Europium-doped Yttrium Vanadate Research Articles

Spectroscopic studies of noble metal incorporated lanthanide vanadates and YF3:Tb3+ nanoclusters encapsulated in hybrid hydrogels

Extensive analysis of europium doped yttrium vanadate (YVO4: Eu3+) and terbium doped yttrium fluoride (YF3:Tb3+) has been evaluated by means of powder X-ray diffractions, scanning electron microscope and luminescence spectroscopy techniques. The results demonstrate noticeable difference in emission spectra for the sample of YVO4: Eu3+ in the presence of Gd3+. As for the influence of the nanocrystal surface, the incorporation of silver content will also affect the intensity of the europium(III) luminescence. In addition, a hydrolytic sol-gel approach and a soft support matter (polyacrylic acid) were employed for the fabrication of YF3:Tb3+ activated hydrogel. The emission spectra gave rise to the intensive green emissions centered at 545 nm due to 5D4→7F5 transition of Tb3+. Temperature elevation experiments were performed and could partially recover the green emissions.

Imaging XPS and photoemission electron microscopy; surface chemical mapping and blood cell visualization

Combined photoemission electron microscopy (PEEM) and imaging x-ray photoelectron spectroscopy (XPS), i.e., electron spectroscopy for chemical analysis in the nanoregion, has been used for surface characterization of bio-relevant and biological samples. In the first example, the authors prepared a gold patterned silicon substrate, stepwise surface modified by self-assembled monolayers followed by quantum dot (QDot) specific linking and investigated by means of work function mapping and elemental imaging in the submicrometer range. Spatially resolved core level images of C1s, V2p, and Y3d are obtained, which verify the selective thiol adsorption on the gold squares and specific binding of europium doped yttrium vanadate QDots on the self-assembled monolayer. The second example is platelet adhesion to Immunoglobulin G modified silicon surfaces, investigated by means of laterally resolved PEEM. Images of platelets clearly show activated cells with a morphology change including an enlarged surface area and elongated pseudopodia, with a lateral resolution of 140 nm. In the last example, neutrophils were allowed to attach to plain silicon surfaces and investigated by means of PEEM and imaging XPS. Here, the cells show a round shaped morphology, as expected. Threshold imaging with work function contrast is used to localize the area of interest, followed by elemental specific mapping on cells in the submicrometer region. Chemical shifts of C1s in photoemission are used to distinguish vital parts of the cell structure. The strong C1s (C-C) signal is achieved from the region of the cell membrane, i.e., high density of phospholipids, while C1s (C-N) and C1s (C-O) signals are obtained from the core of the cell, in good agreement with the presence of cytoplasm and deoxyribonucleic acid containing cell nucleus. The combination of PEEM and imaging XPS is shown here as a tool to deliver new insight into biological samples, i.e., a rapid sample overview is obtained based on low energy secondary electrons with work function contrast, followed by detailed studies in the narrow mode for elemental compositions based on photoemission. This study illustrates the strength of combined PEEM and XPS in the imaging mode on cell studies.

Improving the Short-Wavelength Spectral Response of Silicon Solar Cells by Spray Deposition of YVO4 :Eu3+ Downshifting Phosphor Nanoparticles

Europium-doped yttrium vanadate downshifting phosphor nanoparticles (NPs) have been coated on top of monocrystalline silicon solar cells, having efficiency more than 15%, by a spray deposition technique. The effects of phosphor NPs on solar cells with antireflection coating (ARC) have been studied. The optimized quantity of phosphor NPs provides a photocurrent enhancement of ~2.1% for monosilicon solar cells. External quantum efficiency data of high-efficiency ARC layer-coated silicon solar cells conclusively show that the enhancement in short-wavelength spectral response is mainly due to downshifting effects of the phosphor NPs. A small increment in a long-wavelength spectral response is also observed due to the scattering effects of phosphor NPs, which also results in a small enhancement of effective diffusion length of minority carriers in the base region.

Improved stability and enhanced efficiency of dye sensitized solar cells by using europium doped yttrium vanadate down-shifting nanophosphor

YVO4:Eu3+ nanophosphor improves long-term stability of DSSCs under illumination, due to down-shifting of high energy UV photons to the visible region.

Modified Polysaccharides as New Commodity Materials and for Light-Converting Systems: Syntheses, Characterization and Processing

Potato starch (PS), also one amylose-rich starch (high amylose maize starch, HAMS) and one amlyopectin-rich starch (waxymaize starch, WMS) were used for the syntheses as raw materials. Starch acetates were synthesized by reaction with acetic acid anhydride and potassium carbonate as activator. Tests of thermoplastic processability of the starch acetates were performed by extrusion followed by injection molding to specimens. Glycerine triacetate (triacetin, TAc) was attached as plasticizer to starch acetate. For this system a processing procedure was acquired under variation of different parameters. Starch- and cellulose-based films containing inorganic luminescent quantum dots, namely europium doped yttrium vanadate (YVO4:Eu) and cerium and terbium doped lanthanum phosphate (LaPO4:Ce,Tb) as well as an organic laser dye (naphthaldiimide, LV 570) were prepared by tape casting and air brush technique. Under UV-light exposure, they show a bright fluorescence radiation depending on the incorporate dye or quantum dot.

Preparation and Luminescent Properties of YVO4:Eu3+ Nanofibers by Electrospinning

This paper describes a procedure based on electrospinning for generating europium-doped yttrium vanadate (YVO4:Eu3+) nanofibers with diameters ranging from 30 to 50 nm. The YVO4:Eu3+ nanofibers were obtained through calcining precursory nanofibers, which were prepared through the electrospinning method. Suitable electrospinning parameters, such as concentration of PVP in solution, spinneret tip-to-collector plate distance (TCD), and applied voltage between spinneret and collector plate, are used to obtain thinner and more uniform precursory nanofibers of YVO4:Eu3+, which is important for preparing smaller diameter pure YVO4:Eu3+ nanofibers. The luminescent properties of the YVO4:Eu3+ nanofibers including excitation and emission spectra and fluorescence lifetime were studied. The excitation spectrum shows a broad band extending from 200 to 350 nm, which corresponds to the strong vanadate absorption in YVO4:Eu3+. The emission spectrum is dominated by the red 5D0 --> 7F2 hypersensitive transition of Eu3+. The fluorescence lifetime of Eu3+ 5D0 --> 7F2 (619 nm) is determined to be 493 micros at room temperature, which is basically in accordance with that in the bulk (521 micros).

Stoichiometry of Electrostatic Complexes Determined by Light Scattering

We report on the electrostatic complexation between oppositely charged polymers and inorganic nanoparticles investigated by static and dynamical light scattering. The nanoparticles put under scrutiny were citrate-coated nanocrystals of cerium oxide (CeO2, nanoceria), of iron oxide (γ-Fe2O3, maghemite), and of europium-doped yttrium vanadate (Eu:YVO4) with sizes in the 10 nm range. For the polymers, we have used cationic−neutral diblock copolymers (poly(trimethylammonium ethylacrylate)-b-poly(acrylamide), hereafter referred to as PTEA-b-PAM) with different molecular weights. For the three colloidal dispersions, we show that the electrostatic complexation gives rise to the formation of stable nanoparticle clusters in the 100 nm range. The complexation was monitored by systematic measurements of the scattering intensity vs X, the mixing ratio between nanoparticles and polymers. For five nanoparticle/polymer pairs, namely CeO2/PTEA5K-b-PAM30K, γ-Fe2O3/PTEA5K-b-PAM30K, γ-Fe2O3/PTEA11K-b-PAM30K, Eu:YVO4/PTEA2K-...

Luminescence Characteristics of Red Light Emitting (YVO4:Eu Thin-Film Phosphors Deposited on Si Substrate Using Pulsed Laser Deposition

Europium doped yttrium vanadate (YVO 4 :Eu) phosphor thin films were grown using a pulsed laser deposition (PLD) technique on silicon substrate. The structural characterization carried out on a series of YVO 4 :Eu films at post annealing temperature in the range of 550 °C-1150 °C indicating that films were preferentially (200) oriented at post annealing temperature above 950 °C. Photoluminescence of thin film increased with the increase of post annealing temperature and ambient oxygen pressure though the thin film has the powder-like surface morphology at oxygen pressure above 200 mTorr. Photoluminescence decay from 5 D 1 level of Eu 3 + show the great concentration dependency, which can be used as a good parameter to control the composition of YVO 4 :Eu thin film.

Synthesis and Characterizations of YVO4:Eu Colloids

We present a new process for the synthesis of colloidal europium-doped yttrium vanadate with a particle diameter of about 10 nm. Nanocrystals are produced by precipitation of citrate complexes of rare-earth salts with sodium orthovanadate. NMR and IR studies show that the interaction between citrate ligands and lanthanide ions limits the growth of particles and ensures the stability of the colloidal solutions through electrostatic and steric repulsions. The optimized process leads to stable and highly concentrated transparent colloidal solutions in water (up to 400 g·L-1).

Co-deposition of Luminescent Particles with Electroless Nickel

SUMMARYElectroless nickel composite coatings containing luminescent particles have potential application as indicator coatings and for product authentication. In this paper, composite coatings containing europium doped yttrium vanadate has been prepared. The effects of various parameters, such as concentration of suspension of luminescent particles in bath solution, temperature and pH on the incorporation of YVO4:Eu3 into the nickel matrix have been studied. The conditions for optimum incorporation were bath loading of 15 g dm−3 at 90 °C and pH 5.4. When viewed under UV light of wavelength 254 nm, bright red luminescence was observed for coating prepared under different operating conditions and the intensity increased with increased volume percent incorporation. The corrosion protection characteristic of Ni-P coating was lost due to the presence of luminescent particles. Microhardness remained almost unchanged while the surface roughness increased with the extent of particle incorporation. Optical microscopy of the surface and cross-section of coating revealed an increased density of particle distribution with bath loading. Composite Ni-P coating containing as little as 5.16% (v/v) of YVO4:Eu3+ can be successfully used as an indicator undercoat between the substrate and the functional coating.