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Assessment of Gate Width Size on Lifetime-Based F?rster Resonance Energy Transfer Parameter Estimation
摘要： F?rster Resonance Energy Transfer (FRET) enables the observation of interactions at the nanoscale level through the use of fluorescence optical imaging techniques. In FRET, fluorescence lifetime imaging can be used to quantify the fluorescence lifetime changes of the donor molecule, which are associated with proximity between acceptor and donor molecules. Among the FRET parameters derived from fluorescence lifetime imaging, the percentage of donor that interacts with the acceptor (in proximity) can be estimated via model-based fitting. However, estimation of the lifetime parameters can be affected by the acquisition parameters such as the temporal characteristics of the imaging system. Herein, we investigate the effect of various gate widths on the accuracy of estimation of FRET parameters with focus on the near-infrared spectral window. Experiments were performed in silico, in vitro, and in vivo with gate width sizes ranging from 300 ps to 1000 ps in intervals of 100 ps. For all cases, the FRET parameters were retrieved accurately and the imaging acquisition time was decreased three-fold. These results indicate that increasing the gate width up to 1000 ps still allows for accurate quantification of FRET interactions even in the case of short lifetimes such as those encountered with near-infrared FRET pairs.
关键词： fluorescence lifetime,F?rster Resonance Energy Transfer (FRET),gated ICCD,near infrared (NIR) dyes,time-resolved imaging,gate width,in vivo imaging
更新于2025-09-10 09:29:36
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Hole Conduction of Tungsten Diselenide Crystalline Transistors by Niobium Dopant
摘要： In spite of its ambipolar character, tungsten diselenide (WSe2) is known as one of a few p-type materials among transition metal dichalcogenides and is currently being used as a fundamental building block of homo- and hetero-junctions to meet the essential requirement of electronic devices. Many studies have solved the hole transport of WSe2 by contact engineering; however, another route is shown by an effective p-doping strategy for achieving reliable p-type transistor. Diverse characterization methods confirm the transition of the Fermi level from near midgap in intrinsic WSe2 to lower half bandgap with niobium substitutional doping, leading to a nondegenerate doping level exceeding a 1017–1018 cm?3 hole concentration. As a consequence, current on/off ratio and swing parameter have improved correspondingly as expected. The WSe2 transistors (with and without doping) are examined by the Zerbst-type method to conduct the transient data analysis enabling the systemic characterization of the generation lifetime and surface generation velocity of WSe2. It is demonstrated that the lifetime for WSe2 is commonly in the 0.5–0.1 μs range. The generation velocity is ≈10 000-fold slower than that of the typical crystalline silicon, which is attributed to the ultrathin body nature of the materials.
关键词： p-type,niobium doping,tungsten diselenide,transistors,lifetime
更新于2025-09-10 09:29:36
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Synthesis and photophysical properties of europium pentafluorinated β-diketonate complexes
摘要： Two pentafluorinated β-diketone ligands, 4,4,5,5,5-pentafluoro-1-(4-methoxyphenyl)pentane-1,3-dione (PFMP) and 4,4,5,5,5-pentafluoro-1-(4-dimethylaminophenyl)pentane-1,3-dione (PFAP), had been employed to synthesize six novel europium (III) complexes with ancillary ligands 2,2-dipyridine, 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline. The synthesized europium (III) complexes were characterized by FTIR, 1H NMR, UV–Vis, luminescence spectroscopy, elemental analysis and thermogravimetric analysis. The photoluminescence spectra of these complexes showed the typical europium (III) red emissions in solid state and chloroform solution, assigned to 5D0 → 7Fj (j = 0–4) transitions. The higher values of intensity parameter Ω2 indicated that the europium ion was in a highly polarizable ligand field in these complexes. Europium (III) complexes with the β-diketone PFMP exhibited much better photoluminescence properties than complexes with the β-diketone PFAP. Especially, the europium (III) complex of the β-diketone PFMP with the auxiliary ligand 2,2-dipyridine displayed the longest lifetime value, the highest quantum yield and good CIE color coordinates matching the pure red color (x = 0.67, y = 0.33) in these complexes. In addition, the proposed energy transfer mechanisms and the thermal stability of these complexes were also investigated and analyzed.
关键词： Photoluminescence,Europium complex,Quantum efficiency,Luminescent lifetime,Thermal analysis,Pentafluorinated β-diketone
更新于2025-09-10 09:29:36
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Highly efficient thermally activated delayed fluorescence with slow reverse intersystem crossing
摘要： We report an efficient luminescent molecule exhibiting thermally activated delayed fluorescence with a long-delayed fluorescence lifetime of 0.8 ms. Although the reverse intersystem crossing rate constant is small at 2.1 × 103 s?1, the molecule shows a high photoluminescence quantum yield of 89±2%, indicating the suppression of nonradiative decay from the triplet state.
关键词： Long triplet lifetime,Thermally activated delayed fluorescence (TADF),Reverse intersystem crossing (RISC)
更新于2025-09-10 09:29:36
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MgAl2O4 both as short and long persistent phosphor material: Role of antisite defect centers in determining the decay kinetics
摘要： The present work describes the role of antisite defects centers in determining the phosphor characteristics of MgAl2O4, arising due to inversion nature of the spinel compound. The diverse decay characteristics impart this material both as long persistent bluish phosphor as well as short persistent red phosphors material depending upon the annealing temperature. TL study confirmed the fact that there are several defect centers which acts as electron and hole trap centers inside the band gap. FTIR and DRS study confirmed the presence of antisite defects centers viz. AlMg- or MgAl+, which act as a electron and hole trap centers and thereby delaying the electron-hole recombination process. Lower inversion at higher temperature results in decay in their concentration, as reflected in lifetime values.
关键词： TL,Phosphor,Defect,PL,lifetime
更新于2025-09-10 09:29:36
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Solvent-Assisted Tuning the Size and Shape of CsPbBr3 Nanocrystals via Re-Dispersion Process at Ambient Condition
摘要： All-inorganic CsPbBr3 perovskite nanocrystals are emerging as a new class of semiconductors with outstanding optoelectronic properties and great potential for various applications, such as, lasing, photon detection, photovoltaics etc. This article provides the effect of solvents on the re-precipitation of CsPbBr3 perovskite at room temperature. The results observed for CsPbBr3 perovskite in various anti-solvent showed various cubes (nano to micro size), self-assembly of nanocubes and nanorods. In addition, all the various size (nano to micro), self-assembly of nanocubes and shape-controlled nanorods exhibited band-gap tuning at the green light region. The corresponding microscopy (FE-SEM and HR-TEM) images and photoluminescence quantum yield as well as lifetime decay are presented. To the best of our literature knowledge this is the first report on various solvent assisted studies on CsPbBr3 perovskite nanocrystals.
关键词： CsPbBr3 Nanocrystals,nanocubes,effect of solvents,lifetime decay,nanorods,self-assembly
更新于2025-09-10 09:29:36
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High-mobility indirect excitons in wide single quantum well
摘要： Indirect excitons (IXs) are bound pairs of electrons and holes confined in spatially separated layers. We present wide single quantum well (WSQW) heterostructures with high IX mobility, spectrally narrow IX emission, voltage-controllable IX energy, and long and voltage-controllable IX lifetime. This set of properties shows that WSQW heterostructures provide an advanced platform both for studying basic properties of IXs in low-disorder environments and for the development of high-mobility excitonic devices.
关键词： spectrally narrow emission,indirect excitons,voltage-controllable energy,wide single quantum well,long lifetime,high mobility
更新于2025-09-10 09:29:36
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Metabolic imaging with the use of?fluorescence lifetime imaging microscopy (FLIM) accurately detects mitochondrial dysfunction in?mouse oocytes
摘要： To determine whether metabolic imaging with the use of fluorescence lifetime imaging microscopy (FLIM) identifies metabolic differences between normal oocytes and those with metabolic dysfunction. Experimental study. Academic research laboratories. None. Oocytes from mice with global knockout of Clpp (caseinolytic peptidase P; n ? 52) were compared with wild-type (WT) oocytes (n ? 55) as a model of severe oocyte dysfunction. Oocytes from old mice (1 year old; n ? 29) were compared with oocytes from young mice (12 weeks old; n ? 35) as a model of mild oocyte dysfunction. FLIM was used to measure the naturally occurring nicotinamide adenine dinucleotide dehydrogenase (NADH) and flavin adenine dinucleotide (FAD) autofluorescence in individual oocytes. Eight metabolic parameters were obtained from each measurement (4 per fluorophore): short (t1) and long (t2) fluorescence lifetime, fluorescence intensity (I), and fraction of the molecule engaged with enzyme (F). Reactive oxygen species (ROS) levels and blastocyst development rates were measured to assess illumination safety. In Clpp-knockout oocytes compared with WT, FAD t1 and t2 were longer and I was higher, NADH t2 was longer, and F was lower. In old oocytes compared with young ones, FAD t1 was longer and I was lower, NADH t1 and t2 were shorter, and I and F were lower. FLIM did not affect ROS levels or blastocyst development rates. FLIM parameters exhibit strong differentiation between Clpp-knockout versus WT, and old versus young oocytes. FLIM could potentially be used as a noninvasive tool to assess mitochondrial function in oocytes.
关键词： Mitochondria,aging,mitochondrial unfolded protein response,fluorescence lifetime imaging microscopy,CLPP,FLIM,oocyte
更新于2025-09-10 09:29:36
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Time-resolved double-resonance spectroscopy: Lifetime measurement of the 6?1Σg+(7,31) electronic state of molecular sodium
摘要： We report on the lifetime measurement of the 6 1Σ+g (7, 31) state of Na2 molecules, produced in a heat-pipe oven, using a time-resolved spectroscopic technique. The 6 1Σ+g (7, 31) level was populated by two-step two-color double resonance excitation via the intermediate A 1Σ+u (8, 30) state. The excitation scheme was done using two synchronized pulsed dye lasers pumped by a Nd:YAG laser operating at the second harmonics. The fluorescence emitted upon decay to the final state was measured using a time-correlated photon counting technique, as a function of argon pressure. From this, the radiative lifetime was extracted by extrapolating the plot to collision-free zero pressure. We also report the calculated radiative lifetimes of the Na2 6 1Σ+g ro-vibrational levels in the range of v = 0–200 with J = 1 and J = 31 using the LEVEL program for bound-bound and the BCONT program for bound-free transitions. Our calculations reveal the importance of the bound-free transitions on the lifetime calculations and a large difference of about a factor of three between the J = 1 and J = 31 for the v = 40 and v = 100, respectively, due to the wavefunction alternating between having predominantly inner and outer well amplitude.
关键词： radiative lifetime,lifetime measurement,Na2 molecules,bound-bound transitions,time-resolved spectroscopic technique,bound-free transitions,double resonance excitation
更新于2025-09-09 09:28:46
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Raman scattering studies on very thin layers of gallium sulfide (GaS) as a function of sample thickness and temperature.
摘要： Gallium sulfide is a semiconducting material with a layered structure and a characteristic low interlayer interaction. Because of weak van der Waals forces, GaS crystals are relatively easy to exfoliate to very thin layers. In this work nanometric-GaS layers were obtained by a micro-mechanical exfoliation process and were transferred to Si/SiO2 substrate. The thickness of these layers was estimated from AFM measurements. Raman spectra were collected for different layer thicknesses ranging from one layer to bulk crystal. An analytical function fitted to experimental data is proposed to determine layer thickness from Raman measurements. For the first time, the Raman position and the FWHM of the main Raman peaks were measured on very thin GaS layers as a function of temperature in the range from 80 to 470 K. The first order temperature coefficients of the A1g Raman peaks were determined. Phonon decay due to anharmonic processes at temperatures above 300 K in layers of thickness below 4 nm was observed. Contribution of optical phonon scattering processes to thermal properties of very thin GaS layers is discussed.
关键词： GaS monolayer,anharmonic decay,metal III chalcogenides,layered 2d semiconductors,phonon lifetime
更新于2025-09-09 09:28:46