Flux blended synthesis of novel Y2O3:Eu3+ sensing arrays for highly sensitive dual mode detection of LFPs on versatile surfaces

In the present communication,various fluxes blended Y_2 O_3:Eu~(3+)(5 mol%) nanopowders(NPs) were successfully fabricated by solution combustion method.PXRD pattern confirms body-centered cubic structure of the prepared samples.Energy band gap(Eg) of the fabricated products was estimated and is found to be in the range of 3.13-3.32 eV.Photoluminescence(PL) emission spectra exhibit sharp and intense peaks at ～579,592,614,657,704 nm corresponding to ~5 D_0→~7 F_J(J = 0,1,2,3 and 4) transitions of Eu~(3+) ions.Significance of fluxes for enhancing the PL emissions was extensively studied.Photometric studies of the prepared samples are located in pure red region.Optimized NPs were explored as a novel sensing agent for visualization of latent fingerprints(LFPs) on various surfaces including porous,semiporous and non-porous surfaces followed by powder dusting technique.Various experiments including aging,temperature,scratching and aquatic fresh water treatment tests were performed to evaluate applicability of the fabricated NPs.Visualized LFPs exhibit well defined ridge details including most authenticated sweat pores are also revealed with high sensitivity,selectivity,little background hindrance and less toxicity.Aforementioned results evidence that the method and fabricated NPs can be considered to be simple,rapid and economical and provide novel sensing platform for LFPs visualization in prospective forensic applications.     

Luminescence properties of BaB8O13：Eu under UV and VUV excitation

The phosphor BaB8O13:Eu3+ were synthesized by solid-state reaction, and their luminescent properties were studied under 254 and 147 nm excitation. The excitation spectrum showed two broad bands in the range of 100-300 nm: one was the host lattice absorption with the maxima at 160 nm and the other was Ba-O absorption overlapped with the CT band of Eu3+, which indicated that the energy of the host lat-tice absorption could be efficiently transferred to the Eu3+. The overlapped bands were tended to separate when monitored by different wave-length, which indicated that at least two Ba2+ sites were available in BaB8O13. The emissions of Eu3+ (612 nm) and Eu2+ (405 nm) were both observed in the emission spectra of BaB8O13:Eu3+ under the excitation of either 254 or 147 nm. With the doping concentration of Eu3+ in-creasing, the 612 nm emission was enhanced while 405 nm emission was decreased under 254 nm excitation, which was due to the persistent energy transfer from Eu2+ to Eu3+. While under 147 nm excitation, the 612 nm emission was quenched and the 405 nm emission was en-hanced. It was concluded that the preferential excitation of Eu2+ under 147 nm excitation was one of the reasons for this facts.     

Optical characteristics of Ce,Eu:YAG single crystal grown by Czochralski method

Eu-doped Ce:YAG single crystal (SC) was fabricated by the Czochralski method. The crystal structure, optical and photoelectric property of the constructed w-LED was investigated. The XRD and HRTEM results show that YAG crystal structure has little change when Eu³⁺, Ce³⁺ are doped. Absorption spectra and photoluminescence spectra show that the Ce,Eu:YAG single crystal can effectively absorb the 460 nm blue light to form a broadband emission center at 530 nm, decay curves of the crystal show that the energy transfer between Ce³⁺ and Eu³⁺ is highly suppressed. Compared with commercial Ce:YAG phosphor, Ce,Eu:YAG exhibits better thermal stability.     

Synthesis and characterization of one dimensional semiconducting nanorods and nanobelts

CdSe nanorods, nanobelts are synthesized via a simple sacrificial template assisted solvothermal route at a moderate temperature of 180°C. The influences of introducing sacrificial template, hydrazine hydrate (N₂H₄·H₂O) as the reducing agent, ammonia (NH₃·H₂O) and NaOH as the complexing agent on the morphology and size of the obtained CdSe nanorods and nanobelts are investigated and reported. CdSe nanorods with a mean diameter and length of 25 nm and 82 nm respectively are synthesized and the problem of handling the stacking faults present in the long CdSe is analyzed. The structural phase, morphology and the optical properties of CdSe nanorods and nanobelts are studied using powder X-ray diffraction, TEM/HRTEM, UV-visible absorption spectroscopy and photoluminescence (PL) spectroscopy respectively.     

One pot synthesis of TiO2:Eu3+ hierarchical structures as a highly specific luminescent sensing probe for the visualization of latent fingerprints

In the present work, TiO₂:Eu³⁺ (1 mol%–11 mol%) nano powders (NPs) were prepared via a facile one-pot hydrothermal method by using Epigallocatechin Gallate (EGCG) as bio-surfactant. The optimized TiO₂:Eu³⁺ (5 mol%) NPs can be used as fluorescent labeling agent for visualizing of latent fingerprints (LFPs) on various porous and non-porous surfaces. The obtained results exhibit well defined ridge details with high sensitivity, selectivity, and low background hindrance which show greater advantages as compared to conventional powders. We demonstrated the viability of high-performance security labels thorough excellent luminescence for practical anti-mimetic applications. Morphology of the prepared samples is highly dependent on pH, concentration of the bio-surfactant, temperature and time durations. Photoluminescence (PL) emission spectra exhibit intense red emission at ～ 615 nm due to electric dipole transition (⁵D₀→⁷F₂). Photometric (CIE and CCT) results clearly show the intense warm red emission of the optimized samples. Therefore, this work offers a superior and universal luminescent label, which can be applied to visualize miniature LFPs particulars for individualization and consequently display great prospective in forensic investigation.     

Preparation and Characterization of Sol-Gel Derived Au Nanoparticle Dispersed Y2O3：Eu Films

Gold nanoparticles dispersed Y2O3 films were prepared through a sol-gel method by using yttrium acetate and Au nanoparticles colloid as precursors. The films were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and UV-VIS absorption spectra. XRD patterns and TEM images of Y2O3 ＋ Au films give the same resuits on structure and particle size as that of pure Y2O3 films. The surface plasma resonance （SPR） of Au nanoparticles in Y2O3 ＋ Au film was observed around 550 nm in the absorption spectrum and its position shifts to red with increasing annealing temperature is caused by the increase of dielectric constant of Y2O3 matrix and the size of Au nanoparticles. The second and third order nonlinear optical effects of Y2O3 ＋ Au films were also observed. The photoluminescent properties of Y2O3 ： Eu ＋ Au films were investigated and results indicate that there exist an energy transfer from Eu^3 ＋ to Au nanoparticles and this energy transfer decreases the emission of Eu^3 ＋ in Y2O3 ： Eu ＋ Au film.     

CeO2 nanoscale particles: Synthesis,characterization and photocatalytic activity under UVA light irradiation

CeO_2 nanoparticles(NPs) were synthesized in alkaline medium via the homogeneous precipitation method and were subsequently calcined at 80 ℃/24 h(assigned as CeO_2-80) and 500 ℃/2 h(assigned as CeO_2-500). The as-prepared materials and the commercial ceria(assigned as CeO_2-com) were characterized using TGA-MS, XRD, SEM-EDX, UV-vis DRS and IEP techniques. The photocatalytic performances of all obtained photocatalysts were assessed by the degradation of Congo red azo-dye(CR) under UVAlight irradiation at various environmental key factors(e.g., reaction time and calcination temperature).Results reveal that CeO_2 compounds crystalize with cubic phase, CeO_2-500 exhibits smaller crystallite size(9 nm vs 117 nm) than that of bare CeO_2-com. SEM analysis shows that the materials are sphericallike in shape NPs with strong assembly of CeO_2 NPs observed in the CeO_2-500 NPs. EDX analysis confirms the stoichiometry of CeO_2 NPs. UV-vis DRS measurement reveals that, CeO_2-500 NPs exhibits a red-shift of absorption band and a more narrow bandgap(2.6 eV vs 3.20 eV) than that of bare CeO_2-com. On the contrary, Urbach energy of Eu is found to be increased from 0.12 eV(CeO_2-com) to 0.17 eV(CeO_2-500),highlighting an increase of crystalline size and internal microstrain in the CeO_2-500 NPs sample. Zeta potential(IEP) of CeO_2-500 NPs is found to be 7.2. UVA-light-responsive photocatalytic activity is observed with CeO_2-500 NPs at a rate constant of 10×10~(-3) min~(-1), which is four times higher than that of CeO_2-com(K_(app)=2.4×10~(-3) min~(-1)) for the degradation of CR. Pseudo-first-order kinetic model gives the best fit. On the basis of the energy band diagram positions, the enhanced photocatalytic performance of CeO_2-500 nano-catalyst can be ascribed to O_2~-, 'OH and R'~+ as the primary oxidative species involved in the degradation of RC under UVA-light irradiation.     

Luminescence and Preparation of LED Phosphor Ca8Mg(SiO4)4Cl2:Eu2+

Calcium magnesium chlorosilicate doped by europium, Ca8Mg(SiO4)4Cl2:Eu2 , was prepared by the solid state reaction at high temperature. The compound obtained is pure Ca8Mg(SiO4)4Cl2 phase with cubic structure. Its average particle size is 5 μm, and it has good dispersity and morphological form. The excitation spectrum of Ca8Mg(SiO4)4Cl2:Eu2 is a wide band, which covers from 270 to 480 nm. The emission spectrum is also a wide band peaked at 510 nm. The luminescent intensity reaches to the maximum when the concentration of Eu2 is 2%. The wavelength of emission and excitation of the phosphor with various Eu2 contents keeps constant. This spectrum range matches violet and blue LED chips very well, and its strong luminescence intensity is suitable for a green phosphor of tricolor phosphor of white light LED.     

Luminescence properties of dysprosium doped YVO4 phosphor

Trivalent dysprosium(Dy~(3+)) activated nanocrystalline yttrium vanadate(YVO_4) phosphor was synthesized via co-precipitation method. The prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), optical absorption and photo luminescence(PL) techniques. The XRD patterns reveal the tetragonal crystalline phase. SEM images reveal that Dy doped YVO_4 nanocrystals are agglomerated. EDAX confirms the formation of YVO_4:Dy. FTIR spectrum shows two strong absorption bands at 459 and 761 cm~(-1). Optical absorption spectrum showed the surface defects in the as-prepared samples. The PL emission spectrum shows two characteristic emission bands at 485 and 575 nm. The strong yellow emission peak at 575 nm is assigned to ~4 F_(9/2)→~6 H_(13/2) hyper sensitive transition of Dy~(3+) ions, Study of CIE chromaticity diagram indicates the suitability of the phosphor for the development of yellow-green LEDs.     

Multifunctional Dy (III) doped di-calcium silicate array for boosting display and forensic applications

Latent fingerprints (LFPs) are the major physical evidences for the identification of individuals during crime spot investigation. Till date, numerous methods were followed to visualize LFPs. However, simple, accurate, and cost-effective method has wide scope in advanced forensic field. In our work, Ca₂SiO₄:Dy³⁺ nanopowders (NPs) were fabricated via solution combustion route. The optimized sample was employed for the visualization of overlapped LFPs by the cost effective powder dusting method. The obtained results reveals the complete three levels of ridge characteristics with high sensitivity, reproducibility, selectivity, and reliability on various complex surfaces. The photoluminescence (PL) spectra consist of intense peaks at ～ 480 and 574 nm owing to ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 4f transitions of Dy³⁺ ions, respectively. The photometric properties confirm that the samples exhibit intense white emission with high color purity. Therefore, the prepared NPs could be a definitive choice as an advanced luminescent NPs for forensic, solid state lighting and portable FED devices.     

Preparation and application of ZnO doped Pt-CeO2 nanofibers as electrocatalyst for methanol electro-oxidation

ZnO doped Pt/CeO₂ nanocomposites were prepared by electrospinning and reduction impregnation. X-ray diffraction (XRD), transmission electron microscopy (TEM), energy disperse spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the nanocomposites. It is observed that ZnO and CeO₂ form the hexagonal wurtzite phase and cubic fluorite phase in the nanocomposite, respectively, whilst Pt nanoparticles (NPs) with the number-averaged size of ca. 3.1 nm are uniformly distributed on the surface of nanofibers. The mass fraction of Pt NPs in the nanocomposites is about 10 wt%. The doping of ZnO is effective to promote reactive oxygen species, surface reaction sites and the interaction between Pt and oxides. The catalytic performance of nanocomposites was evaluated by the methanol electro-oxidation, indexed with the catalytic activity, stability of catalyst. As a result, it is found that the nanocomposite exhibits much higher activity and stability for methanol oxidation than the undoped Pt/CeO₂ catalyst.     

Optical Properties of Blue-Emitting BaAl2S4∶Eu Thin-Films for Inorganic EL Display

The optical properties of blue emitting BaAl2S4:Eu thin-films were studied. The emission peak is around 470 nm, whose FWHM (full width at half maximum) is 35 nm. The dielectric constant is 3.03 from transmission spectrum, and the optical band gap is approximately 4.6 eV. It is found that the cubic phase and orthorhombic phase exist in fabricated thin-films. Furthermore, the energy band structure of BaAl2S4:Eu thin-films from X-ray photo-electron spectra (XPS) and the absorption spectra were analyzed.     

Preparation and luminescent properties of CaF2:Ln3+ (Ln:Er,Er/Yb)/Nafion composite films

In this work, CaF_2:Ln~(3+)(Ln:Er,Er/Yb)/Nafion composite films were prepared using Nafion as modifications and matrices by dripping method. The composite films were characterized by Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction(XRD) and scanning electron microscopy(SEM). Composite films are transparent and CaF_2:Ln~(3+)(Ln:Er,Er/Yb) nanoparticles are well dispersed in Nafion films.The thicknesses of CaF_2:Er~(3+)/Nafion and CaF_2:Er~(3+),Yb~(3+)/Nafion composite film are about 77 and 73 μm,respectively. The nanoparticles in composite film possess cubic phase. CaF_2:Er~(3+),Yb~(3+)/Nafion composite film has stronger characteristic emission of Er~(3+) around 1530 nm with full width at half-maximum(FWHM) of 73 nm and longer luminescence lifetimes of 22.04 μs(25.03%) and 100.77 μs(74.97%).     

Enhancement of luminescence intensity and spectroscopic analysis of Eu3+ activated and Li+ charge-compensated Bi2O3 nanophosphors for solid-state lighting

The present work reports the synthesis, characterization, photoluminescence and photocatalytic activity of Eu~(3+)(1 mol%-11 mol%) doped and Li~+(0.5 mol%-5 mol%) co-doped Bi_2 O_3 nanophosphors(NPs) by sonochemical method. The average particle size was estimated using powder X-ray diffraction(PXRD)and transmission electron microscopy(TEM) and is found to be in the range of 30-35 nm. The scanning electron microscopy(SEM) images were highly dependent on sonication time and concentration of epigallocatechin gallate(EGCG) bio-surfactant. The energy gap of doped and co-doped Bi_2 O_3 nanophosphors was estimated using Kubelka-Munk(K-M) function and is found to be in the range of2.9-3.08 eV. The effect of Li+ co-doping on luminescence of optimized Bi_2 O_3:Eu~(3+) was studied and is found about more than 3 fold enhancement of emission intensity. Judd-Ofelt parameters(Ω_2, Ω_4 and Ω_6).transition probabilities(A_T), quantum efficiency(η), luminescence lifetime(τ_(rad)), color chromaticity coordinates(CIE) and correlated color temperature(CCT) values were estimated from the emission spectra and are discussed in detail. The estimated CIE chromaticity co-ordinates are very close to the NTSC(National Television Standard Committee) standard value of red emission. The synthesized NPs show excellent photocatalytic activity of acid red-88 under UV-light irradiation, which can degrade 98.1% in60 min. The decreasing electron-hole pair recombination rate with quick electron transfer ability is predominantly ascribed to the balance between crystallite size, morphology, band gap, defects, surface area, etc. These results show a light for the use of sonochemical route of Bi_2 O_3:Eu~(3+):Li~+ in solid state display and photocatalytic applications.     

Preparation and properties of temperature sensitive paint based on Eu(DBM)3phen as probe molecule

Probe molecule Eu(DBM)3 phen is made up of europium oxide(Eu_2 O_3),dibenzoylmethane(DBM) and1,10-phenanthroline(phen). The temperature sensitive paint(TSP) was compounded by the polymerization of the probe molecule, methyl methacrylate(MMA) and the initiator of benzoyl peroxide(BPO).The structure, morphology, luminescence property of probe molecule and the temperature quenching property of the temperature sensitive paint(TSP) were characterized by infrared spectrometer, UV-vis spectrometer, scanning electron microscopy and fluorescence spectrometer respectively. The infrared spectrum and UV-vis spectra show that Eu and DBM form six membered rings, and Eu-O coordinate bonds form. The nanocrystals are in sphere-like morphology with an average size of approximately100 nm. Fluorescence spectra present that the performance of temperature quenching is excellent,what's more, TSP sample has different temperature sensitivity in various temperature scope. Particularly,under excitation of 286 nm, TSP has a highest temperature sensitivity between 50 and 60 ℃, and the strongest fluorescence emission reaches a peak(615 nm). It indicated that probe molecule(Eu(DBM)_3 phen) has strong luminescent intensity and the temperature quenching properties of Eu(DBM)_3 phen/PMMA is good.     

Ionic liquid mediated morphologically improved lanthanum oxide nanoparticles by Andrographis paniculata leaves extract and its biomedical applications

Greener synthesis of ionic liquid(IL) assisted lanthanum oxide(La_2O_3) nanoparticles(NPs) was followed using Andrographis paniculata leaves extract by hydrothermal method at low temperature,The IL assisted La_2O_3(La_2O_3-IL) NPs were characterized by various properties such as structural,spectral,optical,morphological,and biological studies.Powder X-ray diffraction studies confirm that La_2O_3-IL NPs crystallize in the form of body-centered cubic structure and average crystalline size is shown-43 nm.FTIR and Laser Raman spectroscopy confirm the La-O,O-H and various functional groups.The La-O stretching vibration band attributes at 639 cm~(-1).The optical property of La_2O_3-IL NPs was characterized by UV-Vis and photo luminesce nce spectroscopy.The sharp and intense absorbance peak observed in the UV region at 288 nm can be assigned.In the PL spectrum,we observe two different emission bands like blue and green emission.The morphological and particle size determination were investigated by SEM with EDX spectra and TEM analyses.The agglomerated particles of hexagonal,spherical,and parallelogram shape are observed in the TEM images.The chemical elements,binding energies as well as La metal states on the surface of these synthesized NPs were determined using XPS.La_2O_3 NPs for good biological activities regarding antibacterial and anti-inflammatory potentials could be utilized in different biological applications to the food and biomedical industries.La_2O_3-IL has a high percentage of inhibitions than La_2O_3 and standard diclofenac.     

Lanthanide complexes-functionalized ordered mesoporous TiO2: Multicolor emission (visible and near-infrared luminescence) based on visible-light sensitization

Recently, much attention has been paid to the lanthanide luminescent materials based on the visible-light sensitization for their potential applications in the fields of bio-imaging and optical devices. In this work, the lanthanide complexes have been covalently bonded to the ordered mesoporous titania (OMT) matrix, and the resulting titania-based hybrid ordered mesoporous materials (named as LnDB-OMT, Ln = Eu, Sm, Yb, Nd) were characterized by using Fourier-transform infrared (FT-IR) spectroscopy, small-angle X-ray powder diffraction (SAXD), N₂ adsorption–desorption isotherms, transmission electron microscopy (TEM), fluorescence spectroscopy, and thermogravimetric analysis. Generally, exciting with visible light is advantageous over UV excitation. Of importance here is that, under excitation with visible light, the LnDB-OMT all show characteristic visible (Eu³⁺, Sm³⁺) as well as near-infrared (Sm³⁺, Yb³⁺, Nd³⁺) luminescence of the corresponding Ln³⁺ ions (multicolor emission covered from 500 to 1400 nm spectral region), which is attributed to the energy transfer from the ligands to the Ln³⁺ ions via an antenna effect.     

Luminescence studies of MBrCl： Eu2＋ （M=Ca, Sr, Ba）

Europium doped MBrCl (M=Ca, Sr, and Ba) phosphors were prepared by solid state reaction in reductive atmosphere. Photolu-minescence (PL), photostimulated luminescence (PSL) after X-ray irradiation and optical absorption studies of MBrCl:Eu2+ (M=Ca, Sr, and Ba) revealed that: (1) blue light emission, under the excitation of 300 nm, was observed in all these phosphors; (2) the shape of the emission spectra in CaBrCl:Eu2+ could be changed by varying the bromine/chlorine ratio during synthesis, while that in SrBrCl:Eu2+ and BaBrCl:Eu2+ showed no change; and (3) PSL was observed in SrBrCl:Eu2+ and BaBrCI:Eu2+ after X-ray irradiation. Difference absorption spectrum (DAS) in SrBrCl:Eu2+ showed two broad bands centered at about 470 and 570 nm, and DAS in BaBrCI:Eu2+ showed two bands at about 550 and 675 nm, respectively. This enabled the use of He-Ne laser (633 nm) or even semiconductor light-emitting diodes (LED) instead of gas lasers for photostimulation.     

Luminescent-plasmonic core–shell microspheres,doped with Nd3+ and modified with gold nanoparticles,exhibiting whispering gallery modes and SERS activity

Multifunctional core/shell type,luminescent-plasmonic material composed of lanthanide doped microspheres(≈50 μm) and gold nanoparticles(Au NPs;≈10-20 nm) deposited onto their surface,were successfully prepared(Nd~(3+):YAS@Au).The material was synthesized to combine the luminescence properties of the Nd~(3+)-doped microspheres,i.e.whispering resonance with plasmonic activity of the surface Au NPs,i.e.surface enhanced Raman scattering(SERS) effect,within a single,micro-sized material.The luminescent-plasmonic microspheres were used as the active SERS substrate for detection of the organic probe,and for generation of Whispering Gallery Modes(WGM),which red-shift together with increasing laser power(temperature elevation).The products obtained were analysed with optical,scanning and transmission electron microscopy(SEM and TEM),as well as by Raman,absorption and photoluminescence spectroscopies.     

作为白光LED用铕掺杂氟化镧红色荧光粉的制备与光谱性能研究

采用水热法制备具有单一相六方晶系的LaF₃:Eu3+纳米荧光粉.通过X射线粉末衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、光致发光光谱(PL)和荧光衰减曲线对LaF₃:Eu3+纳米荧光粉进行表征.LaF₃:Eu3+荧光粉的激发光谱主要由250 nm处的宽带(O2-→Eu3+的电荷转移跃迁)和一些尖峰(Eu3+ f-f跃迁)构成,其中位于近紫外区396 nm处有一较强的激发峰.通过发射光谱探测Eu3+在LaF₃晶体中的局部晶场环境.在298 K下激发光谱和发射光谱可知,在六方晶系的LaF₃纳米晶体中的Eu3+晶格位置从D_4h降至到C_2v,这是由于晶格变化所造成的.在396 nm激发下,观测到较优掺杂浓度为10%的LaF₃:Eu3+荧光粉在591 nm(5D₀→7F₁跃迁)处有强烈的红色发射峰.其发光性能表明,LaF₃:Eu3+红色荧光粉在近紫外发光二极管领域具有潜在的应用价值.