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Although considerable research works have witnessed the important modulations of oxygen vacancies on the optical, electrical, and magnetic properties of SnO 2 nanostructures, it is not easy to control oxygen vacancy defects in such systems.The difficulty stems from that oxygen vacancy is a kind of atomic defect, and its distribution is sensitive to process conditions and external factors, which makes direct characterization and purposeful control difficult. The purpose of this work on Ce-doped SnO 2 nanocrystals is to investigate the tolerance of the host lattice to Ce ions, the population and evolution of Ce3+/Ce4+ ions, and the possibility to adjust oxygen vacancies by Ce3+ ions, and then focus on the influence of oxygen vacancy defects on the band gap and luminescence performance. As Ce doping concentration increases from 0 to 12 at.%, the doped system changes from Ce3+ dominated at low doping amount (≤3 at.%) to Ce3+/Ce4+ coexistence at medium doping concentration (3 at.% ∼ 9 at.%), to occurrence of CeO 2 impurity phase at over doping (∼12 at.%). The optimum doping occurs at 6 at.%, which corresponds to the saturated critical point of Ce3+ content and the maximum oxygen vacancy concentration. Importantly, the oxygen vacancies in the current Ce-doped SnO 2 nanocrystals is directly regulated by the Ce3+ ion concentration on the Sn sites, which plays an important role in the band gap tuning and visible light emission. With Ce concentration increasing from 0 to 12 at.%, the band gap monotonicity decreases from 3.36 eV to 3.12 eV, while the intensity of the oxygen vacancy luminescence band first increases and then decreases, with the turning point at 6 at.%. Both band gap narrowing effect and enhanced emission indicate that Ce-doped SnO 2 should be a promising method to design and manufacture visible light responsive SnO 2 based optoelectronic materials by manipulating oxygen vacancy defects. [ABSTRACT FROM AUTHOR]

SrF 2 transparent ceramic is a promising upconversion material due to the low phonon energy. The effect of different sintering temperatures on Er:SrF 2 transparent ceramics was investigated. The suitable sintering temperature for Er:SrF 2 transparent ceramics was 900 °C by hot-pressed sintering in this study. High quality of Er:SrF 2 transparent ceramics with different doping concentrations were obtained. The upconversion luminescence spectra and decay behavior were compared between Er:SrF 2 and Er:CaF 2 transparent ceramics with different Er3+ doping concentration. The green emission of 5 at.% Er:SrF 2 ceramic was much stronger than that of 5 at.% Er:CaF 2 ceramic, while the red emission of Er:SrF 2 ceramic was almost the same as that of Er:CaF 2 ceramic. The upconversion luminescence lifetime of Er:SrF 2 transparent ceramics was longer than that of Er:CaF 2.All the results indicated Er:SrF 2 transparent ceramics was a candidate for green fluorescent upconversion materials. [ABSTRACT FROM AUTHOR]

Traditional inorganic ceramic materials usually exhibit macroscopic rigidity due to the incompatibility to the flexibility mechanism of traditional flexible materials such as sliding of polymer chains or atoms. Recently, new form of nanotechnology has been proposed to be capable of preparing inorganic flexible materials. In this paper, inorganic luminescent material (Ba,Ca)TiO 3 :Pr3+ was prepared into the flexible form by electrospinning technology, and the macroscopic flexibility of pure inorganic (Ba,Ca)TiO 3 :Pr3+ was systematic investigated. The crystal grain size was found to grow after higher temperature calcination, which benefits luminescence. However, lowering the calcination temperature will further optimize the flexibility of the membrane. This study shows that fibrous membrane fabrication is an applicable flexible fabrication strategy for inorganic oxides, which provides an important reference for the design of flexible materials. • Macroscopically self-supporting flexible (Ba,Ca)TiO3:Pr3+ nanofiber membranes were prepared for the first time. • The prepared macroscopic self-supporting flexible (Ba,Ca)TiO3:Pr3+ nanofiber membranes were characterized by a bending stress test system. • The macroscopically flexible nanofiber membrane is inorganic. • The macroscopically flexible inorganic nanofiber membrane has excellent luminescence properties. [ABSTRACT FROM AUTHOR]

• A well-designed multilayer core–shell UCNPs for generating orthogonal RGB luminescence with high color purity is proposed. • A simple approach for modulation of full-color upconversion luminescence in such UCNPs is introduced. • The display matrices based on UCNPs/epoxy AB glue can improve color pixel and optical resolution of color display. • The naked-eye-based volumetric/flat color display images with high color pixel and optical resolution can be achieved. Real three-dimensional (3D) volumetric display, as a pursuable ultimate goal in the field of display, have attracted extensive interest in both fundamental research and various frontier applications. In particular, the emergence of solid-state 3D display technology based on upconversion processes offers a versatile and powerful tool to achieve truly spatial naked-eye 3D displays. However, the realization of a solid-state real 3D volumetric color display with high spatiotemporal resolution in upconversion nanoparticles (UCNPs) at a single nanoparticle level remains a great challenge. Herein, without multiple compositions of UCNPs and high excitation power density or complex pulse excitation modulation, a specifically well-designed nanostructures of multilayer core–shell UCNPs, by manipulating energy transfer pathways, enables us to realize excitation power density-independent orthogonal red–green–blue (RGB) emissions with high color purity by utilizing near-infrared multiwavelength excitations. Notably, full-color emissions, involving red, orange, yellow, green, blue, indigo, violet, and white upconversion luminescence, can be dynamically regulated in this multilayer architecture by adjusting excitation wavelength and power density of the combined 980/808/1560 nm lasers. These emission profiles of multilayer UCNPs make them promising for a wide range of applications. As a proof of concept, we demonstrated their potential for application in real 3D volumetric full-color display. By incorporating such UCNPs into epoxy resin AB glue to construct transparent display matrices, the naked-eye-based 3D volumetric color display images with high color pixel and optical resolution can be achieved by moving the focal point of the laser beams within the stereo display matrices. These findings will benefit the future development of convenient and versatile optical technique for the fine tuning of full-color luminescence in a single nanoparticle level, and provide the possibility to construct true 3D volumetric full-color display technologies with high brightness, nanometer range display resolution, and multi-perspective display. [ABSTRACT FROM AUTHOR]

In this study, we synthesized series of La3Ga5SiO14:Pr3+ phosphors by high-temperature solid-state reactions. For the synthesized phosphors, X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrum (EDS), Raman, infrared (IR), absorption, photoluminescence (PL) and photoluminescence excitation (PLE) characterizations and decay characteristics were performed. The XRD patterns indicate that the synthesized phosphors have the same D32 (P321) structure with La3Ga5SiO14 host. The SEM image and EDS pattern show the irregular morphology and the combined La, Ga, Si, O and Pr elements for the synthesized phosphors. The room temperature Raman and IR spectra show that the phonon modes of the La3Ga5SiO14:Pr3+ phosphors follow the overall mode distributions of La3Ga5SiO14 and no appreciable changes in the phonon properties are observed, indicating that the force fields in the La3Ga5SiO14:Pr3+ lattice are not strongly altered by Pr3+ doping. The UV-Vis absorption spectra show that the phosphors contain a strong absorption band and several moderate bands resulting from the 4f-5d and f-f transitions of Pr3+ ions, respectively. La3Ga5SiO14:Pr3+ phosphors produce white light when λex = 255 nm. On the basis of emission data, the concentration quenching mechanism of the Pr3+ emission was speculated as the dipole-dipole interaction. The decay time and thermal stability were investigated, and the CIE coordinates with the corresponding correlated color temperatures were also calculated. • Crystal analyses of LGS: Pr3+ phosphors. • Detail Raman characteristics of LGS: Pr3+ phosphors. • Generation of white light by LGS: Pr3+ phosphors upon the UV light excitation. • Unique temperature response characteristics of the LGS: Pr3+ phosphor. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a T-shape organic molecule 5-(pyridin-4-yl)isophthalic acid was synthesized via a Suzuki coupling reaction and used as the ligand for a serial of mixed-lanthanide complexes. The chemical compositions of the lanthanide complexes were determined as (Eu x Tb1− x )2L3(H2O)4 by elemental analysis (EA) and thermo gravimetric analysis (TGA). The luminescent properties of the as-synthesized complexes were investigated and the intramolecular energy transfer mechanisms involved, were discussed. Efficient energy transfer from Tb3+ to Eu3+ was observed and controlled by changing the molar ratio of Tb3+ to Eu3+ ions, allowing the color tuning on the luminescent emission of the mixed-lanthanide complexes. [Copyright &y& Elsevier]

Halide perovskite quantum dots have attracted considerable research interest as excellent candidate for photonic and optoelectronic applications due to their unique optoelectronic properties. Stability is prerequisite and therefore is of critical importance. Here we demonstrate highly stable luminescent CsPbBr 3 quantum dots (QDs) can be achieved in different glass matrices via the high temperature melting process and melt-quench method. The microstructure of CsPbBr 3 QDs glass as well as their optical properties are systematically characterized by microscopic techniques and time-resolved spectroscopic techniques. We conclude the surface passivation is the key aspect for the high stability and high luminescence by embedding the quantum dots in the glass matrix. This study provides technical method to form highly stable luminescent solid devices and detailed physical understanding which is critical for the practical applications. • Luminescence in CsPbBr 3 QDs glass were study. • CsPbBr 3 QDs precipitated in 3 kinds of glass matrices. • Exciton recombination is confirmed as the dominant radiative mechanism. • the QDs glass could be flexibly fabricated into various device. [ABSTRACT FROM AUTHOR]

CaF 2 -SrF 2 hosts with substitution disorder of Ca2+/Sr2+ sites in the lattice provide lower local symmetry for RE3+ ions compared with pure CaF 2 or SrF 2 hosts, thereby facilitating more efficient 4f → 4f transitions. Here we report a study of effects of Sr2+ content on microstructure and spectroscopic properties of Nd3+ doped Ca 1-x Sr x F 2 transparent ceramic. Phase and microstructure analyses show that when x is in the range of 0–0.25, Nd: Ca 1-x Sr x F 2 nanoparticles keep pure CaF 2 phase with their size, morphology and agglomeration degree mildly changed. Increasing x from 0 to 0.2 significantly improves the luminescence intensity, emission lifetime and emission cross-section of Nd: Ca 1-x Sr x F 2 , however, hardly affects the concentration quenching. The luminescence intensities and emission lifetimes of x = 0.2 and 0.25 samples are very close, probably indicating SrF 2 phase has already formed in x = 0.25 sample. Based on the spectroscopic properties, the optimal Sr2+ content is found to be x = 0.2. • Nd: Ca 1-x Sr x F 2 keeps pure CaF 2 phase with x in range of 0–0.25, further increasing x leads to the formation of SrF 2 phase. • Changing x (0–0.25) has little influence on size and morphology of Nd: Ca 1-x Sr x F 2 nanoparticles. • I max , τ em, and σ em of Nd: Ca 1-x Sr x F 2 are increased with increasing x from 0 to 0.2, whereas FWHM and β 11/2 are decreased. • The optimal Sr2+ content is found to be x = 0.2. [ABSTRACT FROM AUTHOR]