FWHM Research Articles

Order-disorder behavior in the ferroelectric nematic phase investigated via Raman spectroscopy.

Polar-ordered fluids are of interest both fundamentally and from an application standpoint. The recently discovered ferroelectric nematic phase is an example of a polar-ordered fluid, and while there has been extensive research interest in these materials, some of the fundamental properties are yet to be fully understood. Here, we report the order parameters of one of the first known materials that exhibit a ferroelectric nematic phase, RM734, determined via Raman spectroscopy. Raman spectroscopy been used extensively to determined order parameters in liquid crystals systems but also to probe ferroelectric behavior in solid ferroelectric systems and is therefore a powerful technique to study the ferroelectric nematic phase. A reduction and subsequent recovery of order parameters (Δ〈P_{2}〉≈0.1, Δ〈P_{4}〉≈0.06) is observed near the onset of the N to N_{F} transition, a feature that is confirmed via complementary birefringence measurements. This dip in order parameters has been attributed to splay fluctuations, which occur at the onset of the N_{F} transition; here we suggest a different explanation. A broadening of the full-width half-maxima (FWHM), of the order of 1 cm^{-1}, of the selected Raman peak is observed near the N to N_{F} phase transition, which we relate to either a change in reorientational dynamics or the onset of polar order. The N_{F} transition is analyzed using standard solid ferroelectric frameworks. An energetic barrier associated with the para- to ferroelectric transition is found to be of the order of 2.5±0.6kJ/mol, which is comparable to solid ferroelectric materials.

Non-destructive Analytical Study of Raman Spectra Variations and Mechanisms of Calcite and Aragonite in Modern and Fossilized Oysters.

Oyster fossils are some of the most common bivalve mollusk fossils found all over the world, they are different from other fossils because the oyster is still alive in the present day, and the body structure of modern oyster is almost the same as that of ancient one. Therefore, we designed a control experiment comparing the Raman spectra of minerals from both modern oysters and fossil oysters to explore the mechanism of oyster's fossilization process, which is considered to be helpful for investigating biological evolution or paleoenvironment. The oyster fossil sample was found in Nagi-Cho, Okayama Prefecture, Japan. We focused on the variations of band position and full width half-maximum of ν1 Raman band (symmetric stretching mode) of calcite (CaCO3) from modern and fossil oysters and the mineral conversion between calcite and aragonite (CaCO3) around the adductor muscle inside the oyster. Compared to modern oysters, the ν1 band at around 1086 cm-1 of calcite from oyster fossils shifted to a high wavenumber region, and the possible reason for this phenomenon is considered an elemental substitution between Ca2+ and Mg2+. As for aragonite around adductor muscle in fossil oysters, it has been found by Raman spectra that most of the aragonite has been converted into calcite because calcite has a relatively more stable structure.

Comparative study of spectroscopic properties of Er3+-ion doped K2O/KF-Gd2O3-P2O5 glass systems

The two phosphate glasses with composition 17K2O−17Gd2O3−65P2O5−01Er2O3 and 17KF−17Gd2O3−65P2O5−01Er2O3 composition were synthesized by conventional-melt quenching techniques to study comparatively the spectroscopic, Judd–Ofelt (JO), radiative properties and NIR-luminescent properties. The Urbach energy of K2O−Er and KF-Er samples was 0.3547 and 0.4799 eV. The observed trend is Ω2>Ω4>Ω6 and Ω2>Ω6>Ω4 for JO-intensity-parameters for K2O−Er and KF-Er glasses. Moreover, K2O−Er has higher Ω4 and Ω6 values, thus having more rigidity and viscosity than KF-Er. The measured values of full-width-half-maximum (FWHM) for K2O−Er and KF-Er glasses 54.60 and 58.27, respectively. The measured values of FWHM for K2O−Er and KF-Er glasses were 54.60 and 58.27, respectively. The A R values are 417.61 and 3038 for K2O−Er and KF-Er glasses, respectively. The radiative lifetime (τ R ) for K2O−Er and KF-Er glasses is 2.39 ms and 3.18 ms, respectively. Utilizing McCumber theory the G(λ,β) is positive and population-inversion is more than 0.4 for both glasses. Both samples have flat gain-bandwidth in the range of 1505–1585 nm, which covers the S-, C-, and L-bands of the low-loss optical communication-window. It is evident from all these results that the prepared glass samples have the potential for a low-threshold and high gain NIR laser and optical-fiber amplifier.

A Novel Broadband Green Phosphor La2W2O9: Bi3+, and Its Application in High Color-Rendering Index pc-WLED

Broadband green phosphors have important applications in overcoming the blue-green (cyan) 470–510[Formula: see text]nm gap of phosphor-converted white LED (pc-WLED) and achieving high color rendering index (CRI) white lighting. In this work, a broadband green phosphor La2W2O9: [Formula: see text]Bi[Formula: see text] was synthesized by solid-state method. The phase, morphology and luminescence properties of the series of phosphors were systematically studied. The results showed the La2W2O9: [Formula: see text]Bi[Formula: see text] green phosphor exhibits a wide emission band in the range of 400–800[Formula: see text]nm with full width at half-maximum (FWHM) of 164[Formula: see text]nm, filling the cyan gap and reaching its peak at 550[Formula: see text]nm. The phosphor exhibits broadband excitation, and the excitation range covers the wavelength region of 200–500[Formula: see text]nm, and matches well with commercial ultraviolet LED. With the obtained broadband green phosphor, commercial CaAlSiN3:Eu[Formula: see text] red phosphor, commercial BaMgAl[Formula: see text]O17:Eu[Formula: see text] blue phosphor, and a 365[Formula: see text]nm commercial chip, a warm white pc-WLED device with a high color-rendering index (Ra[Formula: see text]97.4, R1–R15[Formula: see text]90) and low correlated color temperature (CCT[Formula: see text]3610[Formula: see text]K) was fabricated. The results demonstrate the wide range of applications for La2W2O9:Bi[Formula: see text] phosphor in the field of premium warm white LED lighting.

Defect‐Mediated Efficient and Tunable Emission in van der Waals Integrated Light Sources at Room Temperature

AbstractDespite defect‐mediated states in monolayer semiconductors have been considered as efficient emitters in cryogenic conditions, they are severely quenched at room temperature (RT) because of multiple thermal‐induced non‐radiative channels, hindering their practical use. Here, robust and tunable defect‐mediated emissions at RT, designated as D1 (1.82 eV) and D2 (1.62 eV), are discovered in monolayer WS2 through argon plasma treatment, which, via multiple corroborative experiments, are attributed to distinct physical processes: bound excitons associated with sulfur vacancies (Vs) and the band‐to‐acceptor recombination, respectively. Remarkably, the defective sample exhibits over ten‐fold increase in both photoluminescence quantum yield and full‐width at half‐maximum (FWHM) compared to its intrinsic counterpart. Leveraging these pronounced edges, light‐emitting diodes (LEDs) functioning at RT achieve broadband (FWHM: 490 meV) and continuously tunable emission from 1.6 to 2.0 eV, as well as the highest electroluminescence (EL) external quantum efficiency (EQE) of ≈1.39% among transient LEDs based on monolayer semiconductors to date, thereby unveiling a new strategy for emission tailoring at the atomic‐scale limit.

CMOS-compatible plasmonic magnetic field sensor: An alternative approach using ultra-compact MIM configuration

This paper introduces a novel magnetic field sensor (MFS) that utilizes a metal-insulator-metal (MIM) waveguide integrated with a resonator structure and incorporates water-based Fe3O4 magnetic fluid. The sensor uses titanium nitride (TiN) as the plasmonic material which offers numerous advantages over conventional noble plasmonic materials. The sensor takes advantage of the tunable optical properties of the magnetic fluid and TiN to detect changes in the external magnetic field and quantify the magnetic field strength which has been demonstrated using the Finite Element Method (FEM). Our proposed MFS exhibits a high sensitivity of 11.97 pm/Oe, a narrow-band full-width half maximum of 93.66 nm, and a resolution of 8.36 × 10−4 Oe. The sensor is also compatible with complementary metal oxide semiconductor (CMOS) fabrication techniques, which enables chip-scale integration and low-cost production. The sensor can be used for various applications in navigation, military, space, healthcare, and beyond.

Near-Infrared-Emitting Helically Twisted Conjugated Frameworks Consisting of Alternant Donor-π-Acceptor Units and Multiple Boron Atoms.

A novel design strategy to construct bright and narrow near-infrared (NIR) emission materials with suppressed shoulder peaks can significantly enhance their performance in various applications. Herein, we have successfully synthesized a series of helically twisted D-π-A conjugated systems bridged by boron atoms, achieving bright red to near-infrared (NIR) emissions with notably narrow full-width at half-maximum (FWHM) values of 35 nm (0.08 eV) and photoluminescence quantum yields (PLQY) up to 80 %. These compounds display red-shifted emissions up to 753 nm in higher concentrations. Cis/trans configurational isomers of multi-boron-bridged molecule BN3 exhibit similar photophysical properties. The unique combination of boron-induced coordination-enhanced charge transfer (CE-CT) and the helically twisted conjugated framework is pivotal in achieving the red-shifted, narrowband emission. X-ray crystallographic analysis of BN2 and BN3-a reveals that the extension of boron-bridged D-π-A skeletons significantly increases the distortion of the skeleton. Systematic theoretical calculations show how the boron CE-CT mechanism, in conjunction with the helical twist, leads to the narrowing of emission bands while simultaneously red-shifting them into the NIR region. This work could open new avenues for the development of advanced materials with tailored optical properties, particularly in the challenging and highly sought-after NIR spectrum.

Optical resonant cavities carving pathways in tunable wavelength sensitive visible-NIR organic photodetectors

Enhancing the photodetection capabilities of organic photodetectors (OPDs) is crucial for advancing applications in medical monitoring, optical communications, image sensing, and robotics, where a strong, focused peak response at a specific designed wavelength is essential for improving sensitivity, wavelength selectivity, and resolution in imaging systems. By controlled integration of ZnO layers within PBDBT:BTP-4F-based OPDs to form a Fabry-Pérot optical cavity, we developed a cost-effective approach to fabricating highly sensitive OPDs by utilizing PBDBT:BTP-4F organic bulk heterojunctions, and extended its detection wavelengths into the near-infrared (NIR) range. Our design integrates a single silver (Ag) layer that significantly enhances peak detection at a wavelength of 830 ​nm, resulting in a remarkably narrow full-width at half maximum (FWHM) wavelength of 30 ​nm and yielding a photoresponse ten times greater than that of non-resonant devices. Furthermore, by varying the thickness of the ZnO layer from 77 ​nm to 620 ​nm, we achieve high spectral tunability, allowing fine adjustments of the resonant peak across a spectrum ranging from ultraviolet (UV) and visible to NIR wavelengths. This sensitive photodetector is also well-suited for applications in photoplethysmography (PPG), effectively detecting pulse signals in the NIR spectrum which has significant potential in medical diagnostics. This work advances the integration of cost-effective, wavelength-selective spectroscopic visible-NIR OPDs, paving the way for the next generation of sensitive photodetectors.

Exciton Dissociation and Recombination Afford Narrowband Organic Afterglow Through Efficient FRET.

Organic afterglow with long-persistent luminescence (LPL) after photoexcitation is highly attractive, but the realization of narrowband afterglow with small full-width at half-maximum (FWHM) is a huge challenge since it is intrinsically contradictory to the triplet- and solid-state emission nature of organic afterglow. Here, narrow-band, long-lived, and full-color organic LPL is realized by isolating multi-resonant thermally activated delayed fluorescent (MR-TADF) fluorophores in a glassy steroid-type host through a facile melt-cooling treatment. Such prepared host becomes capable of exciton dissociation and recombination (EDR) upon photoirradiation for both long-lived fluorescence and phosphorescence; and, the efficient Förster resonance energy transfer (FRET) from the host to various MR-TADF emitters leads to high-performance LPL, exhibiting small FWHM of 33nm, long persistent time over 10s, and facile color-tuning in a wide range from deep-blue to orange (414-600nm). Moreover, with the extraordinary narrowband LPL and easy processability of the material, centimeter-scale flexible optical waveguide fibers and integrated FWHM/color/lifetime-resolved multilevel encryption/decryption devices have been designed and fabricated. This novel EDR and singlet/triplet-to-singlet FRET strategy to achieve excellent LPL performances illustrates a promising way for constructing flexible organic afterglow with easy preparation methods, shedding valuable scientific insights into the design of narrow-band emission in organic afterglow.

Efficient and spectrally stable pure blue light‐emitting diodes enabled by phosphonate passivated CsPbBr3 nanoplatelets with conjugated polyelectrolyte‐based energy transfer layer

AbstractLead halide perovskites exhibit a very wide color gamut due to their extremely narrow emission spectra, typically characterized by a full‐width at half‐maximum (FWHM) of less than 20 nm. Significant advancements have been made in developing highly efficient and stable green, red, and near‐infrared perovskite light‐emitting diodes (PeLEDs). However, achieving efficient and stable pure blue‐emitting PeLEDs remains a significant challenge. In this work, we successfully synthesized monoanionic octyl‐phosphonate capped CsPbBr3 nanoplatelets (OPA‐NPLs) using a combination of octyl‐phosphonic acid and oleylamine at room temperature, diverging from common approaches that necessitate complex high‐temperature methods, such as hot injection, to accommodate short‐chain ligands. The OPA‐NPLs exhibit pure blue photoluminescence at 462 nm with a FWHM of 14 nm. Compared with CsPbBr3 nanoplatelets synthesized using oleic acid, OPA‐NPLs demonstrate significantly improved thermal stability and higher photoluminescence quantum yield (PLQY) of 90%. Additionally, we introduced Poly[(9,9‐bis(3′‐((N,N‐dimethyl)‐N‐ethylammonium)‐propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene)]dibromide (PFN‐Br), a conjugated polyelectrolyte material, as a hole transport layer. This facilitated energy transfer between PFN‐Br and the CsPbBr3 nanoplatelets. The resulting device demonstrated an electroluminescence peak at 462 nm, an extremely narrow FWHM of 14 nm, and a maximum external quantum efficiency (EQE) of 4%. Notably, the device maintained pure blue emission without spectral peak shift even during degradation caused by excess joule heating.image

A novel Cr3+-doped MgGaBO4 phosphor: Expanding the horizons in plant illumination

Near-infrared (NIR) spectroscopy technology has demonstrated unparalleled efficacy in night vision, iris authentication, plant illumination, food inspection, and various other domains. Nonetheless, the quest for novel phosphors exhibiting superior luminescent efficiency and enduring thermal stability persists as a formidable obstacle. In this study, phosphors MgGaBO4: Cr3+, Al3+ were successfully synthesized by high-temperature solid-phase reaction method. Firstly, starting from MgGaBO4: Cr3+, the crystal field environment around Cr3+ ions was modulated by replacing Ga3+ with Al3+ to further improve the luminescence performance of the phosphor. The emission peak wavelength of MgGaBO4: 0.0075Cr3+,0.005Al3+ phosphor was about 756 nm, the full width at half-maximum (FWHM) was about 174 nm under the blue light excitation of 440 nm. In addition, the luminescence intensity at 100 °C remains at 77.41 % of that at room temperature. Finally, the excellent moisture resistance of this phosphor was demonstrated. This work not only introduces a novel broadband NIR phosphor with promising application potential in advanced agricultural lighting but also proposes a synergistic enhancement strategy for effectively improving the performance of broadband NIR phosphor-converted LED light sources.

Electron–photon–phonon interactions in Dirac semimetals: Magneto-optical absorption and mobility analysis

We study the magneto-optical properties of Dirac semimetal (DSM) slabs with particular emphasis on Cd3As2 through electron–photon–phonon interactions, focusing on the magneto-optical absorption coefficient (MOAC) and full-width at half maximum (FWHM). Studying the Landau level (LL) energy of DSMs in the (xy) plane and the z-direction revealed a unique deviation from the square root dependence on the magnetic field, distinguishing DSMs from other semiconductors. At high magnetic fields, the electron–hole symmetry in the LL spectrum is broken, indicating a topological phase in DSMs. For undoped DSMs, MOAC is driven by interband transitions, with peaks from one-photon absorption being smaller and positioned to the left of two-photon ones. Increasing the magnetic field increases peak values. FWHM for one- and two-photon processes increases with the magnetic field and follows a T dependence on temperature. In doped DSMs, both intraband and interband transitions occur, with new interband peaks emerging at higher temperatures near the Fermi energy. Increased electron density shifts the peak position slightly toward higher energy. Peaks from optical phonon emission are consistently higher and located to the right of those from optical phonon absorption, indicating a stronger emission process. The FWHM data allow for the estimation of electron mobilities, and using a reasonable broadening parameter, our predicted mobility values agree with experimental results.

Measurement of energy resolution with the NEXT-White silicon photomultipliers

The NEXT-White detector, a high-pressure gaseous xenon time projection chamber, demonstrated the excellence of this technology for future neutrinoless double beta decay searches using photomultiplier tubes (PMTs) to measure energy and silicon photomultipliers (SiPMs) to extract topology information. This analysis uses 83mKr data from the NEXT-White detector to measure and understand the energy resolution that can be obtained with the SiPMs, rather than with PMTs. The energy resolution obtained of (10.9 ± 0.6)%, full-width half-maximum, is slightly larger than predicted based on the photon statistics resulting from very low light detection coverage of the SiPM plane in the NEXT-White detector. The difference in the predicted and measured resolution is attributed to poor corrections, which are expected to be improved with larger statistics. Furthermore, the noise of the SiPMs is shown to not be a dominant factor in the energy resolution and may be negligible when noise subtraction is applied appropriately, for high-energy events or larger SiPM coverage detectors. These results, which are extrapolated to estimate the response of large coverage SiPM planes, are promising for the development of future, SiPM-only, readout planes that can offer imaging and achieve similar energy resolution to that previously demonstrated with PMTs.

Four‐Membered Ring‐Embedded Cycloarene Enabling Anti‐Aromaticity and Ultra‐Narrowband Emission

AbstractThe synthesis of fully fused π‐conjugated cycloarenes embedded with nonbenzenoid aromatics is challenging. In this work, the first example of four‐membered ring‐embedded cycloarene (MF2) was designed and synthesized in single‐crystal form by macrocyclization and ring fusion strategies. For comparison, single bond‐linked chiral macrocycle MS2 without two fused four‐membered rings and its linear‐shaped polycyclic benzenoid monomer L1 were also synthesized. The pronounced anti‐aromaticity of four‐membered rings significantly adjusts the electronic structures and photophysical properties of cycloarene, resulting in an enhancement of the photoluminescence quantum yield (PLQY) from 10.66 % and 10.74 % for L1 and MS2, respectively, to 54.05 % for MF2, which is the highest PLQY among the reported cycloarenes. Notably, owing to the embedded anti‐aromatic four‐membered rings that reduce structural displacements, MF2 exhibits an ultra‐narrowband emission with a single‐digit full‐width at half‐maximum (FWHM) of only 7 nm (0.038 eV), which sets a new record among all reported organic narrowband luminescent molecules, and represents the first example of ultra‐narrowband emission in conventional polycyclic aromatic hydrocarbons (PAHs) devoid of heteroatoms.

Performance evaluation of a 4D similarity filter for dynamic CT angiography imaging of the liver.

Dynamic computed tomography (CT) angiography of the abdomen provides perfusion information and characteristics of the tissues present in the abdomen. This information could potentially help characterize liver metastases. However, radiation dose has to be relatively low for the patient, causing the images to have very high noise content. Denoising methods are needed to increase image quality. The purpose of this study was to investigate the performance, limitations, and behavior of a new 4D filtering method, called the 4D Similarity Filter (4DSF), to reduce image noise in temporal CT data. The 4DSF averages voxels with similar time-intensity curves (TICs). Each phase is filtered individually using the information of all phases except for the one being filtered. This approach minimizes the bias toward the noise initially present in this phase. Since the 4DSF does not base similarity on spatial proximity, loss of spatial resolution is avoided. The 4DSF was evaluated on a 12-phase liver dynamic CT angiography acquisition of 52 digital anthropomorphic phantoms, each containing one hypervascular 1cm lesion with a small necrotic core. The metrics used for evaluation were noise reduction, lesion contrast-to-noise ratio (CNR), CT number accuracy using peak-time and peak-intensity of the TICs, and resolution loss. The results were compared to those obtained by the time-intensity profile similarity (TIPS) filter, which uses the whole TIC for determining similarity, and the combination 4DSF followed by TIPS filter (4DSF + TIPS). The 4DSF alone resulted in a median noise reduction by a factor of 6.8, which is lower than that obtained by the TIPS filter at 8.1, and 4DSF + TIPS at 12.2. The 4DSF increased the median CNR from 0. 44 to 1.85, which is less than the TIPS filter at 2.59 and 4DSF + TIPS at 3.12. However, the peak-intensity accuracy in the TICs was superior for the 4DSF, with a median intensity decrease of -34 HU compared to -88 and -50 HU for the hepatic artery when using the TIPS filter and 4DSF + TIPS, respectively. The median peak-time accuracy was inferior for the 4DSF filter and 4DSF + TIPS, with a time shift of -1 phases for the portal vein TIC compared to no shift in time when using the TIPS. The analysis of the full-width-at-half-maximum (FWHM) of a small artery showed significantly less spatial resolution loss for the 4DSF at 3.2 pixels, compared to the TIPS filter at 4.3 pixels, and 3.4 pixels for the 4DSF + TIPS. The 4DSF can reduce noise with almost no resolution loss, making the filter very suitable for denoising 4D CT data for detection tasks, even in very low dose, i.e., very high noise level, situations. In combination with the TIPS filter, the noise reduction can be increased even further.

Dual‐Core Engineering for Efficient Deep‐Blue Multiple Resonance Thermally Activated Delayed Fluorescent Materials

AbstractDeveloping narrowband blue multiple resonance (MR) organic emitters with Commission Internationale de L'Eclairage (CIE) y coordinates <0.1 is essential for advanced display technologies. This study proposes a deep‐blue thermally activated delayed fluorescence (TADF) emitter, named 2BNO, which integrates two independent MR cores. Unlike many TADF materials with single‐bonded dual emitting cores, 2BNO utilizes a steric hindrance‐assisted fluorene bridge to achieve an orthorhombic molecular structure. The dual‐core MR‐TADF emitter shows enhanced light absorption and a high photoluminescence quantum yield. Notably, the emission of 2BNO is not significantly redshifted compared to single‐core compounds and maintains a narrow full width at half‐maximum (FWHM) of 24 nm with CIE coordinates of (0.147, 0.041) in 2Me‐THF solution, nearing the BT.2020 blue standard. Organic light‐emitting diodes (OLEDs) incorporating 2BNO as the emitter exhibit deep‐blue emission at 460 nm with a narrow FWHM of 29 nm and CIE coordinates of (0.14, 0.09). The dual emitting core design significantly improves device efficiency, achieving a high external quantum efficiency (EQE) of 19.8%. The dual‐core molecular design strategy in this work is demonstrated to be effective in promoting the efficiency of the TADF emitters while preserving deep‐blue color purity.

Modulating Charge‐Transfer Excited States of Multiple Resonance Emitters via Intramolecular Covalent Bond Locking

AbstractAdvanced multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters with high efficiency and color purity have emerged as a research focus in the development of ultra‐high‐definition displays. Herein, we disclose an approach to modulate the charge‐transfer excited states of MR emitters via intramolecular covalent bond locking. This strategy can promote the evolution of strong intramolecular charge‐transfer (ICT) states into weak ICT states, ultimately narrowing the full‐width at half‐maximum (FWHM) of emitters. To modulate the ICT intensity, two octagonal rings are introduced to yield molecule m‐DCzDAz‐BNCz. Compounds m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit bright light‐green and green fluorescence in toluene, with emission maxima of 504 and 513 nm, and FWHMs of 28 and 34 nm, respectively. Sensitized organic light‐emitting diodes (OLEDs) employing emitters m‐CzDAz‐BNCz and m‐DCzDAz‐BNCz exhibit green emission with peaks of 508 and 520 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.12, 0.65) and (0.19, 0.69), and maximum external quantum efficiencies (EQEs) of 30.2 % and 32.6 %, respectively.

Multiple Enol-Keto Isomerization and Excited-State Unidirectional Intramolecular Proton Transfer Generate Intense, Narrowband Red OLEDs.

A novel series of excited-state intramolecular proton transfer (ESIPT) emitters, namely, DPNA, DPNA-F, and DPNA-tBu, endowed with dual intramolecular hydrogen bonds, were designed and synthesized. In the condensed phase, DPNAs exhibit unmatched absorption and emission spectral features, where the minor 0-0 absorption peak becomes a major one in the emission. Detailed spectroscopic and dynamic approaches conclude fast ground-state equilibrium among enol-enol (EE), enol-keto (EK), and keto-keto (KK) isomers. The equilibrium ratio can be fine-tuned by varying the substitutions in DPNAs. Independent of isomers and excitation wavelength, ultrafast ESIPT takes place for all DPNAs, giving solely KK tautomer emission maximized at >650 nm. The spectral temporal evolution of ESIPT was resolved by a state-of-the-art technique, namely, the transient grating photoluminescence (TGPL), where the rate of EK* → KK* is measured to be (157 fs)-1 for DPNA-tBu, while a stepwise process is resolved for EE* → EK* → KK*, with a rate of EE* → EK* of (72 fs)-1. For all DPNAs, the KK tautomer emission shows a narrowband emission with high photoluminescence quantum yields (PLQY, ∼62% for DPNA in toluene) in the red, offering advantages to fabricate deep-red organic light-emitting diodes (OLED). The resulting OLEDs give high external quantum efficiency with a spectral full width at half-maximum (FWHM) as narrow as ∼40 nm centered at 666-670 nm for DPNAs, fully satisfying the BT. 2020 standard. The unique ESIPT properties and highly intense tautomer emission with a small fwhm thus establish a benchmark for reaching red narrowband organic electroluminescence.

Improvement of luminescence properties in Zn2.1Mg0.9Ta2O8:Cr3+ by the cation substitution and its application in biological nondestructive testing and night vision lighting.

Recently, it is of great significance to explore near-infrared (NIR) phosphor with more application prospects. In this work, a series of Zn2.1 Mg(0.9 - y)GaySnyTa(2 - y)O8:0.003Cr3+ NIR broadband phosphors with high quantum yields and high thermal stability are discovered by uniquely replacing [Mg2+-Ta5+] in Zn2.1Mg0.9Ta2O8 with [Ga3+-Sn4+]. Under 460 nm excitation, Zn2.1Mg0.85Ga0.05Sn0.05Ta1.95O8: 0.003Cr3+ depicts the 600-1100 nm broadband emission with a full-width at half maximum (FWHM) of 210 nm, and the quantum yields can reach 61.2%. Finally, the phosphor was mixed with epoxy resin and encapsulated in a 460 nm blue light emitting diode (LED) chip to convert the NIR LED by phosphor (NIR pc-LED), which was applied in the field of biological nondestructive testing and night vision lighting.

Parallel Analogy Method for Measuring FRD of the FASOT-IFU

A fiber integral field unit (IFU) was chosen for the Fiber Array Solar Optical Telescope (FASOT) to obtain high-spectral-resolution polarization solar spectral images. This IFU features a dual-array-end design, complemented by a dozen slit ends. Each consists of 2 sub-slits corresponding to the dual array ends. In order to accurately and quickly measure the focal ratio degradation of 8064 fibers in FASOT-IFU, a parallel analogy method (PAM) for FASOT-IFU was proposed. This method primarily relies on characterizing the focal ratio based on the full-width at half-maximum (FWHM) of the fiber’s output spot, and the linear relationship between the output focal ratio of the spot and the FWHM. By precisely calculating the focal ratio of the positioning fiber in the FASOT-IFU and treating it as a reference, the output focal ratio of the working fiber can be obtained by comparing the FWHM of the working fiber spot and the positioning fiber spot at the same emission distance. The average value of the output focal ratio by PAM corresponding to the 4032 fibers from Array A of the IFU is 6.0 and the standard deviation is 0.6. The values corresponding to the Array B are 6.2 and 0.40, respectively. The mean value exceeds the contractually specified F/5.5, and the proportion of optical fibers with a focal ratio greater than 5.5 accounts for 88% of the total number of optical fibers, meeting the design requirements of the FASOT system.