Luminescence Emission Spectra Research Articles

Development of Na2O-MO-Bi2O3-B2O3-Sm2O3 glasses (MO=Ba/Mg) for laser and scintillation application.

Na2O-MO-Bi2O3-B2O3-Sm2O3 glasses (MO=Ba/Mg) were developed for the light emitting materials applications. Four broad emission peaks were observed at transitions 4G5/2 → 6HJ (J=5/2, 7/2, 9/2 and 11/2). The maximum transition occur at 600 nm. Concentration quenching were observed at 0.5 mol% of Sm3+ ion for both glasses. The X-ray luminescence spectra were found similar to the photoluminescence spectra. The Judd Ofelt (JO) parameters for Sm3+ in the present glasses were procure from the absorption and emission spectra. The important parameters for the laser materials like quantum efficiency, stimulated emission cross section and radiative decay time were explained in detail in the present study. The lifetime were found decreasing with Sm3+-concentration which is the evident of energy transfer between Sm3+ ions. The energy transfer process were further explained by applying IH model. The orange emission from the present glasses were confirmed from CIE chromoticity diagram. According to the present results it is suggested that at 404 nm excitation and 600 nm emission the NMgBiBSm1.0 glass is suitable for the orange emitting devices and from X-ray luminescence emission spectra the present glass might be used for scintillation purpose.

Solid solution of novel LixByGdEu (WO4)2 (B=Na, K) red phosphors: Influence of Na/K substitution on microstructures, Judd-Ofelt and luminescence properties for WLED applications

In the present investigation, new materials of the type LixByGdEu(WO4)2 (B= Na, K) have been synthesized by solid state reaction. The influence of Li/K and Li/Na ions on the photoluminescence properties and structures are presented in detail. Rietveld refinement indicates the crystalline phase of the compounds and incorporation of doping leads to change in the interatomic distance. The SEM observations shows that all the prepared phosphors have spheroid, bi-pyramidal shape with different grain size. An Optical energy bandgap of 3.0 and 3.2 eV were observed for LixByGdEu(WO4)2 (B= Na, K) phosphors. The Photoluminescence spectra shows that the phosphors can be excited by near UV light which is relevant for lighting technology. Luminescence emission spectrum reveals the two characteristic emissions located at 613 nm (electric dipole) and 586 nm (magnetic dipole). The 5D0→7F2 electric dipole transitions are dominant, indicating that Eu3+ ion occupies the single crystallographic site without the stark splitting in the host matrix. Interestingly, doping of Na, K shows 40% enhancement of photoluminescence intensity than reported LiGdEu(WO4)2 phosphor. The critical distance of energy transfer is found be 10 Å indicating the multipole-multipole interactions. Judd Ofelt (J-O) theory is implemented to explore the luminescence behavior and local structure around activator with respect to Eu3+ ion. The JO intensity parameter trend i.e, Ω2 > Ω4 indicate that the asymmetric environment around the activator. In addition, the Cathodoluminesence study also suggests the intense red emission of phosphors at low voltage and current. The chromaticity coordinates of the phosphors are much closer to NTSC trichromatic coordinates indicating the promising red phosphors with excellent luminescence properties. The CCT values around 3500K reveals that the LixByGdEu(WO4)2 (B= Na, K) red phosphors can be used for warm white LED applications.

Dual-storage phosphor proton therapy dosimetry: Simultaneous quantification of dose and linear energy transfer.

To investigate the feasibility of using the high Zeff storage phosphor material BaFBrI:Eu2+ in conjunction with the low Zeff storage phosphor material KCl:Eu2+ for simultaneous proton dose and linear energy transfer (LET) measurements by (a) measuring the fundamental optical and dosimetric properties of BaFBrI:Eu2+ , (b) evaluating its compatibility in being readout simultaneously with KCl:Eu2+ dosimeters, and (c) modeling and validating its LET dependence under elevated proton LET irradiation. A commercial BaFBrI:Eu2+ storage phosphor detector (Model ST-VI, Fujifilm) was characterized with energy dispersive x-ray spectroscopy (EDS) analysis to obtain its elemental composition. The dosimeters were irradiated using both a Mevion S250 proton therapy unit (at the center of a spread-out Bragg peak, SOBP) and a Varian Clinac iX linear accelerator with the latter being a low LET irradiation. The photostimulated luminescence (PSL) emission spectra, excitation spectra, and luminescent lifetimes of the detector were measured after proton and photon irradiations. Dosimetric properties including dose linearity, dose rate dependence, radiation hardness, temporal, and readout stabilities were studied using a laboratory optical reader after proton irradiations. In addition, its proton energy dependence was analytically modeled and experimentally validated by irradiating the detectors at various depths within the SOBP (Range: 15.0g/cm2 , Modulation: 10.0g/cm2 ). The active detector composition for the high Zeff storage phosphor detector was found to be BaFBr0.85 I0.15 :Eu2+ . The BaFBr0.85 I0.15 :Eu2+ material's excitation and emission spectra were in agreement under proton and photon irradiations, with peaks of 586±1nm and 400±1nm, respectively, with a full width at half maximum (FWHM) of 119±3nm and 30±2nm, respectively. As dosimeter response under photon irradiation is generally believed to be free from LET effect, these results suggest LET independence of charge storage center types resulted from ionizing radiations. There is sufficient spectral overlaps with KCl:Eu2+ dosimeters allowing both dosimeters to be readout under equivalent readout conditions, that is, 594nm stimulation and 420nm detection wavelengths. Its PSL characteristic lifetime was found to be less than 5 microseconds which would make it suitable for fast 2D readout post irradiation. Its 420nm emission band intensity was found to be linear up to 10Gy absolute proton dose under the same irradiation conditions, dose rate independent, stable in time and under multiple readouts, and with high radiation hardness under cumulative proton dose histories up to 200Gy as tested in this study. BaFBr0.85 I0.15 :Eu2+ showed significant proton energy-dependent dose under-response in regions of high LET which could be modeled by stopping power ratio calculations with an accuracy of 3% in low LET regions and a distance-to-agreement (DTA) of 1mm in high LET regions (>5keV/μm). We have proven the feasibility of dual-storage phosphor proton dosimetry for simultaneous proton dose and LET measurements. BaFBr0.85 I0.15 :Eu2+ has shown equally excellent dosimetry performance as its low Zeff complement KCl:Eu2+ with distinctive LET dependence merely as a result of its higher Zeff . These promising results pave the way for future studies involving simultaneous proton dose and LET measurements using this novel approach.

Role of native and impurity defects in optical absorption and luminescence of Li2MoO4 scintillation crystals

The Li2MoO4 crystals have been considered as perspective cryogenic scintillation materials to be used in elementary particle physics experiments related to dark matter search and properties of neutrino. Since the crystals may be used as cryogenic scintillators, the native vacancies, uncontrolled impurities and other defects play the key role in worsening of their scintillation characteristics. The paper presents complex experimental and computational studies of the electronic structure and optical properties of Li2MoO4 crystals. The studies are aimed to explain peculiarities of the optical (luminescence) properties of Li2MoO4 using the electronic structure results obtained for a wide range of point defects and their combinations. For investigations, several samples of Li2MoO4 with different defectiveness were grown using Czohralski method and characterized by SEM and ICP-OES technique. Luminescence emission spectra of the samples under X-ray and laser excitations, optical and IR absorption spectra, TSL characteristics of the samples were recorded and analyzed. Ability to incorporate some gases was examined by measuring absorption spectra after one-year storage of the samples at ambient conditions. The electronic structures of several kinds of point defects (natural vacancies, iso- and aliovalent cationic and anionic substitutions, interstitial ions and molecular groups) in Li2MoO4 were calculated using the DFT-based plane-wave pseudopotential method. Geometries of lattice relaxations around defects, partial densities of states and energies of defect formation were calculated and analyzed together with experimental results. Performed analysis allowed making several conclusions regarding the origin of spectral components of intrinsic and defect-related luminescence, formation of defect-related bands in the optical and IR absorption spectra, dependence of TSL characteristics on sample defectiveness. It was found that isovalent cationic substitutions on lithium positions are presented in substantial concentrations in the Li2MoO4 samples and such defects form shallow traps which can affect scintillation characteristics in cryogenic experiments. Substantial effect of gases inclusions on the optical characteristics of crystals can be related to the peculiarity of the crystal lattice structure - the presence of empty "channels", which can incorporate molecular objects like H2O, -CH3 or -OH.

The luminescent emission and quantum optical efficiency of Cd1-xSrxSe QDs developed via ions exchange approach for multicolor-lasing materials and LED applications

A new family of Cd1-xSrxSe semiconductor quantum dot was synthesized using ions exchange method. The TEM measurement inspected that the Cd1-xSrxSe crystals have spherical particles with mean sizes in the range of 3.1 nm to 7.8 nm reliant to the quantity of Sr-dopant assimilated in CdSe. The optical absorbance spectra indicated that the Sr-dopant created sublevels within the bandgap of the CdSe, which caused a red shift displacement of the spectral curves. The luminescent emission spectral bands showed an improvement of the intensity of the luminescent emission spectra and narrowing of their bandwidth. It is also showed that the bandgap lowered from 3.62 eV to 2.74 eV. The Sr-dopant enhanced the quantum yield from 23 % to 87 %. The intensive, sharp luminescent emission light emerged from the developed Cd1-xSrxSe QD crystals with quantum efficiency of 87 %, pave the way for a novel family of QDs capable to be employed for lasing and multicolor light emitting diodes application.

Development of highly luminescent and color-tunable Zn1-xPmxTe QDs synthesized using 4,4-bis-N-1-naphyl-N-phenylaminobiphenyl assisted microwave technique for solar cell applications

A new family based on the synthesis of highly luminescent and color-tunable Zn1-xPmxTe QDs using 4,4-bis-N-1-naphyl-N-phenylaminobiphenyl assisted microwave technique. This new series of Zn1-xPmxTe QDs showed remarkable optoelectronic properties. The promethium ions exhibited a modulating of the bandgap of ZnTe Qs, where the bandgap reduced from 3.06 eV to 2.8 eV and the particle size changed from 1.4 nm to 4.3 nm. The promethium ions created trap levels within the ZnTe bandgap which leads to highly luminescent emission spectra exceeded the undoped ZnTe QD by 5 times. The inclusion of promethium ions in ZnTe QDs resulted in color tunable QDs in the visible region. The quantum yield of the Zn1-xPmxTe QDs increased 7%–82%, according to the amounts of promethium ions incorporate ZnTe QDs. Therefore. The developed Zn1-xPmxTe QDs are promising candidate for photovoltaic devices.

Structural and dielectric properties of Cu-doped α-ZnMoO4 ceramic system for enhanced green light emission and potential microwave applications

In this article, the synthesis of the Zn1-xCuxMoO4 ceramic system was carried out by a solid-state reaction route, and their structural, morphological, and optical properties were investigated. The samples were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, FT-IR spectroscopy, and UV–Vis spectrophotometry. Structural analysis confirms the formation of a triclinic structure with space group P $$\stackrel{-}{1}$$ and point group symmetry C1 without any secondary phase formation. The decrease in effective nuclear charge with the introduction of Cu2+ ion decreases the bandgap from 3.57 to 2.78 eV. The potential application in the visible (green) region of the electromagnetic spectrum is supported by the reduction of the bandgap. The increasing Cu2+ concentration is accompanied by Photoluminescence peaks being shifted toward larger wavelength side, covering a broad range of visible region from 300 to 600 nm. The broad range luminescence emission spectra that happened with ZnMoO4 occurred due to the electronic transition between (MoO4)2− complexes or between Mo4d and O2p states. Hakki–Coleman method was applied for the study of microwave dielectric parameters and shows increase of eobs from 8.35 to 12.52 with a simultaneous decrease in dielectric loss (tan δ) from 0.01 to 0.005, respectively. The corresponding quality factor (Q $$\times$$ f) was calculated. The observed high-quality factor could be used as high signal speed microwave materials.

Quantitative proton radiation therapy dosimetry using the storage phosphor europium-doped potassium chloride.

To (a) characterize the fundamental optical and dosimetric properties of the storage phosphor europium-doped potassium chloride for quantitative proton dosimetry, and (b) investigate if its dose radiation response can be described by an analytic radiation transport model. Cylindrical KCl:Eu2+ dosimeters with dimensions of 6mm diameter and 1mm thickness were fabricated in-house. The dosimeters were irradiated using both a Mevion S250 passive scattering proton therapy system and a Varian Clinac iX linear accelerator. Photostimulated luminescence (PSL) emission spectra, excitation spectra, and luminescence lifetimes were measured for both proton and photon irradiations. Dosimetric properties including radiation hardness, dose linearity, signal stabilization, dose rate sensitivity, and energy dependence were studied using a laboratory optical reader after irradiations. The dosimeters were modeled using physical quantities including mass stopping powers in the storage phosphor and water for a given proton beam, and mass energy absorption coefficients and massing stopping powers in detector and water for a given photon beam. KCl:Eu2+ exhibited optical emission and stimulation peaks at 421 and 560nm, respectively, for both proton and photon irradiations, enabling postirradiation readouts using a visible light source while detecting the PSL using a photomultiplier tube. KCl:Eu2+ showed a linear response from 0 to 8Gy absorbed dose-to-water, a large dynamic range up to 60Gy, dose-rate independence measured from 83 to 500MU/min, and a PSL lifetime of <5ms that is sufficiently short for supporting rapid scanning in a two-dimensional geometry. KCl:Eu2+ was highly reusable with only a slight signal decrease of ~3% at accumulated doses over 100Gy, which could be managed by a periodic recalibration. The detected PSL signal strength of the dosimeter in the proton field had been calculated accurately to a maximum discrepancy of 2% using known physical quantities along with its prior signal strength as measured in a photon field at the same dose-to-water. This discrepancy might be attributed to an under-response due to linear energy transfer (LET) effect. However, comparisons of depth-dose measurements in a spread-out Bragg peak (SOBP) field with a parallel-plate ionization chamber showed no clear evidence of LET effects. Furthermore, range measurements agreed with ionization chamber measurements to within 1mm. KCl:Eu2+ showed linear response over a large dynamic range for proton irradiations and reliably reproduced SOBP measurements as measured by ionization chambers. Its relatively low atomic number of 18 and near LET independence make it suited for quantitative proton dosimetry. In addition, its high radiation hardness means that it can be reused numerous times. Any potential measurement artifacts encountered in complex irradiation conditions should be able to be corrected for using known physical quantities.

Spectroscopic investigation on Europium (Eu3+) doped strontium zinc lead phosphate glasses with varied ZnO and PbO compositions

A series of europium (Eu3+) doped SrO + ZnO + PbO + P2O5 glasses with varied ZnO and PbO compositions have been prepared by melt quenching method. The structural and optical properties of the samples are analysed by XRD, FTIR, absorption, optical band gap energy, excitation, phonon sideband (PSB) spectrum, luminescence emission, decay profile and CIE chromaticity coordinates. The most intense emission is found at 611 nm (red) corresponding to 5D0 → 7F2 transition. Using the luminescence emission spectra, the branching ratio (βm), effective bandwidth (Δλeff) and emission intensity ratio (R) have been calculated. The decay profile of the 5D0 excited state is fitted with a single exponential function and thereby lifetime is evaluated. The high colour purity of 97.4% in the red region is estimated for the EuSr30ZnPbP glass. The luminescence properties indicate that the present glasses could be used for red laser materials and optical display devices.

Structure, Raman and luminescence characteristics of Zn1-xHfxO (0≤x≤0.1) nanocrystals prepared via N-(methyl)mercaptoacetamide assisted microwave approach

A series of Zn1-xHfxO (0 ≤ x ≤ 0.1) nanocrystals was synthesized via the N-(methyl)mercaptoacetamide assisted microwave approach. The influence of the Hf dopant on the crystal structure, Raman lattice vibrations, and luminescent emission spectra was studied. XRD measurements revealed that the inclusion of the Hf dopant in the Zn cites instigated the expansion of the ZnO lattice while preserving its hexagonal structure. The XRD, SEM and DLS measurements demonstrated that the Hf dopant increased the size of ZnO nanocrystals from 2.5 ± 0.1 nm to 11.5 ± 0.1 nm. The EDS spectra confirmed the stoichiometry of the prepared samples. The zeta potential measurement revealed that the Hf dopant is incorporated within the ZnO nanostructure. The Raman spectra showed that the Hf dopant was efficiently incorporated into the ZnO crystals without altering its internal structure. The UV–vis. spectroscopy indicated that the partial substitution of Zn atoms by Hf atoms leads to modulation of the optical bandgap. Luminescence measurements revealed that the inclusion of the Hf dopant in the Zn cites resulted in suppression of the ZnO crystal defects. The XPS measurements confirmed that the inclusion of Hf dopant in the Zn cites resulted in a reduction of the amount of oxygen vacancy which actes as a trap centers for the photogenerated electrons. Therefore, a modulation of the visible spectra occurred, while the Hf dopant did not affect the intensity of UV-emission band of ZnO nanocrystals. Therefore, the Zn1-xHfxO (0 ≤ x ≤ 0.1) nanocrystals are favorable as potential candidates for both catalytic and luminescent device applications.

Characterization of the phosphor (Sr,Ca)SiAlN3: Eu2+ for temperature sensing

Laser-induced phosphorescence based on luminescent particles is a suitable technique for remote temperature sensing. The luminescence characteristics of the phosphor (Sr,Ca)SiAlN3:Eu2+ (”SCASN”) were investigated regarding the suitability of the material for phosphor thermometry. The phosphor has a high quantum efficiency, a very broad excitation band, an emission peak centered at about 620 nm and a short lifetime of less than 1μs, which makes it promising for thermometry measurements. After excitation at 532 nm, the luminescence emission reveals a blue shift with increasing temperature, which can be used for temperature calibration based on the two-color intensity ratio method. The excitation and emission characteristics are favorable for measurements in environments containing fuels and oils, which tend to fluorescence after UV-excitation. The phosphor allows for measurements up to 800 K, with a quenching temperature of 530 K. Spectral characteristics are presented for both bulk powder and a surface coating. For the former, a significant shift in the position of the emission peak is observed, which is most probably due to distinct re-absorption. A change in excitation laser fluence slightly affected the luminescence emission spectrum of both bulk material and coating and thus requires consideration in temperature determination.

Selective ultrasound‐assisted aqueous extraction of polyphenols from pomegranate peels and seeds

In this study, the optimization of ultrasound-assisted aqueous extraction of polyphenols from pomegranate peels and seeds was conducted. A 10-min sonication (tu) pre-treatment (≈60 W) accelerated the extraction kinetics and intensified the polyphenol recovery from peels and seeds. Ultrasound pre-treatment permitted the selective recovery of polyphenols from peels by maintaining a constant concentration of the total soluble matter (°Brix) before and after sonication. Two different near-linear correlations were found between soluble matter and polyphenol extraction for the peels’ and the seeds’ extracts. Luminescence emission spectra showed significant differences between peels and seeds extracts (tu = 10 min then diffusion for 200 min) below 450 nm and above 600 nm. Ultrasound pre-treatment enhanced the quantity of the extracted molecules from peels and seeds without affecting their diversity. The optimal ultrasound pre-treatment duration was 10 min, since it ameliorated the polyphenol extraction compared to 5 min, and gave the same yield as 20 min. Practical applications Pomegranate fruits are valuable sources of bioactive compounds (vitamins, antioxidants, flavonoids, and tannins). Their processing results in the formation of byproducts containing peels (78%) and seeds (22%), discarded as waste by the food industry. Pomegranate peels and seeds are rich sources of polyphenols that have high antioxidant, anti-inflammatory, anti-allergic, antimutagenic, and anticancer properties. Ultrasound-assisted aqueous extraction of polyphenols from pomegranate peels and seeds can be used as a “green” technique to intensify the extraction of polyphenols from pomegranate byproducts. An optimized sonication time can prevent the degradation of the bioactive compounds and enhance the extraction of selective polyphenols from pomegranate peels and seeds. The extracts will then be spray dried to obtain highly bioactive powder with many industrial applications.

Phytochemical mediated synthesis of ZnO:Dy3+ nanophosphors: Judd–Ofelt analysis, structural and spectroscopic properties

Abstract In the present work, ZnO:Dy3+ nanophosphors were synthesized by a simple, cost effective and eco-friendly route using the aqueous extract of Azadirachta Indica leaves. The prepared ZnO:Dy3+ nanophosphors were characterized using X-ray diffraction (XRD), Fourier Transformed Infra-Red (FTIR), Raman, UV-VIS diffuse reflectance (UVDR) spectroscopy and Photoluminescence (PL), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX). TEM and X-ray diffraction analyses reveal the hexagonal wurtzite structure of the ZnO nanoparticles in the prepared samples. UV-VIS-NIR spectrum of the ZnO:Dy3+ nanophosphor was analysed on the basis of Judd–Ofelt (J-O) theory and the J–O intensity parameters (Ωλ) were calculated. The radiative properties, such as radiative transition probability, branching ratio, stimulated emission cross-section and optical gain were investigated using the J–O intensity parameters. The photo luminescence emission spectra (PLE) of the Dy3+ doped samples exhibits three emission bands relative to 4F9/2→ 6H15/2 (478 nm), 4F9/2→ 6H13/2 (572 nm) and 4F9/2→ 6H11/2 (663 nm) transitions of Dy3+ ions respectively. The CIE chromaticity color coordinate shows that the ZnO:Dy3+ nanophosphors can be useful for white luminescence applications. The result indicates that the prepared phosphors produce white light emission and can be used for near ultraviolet excited white light emitting diode (NUV WLED) applications.

The optical performance of Cd1 − xTmxTe (0 ≤ x≤ 0.07) QDs synthesized via s,s′-phenylenebis-ethynediyl-phenylene-bisthioacetate assisted microwave approach for laser devices

Here, we have developed a new series of quantum dots based on the incorporation of thulium, Tm, atoms as efficient dopant in the cubic CdTe crystal structure for laser diode application potential. Therefore, Cd1 − xTmxTe (0 ≤ x ≤ 0.07) quantum dots were synthesized using s,s′-phenylenebis-ethynediyl-phenylene-bisthioacetate assisted microwave approach. The measurements of X-ray diffractions implied the preservation of the cubic phase of the CdTe crystals at all Tm dopant contents. The transmission electron microscopy inspected the formation of monodisperse and self-assemble nanoparticles with mean diameter from 1.8 ± 0.2 nm to 5.7 ± 0.3 nm, depending on the amount of Tm incorporated in the CdTe nanocrystals. A modulation of the optical bandgap was observed because of the doping of CdTe with Tm atoms. Highly luminescent emission spectra with tunable colors were obtained. The emission spectra showed sharp intense emitted light with an enhancement of its intensity reached to seven folds compared with the un-doped CdTe crystals. An increasing of quantum yields from 31% to 94% was realized. A decrease of the Stokes shift was observed which implies the synthesis of Cd1 − x TmxTe QDs free of defects for the first time. This unique performance renders the prepared Cd1 − x TmxTe to be potential candidate for the manufacturing of laser diodes.

Supramolecular hydrogel with luminescence tunablility and responsiveness based on co-doped lanthanide and deoxyguanosine complex

Lanthanide (Ln)-based supramolecular hydrogels are a new category of smart optical materials, which are promising for applications in chemistry sensors, bioimaging agents and light-emitting devices. Herein, we report a supramolecular hydrogel with tunable and responsive luminescence, which is based on the assembly of Ln and deoxyguanosine (dG, one of the units of DNA). ESI-TOF-MS, NMR, FTIR, PXRD and simulation results verify the formation of dG/Ln hydrogels. dG/Tb hydrogel emits strong green luminescence, while dG/Eu hydrogel is nonluminous; when Tb is co-doped into dG/Eu, surprisingly we find that co-doped dG/Tb/Eu hydrogel displays tunable luminescence from green, orange to red by simply regulating the stoichiometric ratio of Tb and Eu. A cascade luminescence resonance energy transfer mechanism (from dG to Tb, and to Eu) is proposed in this co-doped system, which is confirmed by luminescence decay curves and emission spectra. Subsequently, luminescence switch is designed based on reversible responsiveness of hydrogel upon Ag+/L-Cys, temperature and pH stimuli via dynamic supramolecular coordination. Our work provides a new route to construct multicolor functional materials.

Facilitating Low-Energy Activation in the Near-Infrared Persistent Luminescent Phosphor Zn1+xGa2–2xSnxO4:Cr3+ via Crystal Field Strength Modulations

Cr3+-activated persistent luminescent phosphors with a spinel structure are emerging materials in bio-imaging applications for their distinctive features of deep biotissue penetration and rechargeable near-infrared persistent emission. To realize the long-term and multicycle imaging purpose, reactivation using in situ external light with deep biotissue penetration is an alternative strategy, apart from the efforts on trap modulations for the host lattice. However, recharging with high-energy ultraviolet /visible photons will result in low activation efficiency because of the absorption by biological tissues. Here, we report a low-energy photon-rechargeable near-infrared persistent material, with rechargeable efficiency 400 times higher than that of the ZnGa2O4:Cr3+ reference material. The crystal field strength and band gap energies can be tailored by control of cation occupancy, contributing the red shift of both the persistent luminescence excitation and emission spectra of the optimized complex spinel samples. The persistent emission red shift is of interest for improved deep tissue penetration for bioimaging, whereas the persistent excitation red shift facilitates the activation of persistent luminescence by low-energy radiation. Furthermore, it demonstrates that increasing the rate of cation site inversion in the spinel can lead to higher storage capacity of charge trapping.

Synthesis and optical characterization of multi-emission NixYb1-xO photonic semiconducting quantum dots prepared using hydrothermal approach for nano-optical colored amplifiers and light emitting diodes

Nanophotonic or nano-optic is sort of nanotechnologies that scrutinize the comportment of light on the scale of nanometer along with the interaction of nanoscale substances with light. The photonic semiconducting nanocrystals with distinctive optical traits became a prevalent category of optical probes and optoelectronic nanodevices. The modulation of photonic semiconducting nanomaterials turned out to be a crucial challenge for efficacious optical applications. Here, highly luminescent photonic semiconductors quantum dots were prepared using hydrothermal approach. The ytterbium,Yb, has been selected as doping atoms in the positions of Ni atoms in the NiO crystals. Different amounts of ytterbium, from 1 to 9 at.%, have been doped in the NiO. The stimulus of ytterbium atoms on the NiO crystal structures and the dimension of NiO crystals were explored via transmission electron microscope and X-ray diffractometer. The optical absorbance features comprised modulations of the optical band gaps, where the ytterbium dopant drifted the band gaps from 3.36 eV to 2.24 eV. The luminescent emission spectral property inspected a distinctive displacement of the emission spectra from UV-light to the red light with brilliant improve of the luminescent emission spectra by 8 folds and increasing the quantum yield by 7 folds. These marvel features boarded the opportunity of using the developed NixYb1-xO photonic crystals in the fields of wave guides, optical switches and optical amplifiers.

The luminescence spectroscopy and the mechanism of photoelectrons transportation for the Zn1-xLuxO nanophotonic crystals synthesized via 3-Mercapto-N-nonylpropionamide assisted microwave approach

Nanophotonic semiconductor crystals have shown great potential in the optoelectronic devices field owing to their unique quantum confinement effect and high luminescence emission spectra. Here, a novel highly luminescent Zn1-xLuxO (0 ≤ x ≤ 0.07) semiconducting oxide quantum dot (SOQDs) has been developed by 3-Mercapto-N-nonylpropionamide assisted microwave approach for the first time. The doping of lutetium, Lu, atoms in the cites of Zn for ZnO hexagonal structures instigated an increase of the crystallite size and the lattice constant parameters. The inclusion of Lu atoms in the ZnO nanophotonic crystals resulted in the formation of monodisperse nanoparticles with mean diameters ranged from 10 nm to 23 nm. The Lu-doped ZnO QDs caused a shift of the absorption spectrum toward the visible spectrum, where the optical band gaps reduced from 3.5 eV to 2.7 eV. The doped ZnO nanophotonic QDs with Lu atoms embarked the increase of the luminescent intensity by 10 times with sharp emission band width. The quantum yields increased from 14 % to 89 % where the Lu atoms acts as population trap levels for the excited electrons of the ZnO conduction band, which resulted in the emergence of high intense lasing light. These remarkable characteristics may open the avenue to use the Zn1-xLuxO semiconducting photonic quantum dot for the fabrication of highly luminescent laser diode.

Development of lasing QD nanostructures with highly luminescent emission spectra based on In1-xScxP QDs prepared via tetradecanoic acid assisted wet chemical route for laser diode applications

New lasing QD nanostructures with intense emission spectra based on In1-xScxP QD crystals were prepared via tetradecanoic acid assisted wet chemical route. The doping of Sc in the In1-xScxP QD crystals instigated increasing of lattice constants and crystallites size of their zinc blende cubic crystals. The images of TEM scrutinized that the formed nanocrystal were highly monodisperse particles and their mean diameter increased from 2.8 nm to 5.9 nm. The images of HRTEM reflected that that the d-spacing increased from 0.583 nm to 0.62 nm upon the increasing of Sc dopant amount in the InP crystals. The spectrum of optical absorption curves showed a displacement toward the long wavelength as the amount of Sc dopants increased in the InP crystals, comprising the decrease of the optical gaps from 2.04 eV to 1.73 eV. The insert of Sc-dopant in the InP QDs inspected a shift of the emission spectra to red light, confirming the decrease of the optical and gap. Moreover, the inclusion of Sc atoms in the In atom cites of the InP QDs gave rise to an enlargement of the luminescent intensity of the emitted lights from these nanocrystals by 9 times. It is found a remarkable decreasing of the Stokes shift reached to 97 % was achieved, implying the surface defects were passivized. The increase of the Sc-dopant in the InP QD crystal resulted in a decreasing of the emission band width by 5 times. The quantum yields changed from 12 % to 78 % due the increasing of the amount of Sc dopant in the InP QD crystals. These outstanding behaviors make these sorts of novel QDs to be served as efficient lasing nanomaterials for the development of laser diode.

Effect of low-density polyethylene on the luminescent properties of thulium-doped yttrium oxide obtained by the polyol technique

In the present work polyethylene is used as a support of yttrium oxide particles doped with thulium atoms and its effect on the luminescent properties is studied. Thulium-doped yttrium oxide was prepared through the polyol method, different values of thulium are explored: 0, 0.5, 1, 1.5, 2.5 and 3.5 at%, as well as different calcinating temperatures: 400, 600, 800 and 1000 °C, are explored in order to determine the synthesis conditions needed for the maximum emission intensity, whose values were 1.5 at% of thulium and 1000 °C. The synthesized powder is dispersed in low-density polyethylene and dispersed as a thin film on glass substrates. The luminescent excitation and emission spectra showed important changes attributed to the influence of the -CH2– chain vibration; in addition, the presence of the polymer had an important influence on the emission decay time: while the powder showed a single emission process with a time of 9.293 μs, the film showed a two decay process with 1.156 μs and 4.086 μs, each.