Enhancement Of Emission Intensity Research Articles

Cyclometalated Iridium(III) Complex with Substituted Benzimidazole: pH Directed Organelle-Specific Localization Within Lysosome.

We report the synthesis and pH dependent emission spectral behaviour of four emissive iridium(III) complexes (Ir1-Ir4) with two isomeric pairs of bis-trifluoromethyl appended benzimidazole ligands. The imidazolyl hydrogen(N-H) has been replaced by phenyl groups (N-Ph) in two ligands to understand the impact of hydrogen bonding on the photophysical properties of the complexes and it indeed plays interesting role in the charge-transfer dynamics. The pH dependent electronic spectral change is observed for two of the complexes. The enhancement of emission intensity is observed at different wavelength for pH<7 and pH>7 for Ir1 and Ir3. The emission sensing of biogenic amines with pka values ranging from 5.80-9.74 is reported along with cellular imaging. The complex Ir1 specifically localizes within lysosome (pH=4.5-5) and thus image this organelle with great precision. The detail electronic spectra and electrochemical behaviour were reported here along with TDDFT results.

Scanning Acousto-Optoelectric Spectroscopy on a Transition Metal Dichalcogenide Monolayer.

The charge carrier dynamics are investigated by surface acoustic waves (SAWs) inside a WSe2 monolayer on LiNbO3 by scanning acousto-optoelectric spectroscopy. A strong enhancement of the PL emission intensity is observed almost over the entire area of the flake. This enhancement increases with increasing amplitude of the wave and is especially strong at or in the vicinity to defects. The latter is attributed to the SAW-driven Poole-Frenkel activation of trapped charge carriers bound to trapping sites at these defects. In addition, the PL intensity exhibit clear periodic modulations at the SAW's frequencyfSAW and at 2 fSAW. These modulations are clear and unambiguous fingerprints of spatio-temporal carrier dynamics driven by the SAW. These occur on sub-nanosecond timescales which are found in good agreement with calculated exciton dissociation times. Mapping and analyzing both effects, this study shows that scanning acousto-electric spectroscopy provides a highly sensitive and local contact-free probe which uncovers distinct local features not resolved by conventional quasi-static photoluminescence techniques. The method is ideally suited to study carrier transport in 2D and other types of nanoscale materials and to reveal dynamic exciton modulation, and carrier localization and activation dynamics in the technologically important megahertz to gigahertz frequency range.

Leveraging photosensitive and thermally stable luminescent Ba2ZnWO6:Eu3+, M+ (M+= Na, K , and Li) nanophosphor for targeted non-invasive and stain-free visualization of cracked tooth syndrome

The cracked tooth syndrome poses a significant challenge in dentistry, thereafter untreated cases often lead to severe complications, such as pulpitis or complete tooth fracture, ultimately contributing to tooth loss. However, the conventional diagnostic methods to visualize microcracks in the tooth suffer from severe drawbacks, such as inaccurate cold stimulation, discomfort with probing, impractical staining techniques, and difficulty in distinguishing harmless craze lines from pathological cracks. To address this challenge, for the first time, we are proposing a novel approach by utilizing luminescent Ba2ZnWO6:Eu3+ (3 mol %), K+ (1 wt %) nanophosphor for improved imaging and diagnosis of cracked tooth syndrome. Herein, the double perovskite structured Ba2ZnWO6:Eu3+ (1–11 mol %), M+ (M+ = Na, K, and Li (1 wt %)) nanophosphors were synthesized via the sonochemical route. The photoluminescence emission spectra of the prepared Ba2ZnWO6:Eu3+ (1–11 mol %) nanophosphors displaying distinct peaks at 583, 595, 613, 662, and 720 nm, which ascribed to transitions from state 5D0 to 7FJ (J = 1–4) state of the Eu3+ ions, respectively. By adopting a strategic charge compensation mechanism, the enhancement in the luminescence emission intensity of about 1.5-fold was achieved after co-doping K+ (1 wt %) with Ba2ZnWO6:Eu3+ (3 mol %) nanophosphor. The photometric studies of the phosphors portray their orange-red emission with excellent quantum efficiency (82.52 %), and color purity (∼ 99 %). The emission intensity was sustained up to 73.71 % at 473 K, indicating excellent thermal stability of the phosphor. The in vitro cytotoxicity assessments of the optimized nanophosphor demonstrated its biocompatibility on normal non-malignant oral fibroblasts. The visualized microcracks in the tooth using optimized Ba2ZnWO6:Eu3+ (3 mol %), K+ (1 wt %) nanophosphor under UV excitation of UV 365 and 395 nm light revealed the orientation of microcracks, crack width, depth of the crack, and microcrack branching without any stain. The aforementioned results demonstrated that the proposed methodology paves the way for a new avenue in dental imaging technology with the potential to revolutionize and improve patient care outcomes.

Qualitative Identification of the Spin‐to‐Orbital Conversion Mechanism Modulated by Rare‐Earth Nd, Gd, and Ho Metals via Terahertz Emission Measurements

AbstractIt is crucial to study the materials that could effectively facilitate the inter‐conversion between charge, spin, and orbital degrees of freedom. In this work, the conversion among these three types of degrees of freedom in Pt/CoFeB/rare‐earth (RE, represents Nd, Gd, and Ho)/Ti multilayers is manipulated. Through terahertz (THz) emission measurements, it is found that the spin current induced by a femtosecond laser is converted into an orbital current via the spin‐orbit coupling of the RE layer. Notably, the light RE (Nd) and heavy RE (Gd and Ho) induce the orbital current with opposite polarization directions, ultimately leading to a weakening or enhancement of the THz emission intensity, respectively. Moreover, the fast Fourier transform reveals that Gd exerts the most significant influence on increasing the whole THz spectrum within the Pt/CoFeB/RE/Ti structure. The findings of RE‐modulated spin‐to‐orbital conversion provide valuable insights into the fundamental transport mechanism of the orbital current.

Cu34S6(PFBT)22(PPh3)6: A Cu12S6 Core‐Based Nanocluster with Long‐Lived Phosphorescent Crystallization‐Induced Emission Enhancement for Selectively Acetonitrile Sensing

AbstractAtomically precise copper nanoclusters with crystallization‐induced emission enhancement (CIEE) have garnered significant academic interests‐ but the rational design of high‐nuclearity Cu nanoaggregates with precise atomic structures and the CIEE effect remains a long‐standing challenge. Herein, a new atomically precise copper nanocluster co‐protected by thiolate, phosphine, and S2− ligands, formulated as Cu34S6(PFBT)22(PPh3)6 (Cu34, PFBT = pentafluorobenzenethiol, PPh3 = triphenylphosphine), is reported, which possesses a typical Cu12S6 core and a Cu22S22P6 shell. Under photoexcitation at 505 nm, Cu34 exhibits strong red‐light emission with a photoluminescence quantum yield of 4.1%. DFT calculations confirm that the emission stems from the ligand‐to‐metal charge transfer (LMCT) transition. This nanoaggregate shows a strong CIEE effect, with the crystalline form exhibiting an 800‐fold enhancement in emission intensity compared to its solution form. An in‐depth structural investigation of the ligand shell reveals that the extensive C−H···F, C−H···π, and π···π interactions significantly restrict the intra‐ and inter‐molecular rotations and vibrations, accounting for the CIEE phenomena. The red emission of Cu34 can be selectively quenched by CH3CN, with a lower detection limit of 9.36 µM (0.38 ppm). This study advances the development of high‐nuclearity copper nanocluster with the CIEE effect and holds significant potential for applications in selectively sensing volatile organic compounds (VOCs).

Fantastic Photons and Where to Excite Them: Revolutionizing Upconversion with KY3F10-Based Compounds

This review delves into the forefront of upconversion luminescence (UCL) research, focusing on KY3F10-based compounds, particularly their cubic α-phase. These materials are renowned for their exceptional luminescent properties and structural stability, making them prime candidates for advanced photonic applications. The synthesis methods and structural characteristics of the existing works in the literature are meticulously analyzed alongside the transformative effects of various doping strategies on UCL efficiency. Incorporating rare earth (RE) sensitizer ions such as Yb3+, along with activator ions like Er3+, Ho3+, Nd3+, or Tm3+, researchers have achieved remarkable enhancements in emission intensity and spectral control. Recent and past breakthroughs in understanding the local structure and phase transitions of single-, double-, and triple-RE3+-doped KY3F10 nanocrystals are highlighted, revealing their pivotal role in fine-tuning luminescent properties. Furthermore, the review underscores the untapped potential of lesser-known crystal structures, such as the metastable δ-phase of KY3F10, which offers promising avenues for future exploration. By presenting a comprehensive analysis and proposing innovative research directions, this review aims to inspire continued advancements in the field of upconversion materials, unlocking new potentials in photonic technologies.

Thiazole-derived pyrazin-2-carbohydrazide chemosensors: Colorimetric & photoluminescent detection of silver ions for theoretical, environmental, and cell imaging

In this work, a simple and versatile chemosensor receptor TZPYZ was synthesized through the combination of thiazole with pyrazine-2-carbohydrazide, resulting in a confirmed chemical structure via various analytical techniques including FT-IR, 1H, and 13C Nuclear Magnetic Resonance Spectroscopy, as well as High-Resolution Mass Spectroscopy analysis. TZPYZ exhibits specific colorimetric and photoluminescent responses to Ag+ ions in a solvent solution consisting of DMSO and H2O (7:3, v/v). Upon addition of Ag+ ions, noticeable changes in absorption spectra occur, resulting in a visible color change from pale yellow to blue. Additionally, an enhanced emission intensity with wavelength at 523 nm, when excited at 410 nm. Notably, TZPYZ demonstrated exceptional selectivity for Ag+ ions over other metal cations, achieving a detection limit (LOD) of 10.6 × 10−9 M and 6.74 × 10−9 M and using the UV–visible & photoluminescent titration method. Interference studies indicated minimal disruption from other metal ions on emission at 523 nm, highlighting TZPYZ discerning capability for Ag+ ions. With a binding affinity of 3.622 × 10−11 M−1, TZPYZ proved effective in detecting Ag+ ions across various water samples, showcasing its practical utility. The mechanism of interaction between TZPYZ and Ag+ ions was investigated using various experimental techniques, including Job’s plot, Benesi-Hildebrand investigations, 1H NMR, and HRMS analysis. Test strips coated with TZPYZ showed selective detection of Ag+ ions, indicating its potential for on-site applications. Furthermore, DFT computations provided insights into the structural and electronic properties of TZPYZ and its complex with Ag+ ions, further elucidating the binding mechanism and stability of the complex. In addition, TZPYZ demonstrated compatibility with biological systems, as fluorescence imaging tests on MCF-7 breast cancer cells confirmed both its non-cytotoxic nature and its proficiency in detecting intracellular silver ions. Based on these findings, TZPYZ is highlighted as a highly sensitive and selective chemosensor for Ag+ ions, with promising applications in environmental analysis and bioimaging.

Sustainable synthesis of fluorescent polymercarbon dots@PVA for sensitive chlortetracycline detection.

Antibiotic residues persist in the environment and represent serious health hazards; thus, it is important to develop sensitive and effective detection techniques. This paper presents a bio-inspired way to make water-soluble fluorescent polymer carbon dots (PCDs@PVA) by heating biomass precursors and polyvinyl alcohol (PVA) together. For example, the synthesized PCDs@PVA are very stable with enhanced emission intensity. This property was observed in a wide range of environmental conditions, including those with changing temperatures, pH levels, UV light, and ionic strength. PCDs@PVA detected the antibiotic chlortetracycline (CTCs) with great selectivity against structurally related compounds and a low detection limit of 20 nM, demonstrating outstanding sensitivity and specificity. We confirmed the sensor's practical application through real sample analysis, yielding recovery rates of 98%-99% in samples of milk, honey, and river water. The synthesized PCDs@PVA fluorescence sensor was successfully used for CTCs detection in real samples.

Boltzmann thermometry: Eu3+-doped monoclinic Y2O3 and Y2O3@SiO2 nanoparticles

During last decade optical thermometry has gained considerable attention due to the possibility to determine temperature remotely in cases when traditional contact methods fail. The most widespread type of optical temperature sensors is based on monitoring luminescence intensity ratio between transition originated from thermally coupled energy levels. Eu3+ ions own the largest energy gap between thermally coupled 5D1 and 5D0 energy levels among all lanthanides, which guarantees a high thermal sensitivity of Boltzmann-type thermometry. Here, uncoated m-Y2O3:Eu3+ and core-shell m-Y2O3:Eu3+@SiO2 nanophosphors have been successfully utilized as ratiometric thermal sensors within the 298–873 K range. It was shown that the calculation method (integral or peak intensities) only slightly affects thermal sensitivity. SiO2 coating significantly enhances emission intensity and increases lifetime, but has no noticeable effect on thermal sensitivity. m-Y2O3:Eu3+ nanophosphor has the best thermometric characteristics of Sr = 0.96 % K-1 at 373K and δT = 0.5 K.

Design and photophysical characterization of dinuclear lanthanide complexes incorporating spacer ligands along with their mononuclear analogues: A comparative study

Two heteroleptic homo-dinuclear complexes of Dy(III) and Sm(III) with pyrazine (pyz) as spacer ligand [Ln(TFPB)3(μ-pyz)Ln(TFPB)3], along with their mononuclear analogue [Ln(TFPB)3(pyz)2] were synthesized and characterized. Diketone TFPB (4,4,4-trifluoro-1-phenyl-1,3-butanedione) was incorporated as main ligand. NMR analysis depicted single peak for pyz protons for dinuclear complexes and two for mononuclear ones, which confirmed the bridging nature of pyz in former complexes. UV spectra revealed two absorption bands despite of the different metal ion and nuclearity of complex, suggesting the absorption of UV-radiation by coordinated moieties inspite of the metal ion involved. The emission spectra exhibited significant intensity of yellow and orange-red peaks for Dy(III) and Sm(III) complexes, respectively, indicating effective sensitization of metal center. The enhanced emission intensity observed in dinuclear Sm-complexes, compared to their mononuclear counterparts, indicates a synergistic effect of the two metal ions on the overall emission properties, rather than a mere additive effect that would be expected from two independent mononuclear units. The photoluminescent properties of synthesized complexes were examined and discussed, suggesting potential applications in display devices. The Correlated Color Temperature (CCT) of these complexes falls within a range suitable for warm light sources and the highest branching ratio observed for 4G5/2 → 6H9/2 (for Sm3+ ion) and 4F9/2 → 6H13/2 (for Dy3+ ion) transitions suggests potential application in laser amplification. The alignment between band gap measurements obtained from UV and CV analyses highlight the possibility of employing these complexes in semiconductor technologies.

Carbon dot enhanced electrodeposited coatings for advanced early-stage corrosion sensing

This work explores a novel approach for metal corrosion by integrating carbon dots (CDs) into electrodeposited (ED) coatings. We detail the synthesis and properties of CDs, making them suitable for corrosion detection. Characterization techniques like Fourier Transform Infrared Spectroscopy (FTIR), Scanning electron microscope (SEM), Energy Dispersive X-ray Analysis (EDX), Fluorescent Microscopy and Photoluminescence Spectroscopy (PL).A Design of Experiment (DOE) optimized parameters like CD concentration, curing temperature, and voltage for improved coating performance. The optimized conditions (0.4 wt% M-CDots, 165 °C curing, and 36.2 V) resulted in enhanced adhesion and corrosion resistance.CD-infused coatings demonstrated superior adhesion and mechanical stability compared to controls. Electrochemical tests confirmed a 10 % improvement in corrosion resistance and PL study demonstrated an approximately 60 % enhancement in emission intensity. The adhesion was not affected by introducing carbon dots to the coating. Monitoring the onset of metal corrosion on samples in salt spray cabinets was achieved through the use of a UV source. The photoluminescence of M-CDs offered real-time, non-destructive monitoring of early-stage corrosion through quenching in the presence of exposed metal surfaces.This research presents a significant advancement by integrating CD-based sensing into corrosion-resistant coatings, holding promise for various industries and leading to improved safety, reduced maintenance costs, and extended equipment lifespans. Notably, the biocompatible and disposable nature of CD-based sensors further enhances their practical application.

Amplified spontaneous emission in β-In2S3–Ag based SQD-MNP superstructures with switching photoluminescence and enhanced photocatalytic activity

Optically modified MNPs coupled with SQDs (super structures) demonstrating tunable emission and enhanced photocatalytic activity are synthesized through homogeneous nucleation of indium chloride, thioacetamide and silver nitrate. Ag nanospheres (1–15 nm) are embedded in the matrix of β-In2S3 quantum dots. Modification of the absorption profile and shift in excitonic binding energy from 3.60 eV to 3.25 eV occurs due to plasmon mediated indirect columbic interaction between the SQDs. Raman spectrum of β-In2S3 (1:1)-Ag Nanohybrids (NHs) shows asymmetric line-shape broadening due to the fano-interaction (electron-phonon interaction) of the triply degenerate F2g mode of SQDs with a continuum of plasmon excitations. The emission spectra of the quantum dots, with significant peak shifting and enhanced intensity, indicates stronger coupling between the SQDs and MNPs. In the proximity of Ag NPs, the defect emission due to IIn (∼708 nm) is completely quenched, and an enhanced blue emission occurs at ∼ 496 nm. Further with increase in pump beam energy, there is a gradual peak maxima shift, spectral distortion, narrowing of emission profile and enhancement in emission intensity, which is attributed to amplified spontaneous emission assisted amplification in the gain media (SQDs). Measurement of photocatalytic efficiency for irradiation of 60 min (400 nm–700 nm) with β-In2S3 (1:1) QDs-Ag NHs as photocatalyst, prompted 100 % degradation while pure β-In2S3 (1:1) QDs as photocatalyst material could attain 98.6 % degradation only after 280 min of irradiation.

Synthesis and luminescence properties of Eu3+-activated Mg3(PO4)2 phosphors and substitution of phosphate with molybdate, tungstate and sulphate

In the present work, trivalent europium (Eu3+) ion activated Mg3(PO4)2 red phosphors have been synthesized through solid-state reaction method. X-ray diffraction (XRD) confirmed the successful formation of Mg3(PO4)2:Eu3+ phosphors with monoclinic phase with space group P21/c (14). The photoluminescence (PL) spectroscopy was used to record the excitation and emission spectrum of Eu3+ activated Mg3(PO4)2 phosphor. Under the excitation of 395 nm, the resultant samples exhibited the characteristic emissions of Eu3+ ions corresponding to the 5D0 → 7FJ transitions. The optimal doping concentration of Eu3+ ions was determined to be 0.5 mol%. The Commission Internationale de l'Eclairage (CIE) coordinates of Eu3+ activated Mg3(PO4)2 phosphor is calculated, which shows strong red emission. In addition, phosphate group replaced with molybdate, tungstate and sulfate group and found enhancement in emission intensity of prepared phosphors. The obtained results demonstrated that the Eu3+-activated Mg3(PO4)2 phosphors are very appropriate red-emitting phosphors for applications in near-ultraviolet-excited white Light emitting diodes (LEDs).

Photoluminescence Study of Undoped and Eu-Doped Alkali-Niobate Aluminosilicate Glasses and Glass-Ceramics.

In this study, the photoluminescence (PL) behavior of two aluminosilicate glass series containing alkali-niobates ranging from 0.4 to 20 mol% was investigated. The glasses exhibit an intense visible emission centered at ~18,400 cm-1 for the peralkaline series and at higher energies (~19,300 cm-1) for the metaluminous glasses. However, the photoluminescence emission intensity varies significantly with the niobate content and the bulk chemistry. PL and fluorescence lifetime measurements indicate that the broad emission bands result from the overlap of different niobate populations, whose distribution changes with niobate content. The distinct PL behavior in the two glass series was related to the structural evolution of the niobate units upon niobium addition. An enhancement of the visible emission was observed for a higher fraction of distorted [NbO6] units. Eu-doping was carried out as a structural probe of the glass network, and also to determine if these glasses could be used as potential rare earth element (REE) activators. The crystal field strength around Eu ions is strongly dependent on the bulk chemistry and the niobate content. Furthermore, the peralkaline series showed energy transfer from the host [NbO6] to Eu3+, confirming the feasibility of exploring niobate glasses and glass-ceramics as lanthanide ion-activated luminescent materials. In addition, glass-ceramics (GCs) containing alkali-niobate phases with a perovskite-like structure were developed and studied to verify the optical performance of these materials. It was verified that the bulk chemistry influences crystallization behavior, and also the photoluminescence response. The transparent GC from the metaluminous series exhibits a quenching of the Eu3+ emission, whereas an enhanced emission intensity is observed for the peralkaline GC. The latter shows a strong excitation-dependent PL emission, suggesting energy transfer and migration of electronic excitation from one Eu population to another. Additionally, Eu3+ emissions arising from the D15 and D25 excited states were observed, highlighting the low phonon energy achievable in niobo-aluminosilicate hosts.

Excitonic Thermalization Bottleneck in Twisted TMD Heterostructures.

Twisted van der Waals heterostructures show intriguing interface exciton physics, including hybridization effects and emergence of moiré potentials. Recent experiments have revealed that moiré-trapped excitons exhibit remarkable dynamics, where excited states show lifetimes that are several orders of magnitude longer than in monolayers. The origin of this behavior is still under debate. Based on a microscopic many-particle approach, we investigate the phonon-driven relaxation cascade of nonequilibrium moiré excitons in the exemplary MoSe2-WSe2 heterostructure. We track exciton relaxation pathways across different moiré mini-bands and identify the phonon-scattering channels assisting the spatial redistribution of excitons into low-energy pockets of the moiré potential. We unravel a phonon bottleneck in the flat band structure at low twist angles preventing excitons from fully thermalizing into the lowest state, explaining the measured enhanced emission intensity and lifetime of excited moiré excitons. Overall, our work provides important insights into exciton relaxation dynamics in flat-band exciton materials.

Magnetic emission intensity enhancement for amorphous alloys by constructing a multi-phase structure with α-Fe nanocrystals

Magnetic emission intensity enhancement for amorphous alloys by constructing a multi-phase structure with α-Fe nanocrystals

From Fluorescence-Transfer-Lightening-Printing-Assisted Conductive Adhesive Nanocomposite Hydrogels toward Wearable Interactive Optical Information-Electronic Strain Sensors.

The interactive flexible device, which monitors the human motion in optical and electrical synergistic modes, has attracted growing attention recently. The incorporation of information attribute within the optical signal is deemed advantageous for improving the interactive efficiency. Therefore, the development of wearable optical information-electronic strain sensors holds substantial promise, but integrating and synergizing various functions and realizing strain-mediated information transformation keep challenging. Herein, an amylopectin (AP) modified nanoclay/polyacrylamide-based nanocomposite (NC) hydrogel and an aggregation-induced-emission-active ink are fabricated. Through the fluorescence-transfer printing of the ink onto the hydrogel film in different strains with nested multiple symbolic information, a wearable interactive fluorescent information-electronic strain sensor is developed. In the sensor, the nanoclay plays a synergistic "one-stone-three-birds" role, contributing to "lightening" fluorescence (≈80 times emission intensity enhancement), ionic conductivity, and excellent stretchability (>1000%). The sensor has high biocompatibility, resilience (elastic recovery ratio: 97.8%), and strain sensitivity (gauge factor (GF): 10.9). Additionally, the AP endows the sensor with skin adhesiveness. The sensor can achieve electrical monitoring of human joint movements while displaying interactive fluorescent information transformation. This research poses an efficient strategy to develop multifunctional materials and provides a general platform for achieving next-generation interactive devices with prospective applications in wearable devices, human-machine interfaces, and artificial intelligence.

Benzocoumarin‐Fused Triskelions Exhibit AIEE Due to Inhibited Molecular Inversion

AbstractDeveloping aggregation‐induced emission luminogens (AIEgens) is a unique strategy for alleviating concentration quenching of π‐conjugated organic compounds. This AIE behaviour can be induced not only in organic dyes with rotors but also in invertible π‐conjugated systems. Herein, intramolecular Ullmann coupling was used to synthesize π‐twisted triskelion‐shaped AIEgens (2F, 2G, and 2H), in which benzo[f], [g], and [h] coumarins were fused into the benzene core to form a helical propeller shape. These structural isomers had unique molecular thicknesses and planarities depending on the fusion mode of the benzocoumarin. The racemic crystals, PPP and MMM, had different overlapping molecular configurations because of their twisted molecular frameworks. Compounds 2F, 2G and 2H demonstrated weak fluorescence emission in diluted solutions resulting from molecular motions caused by the isomerization process during molecular inversion. By comparison, aggregates exhibited enhanced emission intensity. These π‐twisted triskelions exhibited the characteristics of AIEgens.

EMM EMUS Observations of Hot Oxygen Corona at Mars: Radial Distribution and Temporal Variability

AbstractWe present the first observations of the dayside coronal oxygen emission in far ultraviolet (FUV) measured by the Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM). The high sensitivity of EMUS is providing an opportunity to observe the tenuous oxygen corona in FUV, which is otherwise difficult to observe. Oxygen resonance fluorescence emission at 130.4 nm provides a measurement of the upper atmospheric and exospheric oxygen. More than 500 oxygen corona profiles are constructed using the long–exposure time cross–exospheric mode (OS4) of EMUS observations. These profiles range from ∼200 km altitude up to several Mars radii (&gt;6 RM) across all seasons and for two Mars years. Our analysis shows that OI 130.4 nm is highly correlated with solar irradiance (solar photoionizing and 130.4 nm illuminating irradiances) as well as changes in the Sun–Mars distance. The prominent short term periodicity in oxygen corona brightness is consistent with the solar rotation period (quasi–27–day). A comparison between the perihelion seasons of Mars Year (MY) 36 and MY 37 shows interannual variability with enhanced emission intensities during MY 37, due to the rise of Solar Cycle 25. These observations show a highly variable oxygen corona, which has significant implications on constraining the photochemical escape of atomic oxygen from Mars.

Luminescent characteristics at ∼2.9 μm in Lu3+ modified Dy3+/Tm3+ co-doped LiYF4 single crystal

The single crystals specimens comprising 0.3 mol% Dy3+, 0.5 mol% Tm3+ and γ mol% Lu3+ doped LiYF4 (γ = 0, 0.3, 0.5, and 1.5) were meticulously synthesized using the Bridgman method, with the specific aim of catering to applications in the ∼2.9 μm laser domain. The microstructure of the obtained single crystal was investigated by conducting X-ray diffraction (XRD) measurements. The Judd-Ofelt (J-O) intensity parameters of the Dy3+ ion and the impacts of Lu3+ doping on fluorescence characteristics of the 6H13/2 (Dy3+) level were studied. The Dy3+/Tm3+ doped LiYF4 single crystal exhibits ∼52 % enhancement in emission intensity at ∼2.9 μm (Dy3+: 6H13/2→6H15/2) through a favorable introduction of Lu3+ ions into the single crystal at 808 nm LD excitation. The Tm3+/Dy3+/Lu3+ triply doped single crystal exhibited a maximum emission cross section of 2.480 × 10−20 cm2 at 2904 nm. The fluorescent lifetimes of the Dy3+: 6H13/2 level in the single crystals were determined to be located in the range of 2.78 ms–3.33 ms. The microscopic mechanism of energy transfer (ET) between Tm3+ and Dy3+ ions were investigated and the ET coefficients from 3H4 level of Tm3+ ion to 6F5/2 of Dy3+ ion (ET1) and 3F4 of Tm3+ to 6H11/2 of Dy3+ (ET2) in the triply doped single crystal were calculated, yielding values of 3.422 × 10−39 cm6/s and 5.768 × 10−39 cm6/s, separately. The results clearly demonstrated that the mid-infrared luminescence at ∼2.9 μm from Dy3+ ions can be significantly enhanced by the strategic incorporation of appropriate Lu3+ ions into Tm3+/Dy3+: LiYF4 single crystal.