Strong Upconversion Photoluminescence Research Articles

Robust Strategy to Improve the Compatibility between Incorporated Upconversion Nanoparticles and the Bulk Transparent Polymer Matrix.

Traditional transparent polymer nanocomposites combined with functional fluorescent inorganic nanofillers are promising for many advanced optical applications. However, the aggregation of the incorporated functional nanoparticles results in light scattering and will decrease the transparency of nanocomposites, which will restrain the application of the transparent nanocomposites. Herein, a robust synthesis strategy was proposed to modify upconversion nanoparticles (UCNPs) with polymethyl methacrylate (PMMA) to form UCNP@PMMA core@shell nanocomposites though metal-free photoinduced surface-initiated atom transfer radical polymerization (photo-SI-ATRP), and thus, the dispersity of UCNP@PMMA and the interface compatibility between the surface of UCNPs and the bulk PMMA matrix was greatly improved. The obtained PMMA nanocomposites possess high transparency and show strong upconversion photoluminescence properties, which promises great opportunities for application in 3D display and related optoelectronic fields. This strategy could also be applied to fabricate other kinds of functional transparent polymer nanocomposites with inorganic nanoparticles uniformly dispersed.

Up-conversion photoluminescence based on the intrinsic defects in Na 0.5 Bi 0.5 TiO 3 :Yb 3+ ceramics

Abstract Na 0.5 Bi 0.5- x Yb x TiO 3 (NBT: x Yb, x = 0–0.03) ceramics with different Yb doping contents were prepared with a conventional solid-state reaction method. A strong up-conversion photoluminescence (UC PL) based on the intrinsic defect of Na 0.5 Bi 0.5 TiO 3 :Yb 3+ ceramics without doping any rare earth activators under a 980 nm diode laser excitation is found. The effects of annealing, temperatures, and external electric fields on the UC PL were investigated. It is found that the UC emissions can be tuned by both chemical method: annealing at 600 °C under a low oxygen pressure, and physical approach: an application of external electric field upon the ceramics. The possible UC PL mechanism of the defects in the ceramics is also discussed via the UC and down-conversion PL characteristics. The unique UC PL features, which is much different with the conventional rare earth activators, and universality of intrinsic defects in perovskite ferroelectrics open a new window for the development of UC PL materials.

Upconversion photoluminescence of epitaxial Yb3 +/Er3 + codoped ferroelectric Pb(Zr,Ti)O3 films on silicon substrates

Thin films of Yb3+/Er3+ codoped Pb(Zr,Ti)O3 (PZT:Yb/Er) have been epitaxially grown on the SrTiO3 buffered Si wafer by pulsed laser deposition. Strong upconversion photoluminescence was observed in the PZT:Yb/Er thin film. Using piezoresponse force microscopy, polar domains in the PZT:Yb/Er film can be reversibly switched with a phase change of 180°. Ferroelectric hysteresis loop shape with a well-saturated response was observed. The epitaxially grown lanthanide-doped PZT on silicon opens up a promising route to the integration of luminescent functional oxides on the silicon platform.

Strong Upconversion Photoluminescence and Large Ferroelectric Polarization in Er3+–Yb3+–W6+ Triply Substituted Bismuth Titanate Thin Films Prepared by Chemical Solution Deposition

Strong upconversion photoluminescence and large ferroelectric polarization were observed for the first time in layered structure Er3+–Yb3+–W6+ triply substituted bismuth titanate thin films. The thin films were prepared on fused silica and Pt(111)/Ti/SiO2/Si substrates by chemical solution deposition. Two green emission bands and a red one were observed in the upconversion photoluminescence spectra for all the films pumped by a 980 nm laser diode, which correspond to 2H11/2, 4S3/2, and 4F9/2 to 4I15/2 transitions of Er3+ ions, respectively. A two‐photon energy‐transfer process was confirmed by the power dependence of emission intensity. Compared with that of Er3+–Yb3+‐substituted bismuth titanate thin films, the improved photoluminescence is related to the reduced defects such as oxygen vacancies due to B‐site (Ti4+) substitution by W6+ ions, while the large ferroelectric remnant polarization can be attributed to the increased structure distortion and the reduced oxygen vacancies due to cosubstitution of A‐site (Bi3+) and B‐site (Ti4+) by Er3+, Yb3+, and W6+ ions, respectively. The combination of the strong upconversion photoluminescence and the good ferroelectric properties in the thin films would open the possibility of realizing novel multifunctional optoelectronic integration device applications.

Up-conversion photoluminescence characteristics of Yb3+:Er3+:Tm3+ co-doped borosilicate glasses

Yb3+:Er3+:Tm3+co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb3+, Er3+ and Tm3+ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb3+ Stark splitting levels to pump Tm3+ ions and there exists an optimum pump power. The concentration of the Tm3+ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb3+:Er3+:Tm3+ co-doped borosilicate glasses.

Preparation and Upconversion Luminescence of Three-Dimensionally Ordered Macroporous ZrO2: Er3+, Yb3+

The three-dimensionally ordered macroporous (3DOM) ZrO2: Er(3+), Yb(3+) materials were successfully synthesized by the sol-gel method combined with a polystyrene latex sphere templating technique, and their morphologies, surface physicochemical properties, and upconversion photoluminescence (UC-PL) properties were studied. The results indicate that the materials exhibited both porosity and strong UC-PL under the excitation of a 978 nm diode laser. In comparison with the nonporous samples, the relative intensity of the red ((4)F(9/2)-(4)I(15/2)) to the green ((4)S(3/2)/(2)H(11/2)-(4)I(15/2)) emission decreased visibly because of the decreased nonradiative relaxation in the 3DOM materials. It was also observed that the relative intensity of the green emission to the red emission increased significantly with the increasing excitation power. An indirect three-photon populating process occurred for the green emission as the excitation power and Yb(3+) concentration was high enough.

- and -doped as potential gain media for GaAlAs diode laser pumped systems

Single crystals of - and -doped have been grown by top-seeded solution growth. Large concentrations of rare-earth substituents on the site are possible in this crystal on account of the orientation and packing of adjacent coordination polyhedra. Odd-parity distortions of the rare-earth site result in large absorption and emission cross sections for both and . The absorption, emission and lifetime spectroscopy of : are reported. Applications of : and : as gain media in GaAlAs diode-pumped laser devices are discussed in terms of the spectroscopy of these materials. Preliminary experiments connected with such applications are reported. Whilst pumping the materials close to 800 nm, low-threshold, high slope efficiency continuous wave laser action was achieved at in : and strong upconversion photoluminescence close to 550 nm was observed in :.