Increase In Emission Intensity Research Articles

Physical properties and luminescence of highly stable erbium-doped antimony glasses for NIR broadband amplification

Glasses with compositions (0.8-x)Sb2O3−0.2Na2O-(x)WO3-(0.0025) Er2O3, (0 ≤ x ≤ 0.4 mol) has been synthesized by the melt-quenching technique. Physical, optical characteristics and spectroscopy have been identified and investigated. As the glass composition changes, definite variations in physio-optical properties can be observed as well as the temperature of the glass transition (Tg), the density (ρ), molar volume (Vm), bandgap energy (Eg), and the refractive index (n). The Judd-Ofelt theory has been performed using a UV–VIS-NIR absorption spectrum to examine the compositional effect on Er3+ spectroscopic properties. Some basic spectroscopic parameters including electric dipole line strengths, Judd-Ofelt parameters, the rate of radiative probability, and the lifetime of radiative levels, are determined. A high NIR emission at 1.53 μm was observed when exciting glasses at 980 nm. The FWHM, the effective line-width (Δλeff), the emission cross-section (σem), and the gain bandwidth values were calculated using the theory of Füchtbauer–Ladenburg, and the findings were critically analyzed. the decay of fluorescence spectra for the 4I13/2 level was registered, and the lifetime for the studied glasses was calculated. Upconversion luminescence was observed in the green and red regions under 980 nm excitation, with a relative increase in emission intensity due to the added tungsten content. Based on the results obtained, the studied glasses are favorable materials for broadband amplifiers in WDM systems and optical devices.

IMPACT OF INDIUM DOPING ON ZnO THIN FILM SUBJECTED TO APPROPRIATE UHV TREATMENT CHARACTERIZED BY XPS, XRD, AND PL TECHNIQUES

The chemical composition, crystalline structure and optical properties of un-doped ZnO (UZO) and indium (6%)-doped ZnO (IZO) thin films grown on Si substrate were studied using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and photoluminescence (PL) techniques. The results are complementary and confirm each other. The surface is cleaned using checked ultra-high vacuum (UHV) treatment (argon ion sputtering followed by successive heating). For IZO, the XPS analysis displays that the indium incorporates in the ZnO matrix to form the In-O-Zn-type chemical bonds. The PL of UZO reveals structural defects, including oxygen interstitial (Oi), oxygen vacancies (VO), zinc vacancies (VZn) and interstitial zinc (Zni), and they decrease with the In doping and UHV treatment. For IZO, the PL measurements show the great interest of UHV treatment to stimulate the incorporation of indium into the ZnO matrix. There is an increase in the UV emission intensity and improvement of its physical structure. The In (6%) doping of ZnO is convenient to compensate the zinc vacancies (VZn), eliminate Zni and VO, and ensure the structural homogeneity of IZO film. All the detected peaks of the XRD patterns are matched to the wurtzite crystalline structure for both UZO and IZO thin films grown mainly along the (002) orientation plane.

Molecular emission dynamics from a femtosecond filament induced plasma plume

In this study, we investigated the filament-induced plasma properties and the associated molecular emission features from three different non-metallic samples. Graphite, polymethyl methacrylate, and Teflon samples have been ablated using a tightly focused filament, and their emission spectra were analyzed using a time-integrated optical emission spectroscopy technique. The temporal responses and evolution dynamics of molecular species such as CN and C2 from these samples in ambient conditions are compared. The tightly focused filament was generated by focusing the Ti:Sapphire femtosecond pulses having a pulse duration of 29 fs using a short focal length external focusing system. The time-integrated intensified charge-coupled device images of air filament show that the filament survives up to a few nanosecond time duration after the onset of air plasma. The influence of physical and chemical properties of the samples during filament ablation has also been studied by characterizing the optical emission spectra. We find that the molecular signal intensity strongly depends on the sample properties and the position of the sample in the filament. The increase in molecular emission intensity from a graphite sample as a function of incident laser intensity suggests that the tightly focused filament surpasses the intensity clamping value.

Does the new energy demonstration cities construction reduce CO2 emission? Evidence from a quasi-natural experiment in China.

Based on the panel data of 279 cities in China from 2003 to 2017, this paper regards the new energy demonstration cities (NEDC) construction as a quasi-natural experiment, using the double-fixed effect model and the difference-in-differences (DID) method to test its local carbon emission reduction effect and transmission mechanisms and further explores the impact of NEDC on neighboring carbon emissions. Results show that (1) NEDC reduces carbon emission intensity and per capita carbon emission significantly and shows dynamic sustainability. The policy effect has shown a trend of increasing year by year. Moreover, there is significant heterogeneity in the carbon emission reduction effect of NEDC, which produces more significant policy effect in large-scale and non-resource-based cities. (2) NEDC construction reduces carbon emission through green technology innovation effect, innovative elements agglomeration effect, and total factor productivity improvement effect. In terms of the contribution of reducing carbon emission intensity and per capita carbon emission, total factor productivity accounts for 36.7% and 21.5%, respectively, green technology innovation accounts for 18.6% and 23.9%, respectively, the contribution of R&D personnel agglomeration is 7.5% and 8.3%, respectively, and the contribution of R&D capital agglomeration is 5.9% and 9.5%, respectively. (3) From the perspective of spatial effect, the impact of NEDC on carbon emissions presents a "siphon" effect; that is, although NEDC reduces local carbon emissions, it has produced the phenomenon of transfer to neighboring areas, accelerating the increase in the carbon emission intensity of neighboring areas.

Dynamic molecular conformational change leading to energy transfer in F8-5% BSP copolymer revealed by single-molecule spectroscopy.

Polyfluorene-based copolymers such as poly(9,9-dioctylfluorene)-alt-5% [bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylenediamine] (F8-5% BSP) are efficient blue-emitting polymers with various electronic phases: F8 blue-emitting glassy phase, F8 ordered more red-emitting β-phase, and F8/BSP charge transfer (CT) state. Polymer light-emitting device performance and color purity can be significantly improved by forming β-phase segments. However, the role of the β-phase on energy transfer (ET) among glassy F8, β-phase, and F8/BSP CT state is unclear. Herein, we identify dynamic molecular conformation-controlled ET from locally excited states to either the CT state or β-phase in light-emitting copolymers. By conducting single-molecule spectroscopy for single F8-5% BSP chains, we find inefficient intra-chain ET from glassy segments to the CT state, while efficient ET from the glassy to the β-phase. Spontaneous and reversible CT on-off emission is observed both in the presence and absence of the β-phase. The density functional theory calculations reveal the origin of the on-chain CT state and indicate this CT emission on-off switching behavior could be related to molecule torsional motion between BSP and F8 units. The population of the CT state by ET can be increased via through-space interaction between the F8 block and the BSP unit on a self-folded chain. Temperature-dependent single-molecule spectroscopy confirms such interaction showing a gradual increase in intensity of the CT emission with the temperature. Based on these observations, we propose the dynamic molecular motion-induced conformation change as the origin of the glassy-to-CT ET, and thermal energy may provide the activation for such a change to enhance the ET from glassy or β-phases to the CT state.

Impact of Zn-doping on the composition, stability, luminescence properties of silica coated all-inorganic cesium lead bromide nanocrystals and their biocompatibility

Cesium lead halide (CsPbX3: X = I, Br, Cl) nanocrystals (NCs) are believed to be potential candidates for bioimaging applications. However, their low structural stability against polar solvents remains as a major limitation. To improve the NCs stability and maintain high emission intensity, we synthesized silica coated Zn-doped core@shell perovskite NCs via modified ligand assisted reprecipitation (LARP) synthetic method under relatively high humid condition. We systemically varied the composition inside the perovskite structure and then studied their photophysical properties and stability. Interestingly, the Zn-doping amount controls the ratio of CsPbBr3 to Cs4PbBr6 perovskites inside the core and also facilitates the growth of (OA)2PbBr4 shell, enables overall increase in NCs emission intensity and stability. We observed green color emission from these NCs in the spectral range of 494-506 nm with a maximum photoluminescence quantum yield (PLQY) up to 88%. The optimized Zn-doped NCs exhibited nearly four times better water stability compared to the bare NCs and retain emission properties for several months even in highly polar solvents. Finally, we performed biocompatibility test of the NCs generated on biological samples and hydroponics test in a gardenia leaf for their potential bioimaging applications.

Ni2+-Doped Garnet Solid-Solution Phosphor-Converted Broadband Shortwave Infrared Light-Emitting Diodes toward Spectroscopy Application.

Broadband shortwave infrared (SWIR) light-emitting diodes (LEDs), capable of advancing the next-generation solid-state smart invisible lighting technology, have sparked tremendous interest and will launch ground-breaking spectroscopy and instrumental applications. Nevertheless, the device performance is still suppressed by the low quantum efficiency and limited emission bandwidth of the critical phosphor layer. Herein, we report a high-performance Ni2+-doped garnet solid-solution broadband SWIR emitter centered at ∼1450 nm with a large full-width at half-maximum of ∼300 nm, thereby fabricating, for the first time, a directly excited Ni2+-doped garnet solid-solution phosphor-converted broadband SWIR LED device. A synergetic enhancement strategy, adding a fluxing agent and a charge compensator simultaneously, is proposed to deliver a more than 20-fold increase of the SWIR emission intensity and nearly 2-fold improvement of the thermal quenching behavior. The site occupation and mechanism behind the synergetic enhancement strategy are elucidated by a combination of experimental study and theoretical calculation. A prototype of the SWIR LED with a radiation flux of 1.25 mW is fabricated and utilized as an invisible SWIR light source to demonstrate the SWIR spectroscopy applications. This work not only opens a window to explore novel broadband SWIR phosphors but also provides a synergetic strategy to remarkably improve the performance of artificial SWIR LED light sources.

Pressure effect on cathodoluminescence emission intensity recorded in metamorphosed detrital zircons of the Sanbagawa schists

AbstractThe cathodoluminescence (CL) emission and spectra analyses were conducted on detrital zircons in the Cretaceous Sanbagawa schists to describe changes in CL properties of zircons associated with metamorphism. In addition, high‐pressure (HP) and high‐temperature (HT) experiments were conducted on the non‐metamorphosed Miocene Ashizuri igneous zircons, and the CL emission intensities obtained from them were compared with those of the Sanbagawa zircons. As a result, as compared to low‐grade Sanbagawa zircons, the emission intensities of the high‐grade Sanbagawa zircons reduced. The emission intensities produced from the HP‐treated Ashizuri zircons, on the other hand, were twice as high as those generated from untreated zircons, but less than half of those generated from HT‐treated zircons. Combining our results with previous studies on the temperature influence on zircon CL properties, it indicates that increasing metamorphic pressure decreases the increase in the CL emission intensity of metamorphosed detrital zircons resulting from the increasing temperature. The pressure effect on the emission intensity of zircon during metamorphism might be larger than the temperature effect.

Selective and swift-responsive “off-on” rhodamine B based chemosensors: Recognition of multi-metal ions, on-site sensing of Fe(III) in water samples and bioimaging in aqueous media

Distinct “off–on” rhodamine B based chemosensors 3',6'-bis(diethylamino)-2-(2-(diethylamino)ethyl) spiro[isoindoline-1,9′-xanthen]-3-one (2a); 3′,6′-bis(diethylamino)-2-(2-(dimethylamino)ethyl) spiro[isoindole-1,9′-xanthen]- 3-one (2b) are synthesized in a facile single-step reaction and characterized by X-ray crystallography, NMR, Mass, and FT-IR techniques. 2a, 2b; selectively detected Fe+3, Sn+2, and Cr+3, in aqueous media over 17 other environmentally relevant cations. Furthermore, 2a, 2b showed high selectivity towards Fe+3 ion with ∼ 62 fold (2a), ∼21 fold (2b) enhanced emission intensity. A prominent pink color, in < 1 min (∼40 s) was detected under naked eye on sensing Fe+3. Enhanced emission was rationalized by natural transition orbital analysis using DFT and TD-DFT methods. Detection limit and binding constant of Fe+3 for 2a and 2b are estimated as 51.25 ppb (73 nM), 40.3 ppb (59.7 nM), and 0.80 × 103 M−1, 4.59 × 103 M−1, each respectively, indicating their efficiency towards Fe+3 sensing. A test strip method was developed for the on-site qualitative detection of target metal ions, and practical applicability was demonstrated by determining the concentration of Fe+3 ion in real water samples. Probes 2a, 2b further tested in human gastric adenocarcinoma (AGS) cell-lines via in-vitro imaging. The increased emission intensity in 2a, 2b on binding to Fe+3 in AGS cells indicate their potentiality as small-molecule based biological fluorescent probes.

Polythiophene based fluorimetric insight into minute styrene concentration in solution and gas phase

Water immiscible organic solvents dispersed in aqueous phase raise concerns due to persistence in environment and high toxicity. Fast and operation-simple approaches to assess their contents outside specialized laboratories are required. In this work an original approach allowing quantification of minute amounts of styrene present in solution or in gas phase is proposed. Polythiophene - poly[3-(ethyl-6-hexanoate)thiophene-2,5-diyl] (PeHT) - nanoparticles were applied as probes, offering an increase of emission intensity upon the rise of styrene contents in the sample. The response mechanism is based on the interaction of the polymer dye with analyte; at lower concentrations, the increase of emission at wavelengths typical for nanoparticles emission suggests interactions of the analyte with polymer chains in nanostructural form and offers selectivity. On the other hand, with increasing styrene contents in solution, polythiophene tends to form nano-dispersion droplets in the analyte resulting in appearance of emission peak characteristic for solvent dispersed polymer. A linear dependence of emission intensity on styrene concentration in solution was observed within the range from 0 to 200 ppm. The proposed approach benefits from full reversibility of sensors, upon spontaneous evaporation of styrene from solution. Finally, the nanoparticle suspension allows to detect the presence of styrene also in the vapor phase due to its solubilization in water (Henry's Law). Emission changes were observed in case of 0–2100 ppm of styrene vapor in the probe headspace, corresponding to 0–80 ppm styrene in solution. For the sake of comparison another polythiophene derivative, poly(3-octylthiophene-2,5-diyl) (POT), was investigated showing no changes in fluorescence emission spectra in the presence of styrene up to 200 ppm.

Molecular interactions of bovine serum albumin (BSA) with pyridine derivatives as candidates for non-covalent protein probes: a spectroscopic investigation

Research regarding protein–ligand interactions remains a major concern in the fields of chemistry, biochemistry, pharmacology, and food science. Herein, the interaction of selected pyridine derivatives with bovine serum albumin (BSA) was investigated using UV–Vis and fluorescence spectroscopy. A series of 2-amino-4,6-diphenyl-pyridinium-3-carbonitrile derivatives as fluorescent probes for the determination of BSA revealed that the probes investigated lead to a 12–176-fold increase in emission intensity. The calculated binding parameters support the conclusion that probes bind to BSA in 1:1 stoichiometry with moderate strength, and the quenching for pyridine probes is due to static interaction. The calculated negative value of the free energy change indicates that the complexation is a spontaneous process. Furthermore, from the estimated entropy and enthalpy change values, complexation between the pyridine derivatives and BSA was found to occur primarily via van der Waals interaction and hydrogen bonding. The pH-dependent emission experiment showed that BSA detection with the evaluated probes could be conducted at physiological pH = 7.4 with a wide safety range.

Carbazole‐based dual‐functional chemosensor: Colorimetric sensor for Co2+ and fluorescent sensor for Cu2+ and its application

AbstractA new carbazole derivative CNS was prepared by the condensation of 2‐hydrazine benzothiazole with 3‐aldehyde‐6‐naphthalene‐N‐butyl carbazole, which could highly selectively discriminate Co2+ and Cu2+ in different solvent systems. CNS could enable the recognition of Co2+ by the “naked eye,” with the color changing from colorless to pale yellow in DMSO/H2O (v/v = 1:1). The addition of Cu2+ made the fluorescence emission intensity increase nearly 10 times, which was accompanied by a weak blue shift of the emission peak in CH3CN. Under the illumination of 365 nm ultraviolet lamp, the color of the CNS solution changed from light blue to dark blue after Cu2+ was added. The binding process could be reasonably speculated by spectrometric titrations, 1H NMR, mass spectrometry (MS) analysis, and density functional theory (DFT) calculation. The results of fluorescence electron microscopy showed that CNS could be used as a fluorescent sensor to detect Cu2+ in Hela cells. In addition, CNS was successfully used for the detection of Cu2+ in actual water samples.

Modulated photoluminescence and photodynamic efficiency of hydroxyapatite-methylene blue@carbon-ions by ion-π coupling interactions

As a noninvasive methodology, image-guided photodynamic therapy is promising to treat diseases without inducing drug resistance with chemotherpy in clinical applications. The photo-related properties of methylene blue (MB) as flurophore/photosensitizer are closely related with energy and charge transformations in multifunctional drug delivery systems. Herein, MB monomers are combined by citrate- and β-cyclodexin-modified hydroxyapatite (HAp) with ions-doped carbon shells prepared by hydrothermal carbonization of glucose. Photoluminescence and photodynamic efficiency are tuned by ion-π coupling interactions between ions (M) and MB molecules in HAp-MB@C-M. With increased addition of Zn2+ ions during carbonization, narrowed absorbance peaks to low excitonic band without additional decay channels are observed for HAp-MB@C-Zn with increased emission intensities. As energy decay pathways, ring vibrations of MB are quite weak with small infrared peaks for these fluorochromes with increased luminescence emissions. High oscillate strength contributes to the increased generation efficiency of singlet oxygen for MB released from HAp-MB@C-Zn. The present studies would shed light on the modulations of aggregation states of photosensitizers and their photo-related properties of luminescence emission and therapy efficiency to meet the simultaneous requirements of image-guided photodynamic therapy.

Design, Synthesis, and Evaluation of Near-Infrared Fluorescent Molecules Based on 4H-1-Benzopyran Core.

A series of novel fluorescent 4H-1-benzopyrans was designed and developed as near-infrared fluorescent molecules with a compact donor–acceptor-donor architecture. Spectral intensity of the fluorescent molecules M-1, M-2, M-3 varied significantly with the increasing polarities of solvents, where M-3 showed high viscosity sensitivity in glycerol-ethanol system with a 3-fold increase in emission intensity. Increasing concentrations of compound M-3 to 5% BSA in PBS elicited a 4-fold increase in fluorescence intensity, exhibiting a superior environmental sensitivity. Furthermore, the in vitro cellular uptake behavior and CLSM assay of cancer cell lines demonstrated that M-3 could easily enter the cell nucleus and bind to proteins with low toxicity. Therefore, the synthesized near-infrared fluorescent molecules could provide a new direction for the development of optical imaging probes and potential further drugs.

Inspection of contamination in nitrogen plasmas by monitoring the temporal evolution of the UV bands of NO-γ and of the fourth positive system of N2

In this study, contamination by oxygen species in nitrogen plasmas produced by the active screen system used for plasma nitriding has been investigated by optical emission spectroscopy in the spectral range of 200–900 nm. Temporal evolution of emission intensity of different species (N2, N2+, NO, OH, H, NH, and Fe) was monitored, as well as electrical characteristics (current and voltage) of the discharge produced by a pulsed unipolar power supply. In nitrogen plasma, it was found that the emission of oxygen-containing species (NO and OH) decreases with time, while Fe emission intensity increases. Such behavior is observed only when the discharge is initiated immediately after venting the reactor. Starting from the hypothesis of contamination of the reactor walls by water vapor, we propose an explanation based on the synergistic effect between the temperature and the reactive nitrogen created by the plasma. Such a long decay of NO emission was not observed in N2–H2 gas mixtures. After decontamination, the fourth positive system of N2 could be observed. Such a not commonly observed system can be used as a tool to control reactor cleanliness in pure nitrogen discharge for nitriding applications.

A Limitation of Using Dithionite Quenching to Determine the Topology of Membrane-inserted Proteins.

Determining the topology of membrane-inserted proteins and peptides often relies upon indirect fluorescent measurements. One such technique uses NBD, an environmentally sensitive fluorophore that can be covalently linked to proteins. Relative to a hydrophilic environment, NBD in a hydrophobic environment shows an increase in emission intensity and a shift to shorter wavelengths. To gain further insight, NBD fluorescence can be chemically quenched using dithionite. As dithionite is an anion, it is only expected to penetrate the outer leaflet interfacial region and should be excluded from the hydrocarbon core, the inner leaflet, and the lumen of LUV. This assumption holds at neutral pH, where a large number of NBD/dithionite experiments are carried out. Here, we report control experiments in which LUV were directly labeled with NBD-PE to assess dithionite quenching in acidic conditions. Results showed that at acidic pH, dithionite moved more freely across the bilayer to quench the inner leaflet. For the buffer conditions used, dithionite exhibited a sharp change in behavior between pH 5.5 and 6.0. Therefore, in acidic conditions, dithionite could not differentiate in which leaflet the NBD resided.

Effect of Co concentration and temperature on the energy transfer process between Mn2+ and Co2+ ions in Zn0.99-xMn0.01CoxTe nanocrystals

In this paper, we report a P2O5 – ZnO – Al2O3 – BaO – PbO glass system study, nanostructured with Zn0.99-xMn0.01CoxTe nanocrystals (NCs), synthesized by a fusion method. Transmission electron microscopy (TEM) images confirm the formation and electron paramagnetic resonance (EPR) spectra confirm the substitutional incorporation of Mn2+ and Co2+ ions in these NCs. The overlap between the Mn2+ ion emission bands and the Co2+ ion absorption bands suggests that an efficient resonance energy transfer from Mn2+ to Co2+ ions can be expected in these NCs. Indeed, the increase in emission intensity of Co2+ ions and the decrease in emission intensity of Mn2+ ions, as well as the decrease in lifetime emission of Mn2+ ions, with increasing cobalt concentration, confirm the nonradiative energy transfer from Mn2+ to Co2+ ions. On the other hand, temperature dependent measurements show the thermally activated energy transfer process via carriers of the lower energy states for those of the low energy.

Tunable luminescence of Tb3+ doped SiO2-TiO2-PDMS hybrid ORMOSILs

A new class of SiO2-TiO2-PDMS hybrid ORMOSILs doped with Tb3+ ions were synthesized by non-hydrolytic sol-gel method. The host matrix was developed from both organic and inorganic constituents and when doped with Tb3+ making it suitable for a wide range of optical applications. The X-ray Diffraction (XRD) analysis confirmed the amorphous nature of the samples. The Fourier Transform Infra-Red (FTIR) analysis confirmed the unaltered chemical structure of the samples while the Thermogravimetric (TG) analysis established its thermal stability. The photoluminescence (PL) analysis demonstrated that the Tb3+ doped samples emit blue light along with the characteristic Tb3+ emission when excited at 276 nm. This confirms the existence of a host to Tb3+ energy transfer pathway in the doped sample. These samples were also excited at 352, 369, 378 and 487 nm wavelengths which give similar emission spectra, but with increasing emission intensity. The Judd-Ofelt (JO) intensity parameters and the radiative properties of 5D4→7F3, 4, 5 transitions were also evaluated from the emission spectra. High values obtained for branching ratio and stimulated emission cross-section for the 5D4→7F5 transition make the material suitable for optical amplification. Furthermore, the CIE co-ordinates were calculated and found that color tuning is possible from blue to green region with Tb3+ doped SiO2-TiO2-PDMS ORMOSILs when excited at different wavelengths.

Optical and radioluminescence properties of ZnO:Zn as a function of reduction degree and treatment temperature

The aim of this work is to highlight the correlation between treatment conditions, composition, and structure of reduced zinc oxide (ZnO:Zn) with optical and radioluminescence properties for the production of high yield scintillating powders. Purchased zinc oxide (ZnO) powders (≈0.35 ± 0.15 μm) were thermally reduced in Ar/H2 (3%) atmosphere at temperatures ranging between 600 (≈0.40 ± 0.17 μm) and 1000 °C (≈6.4 ± 1.6 μm), obtaining ZnO:Zn powders. The reduction degree, evaluated through energy dispersive spectroscopy, showed a linear increase from 0% up to 20% (800 °C sample), reaching a plateau condition at about 25% for the highest treatment temperatures (1000 °C sample). Structural analysis highlighted the existence of a threshold temperature, previously reported in the literature, around 800 °C, beyond which (i) the grain size remarkably increases, (ii) the shape changes from hexagonal to round-shaped, and (iii) the intensity of electron spin resonance (ESR)-active defects at g = 1.9596 decreases for a new resonance at g = 2.0105. Additionally, a substantial variation, from 5.63 ± 0.02 down to 5.2 ± 0.1 g/cm3, of the skeletal density and a slight contraction of the optical bandgap are observed. Unlike the structural properties, PL and x-ray radioluminescence showed a continuous increase of the green emission intensity, associated with ESR-active ionized oxygen vacancies and ESR non-active recombination centers, and of the PL defective lifetimes (33 ns &amp;lt; τfast &amp;lt; 88 ns, 395 ns &amp;lt; τslow &amp;lt; 930 ns).

Photoluminescence studies on dysprosium doped glass ceramics containing α-Na3AlF6 crystalline phase for white light emission

The present work focuses on Dy3+ doped 20SiO2-(20-x) B2O3–10Al2O3–10ZnO–30NaF–10ZnF2 glass ceramics (GCs), a white light emitting material prepared by conventional melt-quenching technique and thermal treatment. The glass ceramics exhibited good morphological evolution of α-Na3AlF6 crystals at elevated temperatures. Bandgap values are obtained lower for glass ceramics compared to precursor glass which almost tends to come closer to the bandgap value of semiconductor. A good photoluminescence (PL) performance is monitored in glass ceramics with increased emission intensity having two dominant peaks at 482 and 575 nm. Stimulated emission cross section in glass ceramics obtained higher for the level 6H13/2 characterize their significance in laser active media. Quantum efficiency is achieved greater than 80% for glass ceramics ensures their appropriateness for LEDs application. In particular, the yellow to blue intensity, colour coordinates and colour correlated temperature have been evaluated for glass ceramics. With the formation of α-Na3AlF6 crystalline phase surrounded by Dy3+ ions, the PL properties in glass ceramics is enhanced notably. The obtained glass ceramics should be acknowledged as a promising material in white-LEDs and optoelectronic devices applications.