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Single-cell redox states analyzed by fluorescence lifetime metrics and tryptophan FRET interaction with NAD(P)H
摘要： Redox changes in live HeLa cervical cancer cells after doxorubicin treatment can either be analyzed by a novel fluorescence lifetime microscopy (FLIM)-based redox ratio NAD(P)H-a2%/FAD-a1%, called fluorescence lifetime redox ratio or one of its components (NAD(P)H-a2%), which is actually driving that ratio and offering a simpler and alternative metric and are both compared. Auto-fluorescent NAD(P)H, FAD lifetime is acquired by 2- photon excitation and Tryptophan by 3-photon, at 4 time points after treatment up to 60 min demonstrating early drug response to doxorubicin. Identical Fields-of-view (FoV) at each interval allows single-cell analysis, showing heterogeneous responses to treatment, largely based on their initial control redox state. Based on a discrete ROI selection method, mitochondrial OXPHOS and cytosolic glycolysis are discriminated. Furthermore, putative FRET interaction and energy transfer between tryptophan residue carrying enzymes and NAD(P)H correlate with NAD(P)H-a2%, as does the NADPH/NADH ratio, highlighting a multi-parametric assay to track metabolic changes in live specimens.
关键词： Fluorescence Lifetime Imaging Microscopy (FLIM),single-cell analysis,NADPH/NADH ratio,NAD(P)H,redox,FAD,fluorescence lifetime redox ratio (FLIRR),NAD(P)H-a2%
更新于2025-11-21 11:24:58
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Luminescence and anion recognition performance of mononuclear Eu(III) complexes with N- and O- donor pyridine derivatives
摘要： A series of Eu(III) complexes with pyridine-2-carboxamide (PCA), pyridine-2-carboxaldoxime (PCAO), pyridine-2,3-dicarboxylic anhydride (PDCA) or pyridine-2-methanol (PM) as primary ligands and 4,4′-dimethoxy-2,2′-bipyridine (DMBP) as ancillary ligand were synthesized. The interaction between the ligands and complexes were confirmed by FT-IR study. The complexes were abbreviated as [Eu(PCA)3DMBP].Cl3 (C1), [Eu(PCAO)3DMBP].Cl3 (C2), [Eu(PDCA)3DMBP].Cl3 (C3) and [Eu(PM)3DMBP].Cl3 (C4). Optical studies were done by UV–vis spectroscopy and PL spectroscopy. The highest intrinsic luminescent quantum yield (53.42%) and lifetime value (1456 μs) were found for C3. Lowest quantum yield was exhibited by C2. Anion sensing studies of all the complexes were done by UV–vis and PL spectroscopy and it was observed that complex C1 showed remarkable change in optical properties upon addition of F? and HSO4? ions. Thus C1 can be used as optical sensor for F? and HSO4? ions. The FQD for F? and HSO4? ions were found to be 6.55 and 3.58 respectively for C1.
关键词： Sensing performance,Antenna effect,Hydrogen bonding,Optical sensor,Lifetime decay
更新于2025-11-21 11:18:25
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Measuring the interaction of transcription factor Nrf2 with its negative regulator Keap1 in single live cells by an improved FRET/FLIM analysis
摘要： Transcription factor NF-E2 p45-related factor 2 (Nrf2) and its principal negative regulator, Kelch-like ECH-associated protein 1 (Keap1), comprise a molecular effector and sensor system that robustly responds to perturbations of the cellular redox homeostasis by orchestrating a comprehensive cytoprotective program. Under homeostatic conditions, Nrf2 is a short-lived protein, which is targeted for ubiquitination and proteasomal degradation. Upon encounter of electrophiles, oxidants or pro-inflammatory stimuli, the cysteine sensors in Keap1 are chemically modified, rendering Keap1 unable to target Nrf2 for degradation, and consequently leading to accumulation of the transcription factor and enhanced transcription of cytoprotective genes. Detailed understanding of the protein-protein interactions between Nrf2 and Keap1 has been achieved by use of various in vitro systems, but few assays are available to assess these interactions in the context of the living cell. We previously developed an imaging-based FLIM/FRET methodology to visualise and measure the interaction between Nrf2 and Keap1 in single cells. Here, our goal was to improve this methodology in order to increase throughput and precision, and decrease cell-to-cell variability. To eliminate the possibility of orientation bias, we incorporated a flexible linker between Keap1 and the FRET acceptor fluorescent protein tag. To ensure the correct image capture of Nrf2 fused to the FRET donor fluorescent protein tag, we matched the maturation time of the fluorescent tag to the half-life of the endogenous Nrf2, by using sfGFP as the FRET donor. Using a global binning approach increased the assay throughput, whereas including the measured Instrument Response Function in the analysis improved precision. The application of this methodology revealed a strong covariation of the results with the expression level of the acceptor. Taking the acceptor level into account circumvented cell-to-cell variability and enhanced sensitivity of the measurements of the Keap1-Nrf2 interaction in live cells.
关键词： FRET,live cell imaging,fluorescence lifetime,FLIM,sfGFP,protein-protein interaction,global binning,Keap1,Instrument Response Function,Nrf2
更新于2025-11-21 11:08:12
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Assessment of Bulk and Interface Quality for Liquid Phase Crystallized Silicon on Glass
摘要： This paper reports on the electrical quality of liquid phase crystallized silicon (LPC-Si) on glass for thin-film solar cell applications. Spatially resolved methods such as light beam induced current (LBIC), microwave photoconductance decay (MWPCD) mapping, and electron backscatter diffraction were used to access the overall material quality, intra-grain quality, surface passivation, and grain boundary (GB) properties. LBIC line scans across GBs were fitted with a model to characterize the recombination behavior of GBs. According to MWPCD measurement, intra-grain bulk carrier lifetimes were estimated to be larger than 4.5 μs for n-type LPC-Si with a doping concentration in the order of 1016 cm?3. Low-angle GBs were found to be strongly recombination active and identified as highly defect-rich regions which spatially extend over a range of 40–60 μm and show a diffusion length of 0.4 μm. Based on absorber quality characterization, the influence of intra-grain quality, heterojunction interface, and GBs/dislocations on the cell performance were separately clarified based on two-dimensional (2-D)-device simulation and a diode model. High back surface recombination velocities of several 105 cm/s are needed to get the best match between simulated and measured open circuit voltage (Voc), indicating back surface passivation problem. The results showed that Voc losses are not only because of poor back surface passivation but also because of crystal defects such as GBs and dislocation.
关键词： Bulk lifetime,heterojunction,grain boundaries (GBs),two-dimensional (2-D)-device simulation,liquid phase crystallized silicon (LPC-Si),light beam induced current (LBIC)
更新于2025-11-14 15:25:21
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Excellent exciton luminescence of CsPbI3 red quantum dots in borate glass
摘要： We have fabricated CsPbI3 perovskite quantum dots in a borate glass by melt-quenching technique. Three representative samples with different treatment conditions are investigated. As treatment condition enhances, energy gap is extracted as 1.75-1.76eV, and photoluminescence peak is adjustable from 675 to 691nm. Full width at half-maximum (FWHM) varies from 43 to 37 nm. PL intensity first increases and then decreases with increasing excitation wavelength, but the peak wavelength and line-shape are independent. High PLQY values of 23.8%-61.4% are obtained. The high PLQY values are attributed to good crystal quality and less energy dissipation. PL lifetime is fitted as 24.0-28.2ns and 100.2-123.0ns for short and long lifetime components in bi-exponential function. For temperature from 25 to 125 oC, PL intensity decreases, but it is reversible. Exciton binding energy is extracted in the level of 375-454meV. The FWHM broadening from 39 to 49nm and peak blue-shift from 690 to 685nm are investigated.
关键词： Photoluminescence quantum yield,Lifetime,CsPbI3,Temperature dependence,Quantum dots glass,Exciton
更新于2025-11-14 15:23:50
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Radiative and non radiative recombinations study in the novel nanocomposites BiVO4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiVO4/3DOM-ZnO: Application to the photocatalysis
摘要： A theoretical investigation of optical proprieties of three nanostructures such as BiOV4/3DOM TiO2, ZnO/3DOM TiO2 and BiOV4/3DOM ZnO has been presented and discussed. The study based on a one band effective mass approximation model was developed to calculate the charge carrier energies on various parameters of nanostructures including their size. We computed the optical properties for both spherical BiVO4 and ZnO nanoparticles incorporated in the three dimensionally ordered macroporous inverse opal TiO2 nanocomposites (3DOM-TiO2 ). At first and by solving a three dimension Schr?dinger equation we calculated the dependence of charge carriers energies on the size of nanoparticles. Then we investigated the variation of the excitonic energy of BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO as function of the radius of these nanostructures into taken account the effects of dielectric and coulomb interaction between charge carriers. We showed that the radiative recombination lifetime is enhanced with decreasing BiVO4 and ZnO quantum dots (QDs) size. It was found that as the size of the dot is reduced the confinement of charge carriers and the optical gap are increased. The optical gap of the ZnO/3DOM-TiO2 is larger than both BiOV4/3DOM-TiO2 and BiOV4/3DOM-ZnO especially for small radius. It was also found that radiative life time in the BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO increased by increasing the radius of these nanostructures. In addition, we have also showed that, the radiative lifetime in the ZnO/3DOM-TiO2 nanostructure is less than both BiOV4/3DOM-TiO2 and BiOV4/3DOM-ZnO nanostructures. Finally, we have studied and discussed the Auger process in BiOV4/3DOM-TiO2, ZnO/3DOM-TiO2 and BiOV4/3DOM-ZnO nanostructures. At first, we have showed that the auger process is important when the radiuses of nanostructures are less than 2nm. Then we have also showed that this process is more important for ZnO/3DOM-TiO2 compared to the other nanostructures.
关键词： Photocatalysts,radiative lifetime,Auger recombination lifetime,nanocomposites
更新于2025-09-23 15:23:52
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Radiative transition probabilities between low-lying electronic states of N <sub/>2</sub>
摘要： This work mainly investigates the transition dipole moments (TDMs) and radiative transition probabilities of dipole-allowed transitions between the b1Σu+, a''1Σg+, 13Σg-, 23Σg-, C'3Σu+, B'3Σu-, W3Δu, 23Σu+ and H3Υu states of N2. Many of these transition properties are previously unknown. For completeness, another 14 electronic states that correlate to four lowest dissociation limits are also calculated. The potential energy curves (PECs) are calculated at the valence internally contracted multireference configuration-interaction (icMRCI) level of theory, along with the Davidson correction, the core-valence (CV) correction and the scalar relativistic correction, as well as the basis-set extrapolation. These corrections, especially the CV correction, greatly improve the accuracy of the PECs, as shown by the excellent agreement of the fitted spectroscopic parameters with the available experimental data. In order to verify the accuracy of transition properties, we calculate the Einstein coefficients of the extensively studied B3Σg- - A3Σu+, C3Σu+ - B3Σg-, W3Δu - B3Σg-, B'3Σu- - B3Σg-, C'3Σu+ - B3Σg-, w1Δu - a1Σg+, a1Σg+ - a'1Σg- and b1Σu+ - X1Σg+ band transition systems and compute the radiative lifetimes of N2 B3Σg-, C3Σu+ and W3Δu states, which are in good agreement with the experimental data. Similar accuracy can be assumed for the previously undetermined 13Σg- - B'3Σu-, 23Σg- - B'3Σu-, 23Σg- - C'3Σu+, 23Σu+ - B3Σg- and b1Σu+ - a''1Σg+ band transition systems. The large Einstein coefficients of these band systems can provide guidelines for observing such newly predicted band transitions in the appropriate spectroscopy experiments.
关键词： radiative lifetime,Spectroscopic parameter,radiative transition probability,transition dipole moment,N2
更新于2025-09-23 15:23:52
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Smartphone-based apparatus for measuring upconversion luminescence lifetimes
摘要： Luminescence lifetime detection plays an important role in time-resolved detection and research. However, the traditional instruments always require expensive detectors such as time-correlated single photon counter or streak camera. Herein, a low-cost and miniaturized apparatus for measuring upconversion luminescence lifetimes was developed by using a smartphone equipped with a 980 nm CW laser and a motor. When the motor was driving the sample circling at a high linear velocity, the excited sample would emit a luminescence arc, which could be photographed by the phone camera. The rotating rate could be measured by a tuner APP and then used for transferring arc length to delay times. By analyzing the grayscale distribution of the luminescence arc, the luminescence decay curve was obtained, which was then used for exponential fit and calculating lifetimes. The whole system was not only remarkably cheaper but also more miniaturized than traditional instruments for measuring luminescence lifetimes, indicating the promising applications in point of care testing for time-resolved luminescence detection for bioanalysis and disease diagnosis.
关键词： Lanthanide upconversion,Luminescence lifetime,Time-resolved,Motor,Smartphone
更新于2025-09-23 15:23:52
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Depth Profiling of Carrier Lifetime in Thick 4H-SiC Epilayers Using Two-Photon Absorption
摘要： Depth profiling of the ambipolar carrier lifetime was performed in n-type, 140μm thick silicon carbide (SiC) epilayer using excitation by two-photon absorption (TPA) with a pulsed 586nm laser, and confocal measurement of time resolved photoluminescence (TRPL) decay from the excited region. A depth resolution of ≈10μm was obtained. The PL decay curves were analyzed using a recently developed formalism that takes into account the TPA excitation, carrier diffusion and surface/interface recombination. The carrier lifetime decreases near the top surface of the epitaxial layer as well as near its interface with the substrate.
关键词： Carrier lifetime profiling,Silicon Carbide
更新于2025-09-23 15:23:52
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A Study on the Solvent Vapor Induced Film Formation of PS/AgNPs Composites
摘要： In this study, pyrene (P) tagged polystyrene (PS) latex dispersions and silver nanoparticles (AgNPs) were mixed at various weight fractions in the range between 0 and 50 wt%. The prepared mixtures were dropped on the glass substrates by considering drop casting method and were dried at the room temperature. The resultant powder films were then exposed to solvent vapor to monitor how film formation and morphological behaviors of PS/AgNPs composites are altered. Film formation behavior of composites was assessed via fast transient fluorescence (FTRF) which measures the ?uorescence lifetimes of P from its decay traces during vapor exposure process. It was observed that pyrene lifetimes decreased as vapor exposure time, t increased. A Stern–Volmer kinetic analysis was used for low quenching ef?ciencies to interpret the decrease in pyrene lifetimes. UV-Vis (UVV) technique was employed to monitor optical transparency of the films. In the range of 0-20 wt% of AgNPs content, smooth and transparent films were obtained. However, above this range, the films were seen that they have low transparency and poor film formation since the increment in AgNPs content was lead to aggregations. The Prager–Tirrel model was employed to the FTRF data to obtain back-and-forth frequencies, ν, of the reptating PS chains during vapor induced ?lm formation process. SEM images of the samples were taken after film formation process is completed and were found to be consistent with optical and fluorescence quenching data.
关键词： Polystyrene latex,film formation,reptation frequency,fluorescence lifetime,nanocomposites,crossing-density,Silver nanoparticles,vapor-induced
更新于2025-09-23 15:23:52