Luminescence Modulation Of Rare Earth Doped Lanthanide Oxide Inverse Opal Photonic Crystals

Photonic crystal（PC） has been attracted extensive attention since the conceptwas put forward for the first time by Yablonovitch and John in1987. PCs arematerials that posses long-scale periodicity in their dielectric constants which leads tothe formation of photonic band gap (PBG). PBG could prohibit light in a certainfrequency just like the electron moves in the semiconductor. The three-dimensionalPC structure with the visible and near-infrared PBG has been widely applied, whichprovides a new method and thought for developing the optoelectronic devices. In theextraordinary properties of the PCs, a very important aspect is the modulation on thespontaneous emission of the embedded luminescence centers. It’s of great importanceto probe into the modulation on spontaneous radiation, which helps us understand thenature of emission and improve the emission efficiency in the macroporous matrix.Another character of the PC material is that it could inhibit the local thermal effectand reduce the non-radiative relaxation. To explore the inhibition on the local thermaleffect in PC structure could help us figure out the population mechanism of theupconversion emission and greatly enhance the upconversion efficency. In this thesis,we chose the rare earth ions doped inverse opal PC (IOPC) as the object. Firstly,Research on the modulation effect on the spontaneous radiation of Eu3+ions in Lu2O3:Eu3+IOPC is carried on. Secondly, it’s the research of modulation on the nonradiativerelaxation and the cross relaxation in some oxide hosts. what’s the most important isthat it proves IOPC could effectively inhibit local thermal effect and improve theupconversion emission in NaGd(WO4)2:Yb3+/Tm3+. Specific results in the experimentare listed below:1) The three-dimensional Lu2O3:Eu3IOPCs with controllable lattice constantswere prepared by the self-assembly method using PMMA as the template. The effectof modification of PC on emission spectra and dynamics of Eu3ions wassystemically studied. First, this work further support our previous conclusion that inweakly modified PCs, the increase of5D0-7FJradiative lifetime for Eu3+ions wasmainly due to modulation of the effective refractive index (Neff), rather than thedensity of optical states (DOS). Second, it is interesting to observe that SDR in5D1 increased linearly with the decreasing lattice constants, which was due to the changein5D1–5D0nonradiative relaxation of the IOPC samples. Third, it was found that thetemperature quenching of Eu3ions in the IOPCs could be suppressed considerablythan the REF sample. Furthermore, sensitive dual functional refractive index detectionwith infiltrated solutions was realized by monitoring the variation in PSB of theIOPCs and the lifetime of5D0–7F2transition for Lu2O3:Eu3.2) The UCL of Yb3+and Er3+co-doped GdVO4, NaGd(WO4)2and Y2O3which arewith different phonon thresholds were systemically studied and compared. Due to themodulation of large phonon of host lattices, the UCL in GdVO4and NaGd(WO4)2,demonstrated dominant green emission of2H4411/2, S3/2I15/2all the time, which presentsthat the nonradiative transition of4F7/2-2H11/2played a overpowering role compared tothe cross relaxation process of4F7/2+4I11/24F9/2+4F9/2in the populating. In the threelattices, the intensity ratio of the UCL to near-infrared DCL for Er3+increased greatlywith the increase of phonon threshold, indicating that the modulation of suitablephoton energy is an important factor to improve the competition of UCL in the oxidecompounds. In comparison with the optimal Y2O3:5%Yb3+/1%Er3+, the UCL ofNaGd(WO4)2:40%Yb3+/2%Er3+was enhanced by a factor of as high as~120and evencomparable to that of the NaYF4:Yb3+/Er3+commercial powders. This work points outthat efficient UCL phosphors could be also obtained in some oxide compounds withsuitable phonon threshold.3) The three-dimensonal NaGd(WO4)2: Yb3+/Tm3+IOPCs were prepared by theself-assembly method using PMMA as the template. The modification of PC effect onemission spectra and dynamics of Tm3+ions was systemically studied. Itcan be clearlyobserved that, in the IOPCs samples the ratio of UCL to UCL+DCL increases2.8-8times compared to the corresponding REF samples. In optimum sample the ratio ofUCL to UCL+DCL is as high as66%. Furthermore, remarkable enhancement offour-photon UCL of1D2-3H6/3F4was observed, indicating that the IOPC is a helpfulmicrostructure to realize high-order UCL. These facts can be both attributed to theinhibition of radiative and nonradiative relaxation in the IOPCs, which was furtherevidenced by UCL dynamics. This work indicates that the IOPC structure is aneffective device for improving the efficiency of UCL in oxide hosts with large phononenergy.