Relative Fluorescence Intensity Ratios Research Articles

The effect of zinc ions on the fluorescence spectra of (La, Zn)OF:Sm 3+ powder phosphors

This paper reports the fluorescence properties of a new series of (La, Zn) OF:Sm 3+ powder phosphors. The measured fluorescence spectra were analyzed by computing the color coordinates ( X ̄ , Y ̄ ) and relative fluorescence intensity ratios (ED/MD). A bright yellowish-orange color was observed from these powder phosphors under a UV-source due to the confirmation of the transitions 4G 5/2→ 6H 5/2, 4G 5/2→ 6H 7/2, and 4G 5/2→ 6H 9/2. Scanning electron microscopic studies were performed to understand the average grain size of the synthesized powder phosphors.

Determination of heparin-induced IgG antibody in heparin-induced thrombocytopenia type II.

Heparin-induced thrombocytopenia is a relatively uncommon but severe side-effect of heparin therapy. Heparin-induced IgG antibody has been elucidated to be the main isotype and the most pathogenic antibody in the pathophysiology. As affected patients are at high risk of developing thrombotic events, confirmation of the clinical diagnosis and avoidance of heparin re-exposure are important and desirable. In the present study, heparin-induced IgG was measured by the binding of neoantigens, which were prepared by incubating FITC-heparin with platelet factor 4 present in normal serum. The cross-reactivities of heparin-induced IgG with low-molecular-weight heparin and danaparoid were analysed by competitive binding. A total of 81 clinically suspected heparin-induced thrombocytopenia type II patients were analysed. Thirty-seven of 38 heparin-induced thrombocytopenia type II patients, in whom thromboembolism was confirmed by objective methods, had elevated relative fluorescence intensity ratios (patient normal control) and 36 had positive heparin-induced platelet activation results. The prevalence of heparin-induced IgG in heparin-induced thrombocytopenia type II patients was 97.4%. Positive heparin-induced IgG results were: 0/319 healthy volunteers, 0/38 other thrombo-cytopenia and 2/56 heparin/low-molecular-weight heparin-receiving patients without thrombocytopenia, 2/41 hyperbilirubinaemic patients and 2/50 hyperlipidaemic patients. A small amount of cross-reaction assays showed similar results as obtained in heparin-induced platelet activation. Our results suggest that a very high frequency of heparin-induced IgG in heparin-induced thrombocytopenia type II patients can be detected using a novel antigen assay. The rapid determination of pathogenic heparin-induced IgG may be a useful tool for the rapid diagnosis of heparin-induced thrombocytopenia type II that could facilitate further management of the patients.

Fluorescence spectra of Sm 3+-doped rare earth oxybromide powder phosphors

The fluorescence properties of a new family of Sm 3+-doped powder phosphors of GdOBr, (Gd 0.9Y 0.1)OBr, (Gd 0.6Y 0.4)OBr, (Gd 0.3Y 0.7)OBr, and YOBr are reported. The measured fluorescence spectra have been analysed by computing the colour coordinates ( X̄, Ȳ) and stimulated emission cross-sections ( σ p E, cm 2). These Sm 3+-phosphors display bright reddish-orange colour due to transitions 4 G 5/2→ 6 H 9/2 (red) and 4 G 5/2→ 6 H 7/2 (orange) under a UV source. The relative fluorescence intensity ratios (red/orange) for the different measured emission levels were also evaluated in order to examine the Gd–Y, host composition effects on fluorescence behaviour.

Determination of heparin-induced IgG antibody by fluorescence-linked immunofiltration assay (FLIFA)

A fluorescence-linked immunofiltration assay (FLIFA) was developed for the determination of heparin-induced IgG in heparin-induced thrombocytopenia (HIT) type II patients. Protein A was immobilized on a nitrocellulose membrane to bind heparin-induced IgG of HIT type II patients. Fluorescein-5-isothiocynate (FITC)-heparin was added to platelet factor 4 present in normal serum to form the neo-antigen which was captured by heparin-induced IgG. The heparin-induced IgG was quantified by the relative fluorescence intensity (RFI) of bound FITC-heparin. Values were expressed as a RFI ratio (RFI patient / RFI normal) and were 1.965±0.413 in HIT type II patients ( n=36) and 1.064±0.162 in healthy controls ( n=50, p<0.0001). The intra- and inter-assay coefficients of variation were 4.9 and 10.4%, respectively. The heparin-induced IgG FLIFA will be useful in individual and epidemiological studies in patients during treatment with heparin. The FLIFA technique offers an alternative, rapid and sensitive methodological approach for studies on the interaction between antigen–antibody or ligand–receptor.

Fluorescence spectra of Eu3+-doped lanthanide oxybromide-based powder phosphors

This paper reports the fluorescence properties of a new series of Eu3+-doped powder phosphors based on GdOBr, LaOBr and YOBr. A bright red emission (5D0→7F2) was observed from all of the powder phosphors under a UV source and this situation was confirmed by fitting the colour coordinates (X̄, Ȳ) in the CIE chromaticity diagram. The relative fluorescence intensity ratios for the different measured emission levels were also evaluated in order to examine the host matrix compositional effects on the fluorescence behaviours. The best fluorescent performance was observed from (Gd0.8, Y0.2)OBr in the case of a dual lanthanide oxybromide host and from LaOBr in the case of a single lanthanum oxybromide host. For the measured fluorescent transitions, the stimulated emission cross sections (σEp cm2) were also calculated. The (Gd0.8, Y0.2)OBr, and LaOBr powder phosphors could be suggested as two promising materials, among these studied, for red colour emission and for use in certain electronic systems.

Photoluminescence spectra of LaOBr:Eu 3+ powder phosphors

This paper repons the fluorescence spectra of powder phosphors of LaOBr:Eu 3+ (in six concentrations). These phosphors are brightly fluorescent with a reddish-orange colour under a UV source and they are assigned to a transition ( 5D 0 → 7F 2) at 615 nm. Colour richness has been assessed by computing the colour coordinates [X, Y] by means of the CIE chromaticity diagram. The relative fluorescence intensity ratios ( R) for the different fluorescent bands measured have also been determined.

Fluorescence Spectra of Tb3+: Ln2O2S Powder Phosphors

The photoluminescence spectra of Tb3+ doped lanthanide oxysulfides (Y2O2S, La2O2S and Gd2O2S) powder phosphors are reported. These phosphors display bright fluorescent green under a UV source. The colour emission richness has been understood by computing the colour co-ordinates ([Xbar],[Ybar]). From their recorded photoluminescence spectra, the relative fluorescence intensity ratios have also been determined to examine the host material effects.

Fluorescence spectra of Eu 3+:Ln 2O 2S (Ln = Y, La, Gd) powder phosphors

This paper reports the preparation and analysis of the photoluminescence spectra of Eu 3+-doped lanthanide oxysulfide [Y 2O 2S, La 2O 2S, and Gd 2O 2 S]powder phosphors. These phosphors have displayed bright red color under a UV source. The richness of the red color has been verified by determining their color coordinates (X̄, Ȳ) from the CIE standard charts, and this red emission has been assigned to the transition [ 5D 0 → 7F 2]at 625 nm. Besides this stronger emission transition, four weaker fluorescent transitions have been observed, and for these the relative fluorescence intensity ratios (R) have been determined.

Fluorescence spectra of Sm 3+-doped lanthanide oxychloride powder phosphors

The fluorescence properties of Sm 3+-doped LaOCl, GdOCl, YOCl, (La, Gd)OCl, (La, Y)OCl and (Gd, Y)OCl powder phosphors are reported. The measured photoluminescence spectra have been analysed by determining their colour coordinates ( X ̄ , Y ̄ ), the relative fluorescence intensity ratios ( red orange ) and their stimulated emission cross sections ( σ P E ). These Sm 3+-phosphors have displayed bright reddish-orange colour due to the transitions 4G 5 2 → 6H 9 2 (red) and 4G 5 2 → 6H 7 2 (orange) under a UV source (150 W xenon arc lamp). The LaOCl phosphor could be suggested as a promising material for the reddish-orange colour emission for its use on the screens of optical electronic systems.

Fluorescence spectra of Tm 3+-doped rare earth oxychloride powder phosphors

This paper reports the fluorescence properties of a new family of Tm 3+-doped powder phosphors of LaOCl, GdOCl, YOCl, (La,Gd) OCl, (La,Y)OCl and (Gd,Y)OCl. A bright blue emission ( 1D 2→ 3F 4 was observed from all these phosphors under a UV lamp and this situation was confirmed by fitting the colour coordinates ( ;) in the IEC chromaticity diagram. The relative fluorescence intensity ratios ( R) for the different measured emission levels were also evaluated in order to examine the host matrix compositional effects on the fluorescence behaviours. For the measured fluorescent transitions, the stimulated emission cross sections (σ p E) were also computed.

Fluorescence spectra of Er3+:REOCl (RE = La, Gd, Y) powder phosphors

Fluorescence properties of Er3+-doped LaOCl, GdOCl, YOCl, (La,Gd)OCl, (La,Y)OCl and (Gd,Y)OCl powder phosphors are reported. The measured fluorescence spectra have been analysed by determining the colour coordinates (X¯,Y¯), relative fluorescence intensity ratios (R) and also the stimulated emission cross sections (σpE). These erbium-doped phosphors displayed bluish-green colour under a UV lamp.

Spectrofluorimetric determination of traces of zinc with the cadmium—α,β,γ,δ-tetrakis(4-sulphophenyl) - porphine complex

A highly sensitive spectrofluorimetric method for the determination of zinc was established by using the metal ion substitution reaction of the cadmium—α,β,γ,δ-tetrakis(4-sulphophenyl)porphine (H2P4−) complex with zinc ion. The zinc complex, ZnP4−, was quantitatively formed within 3 min at room temperature in the pH range 10–11. The relative fluorescence intensity ratio, F(ZnP4−)/F(CdP4−), was 37.0 at λ(em) = 604 nm [λ(ex) = 422 nm]. The calibration graph was linear over the concentration range 5–100 ng Zn2+ ml−1 in sample solution. The detection limit (signal-to-noise ratio = 3) was 0.15 ng Zn2+ ml−1 and the relative standard deviation was 1.39% for 16.6 ng Zn2+ ml−1 (ten determinations). Results are given for the application of the method to the determination of Zn2+ in tap water.

Solvent effects on electronic absorption and fluorescence spectra of salicylaldehyde 2-pyridylhydrazone and indolaldehyde 2-salicylhydrazone: Ground and excited state dissociation constants

The absorption and fluorescence spectra of salicylaldehyde 2-pyridyl-hydrazone (SAPH) and indolaldehyde 2-salicylhydrazone (IASH) were studied in various solvents. The relative fluorescence intensity and efficiency ratio are reported. Highly polar solvents cause red shifts in SAPH and blue shifts in IASH which indicate that the long-wavelength bands of the neutral molecule arise from π → π* and n → π* transitions respectively. The ground state dissociation constants p K a of SAPH and IASH were measured spectrophotometrically and spectrofluorometrically in 40 vol.% ethanol—water solutions. The corresponding p K a reveal that the compounds have an increased acidity in the excited state.