Decay Lifetime Research Articles

SURG-57. FLUORESCENCE LIFETIME IMAGING (FLIM) PROVIDES HIGHLY ACCURATE, DYE-FREE TUMOR MARGIN DETECTION DURING GLIOMA RESECTIONS

Abstract INTRODUCTION Fluorescence guided tumor margin detection is an important tool to enhance the extent of resection for gliomas. Existing dyes, such as 5-ALA, require planned administration, surgical resection in dark conditions, and are only effective for high-grade tumors. We have developed a novel laser scanning probe to assess tissue autofluorescence decay (lifetime) which allows tumor margin detection without exogenous dyes and under normal room light conditions. This technology has been optimized for margin detection in low-grade and high-grade gliomas. METHODS Patients undergoing craniotomy for resection of gliomas were enrolled. During resection of the final tumor margin, multiple 1x1 mm regions were scanned with FLIm and biopsied for evaluation by a neuropathologist. FLIm data and ground truth pathology were processed by a machine-learning algorithm to develop classifiers for the FLIm data. Classifiers were then applied to the full data set to determine the accuracy of FLIm predictions. RESULTS 12 patients with non-enhancing (LGG) and 25 patients with enhancing (HGG) tumors were enrolled, with a total of 228 biopsies obtained. For LGG, sensitivity of FLIm for detection of residual tumor was 0.89 (95% CI 0.8-0.98) with a specificity of 0.92 (95% CI 0.86-0.97), resulting in a positive predictive value of 0.76 and negative predictive value of 0.96 with an overall accuracy of 0.91. For HGG, sensitivity of FLIm for detection of residual tumor was 0.92 (95% CI 0.84-1.0) with a specificity of 0.95 (95% CI 0.91-0.99), resulting in a positive predictive value of 0.90 and negative predictive value of 0.96 with an overall accuracy of 0.94, exceeding reported values for 5-ALA. CONCLUSION FLIm can distinguish between residual low and high-grade glioma and normal brain at resection margins with very high sensitivity and specificity. This quantitative technology does not require administration of exogenous dyes and can be used under normal room light illumination.

Dual Emission and Low-Temperature Afterglow in Xanthone-Dibenzoazepine for High EQE Host-Guest OLEDs with Low-Efficiency Roll-Off.

Research has been driven to demonstrate organic light-emitting diodes (OLEDs) with high efficiency, and in the quest for new materials, thermally activated delayed fluorescence (TADF) emitters have been employed. Preparation of donor-acceptor (D-A) π-conjugates is a useful guideline for developing TADF emitters. TADF emitters have shown excellent progress and high maximum external quantum efficiency (EQEmax) for OLEDs in the recent past; however, they suffer with substantial roll-off resulting in a decrease in their efficiency. In order to have efficient OLED emitters with less efficiency roll-off, we designed a xanthone-amine derivative with twisted electron-rich dibenzoazepine having limited rotation at the donor-acceptor bond. Xan-Azepine shows solvent polarity-dependent fluorescence in the range of 441- 597 nm having a lifetime below 10 ns. At 77 K in Me-THF, a triplet at 557 nm was observed having a decay lifetime of 0.75 s and an afterglow for about 6 s. In powder, it shows dual emission, i.e., fluorescence (490 and 6 ns) and phosphorescence (530 nm and 192 μs) at ambient conditions. The energy difference between the singlet and triplet energy levels of Xan-Azepine is found to be 0.18 eV in the powder sample. Its blend in 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) showed delayed fluorescence with a lifetime of 118 μs at 300 K, while it reduced to 84 μs at 150 K. These observations suggest the TADF nature of Xan-Azepine in its CBP blend. OLED devices of Xan-Azepine showing a turn-on voltage of 2.8 V and a EQEmax of 12% were successfully fabricated. In the doped films of Xan-Azepine (5 wt %) with CBP, a maximum luminescence of 5980 Cd/m2 at a current density of 70 mA/cm2 was obtained, resulting in devices with low-efficiency roll-off (2.75%).

Investigation of UV-blocking and photon-down conversion characteristics of PMMA@ CH3NH3PbBr3:WO3 polymer nanocomposites

Herein, methyl ammonium lead bromide: Tungsten trioxide (CH3NH3PbBr3:WO3) nano heterojunction and polymethyl methacrylate (PMMA) polymer composite films of different weight percentage (wt%) proportions of CH3NH3PbBr3:WO3 nanoparticles (0, 0.5, 1.0, 1.5 and 2.0 wt%) were prepared. The structure, morphology and thermal features of CH3NH3PbBr3:WO3 heterojunctions and PMMA@CH3NH3PbBr3:WO3 nanocomposites were investigated using X-ray diffraction (XRD), Fourier Transform-Infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM) and Differential scanning calorimetry (DSC) techniques. The characterization data revealed decrease in crystallinity (up to 7.97%) and glass transition temperature (Tg) with increase in the concentration of CH3NH3PbBr3:WO3 nanoparticles in PMMA nanocomposites. The UV-visible absorbance and transmittance data of PMMA nanocomposites recorded using UV-visible spectroscopy was used to mathematically deduct the optical characteristics such as absorption coefficient, optical band gap, refractive index, extinction coefficient, finesse coefficient, optical conductivity and Urbach energy. The deducted data revealed improved UV-shielding, refractive index and optical conductivity values while the optical band gap and Urbach energy was found to decrease with concentration of dopant. The experimental data of different PMMA@CH3NH3PbBr3:WO3 composite films showed excellent UV- blocking properties in the wider wavelength range of 259-322nm(4.80eV-3.850eV). The PMMA nanocomposites with 2.0 wt% CH3NH3PbBr3:WO3 filler composition exhibited highest UV-shielding behavior with maximum UV-absorption in the wavelength range of 260 to 300nm. The pristine PMMA films showed a PL emission peak at 410nm while the PMMA nanocomposites exhibited strong emissions in the wavelength range of 485-520nm. The observed hydrophobicity, redshift and longer lifetime decay of 34.3 ns for PMMA nanocomposites is attributed to the incorporated CH3NH3PbBr3:WO3 heterojunction nanoparticles. The chromaticity profile suggested that the emission color changed from blue to green as the filler dose of CH3NH3PbBr3:WO3 varied from 0 to 2.0 wt%. Additionally, the findings from the study reveal that incorporation of CH3NH3PbBr3:WO3 into the PMMA matrix enhances UV-absorption, optical conductivity, hydrophobicity, thermal stability, electrical conductivity and photon-down conversion properties of PMMA which make the material suitable for photonic, photovoltaic, optoelectronic and light emitting diode applications.

The Role of Spacers as a Probe in Variation of Photoluminescence Properties of Mono- and Bi-Nuclear Boron Compounds.

A series of N,O donor-based mono- and binuclear four-coordinated boron complexes were synthesized. Depending on the substitution and spacer, these complexes exhibit intense blue, green and yellow emission in solution states. Notably, the fluorescence quantum yields (ΦF) and fluorescence decay (lifetime, τ) of mononuclear boron complexes (2 a-2 e) were higher than the binuclear boron complexes (2 f-2 k). The lowest lifetime and quantum yield in binuclear boron complexes were due to intramolecular rotation induced non radiative processes. The disulphide spacer-based boron complexes 2 i-2 k showed aggregation-caused quenching in the THF/H2O mixture whereas no other complexes were ACQ responsive. These complexes show large Stokes shift, one of them i. e. 2 e has the highest Stokes shift of 130 nm. Further, the electrochemical study suggests the presence of two redox incidences. Theoretical studies show close corroboration between the TD-DFT computed and experimentally measured absorption maxima as well as DFT (GIAO) calculated and experimentally measured 11B NMR values. This complements the appropriate selection of the theoretical methods to shed light on the electronic transitions in the mono- and binuclear BF2 complexes.

Is doublet-triplet splitting necessary?

We demonstrate that it is not necessary to substantially break the mass degeneracy between the Standard Model Higgs boson doublet and the corresponding scalar leptoquark, where these two fields comprise a single five-dimensional SU(5) representation. More precisely, we show that the experimental data on partial proton decay lifetimes cannot place any meaningful bound on the mass of the scalar leptoquark, also known as the color triplet, if one includes effects of higher-dimensional operators. We use the Georgi-Glashow model for our demonstration and point out that the complete suppression of proton decay via the scalar leptoquark mediation is not in conflict with the partial suppression of the gauge mediated two-body proton decay signatures. Finally, we derive a proper limit on the cutoff scale of the aforementioned higher-dimensional operators and outline how this scenario could be tested. Published by the American Physical Society 2024

AN EX-VIVO SPECTRAL AND LIFETIME-DECAY ANALYSIS OF 5-ALA DERIVED PPIX flUORESCENCE: OBJECTIVE flUORESCENCE MAPPING IN GLIOMA SURGERY

Abstract AIMS 5ALA/Protoporphyrin IX (PpIX) fluorescence guided surgery (FGS) in high-grade glioma has been shown to increase resection and survival, despite this benefits are limited in low-grade glioma by low emission and subjective interpretation. Quantitative fluorescence could address these issues, however is challenging due to photobleaching and variations in tissue induced distortion and PpIX photochemical state that are poorly understood. Lifetime-decay measures intrinsic fluorophore properties and is not influenced by these factors, but is difficult to measure intra-operatively. We used paired optical and fluorescence spectroscopy with lifetime decay mapping to characterise PpIX emission within the glioma tissue microenvironment. METHOD Biopsies were collected from 20 patients undergoing glioma FGS, along with 4 controls from partial temporal lobectomies. Paired measurements of emission and lifetime were matched with optical property readings. Lifetime and emission ratios at 635 and 620nm were calculated (PpIX635/620), corresponding to the primary emission peak for the photochemical states of PpIX in tissue. Raw and optically corrected emission was correlated with lifetime decay. RESULTS 205 specimens were analysed by WHO grade (56 Grade4, 66 Grade3, 37 Grade2, 20 control). PpIX635/620 emission was 0.93 in control (CI 0.91-0.95), 1.03 in grade 2 tumours (CI 0.95-1.26), 1.56 in grade 3 (CI 1.22-1.91) and 6.99 (CI 5.78-8.20) in grade 4. PpIX635/620 lifetime correlated with emission (R2 =0.98, range 0.94-1.57). Correlation of emission with lifetime readings improved significantly following optical correction at 635nm (raw R2 =0.81, corrected R2 =0.90) and 620nm (raw R2 =0.44, corrected R2 =0.86). CONCLUSION PpIX620 and PpIX635 photochemical states are present in human glioma, with an increase in PpIX635/620 suggesting increased WHO grade. The ability to distinguish these forms holds the potential to provide real-time data for tumour differentiation and pathology. Accurate characterisation and correction of tissue induced distortion significantly improves the ability to detect, characterise and quantify PpIX intra-operatively.

Combustion synthesis and photoluminescence of Ca2SrWO6:Dy3+ double perovskite: An approach for white light emission

Luminescent Ca2SrWO6:Dy3+ double perovskites are synthesized via the combustion route of material synthesis, wherein urea is taken as fuel. The as-prepared phosphor series comprehensively characterized for their structural and photoluminescence (PL) properties. The Rietveld refinement of XRD data revealed monoclinic crystallized microcrystals with mixed particles of the size of less than 1 µm, studied via SEM. Ca2SrWO6:Dy3+ displayed standard Dy3+ transitions 4F9/2–6H15/2 (blue emission) and 4F9/2–6H13/2 (yellow emission) collectively resulted in white light emission, confirmed via CIE study. Under 278 and 388 excitations, 2 mol% doping of Dy3+ found to be optimum concentration, beyond which concentration quenching is observed due to dipole–dipole interaction. The Y/B ratio ∼1 shows potential to produce white light and make phosphor suitable for WLED applications. The Ca2SrWO6:Dy3+ phosphor displayed notably high thermal stability with PL intensity persisted 77.6 % at LED burning temperature (150 °C) when compared to PL intensity attained at room-temperature, which is basically due to the rigid perovskite structure. In addition, the PL decay lifetime of 4F9/2 state was calculated by utilizing decay curves. Subsequently, the PL quantum efficiency and non-radiative relaxation rate are determined. The theoretical model of Auzel’s fit function is used to calculate to quantum efficiency and was found to be 93.27 % for Ca2SrWO6:2 % Dy3+ phosphor. Moreover, the photometric results reveals that the CIE points are lies in white region of CIE diagram with comparable CCT. The collective results indicated the utility of the phosphor for potential WLED applications.

Gamma-ray irradiation-induced effects on Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glass: Structural, optical, luminescence, and radiation shielding properties

In the present study, we report the gamma (γ) ray irradiation-induced structural, optical, luminescence and radiation shielding properties of Er3+-doped Li2O-Bi2O3-B2O3-TeO2 glasses prepared by melt-quenching technique. It was evidence of the slight reductions in density and refractive index while maintaining stable optical properties upon the γ irradiation. Additionally, increased molar volume and polarizability indicated a less compact network. Raman spectroscopy shows broadened peaks and intensity reductions at key vibrational modes. The UV–Vis–NIR absorption spectra reveal the shift in the absorption edge and reduction in the intensities of Er³⁺ absorption bands (around 450, 520, 550, and 650 nm) with higher radiation doses, indicating radiation-induced damage. It was found that the band gap values decreased from 2.58 eV to 1.30 eV for un-irradiated glass to 90 kGy irradiated glass, and Urbach energy was found to increase from 0.18 to 1 eV respectively, indicating structural disorder and localized states within the band gap. PL emission spectra demonstrated intensity changes and peak shifts with γ radiation dose while maintaining a dominant green emission from 4S3/2 → 4I15/2 and 2H11/2 → 4I15/2 transitions, supported by the CIE diagram analysis. The NIR emission spectra also displayed a peak at 1530 nm with decreasing intensity, indicating defect-induced non-radiative recombination centres. Luminescence lifetime decay profiles indicated reduced lifetimes at higher γ doses, suggesting introduced non-radiative decay pathways. Furthermore, Phy-X software analysis highlighted effective γ-ray shielding influenced by chemical composition and photon flux, with MAC sharply decreasing to 1.8 cm2/g at 0.1 MeV and stabilizing, while LAC showed reduced attenuation efficiency at higher energies. HVL and TVL increased with energy, stabilizing around 4–5 cm and 15–16 cm, respectively, necessitating thicker materials for effective shielding at higher photon energies. MFP rapidly increased to 6–7 cm at 2 MeV, stabilizing at higher energies, while Zeff decreased sharply before stabilizing around 1 MeV. The EBF and EABF trends exhibited higher values at low energies, stabilizing at higher energies, indicating effective photon interaction and resonance effects.

Green Synthesis of Boric Acid Modified Bismuth Based Non-Toxic Perovskite Quantum Dots for Highly Sensitive Detection of Oxytetracycline.

In recent years, perovskite quantum dots (PQDs) have successfully attracted widespread attention due to their excellent optical properties. However, the instability and toxicity problems of perovskite quantum dots are the main obstacles limiting their applications. In this work, bismuth-based perovskite quantum dots were synthesized by a ligand-assisted reprecipitation method, based on which a novel boric acid-functionalized bismuth-based non-toxic perovskite quantum dots fluorescent sensor (Cs3Bi2Br9-APBA) that can be stabilized in the ethanol phase was prepared by a boron affinity technique. Based on the covalent binding interaction of Cs3Bi2Br9-APBA with oxytetracycline (OTC), a highly selective and sensitive method for the detection of OTC was developed, which effectively solved the problems of poor stability and toxicity in the application of perovskite quantum dots. Under the optimal conditions, the fluorescence intensity of the synthesized Cs3Bi2Br9-APBA was linear with the concentration range of 0.1 ∼ 18 µM OTC, and the detection limit could reach 0.0802 µM. The fluorescence detection mechanism was explored and analyzed by spectral overlap analysis, suppression efficiency study of observed and corrected fluorescence, and fluorescence lifetime decay curve fitting, the mechanism of OTC detection by Cs3Bi2Br9-APBA was identified as the inner filter effect (IFE). In addition, the sensor successfully realized the quantitative detection of trace OTC in the environment, and our study provides a new idea for the preparation of green perovskite materials with high stability and selectivity.

Milling-Induced "Turn-off" Luminescence in Copper Nanoclusters.

Atomically precise copper nanoclusters (NCs) attract research interest due to their intense photoluminescence, which enables their applications in photonics, optoelectronics, and sensing. Exploring these properties requires carefully designed clusters with atomic precision and a detailed understanding of their atom-specific luminescence properties. Here, we report two copper NCs, [Cu4(MNA)2(DPPE)2] and [Cu6(MNA-H)6], shortly Cu4 and Cu6, protected by 2-mercaptonicotinic acid (MNA-H2) and 1,2-bis(diphenylphosphino)ethane (DPPE), showing "turn-off" mechanoresponsive luminescence. Single-crystal X-ray diffraction reveals that in the Cu4 cluster, two Cu2 units are appended with two thiols, forming a flattened boat-shaped Cu4S2 kernel, while in the Cu6 cluster, two Cu3 units form an adamantane-like Cu6S6 kernel. High-resolution electrospray ionization mass spectrometry studies reveal the molecular nature of these clusters. Lifetime decay profiles of the two clusters show the average lifetimes of 0.84 and 1.64 μs, respectively. These thermally stable Cu NCs become nonluminescent upon mechanical milling but regain their emission upon exposure to solvent vapors. Spectroscopic data of the clusters match well with their computed electronic structures. This work expands the collection of thermally stable and mechanoresponsive luminescent coinage metal NCs, enriching the diversity and applications of such materials.

Preparation and significant enhancement of upconversion luminescence of α-Ba2ScAlO5:Yb3+/Er3+ phosphors by Ca2+ ions doping

The intensity of upconversion luminescence (UCL) poses a significant challenge for oxides characterized by high phonon energy. Herein, a significant enhancement of red UCL is achieved through the introduction of an intermediate band (IB) in α-Ba2ScAlO5: Yb3+/Er3+ by Ca2+ ions doping. The absorption spectra verify the existence of the IB. The IB of α-Ba2ScAlO5: Yb3+/Er3+/Ca2+ increases the host's absorption of excited photons, provides more electrons for the excitation of Er3+, and realizes the enhancement of UCL emission. The optimal concentration of Ca2+ in α-Ba2ScAlO5: 0.2Yb3+, 0.03Er3+ is 0.15. Compared with undoped Ca2+ samples, the red and green UCL intensity of α-Ba2ScAlO5: Yb3+, Er3+, 0.15Ca2+ increased by 48.2 and 10.6 times, respectively. The mechanism of Ca2+ enhanced UCL was investigated by analyzing the UCL spectra, absorption spectra and lifetime decay curves of α-Ba2ScAlO5: Yb3+/Er3+/Ca2+. The temperature-dependent UCL properties of α-Ba2ScAlO5: Yb3+/Er3+/Ca2+ were also studied by the 2H11/2 (525 nm) and 4F9/2 (667 nm) energy level radiation transitions. The observed linear correlation between luminescence intensity and temperature, coupled with its high sensitivity, indicates the promising potential for temperature sensing applications. This study not only opens a new avenue for enhancing UCL but also holds significant implications for sparking widespread interest in non-contact temperature sensing applications leveraging UCL.

A Generic Analysis of Nucleon Decay Branching Fractions in Flipped SU(5) Grand Unification

In flipped SU(5) grand unified theories, the partial decay lifetimes of certain nucleon decay channels depend generically on an unknown unitary matrix, which arises when left-handed lepton fields are embedded into anti-fundamental representations of SU(5). This dependency is particularly relevant when the neutrino mass matrix has a generic structure, introducing uncertainty in the prediction of nucleon decay branching fractions within flipped SU(5). In this paper, we demonstrate that this uncertainty can be parametrized using two parameters, which can be determined by measuring the partial lifetimes of p→π0e+, p→π0μ+, and n→π0ν¯. In addition, we establish upper limits on the ratios of the decay widths of these channels, offering a potential method to test flipped SU(5) in future nucleon decay experiments.

Comparative investigation of structural, morphological and temperature-dependent photoluminescence characteristics of trivalent rare-earth-activated NaCaPO4 phosphors for solid-state lighting applications

This study explores the synthesis, structure, morphology, and photoluminescence features of trivalent RE3+-activated NaCaPO4 phosphors, aiming to develop phosphor materials for white-light-emitting diode (WLED) applications. Single-phase polycrystalline NaCa(1-x) REx3+ PO4 (REx3+ = Sm, Eu, Dy, and Tb) phosphor materials with various REx3+-doping percentiles were produced by a solid-state reaction process, which were analyzed using various characterization techniques. The FullProf Suite software program was used for phase evidence and crystalline structure analysis, confirming the composition of orthorhombic materials as a single phase. FE-SEM micrographs revealed asymmetrically stacked morphologies across all the compositions. This study reveals that trivalent RE3+-activated phosphors produced exceptional PL outcomes. Dexter's and Blasse's approaches were used to establish the interaction mechanisms and critical energy transfer ranges as dipole-dipole. Lifetime decay patterns were used to fit a bi-exponential function and the resulting values were approximated in milliseconds. This study reveals that trivalent RE3+-activated NaCaPO4 phosphors, with their thermal resilience and color integrity, have potential applications in solid-state lighting (SSL) technology.

Fiber temperature sensor based on dual-wavelength emitting Mg0.388Al2.408O4: Mn2+/Mn4+ phosphors for real-time temperature monitoring

Single doped Mg0.388Al2O3.408O4 phosphor was prepared and multivalent Mn ion (Mn2+ and Mn4+) emission was achieved in a single host. The structure, morphology, and luminescence characteristics of Mn ions in Mg0.388Al2O3.408O4 were discussed in detail, especially the temperature dependent emission characteristics of Mn ions. Based on the fluorescence intensity ratio (FIR) of Mn2+versus Mn4+ and the decay lifetime of Mn4+ emission as the temperature readout, a dual-mode optical temperature-sensing mechanism was proposed and studied in the temperature range of 293–473 K. The maximum relative sensitivities (Sr) are derived as 2.83 % K−1 (at 373 K based on FIR) and 3.40 % K−1 (at 473 K based on decay lifetime), respectively. The temperature sensing characteristics of Mg0.388Al2.408O4: Mn2+/Mn4+ powders in a full fiber system were studied, which can provide thermal-sensitive emissions at dual-wavelengths for stable ratiometric temperature sensing with good precision and repeatability. The constructed all fiber temperature sensing system has been applied in the on-line monitoring of CPU temperature.

Ligand field exciton annihilation in bulk CrCl3.

The layered van der Waals material CrCl3 exhibits very strongly bound ligand field excitons that control optoelectronic applications and are connected with magnetic ordering by virtue of their d-orbital origin. Time-resolved photoluminescence of these exciton populations at room temperature shows that their relaxation is dominated by exciton-exciton annihilation and that the spontaneous decay lifetime is very long. These observations allow the rough quantification of the exciton annihilation rate constant and contextualization in light of a recent theory of universal scaling behavior of the annihilation process.

Mn2+ doped Zn2SiO4 phosphors: A threefold-mode sensing approach for optical thermometry in the visible region at 525 nm

Optical functional materials such as nanostructured silicates have been studied for photonics applications involving energy conversion. In this scenario, we studied Zn2SiO4:Mn2+ nanostructured powders prepared by combustion synthesis for optical thermometry based on photon downshifting. The structural analysis showed that Zn2SiO4 particles were found embedded in clustered silica nanoparticles. The photoluminescence analysis showed that the samples exhibit intense green emission (centered around 525 nm), corresponding to the electronic transition 4T1 → 6A1 of Mn2+, when exposed to a low power ultraviolet lamp (centered around 255 nm). The temperature sensing performance of this material was evaluated using three different methodologies, i.e. the luminescence decay time constant, the spectral full width at half maximum, and the luminescence peak intensity from the 4T1 → 6A1 radiative transition. The thermometric analysis based on luminescence peak intensity provided a maximum relative sensitivity of ∼4.9x10−3 K−1 at 498 K, while the decay lifetime and the spectral width at half maximum provided maximum relative temperature sensitivities of ∼2.9x10−3 K−1 at 523 K and ∼1.7x10−3 K−1 at 298 K, respectively.

Key Components Degradation in Proton Exchange Membrane Fuel Cells: Unraveling Mechanisms through Accelerated Durability Testing

In the process of promoting the commercialization of proton exchange membrane fuel cells, the long-term durability of the fuel cell has become a key consideration. While existing durability tests are critical for assessing cell performance, they are often time-consuming and do not quickly reflect the impact of actual operating conditions on the cell. In this study, improved testing protocols were utilized to solve this problem, which is designed to shorten the testing cycle and evaluate the degradation of the cell performance under real operating conditions more efficiently. Accelerated durability analysis for evaluating the MEA lifetime and performance decay process was carried out through two testing protocols—open circuit voltage (OCV)-based accelerated durability testing (ADT) and relative humidity (RH) cycling-based ADT. OCV-based ADT revealed that degradation owes to a combined mechanical and chemical process. RH cycling-based ADT shows that degradation comes from a mainly mechanical process. In situ fluoride release rate technology was employed to elucidate the degradation of the proton exchange membrane during the ADT. It was found that the proton exchange membrane suffered more serious damage under OCV-based ADT. The loss of F− after the durability test was up to 3.50 × 10−4 mol/L, which was 4.3 times that of the RH cycling-based ADT. In addition, the RH cycling-based ADT had a significant effect on the catalyst layer, and the electrochemically active surface area decreased by 48.6% at the end of the ADT. Moreover, it was observed that the agglomeration of the catalysts was more obvious than that of OCV-based ADT by transmission electron microscopy. It is worth noting that both testing protocols have no obvious influence on the gas diffusion layer, and the contact angle of gas diffusion layers does not change significantly. These findings contribute to understanding the degradation behavior of proton exchange membrane fuel cells under different working conditions, and also provide a scientific basis for developing more effective testing protocols.

Spectra and decay properties of higher lying BC meson states

In this work, the spectra and decay properties of [Formula: see text] mesons [Formula: see text]) have been investigated using a nonrelativistic potential model incorporating corrections from LQCD. The nonrelativistic Schrödinger wave equation is solved numerically using the Matrix Numerov Method. Using the obtained masses and wave functions, decay widths, lifetime, branching ratios and radiative decay widths are computed for the [Formula: see text] system. Influence of the bound state effect on decay width of [Formula: see text] mesons is also analyzed. We compare the obtained results with the experimental data and with other theoretical models.

Generation of singlet oxygen inside living cells: correlation between phosphorescence decay lifetime, localization and outcome of photodynamic action

Photodynamic therapy (PDT) is a promising alternative treatment for localized lesions and infections, utilizing reactive oxygen species (ROS) generated by photosensitizers (PS) upon light activation. Singlet oxygen (1O2) is a key ROS responsible for photodynamic damage. However, the effectiveness of PS in biological systems may not correlate with the efficiency of singlet oxygen generation in homogeneous solutions. This study investigated singlet oxygen generation and its decay in various cellular microenvironments using liposome and ARPE-19 cell models. Rose Bengal (RB), methylene blue (MB), and protoporphyrin IX (PpIX) were employed as selected PS. Lifetimes of singlet oxygen generated by the selected photosensitizers in different cellular compartments varied, indicating different quenching rates with singlet oxygen. RB, located near cell membranes, exhibited the highest phototoxicity and lipid/protein peroxidation, followed by PpIX, while MB showed minimal cytotoxicity in similar conditions. Singlet oxygen decay lifetimes provide insights into PS localization and potential phototoxicity, highlighting the importance of the lipid microenvironment in PDT efficacy, providing useful screening method prior to in vivo applications.Graphical abstract

The influence of Ho3+ ions on the optical and luminescence properties of fluoro borosilicate (SBNC) glasses for green laser applications

The holmium (Ho3+) ions-based fluoro borosilicate (SBNCHo) glasses have been prepared using the traditional melt quenching technique with varying concentrations of Ho3+ ions. Physical parameters were analyzed using x-ray diffraction, energy dispersive analysis of x-rays, fourier transform infrared spectroscopy, optical, luminescence, and Commission International de I'Eclairage (CIE) studies. Judd-Ofelt spectral intensity parameters were evaluated for SBNCHo_1.0 (Ω2 = 5.292 x 10-20 cm2, Ω4 = 3.062 x 10-20 cm2 and Ω6 = 3.376 x 10-20 cm2) glass, optical bandgaps were estimated using optical absorption studies. The Photoluminescence emission spectra were recorded for synthesized glasses with 452 nm excitation. The stimulated emission (σe = 1.40 x 10-20 cm2) for the intense green radiation (5S2 (5F4) → 5I8) was calculated. The lifetime decay profile was analyzed for all the synthesized glasses. From the CIE color coordinates of SBNCHo glasses, the color purity was estimated to be (SBNCHo_1.0 (98.6 %)). These results strongly support the applicability of SBNCHo_1.0 glass for green laser applications.