inverse opal photonic crystrals(IOPCs)by the sol-gel method,and the upconversion was studied,respectively.(1)Fabricated Bi2WO6 : Yb3+,Tm3+ nanopowder by the sol-gel method with citric acid(CA)and edetic acide(EDTA)as chelating agent.Constantly change the amount of chelating agent,we obtain the precursor sol with better liquidity when Bi2WO6: EDTA: CA = 1 mol: 2 mol: 0 mol,then through 450?,4 h sintering the pure tungsten acid bismuth nanopowder can be produced.Fabricated the Bi2WO6:Yb3+,Tm3+nanopowder with the doped percentage as 4%:1%,6%:1%,8%:1%and 10%:1%.Under the excitation of 980 nm laser diode,the samples present the green and red emissions around 455 nm,480nm and 686 nm,corresponding to1D2?3F4(455nm),1G4?3H6(480nm),1G4?3F4(656nm)and3F2?3H6(686nm)energy level transition process,when the doping concentration is Yb3+:Tm3+= 6%:1% the upconversion will be the strongest.(2)The opal structure were dipped in Ba TiO3:Yb3+,Er3+,Tm3+precursor solution,and thus the voids among these colloidal spheres were filled by the sol solution through the capillary action.Then the samples were heated to remove polystyrene opals after aged 24 hours at room temperature.Finally,the IOPC samples with the photonic band gap(PBG)at 470 nm and 635 nm were forming and denoted as IOPC1,IOPC2,respectively.Under the excitation of 980 nm laser diode,the samples present the blue,green and red emissions around 480,525,550 and 660 nm.It is significant to observe that the 525 nm,550nm green emission increased obviously in case the480 nm blue emission inhibited by the PBG effect in the IOPC1 that the blue emission completely covers the PBG.Due to the inhibition of the photonic band gap,the blue emission 480nm(Tm3+:1G4?3H6)inhibited,lead to the enhancement of the energy back transfer(EBT)process: 1G4(Tm3+)+4I15/2(Er3+)?3F4(Tm3+)+4F9/2(Er3+),then through the cross relaxation(CR)process:24F9/2?4I11/2+2H11/2/4S3/2+phonon energy,the population of 2H11/2 and 4S3/2 will increased,lead to green emission enhanced.When the red emission partly covers the PBG in the IOPC2,the 660 nm red emission inhibited,lead to the enhancement of the energy transfer4F9/2(Er3+)+3F4(Tm3+)?4I15/2(Er3+)+1G4(Tm3+),then the population of 1G4 was increased,lead to the enhancement of 480 nm emission.Meanwhile,the CR:24F9/2?4I11/2+2H11/2/4S3/2+phonon energy was also enhanced,the population of4S3/2 was increased,lead to the enhancement of 552 nm emission.