UV-vis Luminescence Research Articles

UV–Vis luminescence in β-Ga2O3: Eu nanopowders obtained by mechano-chemical synthesis

UV–Vis luminescence in β-Ga2O3: Eu nanopowders obtained by mechano-chemical synthesis

Near infrared fluorescence properties of Tb4+ and Tb3+ inter-conversion states in CaF2:Yb3+nanocrystals

Near infra-red emission was enhanced in calcium fluoride (CaF2) co-doped with terbium ions and ytterbium (Yb3+) under a 325 nm laser excitation wavelength, during investigations performed for possible application in Si solar cells. Tb3+ ions were oxidized to Tb4+ ions and emission enhancement occurred due to a cooperative energy transfer mechanism between the Tb4+-Yb3+ couple. The oxidation of Tb3+ ions in CaF2 was achieved by annealing the nanocrystals at 450 °C in air. X-ray diffraction analysis confirmed the cubic face of the CaF2 crystal without any impurity peaks. UV–VIS luminescence and X-ray photoelectron spectroscopy were conducted to probe the conversion of Tb3+ to Tb4+ ions as a function of the annealing time. The main conclusion was that the NIR emission from the Tb4+-Yb3+ couple revealed that down-conversion occurred through a cooperative energy transfer mechanism.

On the Crystal Chemistry of RE2Si2O7: Revisited Structures, Group–Subgroup Relationship, and Insights of Ce3+-Activated Radioluminescence

Polymorphic rare-earth disilicates RE2Si2O7 (RE = La–Lu, Y, and Sc) are attractive materials as thermal barrier coatings and scintillators; however, the orthorhombic E(δ)-type (RE = Eu–Ho and Y) and the triclinic F-type (RE = Sm and Eu) remain structurally controversial hitherto. In this work, we revisit the crystal structures of E(δ)-RE2Si2O7 (Pnma), F-RE2Si2O7 (P1̅), and the monoclinic G-La2Si2O7 (P21/n) by X-ray single-crystal/powder diffraction. The second-harmonic generation (SHG) and/or the local-structure-sensitive VUV–UV–vis luminescence of Ce3+/Eu3+ validate the structure determination. E(δ)-RE2Si2O7 (RE = Eu–Ho) crystallizes in the centrosymmetric Pnma instead of the previous noncentrosymmetric Pna21 (a subgroup of Pnma). Increasing the RE3+ radius results in structural transformations of the reconstructive-type E(δ) ↔ F and translationengleiche subgroup–group relationship F ↔ G (RE = La–Nd). More importantly, we perform a complete survey of 17 structure-types over 63 compounds of RE2Si2O7 and their related transformations depending on the radius of RE3+. On the basis of these studies, one could (i) predict the potential polymorphs of RE2Si2O7, including the high-pressure phase and the RE2Si2O7 solid solutions; (ii) correlate the coefficient of thermal expansion (CTE) with the crystal structure, and (iii) understand the unusual radioluminescence of (Gd,La)2Si2O7:Ce3+ high-temperature scintillators.

Boosting luminescence and MRI evolution via regulation of GdPO4:5%Eu3+ morphologies by H3PO4

A series of GdPO4:5%Eu3+ micro/nanomaterials with different morphologies and crystal structures were successfully prepared by the one-step solvothermal method using only the gadolinium source, the phosphoric acid source and ethanol as solvents, without any surfactants or templates, without further calcination and by adjusting only the ratio of phosphoric acid and gadolinium sources. They all have good dispersion and homogeneity. The morphology of the products was mainly regulated by the ratio of H3PO4 to Gd(NO3)3·6H2O, with ratios of 2:1, 8:1, 16:1, 24:1, 32:1, 40:1 and 48:1 mL/g resulting in the formation of square, pillow, star, carambola, hollow cylinder, drum and jujube shaped GdPO4:5%Eu3+ micro/nanomaterials, respectively. Ratios of 2:1–24:1 and 32:1–48:1 allow for the direct solvothermal synthesis of monoclinic and hexagonal phase gadolinium phosphate, simultaneously. In addition to their crystal structure and morphology, chemical bonding, thermal stability and specific surface area, their luminescence properties and magnetic resonance imaging (MRI) tracing properties have also been studied in comparison. Interestingly, the GdPO4:5%Eu3+ micro/nanoparticles in the carambola shape had a higher photoluminescence intensity and relaxation rate of 0.7709 mM−1 s−1 (r1) among all the morphologies. The possible mechanisms by which various morphologies of GdPO4:5%Eu3+ were prepared in different ratios were analyzed, and the reasons for their effects on the fluorescence and MRI tracer properties were further investigated. This study is of reference significance for the simple-regulated synthesis of rare earth inorganic gadolinium-containing micro/nanomaterials and provides a reliable guarantee for the expansion of their multifunctional applications in UV–Vis luminescence and MRI tracing for implants.

VUV–UV–vis Luminescence, Energy Transfer Dynamics, and Potential Applications of Ce3+- and Eu2+-Doped CaMgSi2O6

Ce3+ and Eu2+ single- and double-doped CaMgSi2O6 phosphors have been prepared by a high-temperature solid-state reaction approach. The VUV–UV–vis luminescence properties are investigated at cryogen...

Ln-CPs constructed from unsymmetrical tetracarboxylic acid ligand: Tunable white-light emission and highly sensitive detection of CrO42-, Cr2O72-, MnO4- in water.

A series of isostructural lanthanide coordination polymers (Ln-CPs), [Ln(Hbptc)(H2O)4]·H2O [Ln=Er (1), Pr (2), Dy (3), Sm (4), Gd (5), Nd (6) and Tb(7); H4bptc=2,3,3',4'-biphenyl tetracarboxylic acid] have been isolated based on an unsymmetrical tetracarboxylic acid. Single-crystal X-ray diffraction analysis reveals that all CPs featured a two dimensional (2D) layer with (6, 6, 6)-connected 63 topology. Luminescent spectra demonstrate that CPs 1-7 exhibit impressive UV-visible luminescence in the solid state at room temperature. More significantly, a single-component white-light material with International Commission on Illumination (CIE) coordinates of (0.335, 0.334) for 4 (Sm-CP), very closing to the pure white-light of (0.333, 0.333) was obtained by finely tuning of the excitation wavelength. In addition, the luminescent detection for anions of 7 is investigated. Fluorescence measurements show that 7 can detect oxoanion pollutants Cr2O72-, CrO42-, and MnO4- anions in aqueous solutions with high selectivity and sensitivity, which suggests that the Tb-CP is a promising functional luminescence probe for toxic oxoanions. The possible mechanisms of the quenching effect were also discussed in detail.

Contactless Detection of Contaminants by UV-VIS Luminescence Spectroscopy

Some modern methods of surface contamination detection use the principle of luminescence for their function. This thesis aims at introducing the principle of the method that is available for the measurement of surface contamination, thesis deals with an innovative surface-detection device using UV-VIS luminescence spectroscopy. In the work is presented the industrial use of the detection of oil contaminants. Another specialized topic is the field of forensic practice - dactyloscopy, where the possible use of the principle of UV-VIS luminescence spectroscopy, the Recognoil device as a possible and effective method of ensuring dactyloscopic traces is proved.

NOVEL ANALYTICAL STUDY FOR REACTION INTERMEDIATES IN THE PRIMARY RADIATION INTERACTION OF DNA USING A SYNCHROTRON RADIATION-INDUCED LUMINESCENCE SPECTROSCOPY

To identify the precise molecular processes to induce DNA lesions, we attempt a novel spectroscopy of X-ray induced luminescence (XIL) using soft X-ray synchrotron radiation, which is a non-destructive analysis of the reaction intermediates in the elementary reaction pathway of damage induction and self-organized restoration. Using a liquid micro-jet technique to introduce aqueous samples in a vacuum chamber, we measure UV-visible luminescence from nucleotide solution as a function of the soft X-ray energy from the nitrogen to oxygen K-edge region. The XIL intensities for the nucleotide solutions are significantly enhanced in the soft X-ray region (410-530 eV) which is ascribed to the K-shell excitation/ionization of nitrogen atoms in the nucleobases. Furthermore, the XIL spectra do not show any signature of X-ray absorption near-edge structure (XANES) of the nucleobases. This is because the luminescence intensities collected from the integral area of the micro-jet only reflect the quantum yield of luminescence of the absorbed X-ray into UV-visible light irrespective of the absorption cross sections, i.e. of XANES. Thus the present result is the first evidence of luminescence as a result of X-ray absorption of aqueous nucleotides.

Two types of lanthanide Schiff base complexes: Synthesis, structure and spectroscopic studies

A series of five Ln(III) salen type complexes, with La(III), Eu(III), Tb(III), Er(III) and Tm(III) cations, were obtained by a template reaction between 5-methylsalicylaldehyde and 4-methyl-1,3-phenylenediamine in the presence of the appropriate Ln(III) nitrate. Two types of complexes of the general formulae [Ln(H2L)3(NO3)3] (type I) [Ln=La (1), Eu (2), Tb (3)] and [Ln(H2L)2(NO3)3EtOH]MeOH (type II) [Ln=Er (4), Tm (5)], where H2L is N,N′-bis(5-methylsalicylidene)-4-methyl-1,3-phenylenediamine, were characterized by elemental analysis, FT-IR, ESI-MS, TG-DTA analysis, UV–Vis luminescence and 1H and 13C NMR spectroscopy. Single-crystal X-ray diffraction revealed that the type I complexes crystallize in the monoclinic P21/n space group, while type II complexes crystallize in the monoclinic Cc space group. The central cations for both type of complexes are nine-coordinated, exclusively by oxygen atoms, and the coordination resembles a distorted tricapped trigonal prism. In the case of type 1 complexes, the central cations are coordinated with three nitrate groups and three H2L neutral molecules, while for type 2 complexes, one of the ligand molecule is replaced by an ethanol molecule. In the latter case, the methanol molecule plays an important role in the crystal packing, taking part in hydrogen bonding which connects the complex molecules into infinite chains. The structural change is due to a decrease of the ionic radii of the lanthanide ions.

Synthesis and photoluminescence properties of tunable emission phosphors Ca4Si2O7F2:Ce3+

The Ce3+ activated phosphors Ca4Si2O7F2:Ce3+ are prepared by a solid state reaction technique. The UV–vis luminescence properties as well as fluorescence decay time spectra are investigated and discussed. The results revealed that there were two kinds of Ce3+ luminescence behavior with 408 and 470 nm emissions, respectively. Under 355 nm excitation, the Ce(1) emission (408 nm) is dominant at low doping concentration, and then the Ce(2) emission (470 nm) get more important with increasing of Ce3+ concentrations in the host. The phosphors Ca4Si2O7F2:xCe3+ show tunable emissions from blue area to green-blue area under near-ultraviolet light excitation, indicating a potential application in near-UV based w-LEDs.

A Novel Charged Iridium (III) Complex for Amine Sensor Application

A new phosphorescent iridium metal with cyclometalated and dimethyl carboxylate bipyridine ligands complex 1 was synthesized and characterized. The ester functional were designed and connected as amine recognition group. The UVVis absorption and luminescence properties of complex 1 were investigated with amine. The result show that complex 1 exhibited high selectivity and efficient signaling behavior n-butylamine in acid catalyst.

Vacuum-UV excitation and visible luminescence of nano-scale and micro-scale NaLnF4:Pr3+ (Ln = Y, Lu)

The UV–Vis luminescence of NaLnF4:Pr3+ (Ln=Y, Lu) materials can be efficiently excited by vacuum UV radiation (VUV) such as the 172nm emission of mercury-free Xe-discharge lamps. In this work, the optical properties of the cubic α-phase and the hexagonal β-phase of NaLnF4:Pr3+ (Ln=Y, Lu) powders are compared regarding particle sizes in the nano- and micrometer regime. Upon VUV excitation, the emission spectra of both crystal phases are found to be dominated by intraconfigurational [Xe]4f2–[Xe]4f2 transitions, which is explained by the chemical properties of the ternary fluorides. Furthermore it is observed that the emission and excitation spectra of nano- and micro-scale powders are very similar, but that the luminescence intensity is affected by the average particle size.

A potential reddish orange emitting phosphor Ca2BO3Cl:Eu3+ for white light-emitting diodes

A series of phosphors Ca2BO3Cl:Eu3+ were synthesized by using a high-temperature solid-state reaction technique, and their UV–vis luminescence properties were investigated. The f–f transitions of Eu3+ in the host lattice were assigned and discussed. The excitation and emission spectra indicate that this phosphor can be effectively excited by ultraviolet (394nm), and exhibit reddish orange emission corresponding to the 5D0→7FJ (J=0, 1, 2) transitions of Eu3+. The influence of the doping concentration and charge compensators on the relative emission intensity of Eu3+ was investigated, and the optimum doping concentration is 0.04. The critical distance Rc was estimated to be 17.1Å in terms of the concentration quenching data. The present study suggests that Ca2BO3Cl:Eu3+ can be a potential candidate as an UV-convertible phosphor for white light-emitting diodes (LEDs).

Synchrotron UV−Visible Multispectral Luminescence Microimaging of Historical Samples

UV-visible luminescence techniques are fre-quently used for the study of cultural heritage materials, despite their limitations for identification and discrimination in the case of complex heterogeneous materials. In contrast to tabletop setups, two methods based on the vacuum ultraviolet (VUV)-UV-visible emission generated at a bending magnet of a synchrotron source are described. The main advantages of the source are the extended wavelength range attained, the continuous tunability of the source, and its brightness, leading to a submicrometer lateral resolution. Raster-scanning microspectroscopy and full-field microimaging were implemented and tested at the DISCO beamline (synchrotron SOLEIL, France). Investigative measurements were performed on a sample from a varnished musical instrument and a paint sample containing the pigment zinc white (ZnO) in order to illustrate some of the challenges analyzing heterogeneous cultural heritage cross-section samples with the novel imaging approach. The data sets obtained proved useful for mapping organic materials at the submicrometer scale and visualizing heterogeneities of the semiconductor pigment material. We propose and discuss the combined use of raster-scanning microspectroscopy and full-field microimaging in an integrated analytical methodology. Synchrotron UV luminescence appears as a novel tool for identification of craftsmen's and artists' materials and techniques and to assess the condition of artifacts, from the precise identification and localization of luminescent materials.

Synthesis and Optical Properties of Calcium Halide-Based Aluminoborate Glasses Codoped with Eu2 + and Eu3 + Ions

Oxy-halide glasses in systems of –– ( = F, Cl, and Br) doped with were prepared by a melt quenching method and their optical properties were characterized by measurements of UV-visible luminescence, hole burning, and electron spin resonance (ESR) spectra. For the - and -based samples, ions were partially reduced during the heating process in ambient atmosphere, so that room temperature persistent spectral hole burning was observed on them. Meanwhile, no obvious band emission or characteristic ESR signal of ion was recorded on the -based samples also prepared in ambient atmosphere, and consequently any hole peak was hardly detected even at . However, hole peaks were produced and persisted at room temperature on the -based samples remelted in a reducing atmosphere. The self-reduction mechanism for ion in the - and -based samples is discussed as well as the hole formation in all samples.

Synthesis and optical characterization of poly(styrene sulfonate) films doped with Nd(III)

In this work, we present a new synthesis and optical characterization of poly(styrene sulfonate) (PSS) films doped with neodymium ions (Nd). The optimization of the Nd-PSS films processing shows that the maximum Nd(III) incorporation is equal to 14%. The absorbance spectra in the UV–Vis-NIR region of Nd-PSS films present the typical transition bands of neodymium chloride (NdCl 3) in aqueous solution. The infrared spectra display the PSS transitions with an enlargement in every band, as a result of Nd coordination. The UV–Vis luminescence of Nd-PSS films exhibits a spectral blue shift and a line shape definition as compared to PSS film, indicating a decrease in the interaction among the aromatic groups. In addition, the Nd-PSS emission at 1052 nm (9505 cm −1 – transition 4F 3/2 → 4I 11/2) was observed, independently of the neodymium concentration. Judd–Ofelt theory was used in order to obtain the Nd radiative transition rates.

Lanthanide Cryptates Entrapment in Aluminum Polyphosphate Gels

In this work, we report for the first time the preparation and spectroscopic investigation of [Tb⊂ Bipy.Bipy.Py(CO 2 Et 2 )] 3+ incorporated in aluminum polyphosphate gels. Gelation occurs under ambient atmosphere at room temperature, which is followed by syneresis, leading to transparent samples after 5-10 days. Transparent auto-standing films were also prepared. The gel samples were characterized by UV-visible absorption spectrophotometry, luminescence spectroscopy and lifetime measurements. The crypate absorption and emission spectra were not greatly affected by its incorporation within the gel matrix. The lifetime of the Tb 3+ 5 D 4 level increases from 0.7 ms to 1.0 ms after entrapment into the gel. The results imply that these systems are promising for application in fluoroimmunoassays, as well as for the design of new optical materials.

Lanthanide Cryptates Entrapment in Aluminum Polyphosphate Gels

In this work, we report for the first time the preparation and spectroscopic investigation of [Tb⊂ Bipy.Bipy.Py(CO 2 Et 2 )] 3+ incorporated in aluminum polyphosphate gels. Gelation occurs under ambient atmosphere at room temperature, which is followed by syneresis, leading to transparent samples after 5-10 days. Transparent auto-standing films were also prepared. The gel samples were characterized by UV-visible absorption spectrophotometry, luminescence spectroscopy and lifetime measurements. The crypate absorption and emission spectra were not greatly affected by its incorporation within the gel matrix. The lifetime of the Tb 3+ 5 D 4 level increases from 0.7 ms to 1.0 ms after entrapment into the gel. The results imply that these systems are promising for application in fluoroimmunoassays, as well as for the design of new optical materials.

The role of tartrate ions in the phosphonate based inhibitor system

Corrosion of steel in oxygen saturated environment is inhibited by insoluble products, with the metals ions existing in the solution, which precipitate on the surface to form a three-dimensional protective layer. Addition of tartrate with organophosphonic acid (2-carboxyethylphosphonic acid) and zinc metal cation enhances the inhibition efficiency of steel in neutral environment. Using weight change method, polarization and AC impedance techniques determined the inhibition efficiencies. The composition of the protective layer was determined by using UV–VIS reflectance, UV–VIS luminescence and ESCA techniques.

Photoluminescence studies in Sc: CaF2 and Sc, Ce: CaF2 crystals

Stokes and anti-Stokes UV-visible luminescence was investigated in γ-irradiated Sc and Sc-Ce doped CaF 2 crystals. Wideband Stokes luminescence under laser or CW lamp excitation was measured: (1) at 380 nm (luminescence decay time τ ~ 17 μs) in Sc: CaF 2 and Sc, Ce: CaF 2 crystals, attributed to Sc 2+ ions and (2) at 300 nm ( τ ~ 40 ns) in Sc, Ce: CaF 2 crystals, due to Sc-Ce aggregate centers. Anti-Stokes luminescence in the 250–350 nm spectral range with a 1 μs lifetime can be explained by exciton luminescence.