Effects of chitosan-RE³⁺-bentonite on growth of Chlorella vulgaris

Bentonite was modified with chitosan and REIs(La3+,Ce3+) to form chitosan-RE3+-bentonite(CRB) . CRB were characterized by DSC and FT-IR. And the inhibitory effects of CRB on the growth of Chlorella vulgaris were investigated. The results indicated that CRB could inhibit the growth of Chlorella vulgaris. The relative conductivity and the generation of malondialdehyde(MDA) increased. In addition,the superoxide dismutase(SOD) and peroxidase(POD) activities decreased. So CRB could be a promising algaecide agent.     

Effects of lanthanum nitrate on growth and chlorophyll fluorescence characteristics of Alternanthera philoxeroides under perchlorate stress

To investigate the effects of exogenous lanthanum (La) on Alternanthera philoxeroides (Mart.) Griseb under perchlorate stress, changes in the growth and physiological parameters were investigated in so...     

Effects of lanthanum on abscisic acid regulation of root growth in Arabidopsis

Rare earth elements(REEs) were reported to have adverse biology effects on plant growth and production. However, whether REEs are involved in plant hormone abscisic acid signal is not clear. Here we reported that REE lanthanum(La) interacted with abscisic acid(ABA) in the regulation of seed germination and root growth in model plant Arabidopsis. La3+at a concentration of 10 μmol/L alleviated ABA depression of seed germination and reversed ABA inhibition of root elongation growth in Arabidopsis. Previous studies showed that ABA could promote root hair development. In the present study, La3+inhibited root hair development promoted by ABA. Moreover, La3+inhibited H2 O2 generation induced by ABA in root cells. Therefore we inferred that La3+might interact with ABA upstream of H2 O2 generation.     

Effect of La3+ on seed germination and seedling growth of Salvia miltiorrhiza

The purpose of this study is to determine the effect of La³⁺ solution on seed germination and seedling growth of Salvia miltiorrhiza. Different concentrations of La³⁺ were used on seed by soaking treated to determine which concentration is the most suitable for the growth of S. miltiorrhiza. Results show that the low concentration of La³⁺ displays the promotion effect on S. miltiorrhiza seed germination rate and germination potential, and the promotion effect reaches the highest level when the concentration of La³⁺ solution is 30 mg/L, the germination index and vigor index are the highest in 20 mg/L, and it can also increase the contents of soluble sugar, soluble protein and chlorophyll. Meanwhile, the activity of antioxidant enzyme system (CAT and SOD) are improved, thus the photosynthesis and resistance of plant are enhanced. On the contrary, when the La³⁺ concentration is high, La³⁺ can inhibit plant growth. Thus La³⁺ displays the "homesis effect" on S. miltiorrhiza growth.     

Effects of cerium on growth and physiological characteristics of Anabaena flosaquae

In the present study, the effects of cerium (Ce) on the growth and physiological changes were investigated in the cyanobacterium Anabaena flosaquae (A. flosaquae) during a 17-day period. The results showed that the content of chlorophyll a (chl-a) and activity of anti-oxidase (e.g. superoxide dismutase, peroxidase, and catalase) increased with Ce3+ concentration in the range of 0.05 to 0.1 mg/L and the growth of A. flosaquae was stimulated. While at around 5 mg/L, the content of malondiadehyde (MDA) increased significantly but the activ-ity of antioxidase reduced, which resulted in the ruin of antioxidant defense system. Compared to the control (Ce3+-free), the population size of live cells declined significantly. Microcystin-LR (MC-LR), the most common and toxic cyanotoxins produced by A. flosaquae, was de-tected and the highest content of MC-LR was observed in 10 mg/L Ce3+ treatment. These results implied that the aqueous environment might suffer a more negative ecological impact when exposed to relatively low Ce3+ concentrations (<0.1 mg/L).)     

Energy transfer and luminescent properties of Tb3+ and Tb3+, Yb3+ doped CNGG phosphors

In this work, calcium niobium gallium garnet (Ca₃Nb_1.6875Ga_3.1875O₁₂ - CNGG) ceramic samples single-doped with Tb³⁺ and co-doped with Tb³⁺ and Yb³⁺ ions were sintered by the solid-state reaction method. The structural characterization of the samples was carried out by X-ray diffraction measurements. The optimal concentration of Tb³⁺ ions corresponding to the maximum luminescence in the green spectral range in CNGG:x at% Tb (x = 0.1, 0.5, 1, 2, 3, 4, and 5) was determined to be 4 at%. The time-resolved luminescence of the ⁵D₄ level (Tb³⁺) in the CNGG:x at% Tb samples was analysed to explore the quenching mechanisms involved in the Tb³⁺ green emission. Co-doped CNGG:4 at% Tb,y at% Yb (y = 0.5, 2, 4, 6, 8, and 10) ceramics were prepared and investigated. It is shown that CNGG:4 at% Tb,y at% Yb phosphors exhibit intense green luminescence under ultra-violet (UV), visible (VIS), and near-infrared (NIR) excitation, thus demonstrating the presence of simultaneous down-conversion (DC) and up-conversion (UC) processes. The dependence of the UC luminescence intensity on the diode laser pumping power was measured and the results indicate a two-photon process based on cooperative energy transfer (CET). Under UV excitation, the lifetime of the ⁵D₄ (Tb³⁺) level slowly increases with increase of Yb³⁺ concentration, suggesting the energy transfer from Yb³⁺ to Tb³⁺ ions, while under NIR excitation, the lifetime of the ⁵D₄ (Tb³⁺) level decreases with increase of Yb³⁺ ions concentration, indicating the presence of a strong energy transfer from Tb³⁺ to Yb³⁺ ions. The highest energy transfer efficiency of ηET ≈42% was determined for the CNGG:4 at% Tb,10 at% Yb sample. The obtained results indicate that CNGG:(Tb³⁺, Yb³⁺) could be efficient new yellowish-green-emitting phosphors.     

Luminescence properties of red phosphors Ca_（10）Li（PO_4）_7：Eu~（3＋）

A series of red phosphors Ca10Li (PO4)7:Eu3+ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spectra,CIE chromaticity and quantum efficiency. Results indicated that the phosphors could be effectively excited by the near ultraviolet (NUV) light (393 nm). The main emission peaks of the phosphor were ascribed to the transition 5D0-7F2 (613 and 617 nm) of Eu3+ ion when samples were excited by...     

Red-emitting CaWO4:Eu3+,Tm3+ phosphor for solid-state lighting: Luminescent properties and morphology evolution

CaWO₄:xEu³⁺,yTm³⁺crystals were obtained by facile synthesis at low temperature by the microwaveassisted hydrothermal method(MAH).The phase formation,morphology,luminescent properties and ene rgy transfer were investigated.The X-ray diffraction(XRD)re sults show the formation of a scheelitelike tetragonal structure without the presence of secondary phases.The growth mechanism of hierarchical micro structures based on self-assembly and Ostwald-ripening processes was evaluated,obtaining different types of morphologies.The luminescence spectra of CaWO₄:Eu³⁺,Tm³⁺at 325 nm excitation show the predominance of red emission at the 5 D0→7 F2(Eu³⁺)transition at 624 nm.This feature signals dominant behavior of the electric dipole type.The presence of Tm³⁺is notably evident in the absorption spectra by the related excitation transitions:3 H6→1 G4,3 H6→3 F3 and 3 H6→3 H4.Color parameters are discussed to characterize CaWO₄:Eu³⁺,Tm³⁺emission.The study of the emission spectrum as a function of the concentration of Eu³⁺(x mol%)and Tm³⁺(y mol%)indicates that the CaWO₄:Eu³⁺,Tm³⁺phosphors show stronger red emission intensity and exhibit the CIE value of x=0.63 and y=0.35.The photoluminescence results show 97%high color purity for CaWO₄:4 mol%Eu³⁺,a high CRI(92%)and a low CCT of 1085 K.These results demonstrate that the CaWO₄:Eu³⁺,Tm³⁺red phosphors are promising as color converters for application in white light-emitting diodes and display devices.     

Cerium relieving the inhibition of photosynthesis and growth of spinach caused by lead

Chloroplasts were isolated from spinach cultured in lead chloride-present, Ce3+-administered, cerium chloride-administered lead chloride-present Hoagland's media or that of Hoagland's media. The experimental study demonstrated the effects of cerium (Ce) on distribu-tion of light energy and photochemical activities of spinach chloroplast grown in lead (Pb)-present media. It was observed that Pb2+ signifi-cantly inhibited photosynthesis in spinach, including light absorption, energy transfer from LHCII to photosystem II, excitation energy dis-tribution from photosystem I to photosystem II, and transformation from light energy to electron energy and oxygen evolution of chloroplasts,and decreased spinach growth. However, Ce3+ treatment to pb2+-present chloroplasts could obviously improve light absorption and excitation energy distribution in both photosystems and increase activity of photochemical reaction and oxygen evolution of chloroplasts. The results suggested that Ce3+ under Pb2+ stress could maintain the stability of chloroplast membrane, and improve photosynthesis of spinach chloro-plast, thus promote spinach growth.     

Hydrothermal synthesis,structure study and luminescent properties of YbPO4:Tb3+ nanoparticles

YbPO₄:Tb³⁺ were synthesized by mild hydrothermal method. The luminescent properties, morphologies and structure of the obtained powders were characterized by photoluminescence (PL) spectra, FESEM, X-ray diffractometer (XRD) and FTIR. The results showed that the prepared YbPO₄:Tb³⁺ nanoparticles were pure tetragonal phase and the average grain size varied with increasing of Tb³⁺ concentration. Hydrothermal temperature was revealed to be the key factor to enhance the emission intensity of YbPO₄:Tb³⁺ phosphors. The spherical nanoparticles could be effectively excited by near UV (369 nm) light and exhibited green performance at 543 nm (⁵D₄→⁷F₅), 489 nm (⁵D₄→⁷F₆) and 586 nm (⁵D₄→⁷F₄). The CIE chromaticity was calculated to be x=0.298, y=0.560. The YbPO₄:Tb³⁺ nanoparticles exhibited potential to act as UV absorber for solar cells to enhance the conversion efficiency.     

Synthesis,structural and optical properties of SrZrO3：Eu3＋phosphor

Eu3+ activated Sr1–xEuxZrO3(x=0.01–0.04) phosphor with perovskite structure was successfully synthesized by using combustion method.The structure,morphology and optical properties of the material were characterized by X-ray diffraction,scanning electron microscopy and fluorescence spectrometry.The XRD results indicated that crystals of SrZrO3:Eu3+ belongs to tetragonal perovskite system.The phosphor could be effectively excited by UV light and the emission spectra results indicated that reddish-orange luminescence of SrZrO3:Eu3+ due to magnetic dipole transition 5D0→7F1 at 593 nm was dominant.Thus,the prepared phosphor showed remarkable luminescent properties which find applications in field emission display(FED) and plasma display panel(PDP) devices.     

Structure and luminescence properties of color-tunable phosphor Sr2La3(SiO4)3F:Tb3+,Sm3+

A series of single-phase and color-tunable phosphors Sr₂La₃(SiO₄)₃F:0.15Tb³⁺,xSm³⁺(SLSOF:0.15Tb³⁺,xSm³⁺) was prepared using solid-state route.The X-ray diffraction(XRD) was used to characterize the phase of the as-prepared samples.The synthesized phosphors have apatite-type structure without other impurities.Sm³⁺ and Tb³⁺ ions substitute La³⁺ into the lattice and form a single...     

Bi3+ assisted luminescence in SrMoO4:Sm3+ red phosphors

In this paper, we report synthesis of pure SrMoO₄, Sm³⁺ (1 at%–5 at%) doped SrMoO₄ and Bi³⁺ (1 at%–3 at%) co-doped in 4 at% Sm³⁺ doped SrMoO₄ (SrMoO₄:4Sm³⁺) phosphors by solution combustion method. The X-ray diffraction (XRD) analysis reveals the tetragonal phase of all samples, also Bi³⁺ co-doping supports crystallite size growth and reduces lattice strain. Absorption analysis of Sm³⁺ doped SrMoO₄ ascertains a decrease in band gap and Bi³⁺ co-doping confirms the emergence of an absorbance peak at around 308 nm attributed to Bi³⁺ energy levels. Photoluminescence (PL) analysis ascertains an increase in emission peaks for Sm³⁺ doped SrMoO₄ up to 4% concentration, which are attributed to an electron transition from ⁴G_5/2 to ⁶H_J (J = 5/2, 7/2, 9/2, and 11/2) energy levels of Sm³⁺ ions. We have explained the effects of Bi³⁺ co-doping on the luminescence of Sm³⁺ doped SrMoO₄. The reduced microstrain and increased crystallinity of the phosphors as a result of Bi³⁺ co-doping and their correlation with the luminescence of Sm³⁺ ions are discussed.     

Rational design of monovalent ions (Li,Na,K) co-doped ZnAl_2O_4:Eu~(3+) nanocrystals enabling versatile robust latent fingerprint visualization

Alkali metal ions(M~+ = Na~+,Li~+,K~+) co-doped ZnAl_2O_4:Eu~(3+)(5 mol%)(ZAE) nanopowders(NPs) were prepared via solution combustion route using Mimosa pudica(MP) leaves extract as a fuel. PXRD results of co-doped samples enhance the crystallinity and grain growth. Photoluminescence(PL) of the prepared ZAE and ZAE:M~+(M~+ = Na~+, Li~+, K~+) NPs shows intense emission peaks in the range of 550-750 nm and ascribed to ~5D_0→~7F_J(J=0-4) transitions of Eu~(3+) ions, respectively. A 2-fold enhancement in PL intensity was observed in Li~+ co-doped samples. The optimized ZnAl_2O_4:Eu~(3+)(5 mol%), Li~+(1 wt%)(ZAEL)NPs were used to visualize LFPs on various porous, semi-porous and non-porous surfaces through robust powder dusting technique. The visualized latent fingerprints(LFPs) reveal well defined level 1-3 ridge characteristics under several tests such as fingerprint aging and fresh water treatment for various time durations. The obtained results clearly evidence that the prepared NPs are quite useful for multifunctional applications such as advanced forensic and solid state lightning.     

VUV spectroscopic properties of rare-earth（RE=Eu,Tb and Dy）-doped A2Zr（PO4）2（A=Li,Na and K） phosphates

This study fully investigated the vacuum ultraviolet excitation spectra of pure and rare-earth（RE=Eu, Tb and Dy）-doped A2Zr（PO4）2（A=Li, Na and K） phosphors. The synthesized Na and Li compounds were characterized by XRD showing two new types of phases after indexation. Although these three pure compounds had different crystal structures, they exhibited similar luminescence properties. For Eu3＋-activated samples, the broad excitation band centered at 217 nm could be attributed to the CT transition between O2–（2p6） and Eu3＋ ions. For Tb3＋-doped samples, two groups of f-d transitions were observed, where a strong broad band at 221 nm was due to the spin-allowed f-d transition. Energy transfer from O2– to Dy3＋was not observed in Dy3＋-doped phosphors, probably because it overlapped considerably with the CT transition from O2– to Zr4＋ at 187 nm.     

Synthesis and photoluminescence properties of Er3+ and Dy3+ doped Na2NbAlO5 phosphors

A series of Ln³⁺ (Ln³⁺ = Er³⁺/Dy³⁺) ions doped Na₂NbAlO₅ (NNAO) phosphors were synthesized by solid-state method. The Er³⁺ and Dy³⁺ ions doped phosphors were characterized by XRD, photoluminescence (PL) and decay profiles. The Ln³⁺-doped samples are consistent with the pure NNAO phase which is analyzed by the X-ray diffraction result. The PL graphs show that the intensity of luminescence increases with the increasing doping concentrations up to their critical certain values and then decreases at higher concentrations due to the concentration quenching effect of Er³⁺/Dy³⁺ ions. The energy level diagrams containing the positions of 4f and 5d energy levels of Er³⁺ and Dy³⁺ ions have been established and studied. In addition, under the ultraviolet light, the prepared NNAO:xLn³⁺ (Ln³⁺ = Er³⁺/Dy³⁺) phosphors show the characteristic green (Er³⁺), cyan (Dy³⁺) emission, respectively. Under the excitation of 365 nm, the quantum efficiencies of NNAO:0.01Er³⁺ and NNAO:0.03Dy³⁺ phosphors are measured to be 61.7% and 72.2%, respectively. The obtained results indicate that the new NNAO:xLn³⁺ (Ln³⁺ = Er³⁺/Dy³⁺) phosphors are promising applications in white-light emitting diodes field.     

An optical thermometer with high sensitivity and superior signal discriminability based on dual-emitting Ce3+/Eu2+ co-doped La5Si2BO13 thermochromic phosphor

A novel non-contact optical thermometer, qualified with high sensitivity and temperature resolution, is urgently needed for temperature measuring of micro devices, moving objects and specific severe environments. Hence, a series of dual-emitting La₅Si₂BO₁₃:Ce³⁺,Eu²⁺ phosphors were synthesized. The two ions show diverse responses with the changing in temperature. The variational emissions of Ce³⁺ and Eu²⁺ can be converted to FIR (fluorescence intensity ratio) signals. The maximal absolute sensitivity S_a and relative sensitivity S_r reach up to 0.07526%/K and 3.2241%/K, respectively. It is worthy noting that the S_a and S_r possess the same variation tendency and both have high values in the low temperature region (293–373 K), showing the great temperature measuring property especially in low temperature region. The temperature sensing characteristics are superior to the results of most previous reports. The energy transfer (ET) process is certified to occur from Ce³⁺ to Eu²⁺ ions. These studies indicate that La₅Si₂BO₁₃: Ce³⁺,Eu²⁺ phosphor could have a good prospect for optical thermometry.     

Photoluminescence and energy transfer in transparent glass-ceramics based on GdF3:RE3+ (RE = Tb,Eu) nanocrystals

In the present work,the transparent oxyfluoride glass-ceramic samples containing GdF_3:RE~(3+)(RE=Tb,Eu) nanocrystals(nGCs) were fabricated via controlled heat-treatment of precursor xerogels prepared using a sol-gel method.The formation of GdF_3 nanocrystalline phase from gadolinium(III) trifluoroacetate was verified based on XRD measurements.The average crystal sizes calculated from Scherrer formula were estimated to～10 nm as well as～6 nm for Tb~(3+)-and Eu~(3+)-doped samples,respectively.The optical behavior of prepared sol-gel samples was evaluated based on photoluminescence excitation(PLE) and emission spectra(PL) as well as luminescence decay analysis.Obtained samples exhibit the ~5D_4→~7F_J(J=6-3,Tb~(3+))and the ~5D_0→~7F_J(J=0-4,Eu~(3+)) emission bands recorded within the visible spectral area under excitation at near-UV(393 nm(Eu~(3+)),351,369,378 nm(Tb~(3+))) as well as middle-UV illumination(273 nm(Gd~(3+))).Additionally,based on recorded decay curves,the luminescence lifetimes(τ_m) for the ~5D_4(Tb3+) and the ~5D_0(Eu~(3+))excited states were also evaluated.In general,recorded luminescence spectra and double-exponential character of decay curves for nGCs indicate a successful migration of Tb~(3+) and Eu~(3+) dopant ions from amorphous silicate framework to lowphonon energy GdF_3 nanocrystal phase.     

Luminescent properties of YVO4·xTa2O5:Eu3+

The samples of YVO₄·xTa₂O₅:Eu³⁺ (x=0.45,0.35,0.25,0.15,0.05)were synthesized by the conventional solid state reaction. The structure of the prepared sample was checked by the X-ray diffraction. XRD measurements at room temperature were confirmed that the prepared YVO₄·xTa₂O₅:Eu³⁺ consisted of two phases. One phase was YVO₄, which is tetragonal according with the JCPDS-Card (17-0341); the other phase was YTaO₄, which is according with the JCPDS-Card (72-2018). The spectrum property of the sample was studied under the VUV. The effects of Ta doped on the luminescent properties of sample were investigated and it was found that some Ta doped could highlight the absorption of matrix in VUV region. The emission spectrum was dominated by the red peaks at 613 and 619 nm due to the electric dipole transition ⁵D₀→⁷F₂ of Eu³⁺. It indicated that Eu³⁺ occupied a site lacking inversion symmetry. There was one band peaked at 155 nm in the excitation spectrum of the sample, it could be assigned to the absorption of the host.     

Synthesis of N,O-rich active site porous polymers and their efficient recovery of Gd(Ⅲ) from solution

Our previous study found that the adsorption performance of porous carbon for Gd(Ⅲ) could be significantly improved by increasing the N,and O functional groups on its surface.Unfortunately,the adsorption capacity of porous carbon is low due to the limited number of N,and O functional groups that can be loaded on its surface.Due to the advantage of customizable functional groups of porous organic polymers(POPs),the triazine-based Tb-MEL and hydroxyl-modified triazine-based Tp-MEL were synthesized...