Strong Emission Research Articles

Electron traps in (Y0.97Zr0.03)2O3 transparent ceramics and its suppression by heavy Eu3+ doping

AbstractIn this paper, Eu3+:(Y0.97Zr0.03)2O3 transparent ceramics with different doping concentrations of Eu3+ were prepared by vacuum sintering. This series of transparent ceramic samples exhibits strong red emission when excited by an electron beam at the keV level. However, color changes observed in the samples after high‐energy electron irradiation. This is due to the capture of electrons by traps related to oxygen vacancies within the Y2O3 lattice. Specifically, under electron beam irradiation, the capture of the electrons by oxygen vacancy‐related defects in the Y2O3 lattice occurs, leading to radiation damage. The color change can be suppressed to some extent by the incorporation of Zr4+ into the Y2O3 lattice, which can effectively suppress the generation of oxygen vacancies. Interestingly, samples with heavy doping of Eu3+ exhibit stronger resistance to electron irradiation damage. Based on the detailed characterizations, including optical transmittance, cathodoluminescence, photoluminescence, thermoluminescence and luminescence decay time, it is found that under heavy doping conditions, Eu3+, which has a stronger cationic character than Y3+ can more effectively suppress the generation of electron traps induced by the oxygen vacancies and the interstitial oxygen in the Y2O3 lattice, thereby enhancing radiation resistance. This research can advance the understanding of defect suppression mechanisms and benefit the application of Y2O3‐based functional transparent ceramics in high‐energy electron and β‐ray irradiation environment.

Revolutionizing Fingerprint Detection: Ce3+ Doped SiO2-Zr2O3:Sr2+ Nanocomposites with Enhanced Luminescence and Selectivity.

Even though fingerprints remain one of the most reliable methods of identification, they are often lost during the recovery process. Accurate fingerprint recognition depends on the contrast between the ridges and substrate. On tough surfaces, such as glossy, colorful, and patterned materials, the contrast is harder to establish. Photoluminescent materials play a crucial role in forensic investigations as they enable the development of procedures that enhance image quality and increase the accuracy of findings from security institutions. Due to the strong emission in the red area at 620nm, the use of trivalent Rare Earth ions (RE3+) doped materials in this work is notable. Because of the unique properties and abundance of cerium, luminous materials based on SiO2-Zr2O3: Ce3+, Sr2+ prepared via sol-gel technique present a more practical alternative for use in criminal investigations compared to current photonic materials. The sample was further co-doped with synthetic (Safranin-O and crystal violet) as well as organic (curcumin and lycopene) photoluminescent dyes. The nanocomposites were examined using X-ray diffraction analysis (XRD), energy-dispersive X-ray analysis (EDX), dynamic light scattering (DLS), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). In conclusion, this work highlights the qualities critical to obtaining higher-resolution latent fingerprint images for potential forensic applications.

Initial Mass Functions of Young Stellar Clusters from the Gemini Spectroscopic Survey of Nearby Galaxies. I. Young Massive Clusters in the Antennae Galaxies

The stellar initial mass function (IMF) is a key parameter to understand the star formation process and the integrated properties of stellar populations in remote galaxies. We present a spectroscopic study of young massive clusters (YMCs) in the starburst galaxies NGC 4038/9. The integrated spectra of seven YMCs obtained with GMOS-S attached to the 8.1 m Gemini South telescope reveal the spectral features associated with stellar ages and the underlying IMFs. We constrain the ages of the YMCs using the absorption lines and strong emission bands from Wolf–Rayet stars. The internal reddening is also estimated from the strength of the Na i D absorption lines. Based on these constraints, the observed spectra are matched with the synthetic spectra generated from a simple stellar population model. Several parameters of the clusters including age, reddening, cluster mass, and the underlying IMF are derived from the spectral matching. The ages of the YMCs range from 2.5 to 6.5 Myr, and these clusters contain stellar masses ranging from 1.6 × 105 M ☉ to 7.9 × 107 M ☉. The underlying IMFs appear to differ from the universal form of the Salpeter/Kroupa IMF. Interestingly, massive clusters tend to have the bottom-heavy IMFs, although the masses of some clusters are overestimated due to the crowding effect. Based on this, our results suggest that the universal form of the IMF is not always valid when analyzing integrated light from unresolved stellar systems. However, further study with a larger sample size is required to reach a definite conclusion.

Enhanced photovoltaic performance and longevity of perovskite modules via interface engineering of transport layer

Abstract This research presents interfacial engineering of large–area perovskite modules. The quality of the interface between the electron transport layer(ETL) and the perovskite layer are studied, because it significantly affects the optoelectronic performance of large–area module devices. In large–area fabrication, film uniformity and interfacial quality are critical, as the ETL/perovskite interface governs both electron extraction and transport efficiency, while also affecting the uniformity and crystallinity of the perovskite. To overcome these issues, using picosecond laser technique (P1,P2,P3) to fabricate large–area modules, integrating monolithic cells in series. Planar SnO2 and mesoporous TiO2 ETL are prepared. Results show that meso–type ETL structures are better suited for large–area modules. The modules with meso–type TiO2 exhibit fewer shunting issues and stronger emission in electroluminescence images. Photoluminescence mapping indicates improved structural uniformity of perovskite. The perovskite module with meso–type TiO2 achieve power conversion efficiency of 18.2% (4cm2) and maintain 80% of initial efficiency after 700 hours.

Observing high dependence of red luminescence on localized symmetry in Mn4+ activated inverse spinel phosphors.

Localized symmetry has been shown to significantly impact the luminescence behavior of Mn4+ ions through the electron-phonon coupling process. Building on this characteristic, three types of inverse spinel structure oxides (Mg2XO4, where X = Ti, Ti/Ge, Ge) doped with Mn4+ were developed, exhibiting strong red emission when exposed to UV and blue light. A thorough examination reveals that the symmetric improvement of the Mn4+ sites within the octahedral environment leads to significant changes in their luminescence behavior, including a suppression of zero-phonon-line (ZPL) emission, a blueshift, and an extension of the luminescence lifetime. Moreover, variable-temperature PL spectra of phosphors are carefully measured. Low-temperature PL spectra demonstrate three distinct sharp emission peaks for Mg2GeO4:Mn4+, while Mg2TiO4:Mn4+ exhibits a broad emission band. The average primary phonon energies involved in the vibronic processes are determined through theoretical fitting of temperature-dependent PL intensities. Lastly, the luminescence dynamics associated with anti-Stokes, ZPL, and Stokes emissions are analyzed. The observed increase in luminescence lifetime indicates a significant impact of the localized environment on luminescence properties.

Fabrication of Eu2O3 doped in high density and transparent silicoborate scintillating glass for synchrotron X-ray radiographic imaging application

In this work, the glass system, xEu2O3 - 10SrO - 20La2O3 - 10Ta2O5 - 10SiO2 - (50-x)B2O3, where x = 0, 1, 3, 5, 7, 9, 11 mol%, was fabricated using the high-temperature melt quenching method. The physical, optical, and luminescence properties of the glass were investigated to determine its suitability as a scintillation material. The transparent glass sample showed a high density and molar volume up to 4.72 g/cm3 and 40.57 cm3/mol, respectively, reflecting that higher NBOs in glass matrix. This result is also supported by X-rays photoelectron spectroscopy (XPS) spectra. Absorption spectra represented peaks in the ultraviolet to near infrared regions, which can be confirmed the presenting of Eu3+ ion in glass matrix. Under UV excitation, the glass doped with 3 mol% of Eu2O3 shows highest intensity while scintillation light (X-rays induced luminescence) was highest performed at 7 mol%. The integral intensity of radioluminescence of glass is 26 % that of commercial BGO scintillator. The photoluminescence quantum yield (PLQY) was measured and the highest PLQY was correspond with emission intensity. The glass scintillator was used for X-ray imaging at beamline 1.2, Synchrotron Light Research Institute (SLRI), Thailand and the spatial resolution was evaluated. Due to the strong light emission at 615 nm from 5D0 → 7F2 transition of Eu3+, this developed scintillating glass has a potential for X-ray imaging material in radiographic application.

One Pot Synthesis of New Benzimidazole Derivatives with Exceptionally High Luminescence Quantum Efficiency.

There are different approaches to the synthesis of benzimidazole. In this article, five new benzimidazole derivatives, BMPO, Me-BMPO, Di-MeBMPO, F-BMPO and Cl-BMPO where (BMPO=3-[(1H)-benzo[d]imidazol-2-yl]pyridin-2(1H)-one), have been prepared. Another study was carried out on luminescence properties and their potential applications for the detection of transition metal ions. From the one-pot synthesis approach, all the derivatives of the benzimidazole compounds were obtained. The compounds were characterized using HRMS, 1HNMR, 13CNMR, and X-ray crystallography. Herein, a mechanism has been deciphered by predicting the release of HCl(g). All compounds showed a strong deep blue emission when dissolved in dimethylacetamide (DMA), with emission wavelengths at 423, 428, 435, 423, and 421 nm, and half-times of 3.64, 2.77, 2, 19, 3.42 and 3.52 ns, respectively. In addition, their emission quantum yields were determined to be 72, 50, 42, 73 and 80%. Five new benzimidazole derivatives, BMPO, Me-BMPO, Di-MeBIPO, F-BIPO, and Cl-BIPO, have been successfully synthesized by the one-pot synthesis method, and their structures are characterized and confirmed. The compounds exhibited exceptional luminescence by emitting a strong blue light in DMA with high fluorescence quantum yields between 42~80%.

A Turn-On Fluorescence Probe Based on GSH-Protected Silver Nanoclusters for the Selective Detection of Pb2.

Glutathione-protected silver nanoclusters (GSH-AgNCs) with good photostability were successfully synthesized through a one-pot heating process. The resultant GSH-AgNCs with an average diameter of ~1.6 nm exhibit red fluorescence (λem = 650 nm), and the fluorescence is excitation independent. Strong aggregation-induced emission (AIE) effect was observed in GSH-AgNCs, which can be induced by solvent and metal ions. In particular, a specific fluorescence enhancement was detected upon interaction with lead ions (Pb2+). A fluorescent probe was designed for off-on detection of Pb2+ based on as-synthesized GSH-AgNCs. Under the optimum parameters, two linear response intervals were found between the relative fluorescence intensity and the concentration of Pb2+ in the range of 10-250 μM (R2 = 0.9900) and 400-1000 μM (R2 = 0.9930). Significant fluorescence color evolutions observed under UV light, resulting in a semiquantitative visual detection of Pb2+. A possible detection mechanism based on the interaction between GSH-AgNCs and Pb2+ is discussed.

MAGAZ3NE: Massive, Extremely Dusty Galaxies at z ∼ 2 Lead to Photometric Overestimation of Number Densities of the Most Massive Galaxies at 3 < z < 4* ∗ The spectra presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National

We present rest-frame optical spectra from Keck/MOSFIRE and Keck/NIRES of 16 candidate ultramassive galaxies targeted as part of the Massive Ancient Galaxies at z > 3 Near-Infrared Survey (MAGAZ3NE). These candidates were selected to have photometric redshifts 3 ≲ z phot <4, photometric stellar masses log(M∗/M⊙) > 11.7, and well-sampled photometric spectral energy distributions (SEDs) from the UltraVISTA and VIDEO surveys. In contrast to previous spectroscopic observations of blue star-forming and poststarburst ultramassive galaxies, candidates in this sample have very red SEDs implying significant dust attenuation, old stellar ages, and/or active galactic nuclei (AGN). Of these galaxies, eight are revealed to be heavily dust-obscured 2.0 < z < 2.7 galaxies with strong emission lines, some showing broad features indicative of AGN, three are Type I AGN hosts at z > 3, one is a z ∼ 1.2 dusty galaxy, and four galaxies do not have a confirmed spectroscopic redshift. In fact, none of the sample has ∣z spec − z phot∣ < 0.5, suggesting difficulties for photometric redshift programs in fitting similarly red SEDs. The prevalence of these red interloper galaxies suggests that the number densities of high-mass galaxies are overestimated at z ≳ 3 in large photometric surveys, helping to resolve the “impossibly early galaxy problem” and leading to much better agreement with cosmological galaxy simulations. A more complete spectroscopic survey of ultramassive galaxies is required to pin down the uncertainties on their number densities in the early Universe.

SAUNAS. II. Discovery of Cross-shaped X-Ray Emission and a Rotating Circumnuclear Disk in the Supermassive S0 Galaxy NGC 5084

Combining Chandra, Atacama Large Millimeter/submillimeter Array, EVLA, and Hubble Space Telescope archival data and newly acquired data from the Apache Point Observatory/Dual Imaging Spectrograph, we detect a double-lobed 17 kpc X-ray emission with plumes oriented approximately perpendicular and parallel to the galactic plane of the massive lenticular galaxy NGC 5084 at 0.3–2.0 keV. We detect a highly inclined ( i=71.2−1.7+1.8◦ ), molecular circumnuclear disk ( D=304−11+10 pc) in the core of the galaxy rotating (V rot(2−1)CO=242.7−6.4+9.6 km s−1) in a direction perpendicular to that of the galactic disk, implying a total mass of log10MBHM⊙=7.66−0.15+0.21 for NGC 5084's supermassive black hole. Archival EVLA radio observations at 6 and 20 cm reveal two symmetric radio lobes aligned with the galactic plane, extending to a distance of R¯=4.6±0.6kpc from the core, oriented with the polar axis of the circumnuclear disk. The spectral energy distribution lacks strong emission lines in the optical range. Three formation scenarios are considered to explain these multiwavelength archival observations: (1) active galactic nuclei (AGN) reorientation caused by accretion of surrounding material, (2) AGN-driven hot gas outflow directed along the galactic minor axis, or (3) a starburst/supernovae driven outflow at the core of the galaxy. This discovery is enabled by new imaging analysis tools including the Selective Amplification of Ultra Noisy Astronomical Signal, demonstrating the abundance of information still to be exploited in the vast and growing astronomical archives.

Identification of Luciferin on Europa through Data Science Analysis of Near-Infrared Mapping Spectrometer (NIMS) Data from the Galileo Orbiter

In this study, we investigated the potential presence of extraterrestrial life on Europa, one of Jupiter’s moons, by exploring the existence of Luciferin, a bioluminescent molecule. This hypothesis is based on Europa’s subsurface oceans and the geothermal conditions created by gravitational forces from Jupiter, similar to Earth’s hydrothermal vents. We reanalyzed raw data from the Near-Infrared Mapping Spectrometer (NIMS) on the Galileo spacecraft, utilizing advanced machine learning and data processing techniques to enhance data quality. This involved cleaning, preprocessing, and normalizing the multidimensional data to reduce noise and correct errors, ensuring more accurate analysis. Our primary focus was on detecting spectral signals that might indicate Luciferin, particularly in the spectral bands around 560-570nm, which are associated with Luciferin’s strong emission. The results were encouraging, as several points of interest showed spectral intensity consistent with the presence of this molecule. Although these findings are preliminary and require further validation, they offer promising evidence of bioluminescence on Europa. If confirmed, this discovery would significantly impact the fields of astrobiology and space exploration, providing crucial insights into the search for extraterrestrial life.

Development of highly thermal-stable blue emitting Y4Al2O9:Bi3+ phosphors for w-LEDs, fingerprint and data security applications

A new blue-emitting Y4Al2O9:Bi3+ (YAO:Bi3+) phosphor is synthesized using the solution combustion method with mushroom extract as a binder. Its structural properties, concentration effects, temperature-dependent luminescence, and performance in LED devices are thoroughly investigated. Upon excitation at 367 nm, a strong blue light emission at 423 nm is observed, attributed to the 3P1→1S0 transition of Bi3+. The quantum efficiency reached approximately 63.5 %. The CIE diagram shows that the emission colour falls within the intense blue region, achieving a colour purity (CP) of 94 %. YAO:Bi3+ exhibits strong absorption in the near-ultraviolet range (330–400 nm), making it suitable for LEDs powered by near-ultraviolet chips. A thermal quenching experiment revealed an activation energy (Ea) of 0.323 eV, indicating that this YAO:Bi3+ phosphor possesses good thermal stability. This study showcases the use of YAO:Bi3+ phosphor in encapsulated LED devices. The device’s Commission Internationale de l’Éclairage (CIE) coordinates are (0.325, 0.310), with a high colour rendering index (CRI) of 94.70 and a low correlated colour temperature (CCT) of 5915 K at a current of 120 mA. These properties indicate that this phosphor is suitable for developing white LED devices powered by near-ultraviolet chips. The optimized YAO:Bi3+ phosphor is employed to enhance the detection of Level I-III fingerprint (FP) details with high resolution and contrast, showing effective visualization of latent fingerprints (LFPs) on various substrates. Furthermore, it is used as a model for developing fluorescent ink, which is applied to different media. The results suggest that YAO:Bi3+ phosphor has significant potential for applications in w-LEDs, advanced forensics, and anti-counterfeiting ink technologies.

&gt;100 m fiber-coupled microchip laser–induced breakdown spectroscopy for remote elemental analysis applications

This study aims to develop ultralong fiber-optic cable (FOC) coupled microchip laser – induced breakdown spectroscopy (mLIBS) to reveal the elemental distribution and local composition of nuclear fuel debris in an accident-damaged reactors at Fukushima Daiichi Nuclear Power Station (FDNPS). Currently at FDNPS, the distance between the area where humans can safely work in a sufficient space and the nuclear fuel debris is expected to be &gt;100 m. Therefore, it becomes crucial to analyze the light transmittance performance of FOC-coupled mLIBS systems over such long distances in a high-radiation environment. Therefore, this study focuses on the influence of gamma radiation dose and FOC length on the transmittance of the visible and near-infrared (NIR) wavelengths through FOCs. Compared with an FOC with low-OH groups, that with high-OH groups exhibits better light transmittance performance in both wavelength regions in a high-radiation environment. Furthermore, the light transmittance performance of the high-OH FOC extended up to 500 m in length is tested in a radiation-free environment. From the measurement results, the maximum FOC length for microchip crystal oscillation is estimated to be &gt;800 m, although attenuation is observed with the increase in FOC length. Finally, we analyze the ultralong FOC–coupled mLIBS system through the detection of gadolinium (Gd) in mixed oxide samples. The strong emission lines of Gd were only available in the visible wavelength region. Therefore, quantitative analysis of Gd is successfully performed in the visible region using the mLIBS system coupled with up to 300-m-long FOCs, with the limits of detection being between 0.1% and 0.2%.

Ultrasensitive electrochemiluminescencent multivalent aptamer sensor based on energy and electron transfer dual quenching tactics.

Anefficient "on-off-on" electrochemiluminescence (ECL) aptasensor utilizing dual-mechanism quenching was constructed for detecting furanyl fentanyl (FuF). The first signal "on" state was achieved by novel dual-ligand zinc metal-organic frameworks (Zn-MOFs), which were synthesized by self-assembly reaction using zinc atom clusters as metal nodes, achieving strong and stable ECL emission. The "off" state was realized by the energy and electron quenching effect of copper-doped WO3. Specifically, in addition to the overlap of the UV-Vis spectrum, energy transfer existed between the acceptor and donor after doping copper. Therefore, copper created a "highway" for electron transfer between the donor and acceptor, which greatly improved the quenching efficiency. Simultaneously, employing multivalent aptamers as capture probes augmented the binding affinity and probability of association between aptamer and target through a synergistic multivalent effect. Consequently, the second "on" state was the ECL signal restored by introducing FuF. Benefiting from the combination of the multivalent aptamers strategy with the "on-off-on" design, the developed aptasensor showed excellent linearity (1.0 × 10-13 to 1.0 × 10-6 g/L) with a low limit of detection of 5.5 × 10-14 g/L (S/N = 3). Additionally, it demonstrates a relative standard deviation (RSD) of less than 5% and good recovery ranging from 97.6 to 102%. The proposed aptasensor presents considerable potential for rapid, sensitive, and accurate determinationof FuF.

Substituent groups effects on AIEgens of fluorenone derivatives: Optical properties, bioimaging, and LED devices

Understanding structure-property relationships is crucial for developing materials with a high fluorescence quantum yield (ΦF) and optimizing their performance. In this study, three fluorenone-carbazole-based molecules (FO-Cz1, FO-Cz2, and FO-Cz3) were synthesized, which have similar structures but varying substituent groups (carbazole, 3,6-di‑tert‑butyl‑9H-carbazole, and 3,6-diphenyl-9H-carbazole). The different substituent groups significantly changed the optical properties of the luminogens. The experimental results confirmed that FO-Cz1, FO-Cz2, and FO-Cz3 were AIEgens, and the introduction of a phenyl group gave FO-Cz3 strong αAIE(I/I0) and greater solid fluorescence quantum yields than FO-Cz1 and FO-Cz2. Analysis of photophysical properties, theoretical calculations, and X-ray crystallography revealed that the emission properties of FO-Cz1, FO-Cz2, and FO-Cz3 were influenced by the use of flexible substituent groups. The substituent groups avoided π-π stacking, reduced non-radiative transitions, and enhanced fluorescence in the aggregated state. Substituent groups on the benzene ring gave FO-Cz3 a tightly-packed structure and strong emission. It was used for cancer cell imaging and LED devices, in which FO-Cz3 exhibited high photostability and biocompatibility, making it a superior photosensitizer for bioimaging and applications in OLED devices. This research sheds light on the AIE behaviors of fluorenone complexes and offers valuable insights for the development of organic luminescent materials.

Upconversion on the Micrometer Scale: Impact of Local Heterogeneity.

The properties of perovskite/naphtho[2,3-a]pyrene (NaPy) upconversion devices are investigated by a combination of atomic force microscopy and photoluminescence mapping to understand the role of microscopic heterogeneity in the ensemble device properties. The results emphasize strong microscopic inhomogeneity across the perovskite/NaPy upconversion device due to local formation of NaPy microcrystals. NaPy shows emission from three distinct states in the solid state: S1' emission at 520 nm, excimer emission at 560 nm, and S1″ emission at 620 nm. Clear spatial differences in the emission spectrum under 405 nm excitation are found, highlighting that there is a strong microcrystal-to-microcrystal variation in the optical properties─emphasizing a need for multimodal measurements. Our results indicate that microcrystals with strong emission from the strongly coupled low-energy state S1″ (J-dimer) show much higher upconversion intensity than those with dominant emission from the high-energy S1' state (I-aggregate). Hence, our results suggest that microcrystals with strong emission from the low-energy state S1″ act as isolated hotspots for upconversion.

Construction of a Dual-Mode Sensing Platform for Ultra-fast Detection of Bisulfite in Food and Environmental Systems.

Sulfur dioxide (SO2) is widely used in food processing to extend the shelf life of food. However, excessive intake of SO2 and its derivatives (HSO3- and SO32-) can cause oxidative damage to the body, and result in several diseases. How to construct probes for rapid real-time detection of HSO3- in the field is beneficial to the developmental needs of practical applications, but it is also very challenging. Here we report a dual-mode fluorescent probe Rh-QL for ultrafast detection of HSO3-, which undergoes a specific 1,4-Michael addition reaction with HSO3- to achieve near-infrared fluorescence turn-on. Probe Rh-QL can rapidly (< 5s) respond to HSO3- with a color change from purple to green and a strong fluorescence emission at 725nm. The probe Rh-QL has been used for the detection of HSO3- in real sugar samples and can be prepared as a portable sensing kit for the detection of HSO3- in the environment due to its high efficiency, rapidity and accuracy. In addition, the probe Rh-QL is able to target label Gram-negative bacteria after reacting with HSO3-, which has the potential to identify the type of pathogenic bacteria.

Rational integration of fluorogenic and quenching activity of dopamine for reversed ratiometric and semi-quantitative visual detection of tyramine

A facile and efficient reversed ratiometric fluorescence (RF) method has been developed for the sensitive and accurate detection of tyramine (Tyr), an essential marker for food spoilage in fermented or aged foods. This method utilizes an “activation-quenching integration” strategy involving the fluorogenic reactivity and quenching capacity of dopamine (DA), the tyrosinase (TYR) catalyzed products of Tyr. Under alkaline conditions, DA reacts with resorcinol to form azamonardine, exhibiting strong blue emission. Additionally, DA is oxidized to o-dopaquinone by TYR, which quenches the red fluorescence of CdTe quantum dots (QDs). Under optimized conditions, a Tyr-specific RF sensor was established, featuring a linear detection range from 0.1 to 6 mg/mL and a detection limit of 8.50 × 10−3 mg/L. The fabricated reversed RF sensing system was successfully applied for quantitative analysis of Tyr in real samples and semi-quantitative visual detection of Tyr in fermented food samples upon integration with a pseudo-color-assisted approach.

Synthesis and Characterizations of Dibenzo-Fused Perioctacene.

Dibenzoperioctacene (DBPO) with extended zigzag edges was synthesized and unambiguously characterized by a combination of nuclear magnetic resonance (NMR), mass spectrometry, and single-crystal X-ray diffraction analysis. Variable-temperature (VT) NMR analysis indicated the closed-shell character of DBPO, yet an electron paramagnetic resonance (EPR) signal was observed at room temperature suggesting its potential open-shell diradicaloid nature. The bond lengths in the single-crystal structure of DBPO aligned more closely with those of open-shell teranthene than closed-shell bisanthene. Spin-unrestricted density functional theory (DFT) calculations using various methods supported that ground state of DBPO might be on the borderline between closed- and open-shell singlet states, with a large singlet-triplet energy gap (ΔEST), consistent with the VT-NMR and EPR results. UV-vis-near infrared (NIR) absorption spectrum showed the longest-wavelength peak at 905 nm, marking the NIR optical properties of DBPO. DBPO exhibited a tendency to react with atmospheric oxygen, which additionally hinted at its possible open-shell character. Furthermore, the oxidized species of non-fluorescent DBPO exhibited strong emission at 820 and 915 nm, which opens its potential for oxygen detection via a "turn-on" NIR fluorescence response.

The long-term influence of a magnetar power in stripped-envelope supernovae. Radiative-transfer modeling of He-star explosions from 1 to 10 years

Much interest surrounds the nature of the compact remnant that formed in core collapse supernovae (SNe). One means to constrain its nature is to search for signatures of power injection from the remnant in the SN observables years after explosion. In this work, we conduct a large grid of 1D nonlocal thermodynamic equilibrium radiative transfer calculations of He-star explosions under the influence of magnetar-power injection from post-explosion age of about one to ten years. Our results for SN observables vary with He-star mass, SN age, injected power, or ejecta clumping. At high mass (model he12p00), the ejecta coolants are primarily O and Ne, with and dominating in the optical, and with strong in the infrared -- this line may carry more than half the total SN luminosity. For lower He-star masses (models he6p00 and he3p30), a greater diversity of coolants appear, in particular Fe, S, Ar, or Ni from the Si- and Fe-rich regions. All models tend to rise in ionization in time, with twice-ionized species (i.e., O Ne S or Fe dominating at sim \,10\,yr, although this ionization is significantly reduced if clumping is introduced. Our treatment of magnetar power in the form of high-energy electrons or X-ray irradiation yields similar results -- no X-rays emerge from our ejecta even at ten years because of high-optical depth in the kilo-electronvolt range. An uncertainty of our work concerns the power deposition profile, which is not known from first principles, although this profile could be constrained from observations. Our magnetar-powered model he8p00 with moderate clumping yields a good match to the optical and near-infrared observations of Type Ib SN\,2012au at both 289--335\,d (power of $1-2 and 2269\,d (power of 1040\ Unless overly ionized (i.e., if the optical spectrum shows only strong we find that all massive magnetar-powered ejecta should be infrared luminous at 5--10\,yr through strong line emission.