Strong green fluorescent hydrogels with Ba2MgSi2O7:Eu2+ phosphor embedded in cellulose

Non‐cytotoxic and green‐emitting fluorescent hydrogels were constructed from a cellulose solution containing Ba₂MgSi₂O₇:Eu²⁺ green phosphor in a NaOH/urea aqueous system. The structure, optical properties and cytotoxicity of these hydrogels were studied. The Ba₂MgSi₂O₇:Eu²⁺ phosphor particles were dispersed evenly in the cellulose hydrogel matrix. Good luminescent properties of Ba₂MgSi₂O₇:Eu²⁺ phosphor were maintained in the hydrogels, leading to strong green emission under ultraviolet excitation. Fluorescent hydrogels have no obvious cytotoxicity in a 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) proliferation test, and have potential use in in vivo applications like optical imaging and drug delivery.     

Long‐Lasting Nanophosphors Applied to UV‐Resistant and Energy Storage Perovskite Solar Cells

Recently, considerable progress is achieved in lab prototype perovskite solar cells (PSCs); however, the stability of outdoor applications of PSCs remains a challenge due to the high sensitivity of perovskite material under moist and ultraviolet (UV) light conditions. In this work, the UV photostability of PSC devices is improved by incorporating a photon downshifting layer—SrAl₂O₄: Eu²⁺, Dy³⁺ (SAED)—prepared using the pulsed laser deposition approach. Light‐induced deep trap states in the photoactive layer are depressed, and UV light‐induced device degradation is inhibited after the SAED modification. Optimized power conversion efficiency (PCE) of 17.8% is obtained through the enhanced light harvesting and reduced carrier recombination provided by SAED. More importantly, a solar energy storage effect due to the long‐persistent luminescence of SAED is obtained after light illumination is turned off. The introduction of downconverting material with long‐persistent luminescence in PSCs not only represents a new strategy to improve PCE and light stability by photoconversion from UV to visible light but also provides a new paradigm for solar energy storage.     

Eu3+对山黧豆中的氨基酸及蛋白质代谢作用的研究

对山黧豆(Lathyrus sativus L.)幼苗整株,喷施一定浓度的Eu3+溶液吸收后,对其相关的生理指标进行测试,结果表明与水喷比较,根中丝氨酸、甘氨酸、丙氨酸、蛋氨酸、亮氨酸、脯氨酸、胱氨酸与对照持平,缬氨酸、酪氨酸、苯丙氨酸、组氨酸略有升高外,其余均低于对照;茎中除精氨酸、脯氨酸、色氨酸略高于对照外,其余均低于对照;叶中除蛋氨酸、色氨酸略高于对照外,其余均低于对照.游离氨基酸总量增加时,茎＞根＞叶,减少时,根＜茎＜叶.蛋白质含量经Eu3+ 处理茎中减少,根和叶中增加;水解酶比活性根＞茎＞叶;Na+、K+-ATPase活力却表现根＞茎＞叶的趋势.表明Eu3+ 对山黧豆生理活性代谢起到一定的调节作用.     

Photoluminescence and structural analysis of trivalent europium doped MLaAl3O7 (M = Ba,Ca, Mg and Sr) nanophosphors

The solution combustion technique was used to synthesize MLaAl₃O₇ (M = Ba, Ca, Mg, and Sr) nanophosphors‐doped with Eu³⁺ using metal nitrates as precursors. The photoluminescence (PL) emission spectra exhibited three peaks at 587–591, 610–616, and 653–654 corresponding to ⁵D₀→⁷F₁, ⁵D₀→⁷F₂, and ⁵D₀→⁷F₃ transitions, respectively. Upon excitation at 254 nm, these nanophosphors displayed strong red emission with the dominant peak attributed to the ⁵D₀→⁷F₂ transition of Eu³⁺. The materials were further heated at 900 and 1050°C for 2 h to examine the consequence of temperature on crystal lattice and PL emission intensity. X‐ray diffraction (XRD) analysis proved that all the synthesized materials were of a crystalline nature. CaLaAl₃O₇ material has a tetragonal crystal structure with space group P421m. Scherer's equation was used to calculate the crystallite size of synthesized phosphors using XRD data. A Fourier transformation infrared study was used to observe the stretching vibrations of metal–oxygen bonds. Infrared peaks for stretching vibrations corresponding to lanthanum–oxygen and aluminium–oxygen bonds were found at 582 and 777 cm^–1 respectively for CaLaAl₃O₇ phosphor material. Transmission electron microscopy images were used to determine the size of particles (18–37 nm for the as‐prepared materials) and also to analyze the three‐dimensional view of these materials. The experimental data indicate that these materials may be promising red‐emitting nanophosphors for use in white light‐emitting diodes.     

Synthesis and luminescent properties of novel BaGd2O4:Eu3+ scintillating phosphor

BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors were synthesized at 1300°C in air by conventional solid‐state reaction method. Phosphors were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence excitation (PLE) spectra, photoluminescence (PL) spectra and thermoluminescence (TL) spectra. Optimal PL intensity for BaGd_2‐xO₄:xEu³⁺ and Ba_1‐yGd_1.79‐2yEu_0.21Na_3yO₄ phosphors at 276 nm excitation were found to be x = 0.24 and y = 0.125, respectively. The PL intensity of Eu³⁺ emission could only be enhanced by 1.3 times with incorporation of Na⁺ into the BaGd₂O₄ host. Enhanced luminescence was attributed to the flux effect of Na⁺ ions. However, when BaGd₂O₄:Eu³⁺ phosphors were codoped with Na⁺ ions, the induced defects confirmed by TL spectra impaired the emission intensity of Eu³⁺ ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrothermal growth of Zn2SnO4:Eu,Ca for red emission

Zinc stannate (Zn₂SnO₄) and Zn₂SnO₄ codoped with Eu³⁺ and Ca²⁺ (ZTO:Eu,Ca) were synthesized by hydrothermal method and characterized with X‐ray diffraction (XRD), energy‐dispersive X‐ray analysis (EDAX), Raman spectrometer, field emission scanning electron microscopy (FESEM), ultraviolet‐visible (UV‐vis) and photoluminescence (PL) spectrophotometers. PL analysis of Zn₂SnO₄ gives broad defect induced emission in the region 500–750 nm. The crystal structure of Zn₂SnO₄ was retained even with a nominal doping of Eu, Ca and its combination in the Zn₂SnO₄. The Eu³⁺ ions were found to occupy the non‐centrosymmetric sites of the Zn₂SnO₄ and gave emissions at 592, 615 and 702 nm. Zn₂SnO₄:Eu,Ca showed red emission at 615 nm attributed to the electronic transition from the excited state ⁵D₀ → ⁷F₂ of the 4f⁶ configuration of Eu³⁺. Nominal codoping of Eu³⁺ and Ca²⁺ ions promoted the quenching of orange emission from Eu³⁺ in Zn₂SnO₄:Eu,Ca.     

Microwave‐assisted sintering synthesis of greenish‐yellow emitting Sr2SiO4:Eu2+ phosphors

Europium ion (Eu²⁺) doped Sr₂SiO₄ phosphors with greenish‐yellow emission were synthesized using microwave‐assisted sintering. The phase structure and photoluminescence (PL) properties of the obtained phosphor samples were investigated. The PL excitation spectra of the Sr₂SiO₄:Eu²⁺ phosphors exhibited a broad band in the range of 260 nm to 485 nm with a maximum at 361 nm attributed to the 5f‐4d allowed transition of the Eu²⁺ ions. Under an excitation at 361 nm, the Sr₂SiO₄:Eu²⁺ phosphor exhibited a greenish‐yellow emission peak at 541 nm with an International‐Commission‐on‐Illumination (CIE) chromaticity of (0.3064, 0.4772). The results suggest that the microwave‐assisted sintering method is promising for the synthesis of phosphors owing to the decreased sintering time without the use of additional reductive agents.     

Persistent luminescence of CaMgSi2O6:Eu2+,Dy3+ and CaMgSi2O6:Eu2+,Ce3+ phosphors prepared using the solid‐state reaction method

CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors were synthesized using the solid‐state reaction method. X‐Ray diffraction (XRD) and photoluminescence (PL) analyses were used to characterize the phosphors. The XRD results revealed that the synthesized CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors were crystalline and are assigned to the monoclinic structure with a space group C2/c. The calculated crystal sizes of CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors with a main (221) diffraction peak were 44.87 and 53.51 nm, respectively. Energy‐dispersive X‐ray spectroscopy (EDX) confirmed the proper preparation of the sample. The PL emission spectra of CaMgSi₂O₆:Eu²⁺,Dy³⁺ and CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphors have a broad band peak at 444.5 and 466 nm, respectively, which is due to electronic transition from 4f⁶5d¹ to 4f⁷. The afterglow results indicate that the CaMgSi₂O₆:Eu²⁺,Dy³⁺ phosphor has better persistence luminescence than the CaMgSi₂O₆:Eu²⁺,Ce³⁺ phosphor. Copyright © 2015 John Wiley & Sons, Ltd.     

Luminescence in Li2BaP2O7

The photo‐, thermo‐ and optically stimulated luminescence in Li₂BaP₂O₇ activated with Eu²⁺/Cu⁺ are reported. Strong thermoluminescence, which is about two times greater than LiF‐TLD 100 was observed in the Eu²⁺‐activated sample. It also exhibited optically stimulated luminescence sensitivity of ~20% that of commercial Al₂O₃:C phosphor. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis of the structure and luminescence properties of Zn2GeO4:Eu3+ according to Judd–Ofelt theory

The preparation and characteristic of nanorod-like Zn₂GeO₄ doped with Eu³⁺ or zinc germanate (ZGO):xEu³⁺ (x = 0 ÷ 0.05), which was synthesized using the hydrothermal method, are described. The influence of Eu³⁺-doping ions on the structure and the optical properties of ZGO was also investigated. According to the photoluminescence spectra, ZGO:xEu³⁺ nanophosphors gave a red emission due to the ⁵D₀→⁷F₂ emission of Eu³⁺ ions. In accordance with Judd–Ofelt theory, the intensity parameters for f–f transitions from the emission and absorption spectrum were determined. At the ⁵D₀ excited state of Eu³⁺, total spontaneous emission probabilities (A_R), lifetimes (τ_R), branching ratios (β_R), and quantum efficiency (η) were calculated. The ZGO:xEu³⁺ (x = 0.02, 0.03, 0.04) phosphor showed the branch ratio β (⁵D₀→⁷F₂) > 60%, indicating that the phosphors prepared here have a promising potential as laser light. The sample with a concentration of 0.04Eu³⁺ achieved the highest quantum efficiency of 84%, suggesting that it has potential light-emitting diode applications.