Analysis Of Decay Curves Research Articles

Luminescence properties of europium doped oxyfluorosilicate glasses for visible light devices

Europium (Eu3+)-doped oxyfluorosiliacte (SALfSfEu: SiO2 + Al2O3 + LiF + SrF2 + Eu2O3) glasses have been fabricated by usual melt-quenching technique. These glasses were characterized through optical absorption, excitation, emission and decay curve analysis. The Judd-Ofelt (JO) parameters have been evaluated from the refractive index and luminescence spectrum of the 1.0 mol% Eu3+-doped glass. The quantitative radiative properties including branching ratio, radiative lifetime and stimulated emission cross-sections of the fluorescent levels were predicted by using the JO parameters. Luminescence intensity increases as for as 0.5 mol% and then decreases with further increasing Eu3+ ion concentration. Photoluminescence quantum yield found to be as high as 74% for 0.05 mol% of Eu3+ ion concentration and decreased by increasing concentration. Luminescence intensity ratio is found to be 3.17 for 1.0 mol% Eu3+-doped SALfSfEu1.0 glass which suggest that the occupation of high degree of symmetry by the Eu3+ ions. Fluorescent decay curves of the emitting level exhibit an exponential behaviour. Lifetime of 5D0→7F2 transition was decreased slightly with increasing Eu3+ ion concentration, however, not significant for 5D1→7F1 transition. Luminescence properties reveal that the red emission at 612 nm found to be suitable for developing the lasers and display devices in the visible region.

Spectroscopic investigations on high efficiency deep red-emitting Ca2SiO4:Eu3+ phosphors synthesized from agricultural waste

Europium doped calcium orthosilicate (Ca2SiO4) phosphors have been synthesized by the conventional high temperature solid-state reaction method in various concentrations from agricultural waste (egg shell as a CaO and rice husk as a SiO2). These phosphors structure from X-ray diffraction and morphology from scanning electron microscopy have been examined. Concentration dependent Eu3+ ions luminescent properties in Ca2SiO4 phosphors have been studied from the excitation, emission and decay curves analysis. The 5D0 → 7FJ transitions observed in luminescence spectrum allows to determine the site symmetry of the Eu3+ ion. A charge transfer band (CTB) at around 260 nm which is due to the Eu–O interaction in the host along with the 4f – 4f excitation bands due to Eu3+ ions in UV and blue regions are observed. The color co-ordinates determined from emission spectra varies with concentrations of Eu3+ ions and are found to fall in the red region. The decay curves show single exponential behavior for all concentrations of Eu3+ ions (0.01–0.4 mol%) and the lifetimes varied from 2.67 to 2.78 ms. It is worth noting that the present material is found to be far better than many red phosphors synthesized by using agricultural waste as raw materials.

A study of low threshold and high gain Nd3+ ions doped SiO2-B2O3-Na2CO3-NaF-CaF2 glasses for NIR laser applications

Fluoroborosilicate glasses of composition 35SiO2-25B2O3-10Na2CO3-15NaF-15CaF2-xNd2O3 (where x = 0.1, 0.5. 1.0, 2.0 mol%) were prepared by melt quenching technique and various physical properties have been calculated. From the absorption spectra J-O Intensity parameters Ωλ (λ = 2, 4, 6) and radiative properties are evaluated by using J-O theory. The high values of Ω2 = 4.213 × 10−20 cm2, Ω4 = 5.345 × 10−20 cm2, Ω6 = 5.526 × 10−20 cm2 suggest that among the prepared glasses 0.5 mol% Nd glass is more asymmetric, more covalent and rigid in nature. The emission spectra were recorded with 808 nm laser as excitation source. The strong NIR emissions were observed at 876 nm, 1056 nm, 1328 nm corresponding to the transitions 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, 4F3/2 → 4I13/2 respectively. Stimulated emission cross -section (σemi) and Gain bandwidth (σemi × Δλeff) were calculated. For 0.5 mol% Nd these values are found to be 3.30 × 10−20 cm2, 11 × 10−26 cm2. From the decay curve analysis the lifetime values for 4F3/2 level have been determined and these values are decreased with increase in Nd3+ ions concentration. These results may suggest that the prepared SBNCNd05 (Nd = 0.5 mol%) glass could be useful for 1056 nm laser applications.

Decay curve analysis for data error quantification in time-domain induced polarization imaging

In recent years, the time-domain induced polarization (TDIP) imaging technique has emerged as a suitable method for the characterization and the monitoring of hydrogeologic and biogeochemical processes. However, one of the major challenges refers to the resolution of the electrical images. Hence, various studies have stressed the importance of data processing, error characterization, and the deployment of adequate inversion schemes. A widely accepted method to assess data error in electrical imaging relies on the analysis of the discrepancy between normal and reciprocal measurements. Nevertheless, the collection of reciprocals doubles the acquisition time and is only viable for a limited subset of commonly used electrode configurations (e.g., dipole-dipole [DD]). To overcome these limitations, we have developed a new methodology to quantify the data error in TDIP imaging, which is entirely based on the analysis of the recorded IP decay curve and does not require recollection of data (e.g., reciprocals). The first two steps of the methodology assess the general characteristics of the decay curves and the spatial consistency of the measurements for the detection and removal of outliers. In the third and fourth steps, we quantify the deviation of the measured decay curves from a smooth model for the estimation of random error of the total chargeability and transfer resistance measurement. The error models and imaging results obtained from this methodology — in the following referred to as “decay curve analysis” — are compared with those obtained following a conventional normal-reciprocal analysis revealing consistent results. We determine the applicability of our methodology with real field data collected at the floodplain scale (approximately 12 ha) using multiple gradient and DD configurations.

Electrochemical, photoluminescence and EPR studies of Fe3+ doped nano Forsterite: Effect of doping on tetra and octahedral sites

For the first time we report on, structural, electrochemical, optical and electron paramagnetic resonance (EPR) properties of Mg2SiO4:Fe3+ nanomaterial synthesized by low temperature (350 °C) solution combustion method. Cyclic voltammetry and electrochemical impedance analysis were carried out to investigate the conduction efficiency and charge transfer resistance of Fe3+ doped Mg2SiO4. The Kubelka–Munk theory was used to calculate the bandgap of the prepared nanomaterial by analysing the diffuse reflectance spectra. Photoluminescence properties were studied by exciting the samples at 375 nm wavelength which results in yellow emission and applicable for warm white light emitting devices. The quantum efficiency of the optimized sample was found to be 46%. The decay curve analysis were carried out for the optimized (3 mol%) sample was found to be 6.4 ms. The EPR spectra were recorded at RT in X-band for Fe3+ (1 & 11 mol%) doped Mg2SiO4.

Optical spectroscopy and luminescence properties of Ho3+ doped zinc fluorophosphate (ZFP) glasses for green luminescent device applications

Ho3+ doped zinc fluorophosphate (ZFP) glasses with molar chemical compositions, (60-x) NH4H2PO4+20ZnO+10BaF2+10NaF+xHo2O3 (where x = 0.1, 0.3, 0.5, 1.0 and 1.5 mol%) were prepared by melt quenching technique. These glasses were characterized through physical, structural, optical, excitation, luminescence and decay curve analysis. From the absorption spectra, spectral intensities (fexp and fcal), Judd-Ofelt intensity parameters (Ω2, Ω4 and Ω6), radiative transition probabilities (AT), radiative lifetimes (τR) and branching ratios (βR) were evaluated for all Ho3+ doped ZFP glass matrices. From the photoluminescence spectra, peak stimulated emission cross-sections (σP) were calculated for all Ho3+ doped ZFP glasses. The Ho3+ doped ZFP glasses show strong green emission at 545 nm and red emission at 656 nm under excitation, 450 nm. The measured lifetimes (τmeas) of (5S2)5F4 level of Ho3+ doped ZFP glasses were obtained from decay profiles. The CIE color coordinates of Ho3+ doped ZFP glasses were calculated from emission spectra and 1.0 mol% of Ho3+ doped ZFP glass matrix gives green emission. Hence, these results confirm that the Ho3+ doped ZFP glasses could be considered as a promising candidate for visible green laser applications.

Structural and luminescence properties of Sm3+-doped Ca2SiO4 phosphors from agricultural waste

Trivalent samarium (Sm3+) ions-doped calcium silicate Ca2SiO4 phosphor powders were successfully prepared by conventional solid-state reaction method using SiO2 and CaO which were obtained from rice husk and egg shells, respectively. The structure of these phosphor powders were studied by X-ray diffraction. Luminescence properties of Sm3+:Ca2SiO4 phosphors were derived using the excitation, emission and decay curve analyses. The luminescence spectra of these phosphors exhibit intense orange-reddish luminescence at 600 nm due to the 4G5/2→6H7/2 transition. The luminescent decay curves for 4G5/2 level of Sm3+ ions measured under 404 nm excitation exhibit non-exponential behaviors at higher Sm3+ concentrations. The non-exponentiality of the decay curves with shortening of lifetimes were explored by Inokuti-Hirayama model and found that the interaction between Sm3+ ions is of dipole-dipole type.

Obstructive sleep apnea and effects of continuous positive airway pressure on triglyceride-rich lipoprotein metabolism

This study aimed to explore lipoprotein metabolism in obstructive sleep apnea (OSA) and the effects of continuous positive airway pressure (CPAP). We studied 15 men with severe OSA [apnea-hypopnea index (AHI) ≥30 events/hour] and 12 age-, BMI-, and waist circumference-matched volunteers without OSA (AHI <5 events/hour). Carotid intima-media thickness (CIMT) was determined by a blind examiner. After 12 h fasting, a triglyceride-rich chylomicron-like emulsion, labeled with [14C]cholesteryl oleate and [3H]triolein, was injected intravenously followed by blood sample collection at preestablished times. Fractional clearance rate (FCR) of the radiolabeled lipids was estimated by compartmental analysis of radioisotope decay curves. Compared with controls, patients with OSA showed a significant delay in both cholesteryl ester FCR (0.0126 ± 0.0187 vs. 0.0015 ± 0.0025 min-1; P = 0.0313) and triglycerides FCR (0.0334 ± 0.0390 vs. 0.0051 ± 0.0074 min-1; P = 0.0001). CIMT was higher in the OSA group: 620 ± 17 vs. 725 ± 29 µm; P = 0.004. Cholesteryl ester FCRs were inversely related to total sleep time <90% (r = -0.463; P = 0.029) and CIMT (r = -0.601; P = 0.022). The triglyceride FCR was inversely correlated with AHI (r = -0.537; P = 0.04). In a subgroup of patients treated with CPAP for 3 months (n = 7), triglyceride FCR increased 5-fold (P = 0.025), but the cholesteryl ester FCR was unchanged. In conclusion, severe OSA decreased lipolysis of triglyceride-rich lipoproteins and delayed removal of remnants. CPAP treatment may be effective to restore the lipolysis rates.

Efficient green phosphor realized by Ce3+→Tb3+ energy transfer in Li3Sc2(PO4)3 for ultraviolet white light-emitting diodes.

A series of Ce3+/Tb3+ doped Li3Sc2(PO4)3 phosphors has been obtained using high temperature solid state reactions. Density functional theory (DFT) calculations using the CASTEP module have given an insight into the bandgap and electronic structures of the hosts. The phase formation and the crystal structure of the prepared samples were verified using X-ray diffraction and Rietveld structure refinement analysis. Samples singly doped with Ce3+ ions had an intense emission centered at 350 nm under UV light irradiation, while samples singly doped with Tb3+ ions exhibited a typical green emission under 230 nm irradiation. Efficient Ce3+→Tb3+ energy transfer can cause the Li3Sc2(PO4)3:Ce3+,Tb3+ samples to have an intense green emission at very low Tb3+ concentrations under 285 nm excitation, making Li3Sc2(PO4)3:Ce3+,Tb3+ an efficient UV-excited green phosphor. The mechanism and critical distance for Ce3+→Tb3+ energy transfer in the phosphor were determined by detailed luminescence decay curve analysis utilizing the I-H model. Moreover, a WLED device was fabricated using our prepared green phosphor.

Quantification of an atmospheric nucleation and growth process as a single source of aerosol particles in a city

Abstract. Effects of a new aerosol particle formation (NPF) and particle diameter growth process as a single source of atmospheric particle number concentrations were evaluated and quantified on the basis of experimental data sets obtained from particle number size distribution measurements in the city centre and near-city background of Budapest for 5 years. Nucleation strength factors for a nucleation day (NSFNUC) and for a general day (NSFGEN) were derived separately for seasons and full years. The former characteristic represents the concentration increment of ultrafine (UF) particles specifically on nucleation days with respect to accumulation-mode (regional background) concentrations (particles with equivalent diameters of 100–1000 nm; N100−1000) due solely to the nucleation process. The latter factor expresses the contribution of nucleation to particle numbers on general days; thus, it represents a longer time interval such as season or year. The nucleation source had the largest effect on the concentrations around noon and early afternoon, as expected. During this time interval, it became the major source of particles in the near-city background. Nucleation increased the daily mean concentrations on nucleation days by mean factors of 2.3 and 1.58 in the near-city background and city centre, respectively. Its effect was largest in winter, which was explained by the substantially lower N100−1000 levels on nucleation days than those on non-nucleation days. On an annual timescale, 37 % of the UF particles were generated by nucleation in the near-city background, while NPF produced 13 % of UF particles in the city centre. The differences among the annual mean values, and among the corresponding seasonal mean values, were likely caused by the variability in controlling factors from year to year. The values obtained represent the lower limits of the contributions. The shares determined imply that NPF is a non-negligible or substantial source of particles in near-city background environments and even in city centres, where the vehicular road emissions usually prevail. Atmospheric residence time of nucleation-mode particles was assessed by a decay curve analysis, and a mean of 02:30 was obtained. The present study suggests that the health-related consequences of the atmospheric NPF and growth process in cities should also be considered in addition to its urban climate implications.

Optical spectra and excited state relaxation dynamics of Sm2+ ions in SrCl2, SrBr2 and SrI2 crystals

Samarium(2+) doped single crystals of SrCl2, SrBr2 and SrI2 with a nominal samarium concentration of 0.12, 0.16 and 0.13at%, respectively, were grown by the Bridgman method.XRD examination revealed that obtained samples are single phase and their structures are consistent with those intentional. Based on preliminary spectroscopic measurement it was ascertained that Sm2+ ions are incorporated without traces of Sm3+ contamination. High resolution absorption, luminescence and excitation spectra as well as luminescence decay curves were measured as a function of temperature in the 4.2–300K region. It was found that structural peculiarities of the host crystals affect strongly spectroscopic features of incorporated Sm2+ ions. At room temperature all systems under study show a broad-band luminescence related to the parity allowed inter-configurational 4f55d1 – 4f6 transitions of Sm2+. At 5K a broad band luminescence vanishes in SrCl2:Sm2+ and a resulting luminescence spectrum shows a rich fine structure consisting of narrow lines that we attribute to magnetic dipole transitions within the 4f6 configuration of Sm2+ ions located in centro-symmetric sites and/or their vibrational side bands. Based on an analysis of luminescence decay curves we attribute numerous narrow lines that appear in luminescence spectra of SrBr2:Sm2+ recorded below 25K to the 5D0 – 7FJ (J = 0–4) intra-configurational transitions of Sm2+ ions located in sites with C4 and C1 symmetry. A long-lived luminescence related to intra-configurational transitions was not observed in SrI2:Sm2+ even at 4.2K.

Investigation on the upconversion luminescence in Ho3+/Yb3+ co-doped Ba3Sc4O9 phosphor

A series of Ba3Sc4O9:Ho3+/Yb3+ phosphors were synthesized by a high-temperature solid-state reaction method. The phase purity and upconversion luminescence were characterized by X-ray diffraction and photoluminescence spectroscopy. The sintering temperature and doping concentrations were optimized to obtain the strongest emission intensity. Under 980nm laser diode excitation, the green (545nm, 5F4/5S2→5I8) and red (665nm, 5F5→5I8) emissions were observed. The cross-relaxation and back-energy-transfer processes play an important role to adjust the emission intensity ratio of Green/Red at different dopant concentrations. Based on the energy level diagrams, the energy transfer mechanisms are investigated in detail according to the analysis of pump power dependence and luminescence decay curves. The upconversion luminescence properties of the phosphor were evaluated and the results show good color monochromaticity and relatively high upconversion luminescence intensity. The Ba3Sc4O9:Ho3+/Yb3+ can be a good candidate for green upconversion material in display fields and fluorescent labeling.

Luminescence and phonon sideband analysis of Eu3+ doped alkali fluoroborate glasses for red emission applications

Trivalent europium (Eu3+) doped alkali fluoroborate glasses (KBZFB) with molar composition 10K2O + 10BaO + 10ZnF2+(70 − x)B2O3 + xEu2O3 (x = 0.1, 1.0, 2 and 2.5 mol%) have been prepared by melt quenching technique. The structural aspects were explored through XRD, FTIR and Raman analyses. The spectroscopic properties were investigated using optical absorption, photoluminescence and decay curve analyses. Under 393 nm excitation, Eu3+ doped KBZFB glasses give intense red emission (612 nm) of Eu3+ ions corresponding to 5D0→7F2 transition. Judd–Ofelt theory has been employed to evaluate the phenomological intensity parameters. Radiative properties like radiative transition probabilities (A), radiative life time (τR) and branching ratios (βR) were also calculated. Phonon sidebands were observed in the excitation spectra on the high energy side of the pure electronic transition 7F0 → 5D2. The phonon energy (ℏω) and the electron–phonon coupling constant (g) were derived from the phonon sideband spectra. The luminescence decay was analyzed and the lifetime of the samples has been estimated. The experimental lifetime is compared with theoretical value and better quantum efficiency is obtained. The emission intensities were characterized using CIE chromaticity diagram and the prepared glasses offer pure intense red emission which is useful for various photonic applications.

Optical spectroscopy and emission properties of Ho3 +-doped gadolinium calcium silicoborate glasses for visible luminescent device applications

The Ho3+-doped gadolinium calcium silicoborate glasses with the composition of 25Gd2O3+10CaO+10SiO2+(55−x)B2O3+xHo2O3, where x=0.0, 0.5, 1.0, 1.5, 2.0 and 2.5mol%, were synthesized by well-known melt quenching method. These glasses have been characterized through physical, structural, optical, visible emission and decay curve analysis. From the absorption spectrum, Judd-Ofelt intensity parameters for 1.0mol% Ho2O3 doped glass have been carried out and were used to examine radiative properties for the important visible emitting levels of Ho3+ ions. The present Ho3+:glasses show strong green emission at 545nm and red emission at 655nm under excitation at 452nm. The radiative decay time and stimulated emission cross-section for the (5S2,5F4)→5I8 transition are found to be 280 μs and 0.63×10−20cm2, respectively. Decay curves for all the concentration of Ho3+ ions exhibit non-exponential nature for (5S2,5F4)→5I8 transition. The decrease in decay times is due to the resonant energy transfer among the excited Ho3+ ions. Hence, these results confirm that the present silicoborate glass system could be considered as a promising candidate for visible green laser applications.

Photoluminescence decay curve analysis of some rare earth doped CeO2 phosphors

CeO2:M (Eu3+, Er3+ and Dy3+) phosphors were synthesized by modified solid-state reaction technique at variable concentrations of Eu3+, Er3+ and Dy3+. This technique is suitable for large-scale production and it is less time-consuming. The prepared samples were characterized by X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), and Photoluminescence (PL) decay curve analysis. XRD patterns of the prepared samples confirm the cubic fluorite crystal structure of all phosphors. Crystallite size was calculated by using well known Scherer’s formula. SEM images express good surface morphology with nanoflower like shape. Comparative studies of photoluminescence decay curves of CeO2:M (Eu3+, Er3+ and Dy3+) with different concentrations of dopant have been done. Decay constants for all prepared phosphors were calculated by curve fitting technique. Samples were excited under UV radiation for few nanoseconds at room temperature. The PL decay curves were measured for 5D0→7F1 transition of CeO2:Eu3+,4S3/2→4I15/2 transition of CeO2:Er3+ and 4F9/2→6H13/2 transition of CeO2:Dy3+ phosphors. Decay curve for CeO2:Eu3+ (1.5 mol%) phosphor shows optimum concentration with higher intensity of photoluminescence signals and comparatively higher decay constants.

Fission-like events in the C12+Tm169 system at low excitation energies

Background: Fission has been found to be a dominating mode of deexcitation in heavy-ion induced reactions at high excitation energies. The phenomenon of heavy-ion induced fission has been extensively investigated with highly fissile actinide nuclei, yet there is a dearth of comprehensive understanding of underlying dynamics, particularly in the below actinide region and at low excitation energies.Purpose: Prime objective of this work is to study different aspects of heavy-ion induced fission ensuing from the evolution of composite system formed via complete and/or incomplete fusion in the $^{12}\mathrm{C}+^{169}\mathrm{Tm}$ system at low incident energies, i.e., ${E}_{\mathrm{lab}}\ensuremath{\approx}6.4$, 6.9, and 7.4 $A$ MeV, as well as to understand charge and mass distributions of fission fragments.Method: The recoil-catcher activation technique followed by offline $\ensuremath{\gamma}$ spectroscopy was used to measure production cross sections of fission-like events. The evaporation residues were identified by their characteristic $\ensuremath{\gamma}$ rays and vetted by the decay-curve analysis. Charge and mass distributions of fission-like events were studied to obtain dispersion parameters of fission fragments.Results: In the present work, 26 fission-like events ($32\ensuremath{\le}Z\ensuremath{\le}49$) were identified at different excitation energies. The mass distribution of fission fragments is found to be broad and symmetric, manifesting their production via compound nuclear processes. The dispersion parameters of fission fragments obtained from the analysis of mass and isotopic yield distributions are found to be in good accord with the reported values obtained for different fissioning systems. A self-consistent approach was employed to determine the isobaric yield distribution.Conclusions: The present work suggests that fission is one of the competing modes of deexcitation of complete and/or incomplete fusion composites at low excitation energies, i.e., ${E}^{*}\ensuremath{\approx}57$, 63, and 69 MeV, where evaporation of light nuclear particle(s) and/or $\ensuremath{\gamma}$ rays are assumed to be the sole contributors. A single peaked broad Gaussian mass dispersion curve has corroborated the absence of any noncompound nuclear fission at the studied energies.

Commendable Eu2+-Doped Oxide-Matrix-Based LiBa12(BO3)7F4 Red Broad Emission Phosphor Excited by NUV Light: Electronic and Crystal Structures, Luminescence Properties.

In this work, we synthesized a new Eu2+-doped oxide-matrix-based LiBa12(BO3)7F4 broad red emission phosphor. It can emit red light peaking at ∼644 nm under NUV excitation with the coordinate at (0.6350, 0.3586) and a sensitive color gamut for eyes. This phosphor with a special kind of tunnel crystal structure and layered distribution of Ba2+ is contributed to longer wavelength emission. By theoretical calculation and analysis using local state density energy band structure simulation of Eu2+ doped in different site, the origin of the observed emission center was distinguished. Furthermore, decay curves analysis also indicated there are three possible Ba2+ sites for Eu2+ to occupy. Temperature-dependent PL spectra appeared anomalous phenomena that the intensity increases first and then decreases, which is due to the traps energy level's contribution of electron's transition. The phosphor also has cathodoluminescence (CL) property which the spectra take on typical current saturation phenomenon. The CL curves indicated that this phosphor has a very good stability under much electron beam bombardment time. After fabricated combining with BAM, (Sr, Ba)2SiO4 and our red phosphor excited under 405-nm NUV chips, warm light LED was obtained. Its CIE coordinate is (0.3475, 0.3416) and the CCT, Ra, and luminous efficiency are 4856 K, 84.1, and 72.6 lm/W, respectively.

Lifetimes of bound excited states of Pt−

SynopsisMeasurements of the radiative lifetimes of the two excited states of the platinum anion Pt− are presented. Pt− ions stored in the cryogenic ion storage ring DESIREE were photodetached at different photon wavelengths and the resulting yield of neutral Pt measured as a function of time was recorded. Analysis of the neutral decay curves show a 2.54 ± 0.10 s lifetime for the higher-lying 5d106s 2S1/2 excited state and a lifetime in the range of 50–200 ms for the lower-lying 5d96s2 2D3/2 excited state. This is the first study to report the lifetime of a bound anion excited state with an electron configuration different from that of the anion ground state.

Sensitized green emission of terbium with dibenzoylmethane and 1, 10 phenanthroline in polyvinyl alcohol and polyvinyl pyrrolidone blends

Tb doped polyvinyl alcohol: polyvinyl pyrrolidone blends with dibenzoylmethane (DBM) and 1, 10 Phenanthroline (Phen) have been prepared by solution cast technique. Bond formation amongst the ligands and Tb3+ ions in the doped polymer has been confirmed employing Fourier Transform Infrared (FTIR) techniques. Optical properties of the Tb3+ ions have been investigated using UV–Vis absorption, excitation and fluorescence studies excited by different radiations. Addition of dimethylbenzoate and 1, 10 Phenanthroline to the polymer blend increases the luminescence from Tb3+ ions along with energy transfer from the polymer blend itself. Luminescence decay curve analysis affirms the non-radiative energy transfer from DBM and Phen to Tb3+ ions, which is identified as the reason behind this enhancement. The fluorescence decay time of PVA-PVP host decreases from 6.02ns to 2.31ns showing an evidence of energy transfer from the host blend to the complexed Tb ions. Similarly the lifetime of DBM and Phen and both in the blend reduces in the complexed system showing the feasibility of energy transfer from these excited DBM and Phen to Tb3+ and is proposed as the cause of the above observations. These entire phenomena have been explained by the energy level diagram.

Fluorescence properties and white light generation from Dy3+-doped niobium phosphate glasses

Niobium phosphate glasses (P2O5+Nb2O5+K2O + Al2O3+Dy2O3) doped with different concentrations of Dy3+ ions have been synthesized by melt quenching technique and characterized through structural and optical measurements to evaluate the fluorescence properties and find their suitability for white light emitting diodes (LEDs). Phonon energy and vibrational groups of the host matrix have been analyzed from Raman spectra. Judd-Ofelt analysis has been applied for 1.0 mol% Dy2O3-doped glass and inturn radiative properties have been evaluated for excited states of the Dy3+ ion. The higher value of stimulated emission cross-section (σe = 6.4 × 10−21 cm2) for the 4F9/2 → 6H13/2 level confirms its potentiality to be used as yellow laser. The decay curves exhibit non-exponential nature at higher concentrations (≥1 mol %) of Dy3+ ion. From the decay curve analysis, the quantum efficiency for the 4F9/2 level of 1.0 mol % Dy3+-doped glass is found to be 92%. The yellow to blue intensity ratios and chromaticity color co-ordinates are found to vary with Dy3+ ion concentrations/excitation wavelengths and are within the white light region.