Temperature Dependence Of Spectra Research Articles

Defect level induced negative thermal quenching of β-Ba3LuAl2O7.5: Yb3+, Er3+ phosphor

Temperature-dependent behavior of phosphors has recently attracted significant research attention. This is due to the widespread applications of phosphors. Unfortunately, the thermal quenching effect in many phosphors greatly limits their performance at high temperatures. Herein, negative thermal quenching phosphor β-Ba3LuAl2O7.5: 0.3Yb3+, 0.03Er3+ is synthesized using the high-temperature solid-state method. X-ray Rietveld refinement and EPR results indicate the defect state of oxygen vacancy. Temperature-dependent upconversion luminescence spectra demonstrate that the green and red emission intensities increase with temperature to reach maximums at 398K and 348K respectively. Diffuse reflectance spectrum and downshifting luminescence spectrum prove that the defect state is near the 4F7/2 state of Er3+ ions. The defect state traps electrons at room temperature and releases them to populate the 4F7/2 state of Er3+ ion at elevated temperatures to cause the observed thermal enhancement of upconversion luminescence. This material's negative thermal quenching effect makes it a suitable candidate for applications in displays and anti-counterfeiting.

Temperature dependence of the near infrared absorption spectrum of single-wall carbon nanotubes dispersed by sodium dodecyl sulfate in aqueous solution: experiments and molecular dynamics study.

Single-wall carbon nanotubes (SWCNT) dispersed in water with the help of sodium dodecyl sulfate (SDS) surfactants exhibit a temperature dependent near infrared (NIR) exciton spectrum. Due to their biocompatibility and NIR spectrum falling within the transparent window for biological tissue, SWCNTs hold potential for sensing temperature inside cells. Here, we seek to elucidate the mechanism responsible for this temperature dependence, focusing on changes in the water coverage of the SWCNT as the surfactant structure changes with temperature. We compare optical absorption spectra in the UV-Vis-IR range and fully atomistic molecular dynamics (MD) simulations. The observed temperature dependence of the spectra for various SWCNTs may be attributed to changes in the dielectric environment and its impact on excitons. MD simulations reveal that the adsorbed SDS molecules effectively shield the SWCNT, with ~ 70% of water molecules removed from the first two adlayers; this coverage shows a modest temperature dependence. Although we are not able to directly demonstrate how this influences the NIR spectrum, this represents a potential pathway given the strong influence of the water environment on the excitons in SWCNTs. Optical absorption measurements were carried out in the UV-Vis-NIR range using a Varian Cary 5000 spectrophotometer in a temperature-controlled environment. PeakFit™ v. 4.06 was used as peak-fitting program in the spectral range 900-1400nm (890-1380meV) as a function of the temperature. Fully atomistic molecular dynamics simulations were conducted using the NAMD2 package. The CHARMM force field comprising two-body bond stretching, three-body angle deformation, four-body dihedral angle deformation, and nonbonded interactions (electrostatic and Lennard-Jones 6-16 potentials) was employed.

Novel self-activated red-emitting CsSrEu (PO3)6 phosphor: Synthesis, luminescent properties and enhancement by partially anion substitution

Novel self-activated red-emitting CsSrEu(PO3)6 was synthesized by high-temperature solid-phase method, and their enhanced luminescence were obtained by the modification of local structure. CsSrEu(PO3)6 was efficiently excited at 394 nm and emitted bright red light centered around 609 nm. Their luminescence intensity of CsSrEu(PO3)6 phosphor substituted by (BO3)3-/(SiO4)4- is about 1.346 or 1.454 times of the initial values respectively. The temperature-dependent luminescent spectra show that the emission intensity of CsSrEu(PO3)6 substituted by (BO3)3-/(SiO4)4- at 423 K remains 90.9 % and 86.6 % of the initial value respectively. The internal quantum efficiency is 88.4 % and 83.5 % respectively. White light-emitting diode fabricated by the phosphors, commercial blue-green phosphors and 395 nm chips show high color quality. The overall results indicate that the CsSrEu(PO3)6 phosphor substituted by (BO3)3-/(SiO4)4- group is promising candidate in warm white LED and anionic group substitution can be used to optimize luminescent properties of phosphors.

Impact of the spatial structure of alkyl chains on properties of thiophene-substituted diketopyrrolopyrroles: Part II – Spectroscopic study

The study concerns the impact of a difference in geometry of the side alkyl chains of oligothiophene derivatives of diketopyrrolopyrrole (DPP) on their spectroscopic properties and aggregation in solutions, in Langmuir layers, and thin films. Using a combination of theoretical and experimental approaches, this study aims to explain the aggregating behaviour of thiophene-substituted DPP derivatives. Various methods were used to characterise the dyes, including absorption spectroscopy also with polarized light, fluorescence spectroscopy, Langmuir techniques, and time-dependent density functional theory (TD-DFT) calculations. The presented results emphasise a significant impact of side alkyl chains on DPP's molecular behaviour, notably evident in thin-layer structures. Interestingly, the deconvolution of the absorption spectra revealed three bands in the red region. Insightful analysis of temperature-dependent absorption, excitation, and emission fluorescence spectra indicates the co-existence of monomer, dimer, and a higher aggregate forms, most likely a tetrameric structures. Moreover, such a complexity of molecular organisation of dyes appears already in the solution. Differences in spectral properties of the dyes studied are robustly visible in changes in the spectra of the air–water interface, where the dye with the branched side group changes the mutual orientation in dimeric structures, leading to the formation of H-type aggregates, which was observed as an almost 20-nm spectral blue shift during Langmuir layer compression. The results presented highlight the need for care in interpretation of the intensity ratio of DPP spectra and spectral shift as the sole determinants of the aggregation state.

Glass transition temperature of Agar-Reduced Graphene Oxide (RGO) Composites using 2-D contour mapping of temperature dependent FTIR spectra

In the present work, composites of Reduced Graphene Oxide (RGO) and Agar have been synthesized via the solution cast method and their structural, thermal and dielectric properties are studied. UV–Visible, X Ray Diffraction (XRD), Raman Spectroscopy and Fourier Transform Infrared (FTIR) have been employed for analyzing structural properties of the prepared samples. Analysis of different peaks in XRD and Raman Spectra suggests the interaction of RGO layers with Agar at the molecular level. FTIR spectra indicate that interaction of Agar with RGO occurs through hydrogen bonding linkage. Further, the Glass transition temperature (Tg) of prepared samples has been determined using 2D contour mapping from temperature-dependent FTIR spectra as well as from the Differential Scanning Calorimetry (DSC)technique. Values of Tg obtained from both techniques have been found in close agreement with each other. In addition to that, value of Tg of Agar increases from 72 °C to 80 °C as an effect of 2 wt.% RGO loading indicating the improvement in the thermal behavior of Agar. Moreover, the dielectric behavior of as-prepared composites demonstrate that the dielectric constant of these composites has been increased in comparison to pure Agar.

Solvatochromism mechanism of perylene diimide radicals stabilized by low barrier hydrogen bond and detection of formaldehyde in real food samples

Formaldehyde (FA) is widely used for food preservation and whitening because of its preservative and bleaching effects. Excessive FA seriously endangers human health, so monitoring FA-treated food is of great significance for food safety. In this paper, perylene diimide radicals with the chirality (BTFPDI) and water-solubility (TFPDI-bPEI) were designed respectively based on our previous studies. Property of solvatochromism induced by these perylene diimide radicals aggregation was demonstrated by the concentration and temperature dependent absorption spectrum and the circular dichroism spectrum. Further the colorimetric monitoring of trace FA in gaseous and liquid was realized by the condensation reaction of FA with amine to induce TFPDI-bPEI aggregation. After the addition of FA, TFPDI-bPEI molecule aggregated in aqueous solution due to the specific reaction of a large number of –NH2 groups with FA, resulting in a blue-shift of the maximum absorption peak from 780 nm to 561 nm, and the detection limit as low as 0.86 μM to FA and the response time of only 20 s. This method could further detect FA in food with good recoveries and detect FA in contaminated food samples.

Spectroscopic and Thermographic Qualities of Praseodymium-Doped Oxyfluorotellurite Glasses.

The thermal stability of oxyfluorotellurite glass systems, (65-x)TeO2-20ZnF2-12PbO-3Nb2O5-xPr2O3, doped with praseodymium was examined. The different concentrations of praseodymium oxide (x = 0.5 and 2 mol%) were applied to verify the thermal, optical and luminescence properties of the materials under study. The relatively high values of the Dietzel (ΔT) and Saad-Poulain (S or H') thermal stability factors determined using a differential thermal analysis (DTA) indicate the good thermal stability of the glass matrix, which gradually improves with the content of the active dopant. The temperature dependence of optical spectra in the temperature range 300-675 K for the VIS-NIR region was investigated. The involved Pr3+ optical transition intensities and relaxation dynamic of the praseodymium luminescent level were determined. The ultrashort femtosecond pulses were utilized to examine a dynamic relaxation of the praseodymium luminescent levels. Although the measured emission of the Pr3+ active ions in the studied glass encompasses the quite broad spectral region, the observed luminescence may only be attributed to 3PJ excited states. As a result, the observed decrease in the experimental lifetime for the 3P0 level along with the increasing activator content was identified as an intensification of the Pr-Pr interplay and the associated self-quenching process. The maximum relative sensitivities (Sr) estimated over a relatively wide temperature range are ~0.46% K-1 (at 300 K) for FIR (I530/I497) and 0.20% K-1 (at 600 K) for FIR (I630/I497), which seems to confirm the possibility of using investigated glasses in optical temperature sensors.

Luminescence and Energy Transfer Properties of Color-Tunable Dy3+, Eu3+ co-Activated NaGdSiO4 Phosphor for WLED with Great Thermo-Stability.

A series of NaGd1-x-ySiO4: y Dy3+-x Eu3+ phosphors were synthesized by a high-temperature solid-phase method. The optimal doping ion concentration of Dy3+ ions for this phosphor was determined to be 1 % from the emission spectra. The energy transfer between Dy3+ and Eu3+ ions at 351 nm was investigated by photoluminescence spectra and fluorescence decay curves. At the excitation wavelengths of 275 nm, 351 nm, 366 nm, and 394 nm, a change from yellow to white to red light can be realized by adjusting the doping concentration of Eu/Dy ions. Particularly, by testing the temperature-dependent fluorescence spectrum of the phosphor, it can be found that the luminous intensity of the phosphor is as high as 96 % when 394 nm excitation is employed at 413 K. It was the maximum at this temperature comparing with other phosphors as far as we know. The color coordinate values show that the NaGd1-x-ySiO4:×Dy3+-y Eu3+ phosphors are very close to the white light color coordinates (x=0.33, y=0.33) under 351 nm excitation. Meanwhile, the correlated color temperature is between 5062-7104 K. These results indicate that this phosphor is a promising candidate for high-quality WLED.

Chemical interaction between the sugar moieties in N, N-di-glycated alanine derivatives

The chemistry of N,N-diglycated amino acids remains unexplored due to their transient nature in the Maillard reaction. Their increased reactivity is attributed to the presence of high concentrations of open ring forms in at least one of their sugar moieties. The N,N-diglycated alanine derivatives were generated in situ via dissociation from their stable precursors the bis[N,N-diglycated alanine]iron(II) complexes, in the alanine/glucose/FeCl2 model system heated at 110 °C for 2 h. The thermal degradations of these complexes were followed in the reaction mixture, using isotope-labelled reactants, such as [13C-3] alanine and [13C–U] glucose, and ESI/qTOF/MS analysis. The N,N-diglycated amino acids exhibited a unique and characteristic chemical interaction between the neighbouring sugar moieties generating hitherto unknown heterocyclic moieties. The origin of these products was tracked by identifying ions incorporating one C-3 atom from alanine and between seven to 12 carbon atoms from the sugar moieties in the same structure. Temperature-dependent FTIR spectra of di-glycated alanine generated through ball milling provided further evidence for their reactivity.

Sustainable Composite Materials Based on Carnauba Wax and Montmorillonite Nanoclay for Energy Storage.

Sustainable composite materials, including carnauba wax, can store energy in the form of latent heat, and containing the wax may allow form-stable melting and crystallization cycles to be performed. Here, it is shown that carnauba wax in the molten state and the abundant nanoclay montmorillonite form stable composites with mass ratios of 50-70% (w/w). Transmission electron microscopy analysis reveals the inhomogeneous distribution of the nanoclay in the wax matrix. Analyses with infrared and multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy prove the chemical inertness of the composite materials during preparation. No new phases are formed according to studies with powder X-ray diffraction. The addition of the nanoclay increases the thermal conductivity and prevents the leakage of the phase change material, as well as reducing the time intervals of the cycle of accumulation and the return of heat. The latent heat increases in the row 69.5 ± 3.7 J/g, 95.0 ± 2.5 J/g, and 107.9 ± 1.7 J/g for the composite materials containing resp. 50%, 60% and 70% carnauba wax. Analysis of temperature-dependent 13C cross-polarization solid-state NMR spectra reveal the enhanced amorphization and altered molecular dynamics of the carnauba wax constituents in the composite materials. The amorphization also defines changes in the thermal transport mechanism in the composites compared to pure wax at elevated temperatures.

Confined Water Dynamics in the Scaffolds of Polylactic Acid.

Resorbable polylactic acid (PLA) ultrathin fibers have been applied as scaffolds for tissue engineering applications due to their micro- and nanoporous structure that favor cell adhesion, besides inducing cell proliferation and upregulating gene expression related to tissue regeneration. Incorporation of multiwalled carbon nanotubes into PLA fibers has been reported to increase the mechanical properties of the scaffold, making them even more suitable for tissue engineering applications. Ideally, scaffolds should be degraded simultaneously with tissue growth. Hydration and swelling are factors related to scaffold degradation. Hydration would negatively impact the mechanical properties since PLA shows hydrolytic degradation. Water absorption critically affects the catalysis and allowance of the hydrolysis reactions. Moreover, either mass transport and chemical reactions are influenced by confined water, which is an unexplored subject for PLA micro- and nanoporous fibers. Here, we probe and investigate confined water onto highly porous PLA microfibers containing few amounts of incorporated carbon nanotubes by Fourier transform infrared (FTIR) spectroscopy. A hydrostatic pressure was applied to the fibers to enhance the intermolecular interactions between water molecules and C=O groups from polyester bonds, which were evaluated over the wavenumber between 1600 and 2000 cm-1. The analysis of temperature dependence of FTIR spectra indicated the presence of confined water which is characterized by a non-Arrhenius to Arrhenius crossover at T0 = 190 K for 1716 and 1817 cm-1 carbonyl bands of PLA. These bands are sensitive to a hydrogen bond network of confined water. The relevance of our finding relies on the challenge detecting confined water in hydrophobic cavities as in the PLA one. To the best of our knowledge, we present the first report referring the presence of confined water in a hydrophobic scaffold as PLA for tissue engineering. Our findings can provide new opportunities to understand the role of confined water in tissue engineering applications. For instance, we argue that PLA degradation may be affected the most by confined water. PLA degradation involves hydrolytic and enzymatic degradation reactions, which can both be sensitive to changes in water properties.

THz spectroscopy on the amino acids L-serine and L-cysteine.

We present a detailed study on the temperature-dependent THz spectra of the polycrystalline amino acids, L-serine and L-cysteine, for wavenumbers from 20 to 120cm-1 and temperatures from 4 to 300K. Even though the structure of these two amino acids is very similar, with a sulfur atom in the side chain of cysteine instead of an oxygen atom in serine, the excitation spectra are drastically different. Obviously, the vibrational dynamics strongly depend on the ability of cysteine to form sulfur-hydrogen bonds. In addition, cysteine undergoes an order-disorder type phase transition close to 80K, documented by additional specific heat experiments, with accompanying anomalies in the THz results. On increasing temperatures, well-defined vibrational excitations exhibit significant shifts in the eigenfrequencies with concomitant line-broadening yielding partly overlapping modes. Interestingly, several modes completely lose all their dipolar strength and are unobservable under ambient conditions. Comparing the recent results to the published work utilizing THz, Raman, and neutron-scattering techniques, as well as with abinitio simulations, we aim at a consistent analysis of the results ascribing certain eigenfrequencies to distinct collective lattice modes. We document that THz spectra can be used to fine-tune the parameters of model calculations and as fingerprint properties of certain amino acids. In addition, we analyzed the low-temperature heat capacity of both the compounds and detected strong excess contributions compared to the canonical Debye behavior of crystalline solids, indicating soft excitations and a strongly enhanced phonon-density of states at low frequencies.

Ultrabroad distribution of multiple anelasticities in O-doped refractory multiprincipal element alloys

The Snoek anelastic internal friction (IF) peak due to stress-induced dipole ordering associated with interstitial atoms was well observed in IF curves of single-principal element alloys (SPEAs) as early as in the 1950s, however, its behavior remains elusive in multi-principal element alloys (MPEAs) to date. Here the temperature-dependent IF spectra of NbTiV0.5Zr refractory MPEAs with varying O contents were presented, and the analysis of these data indicates that for O-doped NbTiV0.5Zr MPEAs, the O addition triggers two anelastic IF peaks (the PO1 and PO2), corresponding to the O-Snoek-type relaxation in random solid solution (RSS) and local chemical ordering (LCO) structures, respectively. The half-peak width of the PO1 is 2–3 times broader than that for SPEAs, associated with the wide O migration energy barrier distribution in MPEAs. These phenomena show a striking contrast to the single and narrow Snoek-type peak observed for SPEAs. Our analysis further reveals an approximate linear correlation between the half-peak width of the Snoek-type peak and the mixing entropy. The introduction of O also shifts grain boundary relaxation peaks (PG) towards higher temperatures. Interestingly, high-temperature anomalous modulus changes were observed for the first time in TiV-based lightweight refractory MPEAs, which is suggested to be originated from the order reduction of the body-centered cubic (bcc) structure at elevated temperatures. Moreover, the 1 at.%O doped NbTiV0.5Zr MPEA with a favorable balance between the peak heights of the PO2 and PG, exhibits outstanding specific yield stress (SYS) among refractory MPEAs while maintaining an elongation as high as 20 %. This work provides not only a bridge between the anelastic behavior of SPEAs and MPEAs for upcoming studies and theories concerning bcc MPEAs with interstitial atoms, but contributes to the holistic design of bcc MPEAs with high strength and excellent ductility.

Photophysics of Benzoxazole and Dicyano Functionalised Diketopyrrolopyrrole Derivatives: Insights into Ultrafast Processes and the Triplet State.

Diketopyrrolopyrrole (DPP) functionalised with an electron donating unit acts as a donor-acceptor molecules that have shown potential for application in dyes and photovoltaics. These molecules offer broad absorption/emission properties and structure-dependent dynamics. In this study, we used femtosecond pump-probe spectroscopy to investigate the photo-initiated dynamics of thiophene linked DPP derivatives. The thio-DPPs are further functionalised by different electrons withdrawing terminal groups, namely benzoxazole and thiophene dicyanide. The benzoxazole derivative is strongly emissive and directly relaxes directly to the ground state chloroform solution. Thiophene dicyanide derivative exhibits distinct spectral evolution in the first 10 ps, associated with structural and vibronic process. Later, it crosses over to the triplet state with a yield of 20 %. In the solid-state (thin film), we observed a signal that resembles singlet fission. However, upon careful analysis of temperature-dependent steady state absorbance spectra, we conclude that these features are due to laser-induced thermal artifacts. We describe a simplified excited state evolution in the thin film that does not include any additional excited states. These findings have significant implications for the analysis of triplet formation, which plays a major role in the photophysics of many organic materials.

Bisphenol a modification and how its structure influences human serum albumin binding force

Bisphenol A (BPA) is an environmental hormone with substantial physiological toxicity to the human body. Three electron-withdrawing derivatives of BPA are synthesized in this study to reduce its toxicity. The interaction mechanism between BPA and its three derivatives with human serum albumin (HSA) is investigated using molecular docking, electrochemistry, circular dichroism spectrum analysis, and fluorescence spectroscopy. Temperature-dependent tests and time-resolved fluorescence spectra reveal that all four compounds dynamically quench the internal fluorescence of HSA. Based on molecular docking and site competition outcomes, four compounds are primarily bound to site I's active pocket. Thermodynamic parameters indicate that the compounds’ interaction with HSA is spontaneous, and introducing weak electron-withdrawing groups changes the action force. Circular dichroism and synchronous fluorescence measurements suggest four compounds impact HSA's structure. The substituents' electron attraction capacity determines their impact. Electrochemical studies examine the effect of electron-absorbing groups on the BPA and HSA binding capacity. Pharmacokinetics showed that nitro-substituted BPA may be a potential superior substitute for BPA. These results indicate crucial practical value, providing theoretical support for future research.

Cr3+ doped Cs2ZnCl4 microcrystals enabling near-infrared emission

As a promising lead-free metal halide, Cs2ZnCl4 has the potential to serve as a host for achieving various photoluminescence emissions with different colors through ion doping. Therefore, studying the optical properties of various ions doped into Cs2ZnCl4 with tetrahedron coordination is of great significance. However, there is still a lack of research on near-infrared (NIR) emission in Cs2ZnCl4. In this study, we successfully synthesized Cs2ZnCl4:Cr3+ crystals using a simple hydrothermal method. The Cs2ZnCl4:Cr3+ exhibits luminescence in the range of 800–1300 nm, with a peak position at 915 nm and a full width at half maximum (FWHM) of 150 nm under 375 nm excitation. Through the analysis of photoluminescence spectra, density functional theory (DFT), lifetime decay curves, temperature-dependent spectra, and time-resolved photoluminescence (TRPL), we confirmed the presence of two potential sites for Cr3+ ion occupancy. Additionally, NIR phosphor-converted light-emitting diodes (pc-LEDs) were fabricated by combining Cs2ZnCl4:Cr3+ with a green LED chip. The night-vision camera captured the distribution of blood vessels and bones in the fingers, demonstrating the promising potential of this material in the field of NIR imaging.

Investigation of hydrogen bonds in proton transfer complexes derived from the reaction of 2- and 4-(N,N-dimethylamino)pyridines with chloranilic acid

New complexes of 2-(N,N-dimethylamino)pyridine with chloranilic acid (2-DMAP + CLA) and 4-(N,N-dimethylamino)pyridine with chloranilic acid (4-DMAP + CLA) were synthesized and characterized by single crystal X-ray diffraction, infrared spectroscopy, thermal analysis methods and 1H, 13C and 15N NMR spectroscopy. The NMR spectroscopies were carried out in both, DMSO solution and in the solid state (CPMAS NMR). The 2-DMAP + CLA and 4-DMAP + CLA complexes crystallize in centrosymmetric P-1 and P21/c space group, respectively.In both complexes, the phenomenon of proton transfer is observed, which results in the formation of strong N+–H···O– hydrogen bonds. Thermal decompositions of 2-DMAP + CLA and 4-DMAP + CLA complexes were studied by thermogravimetric analysis. Temperature dependent IR spectra revealed that methyl groups of 4-DMAP + CLA perform fast stochastic reorientational motion at room temperature which is slowed on cooling while in 2-DMAP + CLA reonrientational motion of CH3 groups is much slower due to steric effects.

Exploring potential of quantum dots for high power solid-state lighting protected by transparent ceramics

When quantum dot diffusion plates (QDDPs) are used as phosphor conversion materials for high-power lighting, transparent ceramics (TCs) can be used to prevent thermal damage of QDDPs. The spectral, suitable for diverse lighting environments, can be precisely calibrated by modifying their ratio. The temperature dependent photoluminescence spectra, fluorescence lifetime, Huang Rhys factor and activation energy of TCs were studied in detail. It was evident from the results that the intensity of TCs remained above 89% even at 423 K, while fluorescence lifetime remained stable, nearly 64 ns. Huang-Rhys factor and activation energy were consistently measured at 1.81 and 0.13 eV, respectively. The extraordinary luminescent stability of TCs revealed their integral role in providing reliable protection for QDDPs. The spectra of LEDs/LDs were successfully predicted using Monte Carlo ray tracing method. The service condition under high-energy laser was studied using finite element method. White light with Commission Internationale de l'Eclairage (CIE) of (0.38, 0.39) and (0.31, 0.34) and luminous efficiency of 58 and 150 lm/W were prepared by combining QDDPs/TCs with LEDs/LDs, and the Color Rendering Index (CRI) reached a remarkable 88.4 and 78.8. A detailed exploration of the proficient thermal management was accomplished using finite element analysis, with the simulated outcomes matching closely with the experimental results.

Temperature and density dependence of Kr L-shell spectrum in hot dense plasmas

Kr L-shell spectroscopy modeling results are discussed in this paper, focusing on the n = 4 to n = 2 line transitions of Be- and Li-like Kr ions. Collisional radiative atomic kinetic and Stark-broadened spectral line shape calculations show electron temperature Te and density ne sensitivity in the spectrum. The combination of the Te dependence due to the relative intensity of Be-like to Li-like line emissions in the range from 1.5 to 3 keV and the ne sensitivity from the Stark broadening effect on the line shapes in the range from 5×1023 to 2×1024/ cc results in a spectrum that can be employed to diagnose Te and ne. Two different collisional radiative atomic kinetic models i.e., Prismspect [J. J. MacFarlane, et al., Int. Fusion Sci. Appl. Conf. Proc. 457 (2003)] and ABAKO [Florido, et al., PRE, 80, 056402 (2009)] produce similar results in level populations and spectra. In x-ray spectroscopy of implosion cores, this Kr L-shell spectrum may prove useful in an intermediate Te range in which Ar is too ionized for its K-shell to be of diagnostic value and Kr is not ionized enough for its K-shell emission to be useful.

Interrupting the long-range energy migration among Eu3+ by the introduction of unequivalent [NaO8] units to achieve both high quenching concentration and quantum yield in NaY2Ga2InGe2O12

In the pursuit of optimizing white light-emitting diodes (WLEDs), Eu3+-doped phosphors have emerged as a key component in strategies that combine ultraviolet (UV) LED chips with red, green, and blue (RGB) tricolor phosphors. However, their application has been notably constrained by concentration quenching and thermal quenching. To address this challenge, we have developed a series of novel red phosphors, NaY2-xGa2InGe2O12:xEu3+. The powder X-ray diffraction (XRD) indicates that the NaY2Ga2InGe2O12(NYGIG) belongs to the garnet family. The [NaO8] unit replaces one-third of the eight-coordinated sites of garnet and leaves the other two-thirds for the [YO8], which helps to prevent long-range energy migration among Eu3+ especially when the eight-coordinated sites were highly substituted. Such a structure feature allowed the NaY2-xGa2InGe2O12:xEu3+ phosphor to achieve an optimal quantum yield of 95.6% at an extremely high Eu3+ doping x value up to 1.2. Moreover, further studies on the temperature-dependent luminescence spectra confirm that an anomalous thermal quenching phenomenon will occur when the NaY2-xGa2InGe2O12:1.2Eu3+ phosphor is properly excited. In application, the combination of the red-emitting NaY2-xGa2InGe2O12:1.2Eu3+, blue-emitting BaMgAl10O17:Eu2+, and green-emitting Zn2SiO4:Mn2+ phosphors can realize high color rendering (CRI∼93) white light with the with CIE coordinates of (0.353,0.350), indicating that the NYGIG:Eu3+ phosphor own a promising potential for WLEDs.