Xvsheng Qiao

Judd-Ofelt analysis and luminescence behavior of Er3+ ions in glass ceramics containing SrF2 nanocrystals

The upconversion luminescence and near infrared luminescence of the Er3+ ions in transparent oxyfluoride glass ceramics containing SrF2 nanocrystals have been investigated. The formation of SrF2 nanocrystals in the glass ceramics was confirmed by x-ray diffraction. The oscillator strengths for several transitions of the Er3+ ions in the glass and glass ceramics have been obtained and then the Judd-Ofelt parameters were determined. The split near infrared emission peaks of the Er3+ ions in the glass ceramics can be observed because the Er3+ ions have been incorporated into crystalline environment of the SrF2 nanocrystals. The upconversion luminescence intensity of Er3+ ions in the glass ceramics increased significantly with the increasing crystallization time. The transition mechanisms of the green and red upconversion luminescence have been ascribed to two-photon process and the blue upconversion luminescence to three-photon process.

Near-infrared emission of Yb 3+ through energy transfer from ZnO to Yb 3+ in glass ceramic containing ZnO nanocrystals

Yb(3+)-doped glass and glass ceramic containing ZnO nanocrystals were prepared by the melting-quenching method and subsequent heat treatment. Intense near-IR emission around 1000 nm that originated from the transition of Yb(3+):(2)F(5/2)→(2)F(7/2) was generated as a result of energy transfer from oxygen interstitials in ZnO nanocrystals to Yb(3+) with energy transfer efficiency of about 10%. The quantum yield for the near-IR emission of Yb(3+) under the excitation of 390 nm was about 16.7%. These materials have potential application in achieving high-efficiency Si solar cells via spectrum modification.

Spectroscopic properties of Er3+ doped glass ceramics containing Sr2GdF7 nanocrystals

The Er3+ doped transparent oxyfluoride glass ceramics containing Sr2GdF7 nanocrystals were prepared and their spectroscopic properties were discussed. The formation of Sr2GdF7 nanocrystals in the glass ceramics was confirmed by x-ray diffraction. The split peaks of the upconversion and near infrared emission bands of the Er3+ doped glass ceramics can be observed. The upconversion luminescence intensity of Er3+ in the glass ceramics increased significantly with the increasing heat treated temperature. The luminescence decay curves and time-resolved spectra indicated that the lifetime of the S3∕24 state of Er3+ in the glass ceramic was longer than that in the glass.The Er{sup 3+} doped transparent oxyfluoride glass ceramics containing Sr{sub 2}GdF{sub 7} nanocrystals were prepared and their spectroscopic properties were discussed. The formation of Sr{sub 2}GdF{sub 7} nanocrystals in the glass ceramics was confirmed by x-ray diffraction. The split peaks of the upconversion and near infrared emission bands of the Er{sup 3+} doped glass ceramics can be observed. The upconversion luminescence intensity of Er{sup 3+} in the glass ceramics increased significantly with the increasing heat treated temperature. The luminescence decay curves and time-resolved spectra indicated that the lifetime of the {sup 4}S{sub 3/2} state of Er{sup 3+} in the glass ceramic was longer than that in the glass.

Establishing the Structural Integrity of Core–Shell Nanoparticles against Elemental Migration using Luminescent Lanthanide Probes

Core-shell structured nanoparticles are increasingly used to host luminescent lanthanide ions but the structural integrity of these nanoparticles still lacks sufficient understanding. Herein, we present a new approach to detect the diffusion of dopant ions in core-shell nanostructures using luminescent lanthanide probes whose emission profile and luminescence lifetime are sensitive to the chemical environment. We show that dopant ions in solution-synthesized core-shell nanoparticles are firmly confined in the designed locations. However, annealing at certain temperatures (greater than circa 350 °C) promotes diffusion of the dopant ions and leads to degradation of the integrity of the nanoparticles. These insights into core-shell nanostructures should enhance our ability to understand and use lanthanide-doped luminescent nanoparticles.

Spectroscopic properties of Er3+ and Yb3+ co-doped glass ceramics containing SrF2 nanocrystals

The spectroscopic properties of Er3+/Yb3+ co-doped 50SiO2–10Al2O3–20ZnF2–20SrF2 glass and glass ceramic containing SrF2 nanocrystals were investigated. The formation of SrF2 nanocrystals in the glass ceramic was confirmed by XRD. The oscillator strengths for several transitions of the Er3+ ions in the glass ceramic have been obtained and the Judd–Ofelt parameters were then determined. The XRD result and Judd–Ofelt parameters suggested that Er3+ and Yb3+ ions had efficiently enriched in the SrF2 nanocrystals in the glass ceramic. The lifetime of excited states has been used to reveal the surroundings of luminescent Er3+ and Yb3+ and energy transfer (ET) mechanism between Er3+ and Yb3+. Much stronger upconversion luminescence and longer lifetime of the Er3+/Yb3+ co-doped glass ceramic were observed in comparison with the Er3+/Yb3+ co-doped glass, which could be ascribed to more efficient ET from Yb3+ to Er3+ due to the enrichment of Yb3+ and Er3+ and the shortening of the distance between lanthanide ions in the precipitated SrF2 nanocrystals.

Spectroscopic properties of Er3+/Yb3+ co-doped 50SiO2-20Al2O3-30CaF2 glass and glass ceramics

A spectroscopic investigation of Er3+/Yb3+ co-doped 50SiO2–20Al2O3–30CaF2 glasses and transparent glass ceramics containing CaF2 nanocrystals is presented. The formation of CaF2 nanocrystals in the glass ceramic was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The Judd–Ofelt parameters of the Er3+ ions in the glass and glass ceramic have been calculated; they suggested that Er3+ ions had been incorporated into CaF2 nanocrystals in the glass ceramics. The upconversion luminescence intensity of the Er3+/Yb3+ co-doped glass ceramic was much stronger than that of the Er3+/Yb3+ co-doped glass. The upconversion luminescence mechanism has been ascribed to a two-photon absorption process for the green and red luminescence and a three-photon absorption process for the blue luminescence.

Femtosecond laser writing of Er 3+ -doped CaF 2 crystalline patterns in glass

We report on the use of 800 nm, 250 kHz femtosecond laser pulses to precipitate Er(3+)-doped CaF(2) crystals inside oxyfluoride glass, which was confirmed with x-ray diffraction analysis. Confocal upconversion luminescence spectra show that the precipitated crystals have greatly enhanced upconversion luminescence intensity in comparison with unmodified glass. We demonstrate the possibility of three-dimensional optical data storage in the glass by the use of the confocal upconversion luminescence imaging.

Luminescence behavior of Er3+ doped glass ceramics containing Sr2RF7 (R=Y,Gd,La) nanocrystals

The luminescence behaviors of Er3+ doped glass ceramics containing Sr2RF7 (R=Y,Gd,La) nanocrystals were investigated. The formation of Sr2RF7 nanocrystals in the glass ceramics was confirmed by x-ray diffraction and high resolution transmission electron microscopy. Energy dispersive x-ray spectroscopy analysis showed that the Er3+ ions were efficiently incorporated in Sr2GdF7 nanocrystals. The efficient upconversion luminescence of the Er3+ in the glass ceramics can be observed. The lifetime of the Er3+ in the glass ceramics was found to be much longer than that in the glass due to the lower phonon energy of fluoride crystals when Er3+ entered efficiently fluoride crystals in the glass ceramics.

Facile Synthesis of γ-In2 Se3 Nanoflowers toward High Performance Self-Powered Broadband γ-In2 Se3 /Si Heterojunction Photodiode

An effective colloidal process involving the hot-injection method is developed to synthesize uniform nanoflowers consisting of 2D γ-In2 Se3 nanosheets. By exploiting the narrow direct bandgap and high absorption coefficient in the visible light range of In2 Se3 , a high-quality γ-In2 Se3 /Si heterojunction photodiode is fabricated. This photodiode shows a high photoresponse under light illumination, short response/recovery times, and long-term durability. In addition, the γ-In2 Se3 /Si heterojunction photodiode is self-powered and displays a broadband spectral response ranging from UV to IR with a high responsivity and detectivity. These excellent performances make the γ-In2 Se3 /Si heterojunction very interesting as highly efficient photodetectors.

Crystalline Hollow Microrods for Site‐Selective Enhancement of Nonlinear Photoluminescence

A class of one-dimensional hollow microstructure is described, which was formed by a kinetically controlled crystal growth process. A hexagonal-phase NaYbF4 microrod comprising isolated holes along the longitudinal axis was synthesized by a one-pot hydrothermal method with the assistance of citrate ligands. The structural void feature modulates light intensity across the microrods as a result of interference arising from light scattering and reflection by the inner walls. A single crystal comprising a structural void was doped with upconverting lanthanide ions. Upon near-infrared excitation of the doped crystal spatially resolvable optical codes were produced.