Emission Decay Profiles Research Articles

UVC Stokes and Anti-Stokes Emission of Ca9Y(PO4)7 Polycrystals Doped with Pr3+ Ions.

The recent COVID-19 pandemic has made everyone aware of the threat of viruses and the growing number of antibiotic-resistant bacteria. It has become necessary to find new methods to combat these hazards. One tool that could be used is UVC radiation, i.e., 100-280 nm. Currently, the available sources of this light are mercury vapor lamps. However, the modern world requires more compact, mercury-free, and less energy-consuming light sources. This work presents the results of our research on a new material in which efficient UVC radiation was obtained. Here, we present the results of research on Ca9Y(PO4)7 polycrystals doped with Pr3+ ions prepared using the solid-state method. The absorption, excitation, emission, and emission decay profiles of praseodymium(III) ions were measured and analyzed. The upconversion emission in the UVC region excited by blue light was observed. Parameters such as energy bandgap, refractive index, and thermal stability of luminescence were determined. The studied phosphate-based phosphor possesses promising characteristics that show its potential in luminescent applications in future use in medicine or for surface disinfection.

Multidimensional stimulation response RTP micron fiber thin film

Purpose The purpose of this research is as follows: DPP-BOH-PVA has been synthesized from 1,1′:3′,1″-terphenyl-5'-boronic acid (DPP-OH) and polyvinyl alcohol (PVA). The afterglow lifetime of DPP-BOH-PVA was studied by changing contents of DPP-OH (1, 2 and 4 Wt.%). These films were characterized with Fourier transform infrared, X-ray diffraction as structural analysis and DSC as thermal analysis. Afterglow lifetimes were evaluated as time-resolved emission decay profile analysis. Fiber films of DPP-BOH-PVA-2-E have been prepared by electrospinning method with the diameter of 5 μm and afterglow life time of 2.1 s (@ 535 nm) under ambient conditions. Stimulus responsive properties with afterglow emission for fiber film were investigated. Design/methodology/approach During the synthesis of the polymer, modification was carried out using DPP-OH/PVA with a molar ratio of 1/4, under an alkalinity medium with ammonium hydroxide and with a temperature of 80°C. Findings XRD results indicate that DPP-BOH-PVA film had high crystallinity, which is crucial for preparing organic room temperature phosphorescence (RTP) materials. Research limitations/implications The reaction mixture must be stirred continuously. Temperature should be controlled to prevent the rapid evaporation of ammonium hydroxide. Practical implications This study provides technical information for the synthesis of multidimensional stimulation response RTP micron fiber thin film. The electrospinning technology may also promote the applications of the large areas of RTP films. Social implications This resin will be used for the multidimensional stimulation response RTP fiber thin film. Originality/value The diameter of fiber film of PP-BOH-PVA-2-E by electrospinning method was in the range of 5 μm, and its afterglow lifetime decayed to be 2.1 s.

Effective role of Co-dopants (Dy3+, Sm3+) on Tunable multicolour emission of Tb3+ doped telluroborate glasses for Natural White light applications

In the current work the efficacy of incorporation of Dy3+ and Sm3+ ions into Tb3+ doped new telluroborate glass as well as their interactions was investigated. In this study, Tb3+ ions were employed as activators and sensitizers for both Dy3+ and Sm3+ ions emissions, which emanate from the excited states of Dy3+ (4F9/2) and Sm3+ (4G5/2) ions through a non-radiative energy transfer process. To validate the emission gamut of the prepared glasses, distinct emission colours were inspected with the CIE 1931 chromaticity analysis and the appropriate correlated colour temperature (CCT) values were estimated. The emission decay profile relating to the Tb3+ ions (5D4 state) of the glasses was investigated. The energy transfer efficiency, which stems from Tb3+ ion to Dy3+ and Sm3+ ions were found to be 49 and 54% respectively. The IH model was successfully used to analyse the interaction mechanism.

Broadband near-infrared luminescence properties of Sc2(MoO4)3:Cr3+ molybdates

The structural and spectroscopic properties of Sc2(MoO4)3 molybdate containing various concentrations of Cr3+ ions were investigated in a temperature range of 80–300 K. The samples were prepared using hydrothermal as well as solid-state reaction methods. The influence of synthesis conditions and the molybdenum source on the structural properties was studied by X-ray diffraction (XRD), IR (infrared), and Raman methods. The optical properties of Sc2(MoO4)3 samples doped with 0.1, 0.5, 1.0, and 2.0 % of Cr3+ ions were investigated. The broadband near-infrared (NIR) luminescence spectra generated from the 4T2 and 2E levels of Cr3+ ions may be attractive for NIR light-emitting diode (LED) applications. Emission decay profiles and the crystal field parameters of Cr3+ ions are discussed. In particular, the mechanism of photoluminescence generation and the thermal quenching path are described in detail.

Insights into visible luminescence and energy transfer mechanism of Eu3+/Dy3+ co-doped dolo-telluro-borate glasses

A series of Eu3+/Dy3+co-doped doro-telluro-borate (DTB) glasses were prepared using the melt-quenching approach and characterized. The absorption, excitation, emission, CIE1931 diagram and fluorescence decay profiles of these glasses were examined. The Judd-Ofelt model calculation was performed. These glasses showed prominent visible luminescence and lasing potency. The emission spectra and fluorescence lifetime decay profiles of the glasses with the increase of Dy3+ suggested an efficient energy transfer process between Eu3+ and Dy3+. The obtained chromaticity coordinates and color correlated temperature (CCT) of these glasses confirmed the emission of reddish-orange tone useful for cool white light displays. It was shown that the multicolor light emission from the studied glasses can be tuned by properly adjusting the Eu3+/Dy3+ co-doping contents. The proposed glass compositions may be advantageous for the construction of low-cost solid-state laser and cool white light emitting diodes.

Investigation of Triangle Terthiophene and Hydroxyphenylbenzothiazole Configured Fluorescent Dye with a Triple Bond Bridge.

A photochromic dye was constructed by incorporation of a carbon-carbon triple bond spaced triangle terthiophene skeleton and hydroxyphenylbenzothiazole. Regular photochromic behavior was investigated with alternated UV (254nm) and visible light (≥ 400nm) irradiation. The color of dye in solution can be cycled between pink and colorless. Additionally, the dye solution strongly fluoresces in THF with the absolute quantum yield (QY) being 0.56. When irradiation with 254nm light, the emissive solution can be effectively quenched to photo-stationary sate (Φ = 0.05). An emission "on-off" cycle could be established based on the UV/visible light irradiation cycle. The photochromic dye also exhibits good photo- and thermal-stability at room temperature. The emission decay profile indicates typical single component character with the fluorescence lifetime being 6.68ns. The emission color was determined by the CIE 1931 coordinates of x = 0.14, y = 0.25 in the blue region.

Sensitization effect of Nd3+ ions on Yb3+/Nd3+ co-doped oxyfluoride glasses and study of their optical, fluorescence, and upconversion abilities for visible laser and NIR amplifier applications

The development of laser technology has created intense demand for optical confinement materials with high performance. Herein the authors have been investigated Yb 3+ -singly doped and Yb 3+ /Nd 3+ -codoped SiO 2 -based oxyfluoride glasses in terms of their optical absorption, and their near-infrared (NIR) and up-conversion (UC) emissions including emission decay profiles. Under 808 nm laser diode (LD) excitation, four NIR emission bands were observed i.e., (Nd 3+ : 4 F 3/2 → 4 I 9/2 , Yb 3+ : 2 F 5/2 → 2 F 7/2 , Nd 3+ : 4 F 3/2 → 4 I 11/2 , and Nd 3+ : 4 F 3/2 → 4 I 13/2 ) in co-doped glasses. NIR emission cross-sections [ (σ emi ) stimulated, (σ M emi ) from Mc-cumber theory] were calculated for 2 F 5/2 → 2 F 7/2 (∼1030 nm) transition of Yb 3+ ion. σ emi was found to be highest (26.27 × 10 −21 cm 2 ) for the Yb 3+ : 2 F 5/2 → 2 F 7/2 transition in N2 glass. UC emission spectra recorded at 980 nm LD show bands centered at 500, 536, 595 & 610, and 664 nm, attributed to 4 G 9/2 → 4 I 9/2 , 4 G 7/2 → 4 I 9/2 & 4 G 7/2 → 4 I 11/2, 4 G 5/2 → 4 I 9/2 , and 4 G 9/2 → 4 I 13/2 transitions, respectively. Decay profiles were analyzed for Yb 3+ : 2 F 5/2 → 2 F 7/2 (∼1030 nm) and Nd 3+ : 4 F 3/2 → 4 I 11/2 (∼1057 nm) transitions at 808 nm LD. Energy transfer (ET) process from Nd 3+ to Yb 3+ in present glasses were detailed.

Enhanced red up-conversion of β-NaYF4:Er3+,Tm3+ microcrystals for bio-imaging applications

Pure red fluorescence generated by near infrared (NIR) excitation is desired for bio-imaging with high biological penetration, but without cell damage or multi-photon photo-toxicity. In this work, β-NaYF4:Er3+ and β-NaYF4:Er3+,Tm3+ microcrystals were synthesized using a novel hydrothermal method. β-NaYF4:Er3+ microcrystals exhibited intense green and red up-conversion emissions under 976 nm laser diode excitation. The introduction of Tm3+ ions into β-NaYF4:Er3+ resulted in strong inhibition of green up-conversion emission (Er3+:2H11/2 /4S3/2→4I15/2) and, consequently, red up-conversion emission (Er3+:4F9/2→4I15/2) was significantly promoted. To simultaneously restrain green up-conversion emissions and enhance red up-conversion emissions, the optimal concentrations of Er3+ and Tm3+ ions were determined to be 20 mol% and 2.0 mol%, respectively. The red/green up-conversion emission intensity ratio increased from ~1.80 (β-NaYF4:20Er3+, mol%) to ~78 (β-NaYF4:20Er3+,2Tm3+, mol%) after the addition of 2 mol% Tm3+ ions to β-NaYF4:20Er3+ (mol%). The red up-conversion emission intensity of β-NaYF4:20Er3+,2Tm3+ was stronger than that for commercial red up-conversion phosphors (NaYF4 and ZnF2) under the same experimental conditions. Based on the results of the emission spectra, luminescence rise, and decay profiles, the mechanism of enhanced red up-conversion emission by Tm3+ ion co-doping in β-NaYF4:20Er3+,2Tm3+ (mol%) was proposed. The bio-fluorescence experiment under NIR excitation proves that β-NaYF4:Er3+,Tm3+ microcrystals have potential applications in bio-imaging.

Warm-white, reddish-orange and orange light generation from lithium-aluminum-zinc phosphate glass tri-doped with Sm3+, Tb3+and Eu3+

Spectroscopic evaluation of Sm3+/Tb3+/Eu3+ doped lithium-aluminum-zinc phosphate glass (LAZSTE), based on photoluminescence spectra and emission decay profiles, is particularly focused on W-LED technology. Tauc's method is employed to find direct and indirect allowed band gap and Urbach energy values. The Judd-Ofelt parameters were evaluated from measured oscillator strengths and subsequently used to estimate various radiative properties for the prominent fluorescent transitions (4G5/2 → 6H5/2, 4G5/2 → 6H7/2 and 4G5/2 → 6H9/2) of Sm3+ ions. The LAZSTE glass excited at 346, 377 and 408 nm, displays warm-white light emission of 2497 K, orange light emission of 1949 K and reddish-orange light emission of 1667 K respectively, according to (0.4753, 0.4121), (0.5306, 0.4130) and (0.6077, 0.3767) CIE1931 chromaticity coordinates, respectively. The Tb3+ and Sm3+ emission decay shortening in presence of Sm3+ and Eu3+, and Eu3+, respectively, suggests that non-radiative energy transfer processes could take place from Tb3+ to Sm3+ and/or Eu3+, and from Sm3+ to Eu3+. The analysis of the Sm3+ and Tb3+ emission decays, performed with the Inokuti-Hirayama model, suggests that all these energy transfer processes are predominantly mediated through an electric dipole-dipole interaction, inside Sm3+-Tb3+-Eu3+ clusters.

Properties of Sm-Doped SrCl2 Crystalline Scintillators

Sm-doped SrCl2 crystals were prepared, and the scintillation properties such as emission spectra, decay profiles, and pulse height were investigated. Under X-ray irradiation, a broad band can be observed at 680 nm, which indicates that the major origin is due to 5d-4f transitions of Sm2+. The decay curve is approximated by one exponential function with a decay time of 10 μs, and the decay time constant is typical for Sm2+. From the pulse height of 137Cs γ-rays, 0.1% Sm:SrCl2 shows a light yield of 33,000 photons/MeV.

Er3+-doped SiO2-based glasses – An exploration of structural, visible, chromatic, and NIR fluorescence characteristics

SiO2-based glasses doped with 1 mol% Er3+ were fabricated via melt-quench process and their structural and visible and NIR (near-infrared) fluorescence features have been investigated. Calculated Judd–Ofelt (J–O) intensity parameters that were deduced from absorption spectra are applied to reckon different radiative factors. Visible emission spectra and decay profiles (for 4S3/2 → 4I15/2 transition) were registered upon λexci.= 379 nm. CIE (Commission International de I'Eclairage), CCT (correlated color temperature), and CP (color purity) values were evaluated from the emission spectra. Also, a NIR luminescence band (4I13/2 → 4I15/2 transition) was identified by 980 nm LD (laser diode). Later, emission cross-section [(σemi) stimulated, (σMemi) from Mccumber theory] values were computed for observed NIR emission. Highest σemi and gain bandwidth (σemi × ∆λeff) were obtained to be 9.18×10−21 cm2 and 517×10−28 cm3 accordingly for 4I13/2 → 4I15/2 transition.

Temperature Dependence of Fundamental Photophysical Properties of [Eu(MeOH-d4)9]3+ Solvates and [Eu·DOTA(MeOH-d4)]- Complexes.

The trivalent lanthanide ions show optical transitions between energy levels within the 4f shell. All these transitions are formally forbidden according to the quantum mechanical selection rules used in molecular photophysics. Nevertheless, highly luminescent complexes can be achieved, and terbium(III) and europium(III) ions are particularly efficient emitters. This report started when an apparent lack of data in the literature led us to revisit the fundamental photophysics of europium(III). The photophysical properties of two complexes-[Eu·DOTA(MeOH-d4)]- and [Eu(MeOH-d4)9]3+-were investigated in deuterated methanol at five different temperatures. Absorption spectra showed decreased absorbance as the temperature was increased. Luminescence spectra and time-resolved emission decay profiles showed a decrease in intensity and lifetime as the temperature was increased. Having corrected the emission spectra for the actual number of absorbed photons and differences in the non-radiative pathways, the relative emission probability was revealed. These were found to increase with increasing temperature. The transition probability for luminescence was shown to increase with temperature, while the transition probability for light absorption decreased. The changes in transition probabilities were correlated with a change in the symmetry of the absorber or emitter, with an average increase in symmetry lowering absorbance and access to more asymmetric structures increasing the emission rate constant. Determining luminescence quantum yields and the Einstein coefficient for spontaneous emission allowed us to conclude that lowering symmetry increases both. Furthermore, it was found that collisional self-quenching is an issue for lanthanide luminescence, when high concentrations are used. Finally, detailed analysis revealed results that show the so-called "Werts' method" for calculating radiative lifetimes and intrinsic quantum yields is based on assumptions that do not hold for the two systems investigated here. We conclude that we are lacking a good theoretical description of the intraconfigurational f-f transitions, and that there are still aspects of fundamental lanthanide photophysics to be explored.

An Europium (III) Luminophore with Pressure-Sensing Units: Effective Back Energy Transfer in Coordination Polymers with Hexadentate Porous Stable Networks.

A luminescent EuIII coordination polymer with O2 -sensing units under air, EuIII -hcpt (hcpt: 2,3,6,7,10,11-hexakis(4-carboxy-phenyl)triphenylene), is reported. The hexadentate carboxylic acids in hcpt ligands play an important role in the formation of tight-packed three-dimensional networks in EuIII -hcpt, giving hyper thermo-stable structures (decomposition temperature=420 °C). The three-dimensional porous network promotes bright luminescence (4f-4f emission quantum yield=70 %). The emission lifetime of EuIII -hcpt under vacuum (0.86 ms) was twice as large as that under O2 (0.48 ms, 1 atom:101.3 kPa). The Arrhenius analysis of the emission decay profile indicates that the back energy transfer (BEnT) from the emitting level of the europium(III) ion to the excited T1 state of the hcpt ligand should be activated at room temperature. The gradual decrease of emission lifetime is caused by the BEnT process in EuIII -hcpt. Finally, an advanced pressure-sensitive luminophore is demonstrated.

Tunable white light emission in zinc phosphate glasses activated with [formula omitted] clusters and Sm3+

Zinc phosphate glasses, activated with Agmn+ clusters and Sm3+, were prepared by the conventional melt-quenching method. The X-ray diffraction patterns revealed that the samples remain amorphous for Ag and Sm3+ contents up to 3.0 and 1.0 mol%, respectively. The Raman and FTIR spectra showed that the main vibrational modes are associated with P–O bonds. The absorption coefficient spectrum of the Ag singly doped glass sample displayed a broad band centered at 318 nm, related to Agmn+ clusters, whereas those co-doped with Sm3+ showed, in addition to the Agmn+ cluster absorption, the well-known Sm3+ absorptions at 343, 360, 374, 401, 415, 438, 465 and 477 nm. The photoluminescence excitation spectrum of the Ag singly doped glass sample exhibited a broadband from 3 to 6 eV (207–413 nm), assigned to superposition of the Ag+: 4 d10 → 4d95s and Agmn+ cluster: S0 → S1 transitions, being the excitation into the Agmn+ clusters attractive for W-LEDs applications. The photoluminescence emission spectra of the Ag singly doped glass sample, upon Agmn+ cluster excitations at 340, 350 and 360 nm, displayed cold white light tonality, with (0.279, 0.300) CIE1931 chromaticity coordinates of 9453 K and bluish-white light tonality with (0.264, 0.276) and (0.259, 0.270) CIE1931 chromaticity coordinates and correlated color temperature values of 12901 and 14201 K, respectively. The global emission of the Ag and Sm3+ co-doped glass samples was, upon 340, 350 and 360 nm excitations, gradually tuned from the bluish and cold white region to the warm white one, as the Sm3+ content was increased, with correlated color temperatures in the 14201-2691 K range. The Sm.3+ emission bands, under excitations at 340 and 350 nm, were attained at expense of radiative and non-radiative energy transfer from the Agmn+ clusters, as revealed respectively by the sinks mounted on the Agmn+ cluster emission bands and the emission decay profile shortening in presence of Sm3+. Analysis of the Agmn+ cluster emission intensity and decay profiles, with the Dexter and Burstein models, showed that Agmn+ cluster cross-relaxation and/or non-radiative energy transfer to Sm3+ might be dominated by an electric quadrupole-quadrupole interaction.

Preparation and Luminescence Properties of A-Type Lutecium Silicate Core–Shell Nanospheres

X-ray radio-luminescence materials have potential application in radiotherapy (RT) and biomedical imaging. Considering that lutecium ions (Lu3+) with high atomic number (Z) have high X-ray attenuation coefficients, Ce3+-doped A-type Lu2SiO5@SiO2 (A-LSO:Ce3+@SiO2) core-shell nanospheres with size in the range of 200-250 nm were prepared through coprecipitation method. The growth mechanism of A-LSO:Ce3+@SiO2 core-shell nanospheres was investigated through determining the phase transition and morphology evolution by XRD, FT-IR, and TEM. The emission spectra, decay profile, and X-ray excited luminescence spectra (XEL) of the obtained samples were collected. The results show that a new type of lutecium silicate core-shell nanospheres A-LSO:Ce3+@SiO2 can be fabricated and exhibit efficient radio-luminescence under X-ray radiation, which has potential application in the diagnosis and therapy of cancer.

Co-emission and energy transfer of Sm3+ and/or Eu3+ activated zinc-germanate- tellurite glass as a potential tunable orange to reddish-orange phosphor

Sm3+/Eu3+ single doped and co-doped zinc-germanate-tellurite glasses were prepared by the glass melting method. Raman and optical spectroscopic properties of Sm3+, Eu3+ and Sm3+/Eu3+ doped TeO2-GeO2-ZnO glasses have been characterized through optical absorption and pulsed/steady fluorescence. Excitation and emission spectra measurements indicated that the energy transfer process Sm → Eu is active in the samples. The concentration of europium ions was varied to provide red emission for possible control over the chromaticity tuning in the red-orange region. Upon 344 nm excitation, the color of the global emission can be adjusted from orange of 2038 K to reddish-orange of 1683 K by increasing the Eu3+ content from 1 up to 2% mol, and co-doped with 0.5% mol Sm3+. Reddish-orange color purity very close to 100% is attained when the phosphors are excited at 406 nm. The time shortening of Sm3+ emission decay in the presence of Eu3+ was attributed to a Sm3+ → Eu3+ non-radiative energy transfer process. From fitting the Sm3+ emission decay profile with the Inokuti-Hirayama model, it was inferred that the energy transfer process could be dominated by an electric dipole-dipole interaction.

Investigation of Different Prototropic Forms of Biologically Active Flavin Lumichrome in the Presence of Liposome.

Herein, we reported the photophysical behavior of lumichrome (LC), one of the biologically active flavin molecules, in the presence of small unilamellar vesicle of anionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). With the help of different spectroscopic techniques, we have proposed that anionic DMPC liposome interacts with the cationic form LC in ground state and in excited state and modulate the spectral properties of LC. Photophysical study reveals that different prototropic forms of LC are present in DMPC liposome medium. In the presence of DMPC liposome, fluorescence emission properties of LC vary with change in excitation and emission wavelengths. This indicates switch over between different structural forms of LC. From fluorescence lifetime measurements and fluorescence lifetime imaging (FLIM) study, it was revealed that emission decay profile of LC was fitted biexponentially in the presence of liposome. It suggests that in the presence of liposome, more than one form of LC is present. We have constructed the time-resolved area-normalized emission spectra (TRANES) of LC in the liposome and found one isoemissive point. This confirmed that two emissive species of LC are present in liposome. FLIM study and FE-SEM study give an idea about the structural feature of the complex between LC and liposome.

Tunable emission and energy transfer in TeO2-GeO2-ZnO and TeO2-GeO2-MgCl2 glasses activated with Eu3+/Dy3+ for solid state lighting applications

The results presented here refer to the tunability of global emission characteristics of Eu3+, Dy3+ and Eu3+/Dy3+ ions, varying the composition glasses; TeO2-GeO2-X (X = ZnO, MgCl2). Also, the influence of exchanging the modifier compound on the global luminescent response of the glasses was analyzed by Raman spectroscopy, excitation and emission spectra, and emission decay profiles. Changes in the Te-O-Te network structure, when MgCl2 substitutes ZnO, were identified from Raman spectrum deconvolution analysis. The energy transfer between Eu3+ and Dy3+ ions, and tunable emission characteristics, were studied under UV excitations that correspond with the emission of InGaN (370–420 nm) based LEDs. The energy transfer process between Eu3+ and Dy3+ ions was studied based on the emission spectra with different excitation wavelengths and time decay curves of the 5D0→7F2 level of Eu3+ at 612 nm. In TGZED and TGMED glasses and upon 351 nm, the time shortening of Dy3+ emission decay in presence of Eu3+ was attributed to an Dy3+→Eu3+ non-radiative energy transfer process. The energy transfer probabilities PD→E and energy transfer efficiency ηD→E were calculated for TGZ and TGM glasses. According to the Inokuti-Hirayama model it might be dominated through an electric dipole-dipole interaction, with efficiency of 5.0% and 1.9% and the obtained γ6 energy transfer parameter values γ6 = 0.082 ± 0.005 and 0.026 ± 0.005 respectively, for TGZED and TGMED glasses. The non-radiative Eu3+→Dy3+ energy transfer was observed too for both glasses TGZED and TGMED, so that transfer of energy is more favored in the oxide vitreous matrix than in the oxide-halide one. The dominated are an electric dipole-dipole interaction with γ6 energy transfer parameter values are 0.072 ± 0.005 (TGZED) and 0.036 ± 0.005 (TGMED), with efficiency 6.9 and 4.1% respectively. In TGM glasses is very low efficiency of non-radiative Dy3+→Eu3+ and Eu3+ →Dy3+ energy transfer that TGZ matrix. Neutral white emissions of 4135, 4567 K were observed in the Dy3+ and 3914 and 242 K, Eu3+/Dy3+ doped TGZ glasses excited at 351 and 388 nm, respectively. Similarly, global emissions of Dy3+ single doped were 4028 and 4123 K, but in Eu3+/Dy3+ double doped TGM glasses are neutral white light of 3929 and 3979 K, respectively. Upon 394 nm excitation, the Eu3+ doped TGZ and TGM glasses displayed reddish-orange global emissions of 1979 and 1964 K, respectively. For excitations at 382 and 394 nm the Eu3+/Dy3+ doped TGZ and TGM glasses emit warm white light of 3414 and 3160 K (382 nm excitation) and reddish-orange of 2123 and 2030 K (394 nm excitation), respectively, depending mostly on the Eu3+ and Dy3+ relative excitation intensity.

Spectroscopic evaluation a new and novel Nd3+/Yb3+ co-doped CdO-V2O5 glass system for 1 μm laser application

Structural and spectral evaluations of Nd3+ and Nd3+/Yb3+ doped CdO-V2O5 glasses based on X-Ray diffraction, Raman spectroscopy, absorption, excitation and emission spectra and decay time profiles, are performed. X-Ray diffraction patterns and Raman spectroscopy revealed that all samples are amorphous (glassy phase) up to 4 mol% of Yb3+, without segregation of any crystalline phase. The optical band gap values determined from the absorption spectra, assuming direct optical band gap, were in the range of 2.13–2.07 eV, depending on the Yb3+ concentration. The emission spectra of the Nd3+ and Nd3+/Yb3+ doped glasses upon Nd3+ excitation at 585 nm, displayed the NIR Nd3+ feature emissions centered at 880, 1060 and 1342 nm, and Yb3+ emission at 977 nm, being the latter one achieved at expenses of energy transfer from Nd3+. According to the shortening of the Nd3+ emission decay profiles such process is not radiative with efficiency in the range of 0.181–0.521, depending on the Yb3+ content. The 880 nm Nd3+ decay fitting using the Inokuti-Hirayama model considering, energy migration among donors, suggested that an electric dipole-dipole interaction might mediate the energy transfer process, within Nd3+-Yb3+ clusters.

Quantitative time domain analysis of lifetime‐based Förster resonant energy transfer measurements with fluorescent proteins: Static random isotropic fluorophore orientation distributions

Förster resonant energy transfer (FRET) measurements are widely used to obtain information about molecular interactions and conformations through the dependence of FRET efficiency on the proximity of donor and acceptor fluorophores. Fluorescence lifetime measurements can provide quantitative analysis of FRET efficiency and interacting population fraction. Many FRET experiments exploit the highly specific labelling of genetically expressed fluorescent proteins, applicable in live cells and organisms. Unfortunately, the typical assumption of fast randomization of fluorophore orientations in the analysis of fluorescence lifetime-based FRET readouts is not valid for fluorescent proteins due to their slow rotational mobility compared to their upper state lifetime. Here, previous analysis of effectively static isotropic distributions of fluorophore dipoles on FRET measurements is incorporated into new software for fitting donor emission decay profiles. Calculated FRET parameters, including molar population fractions, are compared for the analysis of simulated and experimental FRET data under the assumption of static and dynamic fluorophores and the intermediate regimes between fully dynamic and static fluorophores, and mixtures within FRET pairs, is explored. Finally, a method to correct the artefact resulting from fitting the emission from static FRET pairs with isotropic angular distributions to the (incorrect) typically assumed dynamic FRET decay model is presented.