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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]

Polymer-based waveguide amplifiers are essential components in integrated optical systems, as their gain bandwidths directly determine the operating wavelength of optical circuits. However, development of the wideband gain media has been challenging, making it difficult to fabricate devices with broadband amplification capability. Rare earth ion-doped nanoparticles (NPs) are a key component in the gain media, and their full width at half maximum (FWHM) of the emission peak decides the final gain bandwidth of the gain media. Here, KMnF3: Yb, Er, Ce@KMnF3: Yb NPs with the broad full width at half maximum (FWHM) of the emission peak covering the S+C band was prepared. The NPs were synthesized using a hydrothermal method, and the FWHM of the emission peak of NPs reached 76 nm under the excitation of a 980 nm laser. The introduction of Ce3+ ions and a core-shell structure coating greatly enhanced the emission intensity of NPs at C band. Since KMnF3: Yb, Er, Ce@KMnF3: Yb NPs have exceptional broadband luminescence properties at C band, KMnF3: Yb, Er, Ce@KMnF3: Yb NPs can be the potential gain medium in the future polymer-based waveguide amplifiers. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbBr3 perovskites exhibit great potential in optoelectronic application due to their outstanding physical properties for optoelectronics. However, the relatively low luminescence efficiency of the bulk CsPbBr3 crystal hampers its further application. Here, we report a facile method to enhance the optical efficiency of halide perovskite powder via doping the transition metal Ni ions. It is demonstrated that Ni doping results in the formation of the Cs(NiPb)Br3 alloy and also triggers the phase transition of CsPbBr3 from orthorhombic to cubic. Both the Cs(NiPb)Br3 alloy and cubic CsPbBr3 are found to contribute to the asymmetric photoluminescence (PL) spectra in the green-yellow light band. The splitting-peak fitting experiments for the overlapped PL spectrum based on the bi-Gaussian line model reveal that the Cs(NiPb)Br3 alloy dominates the contribution of the observed PL enhancement. The Ni2+ doping is also beneficial for optimizing the crystallinity of the CsPbBr3 perovskite, suppressing the nonradiative recombination and significantly enhancing the photoluminescence consequently. Our investigation provides a novel insight into the effect of environmentally friendly metal doping in perovskites. [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]

Ce3+- or/and Dy3+-doped Mg2Al4Si5O18 phosphors have been fabricated via a sintering process at 1400°C for 5 h and their crystallinity and luminescence characteristics investigated. x-Ray powder diffraction analysis demonstrated that Ce3+/Dy3+ ions entered the Mg2Al4Si5O18 host and formed a solid solution. When excited at 345 nm, Ce3+-doped Mg2Al4Si5O18 phosphor emitted light in the blue region while Dy3+-doped Mg2Al4Si5O18 phosphor emitted light in the yellow region. When excited at 345 nm, emission bands located in both the blue and yellow regions were observed for the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphor. Because of Ce3+ → Dy3+ energy transfers, the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphor showed tunable luminescence, changing from the blue to yellow–green region through the white region with increasing Dy3+ concentration in the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphor. The decay characteristics of the Ce3+ emission in the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphors were also investigated. With increasing Dy3+ concentration, the lifetime of the Ce3+ emission decreased continuously, further confirming the occurrence of Ce3+ → Dy3+ energy transfer. [ABSTRACT FROM AUTHOR]

A photoresponsive hollow molecularly imprinted polymer (PHMIP) was fabricated for photoresponsive recognition and determination of trace bisphenol A (BPA) in aqueous media using a water-soluble azo compound as the functional monomer. The PHMIP was prepared on sacrificial silica microspheres by surface imprinting and subsequent removal of the silica core. The PHMIP displayed photocontrolled recognition for BPA. SEM, TEM, FT-IR, TGA and N 2 adsorption-desorption analyses confirmed successful formation of the hollow structure. The PHMIP displayed higher binding capacity, a larger specific area, and faster mass transfer rate than its corresponding surface molecularly imprinted polymer. The PHMIP was used to determine trace BPA in real samples with a limit of detection of 0.5 ppm. For samples spiked at 0–10 ppm, the BPA recoveries were in the range of 93.0%–99.0%. This PHMIP-based method provides convenient and inexpensive detection method for trace BPA in environmental samples. This method is especially suitable for determining materials that do not possess specific spectroscopic or luminescent properties. [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]

In acidic solution, a serials of water-soluble coordination polymers (CPs) were isolated as zonal 1D-CPs 1,3-propanediaminetetraacetato lanthanides [ Ln (1,3-H 3 pdta)(H 2 O) 5 ] n ·2Cl n ·3 n H 2 O [ Ln =La, 1 ; Ce, 2 ; Pr, 3 ; Nd, 4 ; Sm, 5 ] (1,3-H 4 pdta=1,3-propanediaminetetraacetic acid, C 11 H 18 N 2 O 8 ) in high yields. When 1 eq. mol potassium hydroxide was added to the solutions of 1D-CPs, respectively, two 1D-CPs [Ln(1,3-H 2 pdta)(H 2 O) 3 ] n ·Cl n ·2 n H 2 O [ Ln =Sm, 6 ; Gd, 7 ] were isolated at room temperature and seven 2D-CPs [ Ln (1,3-H 2 pdta)(H 2 O) 2 ] n ·Cl n ·2 n H 2 O [ Ln =La, 8 ; Ce, 9 ; Pr, 10 ; Nd, 11 ; Sm, 12 ; Eu, 13 ; Gd, 14 ] were isolated at 70 °C. When the crystals of 1–4 were hydrothermally heated at 180 °C with 1–2 eq. mol potassium hydroxide, four 3D-CPs [ Ln (1,3-Hpdta)] n · n H 2 O [ Ln =La, 15 ; Ce, 16 ; Pr, 17 ; Nd, 18 ] were obtained. The two 2D-CPs [ Ln (1,3-Hpdta)(H 2 O)] n ·4 n H 2 O (Sm, 19 ; Eu, 20 ) were isolated in similar reaction conditions. With the increments of pH value in the solution and reaction temperature, the structure becomes more complicated. 1–5 are soluble in water and 1 was traced by solution 13 C{ 1 H} NMR technique, the water-soluble lanthanides 1 and 5 show catalytic activity to ester hydrolysis reaction respectively, which indicate their important roles in the hydrolytic reaction. The europium complexes 13 and 20 show visible fluorescence at an excitation of 394 nm. The structure diversity is mainly caused by the variation of coordinated ligand in different pH values and lanthanide contraction effect. Acidic conditions are favorable for the isolations of lanthanide complexes in different structures and this may helpful to separate different lanthanides. The thermal stability investigations reveal that acidic condition is favorable to obtain the oxides at a lower temperature. [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]

All-inorganic CsPbBr3 perovskites exhibit great potential in optoelectronic application due to their outstanding physical properties for optoelectronics. However, the relatively low luminescence efficiency of the bulk CsPbBr3 crystal hampers its further application. Here, we report a facile method to enhance the optical efficiency of halide perovskite powder via doping the transition metal Ni ions. It is demonstrated that Ni doping results in the formation of the Cs(NiPb)Br3 alloy and also triggers the phase transition of CsPbBr3 from orthorhombic to cubic. Both the Cs(NiPb)Br3 alloy and cubic CsPbBr3 are found to contribute to the asymmetric photoluminescence (PL) spectra in the green-yellow light band. The splitting-peak fitting experiments for the overlapped PL spectrum based on the bi-Gaussian line model reveal that the Cs(NiPb)Br3 alloy dominates the contribution of the observed PL enhancement. The Ni2+ doping is also beneficial for optimizing the crystallinity of the CsPbBr3 perovskite, suppressing the nonradiative recombination and significantly enhancing the photoluminescence consequently. Our investigation provides a novel insight into the effect of environmentally friendly metal doping in perovskites. [ABSTRACT FROM AUTHOR]

A water-stable metal-organic framework (MOF) EuNDC has been synthesized for selective detection of the well-known contaminant and toxicant picric acid (PA) in aqueous solution. Due to the photo-induced electron transfer and self-absorption mechanism, EuNDC displayed rapid, selective and sensitive detection of PA with a detection limit of 37.6 ppb. Recyclability experiments revealed that EuNDC retains its initial luminescent intensity and same quenching efficiency in each cycle, suggesting high photostability and reusability for long-term sensing applications. The excellent detection performance of EuNDC makes it a promising PA sensing material for practical applications. [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]

A near infrared luminescent MOFs thermometer (Nd 0.676 Yb 0.324 BTC) was prepared via a simple solvothermal method using Ln 3+ (Ln=Nd, Yb) ions and 1, 3, 5-benznenetricarboxylic acid (H 3 BTC), and characterized by PXRD, TGA, ICP, and photoluminescence (PL) spectrum. These results indicate that the Nd 0.676 Yb 0.324 BTC displays high relative sensitivity and excellent repeatability in the physiological temperature range (288–323 K), and the maximum relative sensitivity is determined to be 1.187% K −1 at 323 K. These NIR luminescent MOFs may have potential applications in physiological temperature sensing. [ABSTRACT FROM AUTHOR]

Design and synthesis of a series of isostructural lanthanide metal-organic frameworks (LnMOFs) serving as phosphors by coordinate the H 2 TIPA (5-(1 H -tetrazol-5-yl)isophthalic acid) ligands and lanthanide ions is reported. The color of the luminescence can be tuned by adjusting the relative concentration of the lanthanide ions in the host framework GdTIPA , and near-pure-white light emission can be achieved. [ABSTRACT FROM AUTHOR]

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]