Luminescence Concentration Research Articles

Thermal and optical investigation of EuF3-doped lead fluorogermanate glasses

Europium-doped lead germanate and lead fluorogermanate glasses are studied by using differential thermal analysis, X-ray diffraction, photoluminescence and fluorescence lifetimes measurements of the 5Dj, j = 0, 1, 2 levels. PbF2 addition increases the thermal stability of the lead germanate glass, while Eu3+ ions promote the crystallization of β-PbF2:Eu3+ nano-crystals embedded in a glassy matrix. In the lead fluorogermanate glasses, Eu3+ ions exhibit a strong affinity for F− ions although oxygen ions are much more numerous. It appears that luminescence concentration quenching is not important, while cross relaxation is very efficient in the glasses. The results allow to propose for these glasses a molecular model in which small fluorine rich island, incorporating the Eu3+ ions in low symmetry sites, are separated from each other by chains of germanate (GeO4)4− ions linked together.

Cathodoluminescence of SiO<sub>2</sub>/Si System

In this paper the new method for determination of luminescent centers concentration are discussed. While the possibility of electron traps determination and definition of its activation energy are suggested. The cathodoluminescent (CL) method was used. The determination of luminescent centers concentration in silicon oxide is based on the measurements of dependences of CL intensity on electron beam current. The presence and energy of activation of electron traps were studied by measurement of rise time and decay of luminescent band during the stationary irradiation of silica by electron beam.

Continuous-flow ATP amplification system on a chip

In this study, we constructed a novel microfluidic device for continuous-flow ATP amplification, using the SU-8:PDMS method. Sepharose beads immobilized with adenylate kinase and pyruvate kinase was packed into a microfluidic chamber to form lamination layer. Dry film type SU-8 was suitable to form a very thick mold for beads column reactor and its dam structure. A good correlation between amplified luminescence and initial ATP concentration was observed in this system. The gradient of amplification when performing six cycles of continuous-flow ATP amplification was 1.72 N .

Luminescent and thermo-optical properties of Nd3+-doped yttrium aluminoborate laser glasses

In this work we performed a thorough spectroscopic and thermo-optical investigation of yttrium aluminoborate glasses doped with neodymium ions. A set of samples, prepared by the conventional melt-quenching technique and with Nd2O3 concentrations varying from 0.1 to 0.75 mol %, were characterized by ground state absorption, photoluminescence, excited state lifetime measurements, and thermal lens technique. For the neodymium emission at 1064 nm (F43/2→I411/2 transition), no significant luminescence concentration quenching was observed and the experimental lifetime values ranged around 70 μs. The obtained values of thermal conductivity and diffusivity of approximately 10.3×10−3 W/cm K and 4.0×10−3 cm2/s, respectively, are comparable to those of commercial laser glasses. Moreover, the fluorescence quantum efficiency of the glasses, calculated using the Judd–Ofelt formalism and luminescence decay, lies in the range from 0.28 to 0.32, larger than the typical values obtained for Nd3+ doped YAl3(BO3)4 crystals.

Upconversion luminescence in Er-doped γ-AlON ceramic phosphors

γ -AlON : Er 3 + phosphors with different Er3+ concentration for upconversion luminescence were prepared by a combination of carbothermal reduction and nitridation and solid-state synthesis methods. The effect of Er3+ content on emission spectra was investigated. Under the excitation of 980 nm diode laser, green emission centered at 548 nm and red emission centered at 666 nm were observed, which are ascribed to the transition of S43/2/H211/2→I415/2 and F49/2→I415/2 of Er3+ ions, respectively. The pump power dependence indicates a two-photon process involved in the upconversion luminescence. The ratio of red emission relative to green emission was enhanced with the increase in Er3+ concentration. The possible mechanisms were discussed.

Spectral broadening and luminescence quenching of 1.53 μm emission in Er 3+-doped zinc tellurite glass

The emission spectra and the lifetime of the lasing transition 4I 13/2→ 4I 15/2 in Er 3+-doped TeO 2-ZnO binary glass have been studied. The investigation includes Raman scattering spectroscopy as well as optical absorption, luminescence, and lifetime measurements techniques. The influence of erbium concentration on the line-shape of this electron transition has been analyzed. It was observed that the increasing of Er 3+ ion concentration, in the 0.2–4 mol% range, results in a structural changes and a significant spectral broadening of the 1.53 μm emission band. Reabsorption has been evoked to explain the broadening of the 4I 13/2→ 4I 15/2 emission line. In the paper, is also reported the effect of the erbium content on the emission intensity of the 4I 13/2→ 4I 15/2 transition as well as on the lifetime of the 4I 13/2 level. Based on the electrical–dipole interaction theory, the luminescence concentration quenching mechanism by hydroxyl groups is analyzed. The data suggest that <10% of hydroxyl groups are coupled to erbium ions in the zinc tellurite glass network.

The role of luxCDE genes in bioluminescence of bacteria

It is revealed that in the bacterial lacking luxCDE genes responsible in the standard scheme for synthesis of aliphatic aldehydes—the substrate for the bacterial bioluminescence—there is an aldehyde factor at sufficient concentration for bright luminescence of these bacteria.

Continuous-flow ATP amplification system for increasing the sensitivity of quantitative bioluminescence assay

We constructed a novel ATP amplification reactor using a continuous-flow system, and this allowed us to increase the sensitivity of a quantitative bioluminescence assay by controlling the number of ATP amplification cycles. We previously developed a bioluminescence assay coupled with ATP amplification using a batch system. However, it was difficult to control the number of amplification cycles. In this study, ATP amplification was performed using a continuous-flow system, and significant linear correlations between amplified luminescence and initial ATP concentration were observed. When performing four cycles of continuous-flow ATP amplification, the gradient of amplification was 1.87 N. Whereas the lower quantifiable level was 500 pM without amplification, values as low as 50 pM ATP could be measured after amplification. The sensitivity thus increased 10-fold, with further improvements expected with additional amplification cycles. The continuous-flow system thus effectively increased the sensitivity of the quantitative bioluminescence assay.

Synthesis process and luminescence properties of Ln 3+ doped NaY(WO 4) 2 nanoparticles

The hydrothermal synthesis process and luminescence properties of Ln 3+ doped NaY(WO 4) 2 nanoparticles have been investigated. Nearly spherical Eu 3+ doped NaY(WO 4) 2 nanoparticles can be observed. The luminescence concentration quenching of Eu 3+ in the NaY(WO 4) 2 nanoparticles was found to be similar to that in the NaY(WO 4) 2 crystals. The upconversion luminescence intensity of the Yb 3+–Er 3+ codoped NaY(WO 4) 2 nanoparticles was found to be much stronger than that of the Er 3+ doped NaY(WO 4) 2 nanoparticles.

Synthesis and Luminescence Properties of Lanthanide (III)-Doped YF3 Nanoparticles

Synthesis process and luminescence properties of trivalent lanthanide ions (Ln3+) doped YF3 nanoparticles have been investigated. To synthesis Ln(3+)-doped YF3 nanoparticles, the mixture of (YCl3 x nH2O + LnCl3 x nH2O), and NH4F was hydrothermal treated at 180 degrees C in a Teflon-liner auto-clave or heated at higher temperatures (400 degrees C - 600 degrees C) in a stove. The XRD patterns showed that the Ln(3+)-doped orthorhombic YF3 nanoparticles with no second phase have been prepared. The solid solution Y(1-x)Eu(x)F3 (x = 0 - 0.4) nanoparticles have been synthesized. The luminescence concentration quenching resulted from resonance energy transfer between neighboring Eu3+ ions occurred at higher Eu3+ concentrations (30 mol%). The upconversion luminescence of Er(3+)-Yb3+ codoped YF3 nanoparticles under 980 nm excitation has also been observed. With increase of heated temperature, the size of the Er(3+)-Yb3+ codoped YF3 nanoparticles increased gradually, and upconversion luminescence intensity increased significantly.

Intermolecular Interaction and a Concentration-Quenching Mechanism of Phosphorescent Ir(III) Complexes in a Solid Film

Solid-state self-quenching processes of highly efficient Ir(III) phosphorescent emitters are investigated by the measurement of thin film photoluminescence quantum efficiency and transient lifetime as a function of doping concentration in a host matrix. The radiative decay rate constant is found to be independent from the average distance between dopant molecules (R), and the concentration-quenching rate constant is shown to be dependent on R(-6). The quenching dependence on R strongly suggests that luminescent concentration quenching in a phosphorescent Ir(III) complex:host film is controlled by dipole-dipole deactivating interactions as described by the Förster energy transfer model.

P‐80: Research of SrTiO3:Pr3+: Al Luminescent Properties under the Photoexcitation

AbstractThe properties of SrTiO3:Pr3+:Al luminescent structure under the photoexcitation are investigated. The excitation spectra of luminescence and photocon‐ductivity are obtained. The relationship between the luminescence intensity and concentration of coactiva‐tor (Al) is explored. It is shown, that two centers of luminescence in the strontium titanate are formed. It can be explained by different location of praseodymium ions in the SrTiO3 host lattice (Pr3+ substitutes Sr2+ and Pr3+ substitutes Ti4+).

Electron Beam Induced Degradation of CaS:Pb Thin Film Phosphor Grown by Atomic Layer Deposition

The effects of electron (e)-beam irradiation on the luminescent and the materials properties of CaS:Pb films were investigated using structural and compositional analysis techniques. Continuous e-beam irradiation on CaS:Pb thin film for 180 min resulted in an approximately 60% decrease of cathodoluminescence (CL) intensity. Transmission electron microscopic analysis indicated that e-beam irradiation induced the precipitation of Pb. The decrease of CL intensity by e-beam irradiation was mostly caused by the decrease of Pb 2 + luminescent center ion concentration due to the precipitation of Pb. E-beam irradiation also resulted in heavy carbonaceous contamination on the surface. The thickness of the carbonaceous layer was approximately 10 nm.

Up-converting phosphor reporters for nucleic acid microarrays.

An important application of robotically spotted DNA microarrays is the monitoring of RNA expression levels. A clear limitation of this technology is the relatively large amount of RNA that is required per hybridization as a result of low hybridization efficiency and limiting detection sensitivity provided by conventional fluorescent reporters. We have used a recently introduced luminescent reporter technology, called UPT (up-converting phosphor technology). Down-converting phosphors have been applied before to detect nucleic acids on filters using time-resolved fluorometry. The unique feature of the phosphor particles (size 0.4 microm) used here is that they emit visible light when illuminated with infrared (IR) light (980 nm) as a result of a phenomenon called up-conversion. Because neither support material of microarrays nor biomolecules possess up-conversion properties, an enhanced image contrast is expected when these nonfading phosphor particles are applied to detect nucleic acid hybrids on microarrays. Comparison of the UPT reporter to cyanin 5 (Cy5) in a low-complexity model system showed a two order of maginitude linear relationship between phosphor luminescence and target concentration and resulted in an excellent correlation between the two reporter systems for variable target concentrations (R2 = 0.95). However, UPT proved to be superior in sensitivity, even though a wide-field microscope equipped with a xenon lamp was used. This higher sensitivity was demonstrated by complementary DNA (cDNA) microarray hybridizations using cDNAs for housekeeping genes as probes and complex cDNA as target. These results suggest that a UPT reporter technology in combination with a dedicated IR laser array-scanner holds significant promise for various microarray applications.

Mesoscopic study of bipolar charge transport in polymer-based devices

We present generalised Monte-Carlo calculations of bipolar charge carrier transport in polydiacetylene (PDA) to assess effects of some key factors on the properties of polymer-based light-emitting diodes (PLEDs). Our mesoscopic model includes specific realisations of the polymer network and examines the effect of polymer structural order on current flow and charge recombination within the polymer layer. Specifically addressed are the issues concerning the fractions of polymer strands contributing to the charge injection processes at electrode interfaces and to electroluminescence (EL). Our results suggest that radiative recombination increases as short chain concentration increases, whereas current efficiency shows an opposite behaviour. Radiative recombination decreases as charge injection efficiency decreases and its internal efficiency seems to saturate for a luminescent chain concentration >30%. Our results also suggest that both current efficiency and space-charge increases as charge injection efficiency decreases. Polymer disorder due to inclusions in the network does seem to contribute to reduce both current and recombination efficiencies.

On Increase in Efficiency of Luminescent Concentration of Mineral Raw Material

The ways are considered for increasing the efficiency of luminescent separation of many types of mineral raw material due to the presence of calcite in them. The versatility of luminescent method for mineral raw material separation is shown by studying apatite-calcite ore beneficiation.

Use of anion exchange resin-packed capillary column for rapid detection of anti-double-stranded DNA antibody in systemic lupus erythematosus serum.

An anti-double-stranded (ds) DNA antibodies in serum-detection system was developed based on flow immunoassay with packed-capillary column. Alkaline phosphatase conjugated DNA (ALP-DNA) and anti-dsDNA antibody were separated from unreacted ALP-DNA on the basis of the difference in isoelectric point. A linear anti-dsDNA antibody dose-response curve was obtained between luminescence intensity and concentration of anti-dsDNA antibody in the range 25-200 IU/mL. This simple technique permits the assay of anti-dsDNA autoimmune antibodies within 7 minutes. These results give reduced detection times compared with those previously reported (Lim et al., 1999) through the use of capillary columns.

Optical and electrical investigations of isoelectronic In-doped GaN films

The optical and electrical properties of isoelectronic In-doped GaN films grown by metalorganic vapor phase epitaxy (MOVPE) were investigated by X-ray, photoluminescence (PL), Hall and Raman measurements. As a result, adequate In-doping quantity causes not only a reduction of yellow luminescence and unintentional background concentration, but an enhanced mobility and decrease in the widths. The improved crystalline and optical qualities of GaN films may be attributed to the decrease in defects.

Determination of the Luminescent Impurity Concentration in Solution in the Presence of Intense Background Luminescence

A method of excitation-emission matrix (EEM) processing is proposed for determining the concentration of polyaromatic hydrocarbons in aqueous media in the presence of an unknown intense background signal exceeding the legitimate signal by a factor of 15–20. The theoretical substantiation and experimental test of the efficiency of the proposed method have been performed with the use an aqueous solution of anthracene as an example.

The luminescent properties of divalent europium complexes of crown ethers and cryptands

The luminescent properties of divalent europium complexes with crown ether, azacrown ether, N-pivot-azacrown ether, and cryptand in methanol or water have been systematically investigated under UV irradiation. These divalent europium complexes show greatly enhanced emission from 417 nm to 488 nm in the visible blue region in comparison with that of the methanol solution of EuCl 2. The aqueous solution of EuCl 2 is non-luminescent. This obvious distinction in luminescent properties between the macrocyclic ligand-coordinated divalent europium and uncoordinated divalent europium is attributed to the “insulation effect” of Eu 2+ ion from the solvent molecules of CH 3OH and H 2O by the macrocyclic crown ether or cryptand encapsulation to divalent europium. Moreover, these macrocyclic ligands provide an additional restriction to the electronic charge expansion of the excited Eu 2+. This also contributes to the enhancement of the Eu 2+ luminescence. Among all the investigated macrocyclic ligands, 15-crown-5 (15C5) affords the largest enhancement to the Eu 2+ emission. The intensity of the Eu 2+–15C5 complex is 690 times that of the EuCl 2 methanol solution with the same Eu 2+ concentration. This special emission enhancement effect is related to the particular complex composition of 1:3 (Eu 2+:15C5) and corresponding configuration of Eu 2+–15C5 complex in methanol. Concerning the mechanism, the luminescence enhancement of divalent europium by complexation with these macrocyclic crown ether or cryptand ligands is found to be initiated from the decrease in non-radiative rate constant rather than from the increase in radiative one. The divalent europium complexes of methacrylate polymeric polyether derivatives such as 15C5-, 18-crown-6- (18C6), and cryptand [2.2.1]- or [2.2.2]-containing polymer and copolymer have also been prepared. Their luminescent properties in solid state have been studied to aim for practical application. As a similar situation to the simple polyether complexes, the divalent europium complex with 15C5-containing polymer or copolymer shows the largest luminescent enhancement effect. Its emission intensity reaches about 20% that of the commercial inorganic luminescence product CaWO 4:Pb (NBS 1026). In addition, the doping effect of several divalent ions, namely Mg, Sr, Ba and Zn in polymeric complexes, has also been investigated according to the luminescence concentration quenching mechanism in solid state luminescence materials. The emission intensity of 15C5-containing polymer europium(II) complex is raised to twice stronger by doping of Zn 2+ ion.