Dependence Of Lifetime Research Articles

Mass Ratio Dependence of Three-Body Resonance Lifetimes in 1D and 3D

Mass Ratio Dependence of Three-Body Resonance Lifetimes in 1D and 3D

Automatic segmentation of lysosomes and analysis of intracellular pH with Radachlorin photosensitizer and FLIM

We report application of the fluorescence lifetime imaging microscopy (FLIM) for analysis of distributions of intracellular acidity using a chlorin-e6 based photosensitizer Radachlorin. An almost two-fold increase of the photosensitizer fluorescence lifetime in alkaline microenvironments as compared to acidic ones allowed for clear distinguishing between acidic and alkaline intracellular structures. Clusterization of a phasor plot calculated from fits of the FLIM raw data by two Gaussian distributions provided accurate automatic segmentation of lysosomes featuring acidic contents. The approach was validated in colocalization experiments with LysoTracker fluorescence in living cells of four established lines. The dependence of photosensitizer fluorescence lifetime on microenvironment acidity allowed for estimation of pH inside the cells, except for the nuclei, where photosensitizer does not penetrate. The developed method is promising for combined application of the photosensitizer for both photodynamic treatment and diagnostics.

Distribution of Seed Electron Phase Space Density Minima in Earth's Radiation Belts

AbstractWe conducted a statistical analysis of local phase space density (PSD) minima across a wide energy range (∼20 keVs to ∼10 MeV), using observations from the Van Allen Probes and the Geostationary Operational Environmental Satellite. We identified deepening minima in PSD profiles of multi‐MeV (∼5% occurrence) and of “seed” electrons (up to 15% occurrence, corresponding to ∼70–100 s keV) and compared their distribution with a 3D diffusion model using the Versatile Electron Radiation Belts (VERB) code. The comparison of the observed and modeled distributions suggests that the PSD minima of seed electrons are likely associated with hiss waves and the corresponding L‐shell dependent electron lifetimes. However, the observed distribution was not fully reproduced by the model, potentially indicating other fast loss mechanisms of seed electrons.

Narrowband red luminescence of tetrahedral-site Fe3+ In Ca8Mg(SiO4)4Cl2

We have measured the excitation and emission spectra, and lifetime for Fe3+ in the Ca8Mg(SiO4)4Cl2 compound. The spectroscopic data of the ferric ion (Fe3+) is interpreted within the framework of the Tanabe-Sugano crystal field theory for ions with the d5 electronic configuration. Quantitative evaluation of the Racah parameters B and C and the crystal field parameter (10 Dq) is provided. The emission and excitation data are consistent for Fe3+ in a tetrahedral-site occupancy. The red emission is assigned to the 4T1 (4G)→6A1 (6S) crystal field transition. The remarkable feature of the luminescence is the positioning of the emission band; it is centered at 623 nm with a Full Width at Half Maximum of 51 nm. To the best of our knowledge this is one of the highest energy emission for the tetrahedral-site Fe3+ ion. The practical implication of this spectral power distribution is discussed. The temperature dependency of the luminescence lifetime and emission intensity are reported.

Radiative and Nonradiative Recombination Processes in AlGaN Quantum Wells on Epitaxially Laterally Overgrown AlN/Sapphire from 10 to 500 K

Radiative and nonradiative recombination processes are investigated in the temperature range from 10 to 500 K for AlGaN quantum wells on epitaxially laterally overgrown AlN/sapphire templates. Time‐integrated photoluminescence (PL) spectroscopy under selective excitation conditions demonstrates that the decrease in the radiative recombination efficiency with increasing temperature is one of the causes of the thermal droop in AlGaN‐based deep‐ultraviolet (DUV) light‐emitting diodes. Time‐resolved PL spectroscopy indicates that not only the decreasing nonradiative recombination lifetime but increasing radiative recombination lifetime with increasing temperature contributes to the thermal droop. The temperature dependence of the radiative recombination lifetime is discussed, revealing that luminescence linewidth is a valuable criterion for designing efficient AlGaN‐based DUV emitters.

Luminescence of some lanthanides in synthetic yttrium gagarinite (NaCaYF6)

NaCaYF6 is the formula for gagarinite. Noting the lack of luminescence studies in this material, we synthesized it using the hydrothermal method and investigated the luminescence of several lanthanides. Characteristic luminescence of Eu[Formula: see text], Dy[Formula: see text], Sm[Formula: see text] and Tb[Formula: see text] was observed. Detailed results on photoluminescence emission and excitation spectra, lifetime, chromaticity coordinates and concentration dependence of emission intensity are presented. Except for Tb[Formula: see text], which exhibits f-d excitation, the luminescence of other activators got quenched at 1[Formula: see text]mol % concentration. Eu[Formula: see text] emission in this host was peculiar, in that the emissions from higher 5D states were observed. Luminescence characteristics are explained using the known energy level diagrams for the lanthanide activators.

Photoluminescence of combinatorically sputtered Al2O3–Y2O3 thin films with a Cr3+ and Nd3+ co-doping concentration gradient

The characterization of a wide range of luminescent thin films can be a long and tedious endeavor. With reactive combinatorial sputtering of multiple metal targets, it possible to fabricate thin films with a gradient in composition simply by not rotating the substrate. In this work, combinatorically sputtered thin films of Cr3+ and Nd3+ doped in the Al2O3–Y2O3 system (YAlO) are studied for thin film based luminescent solar concentrators (TFLSCs) application. Contrary to mm's thick plate type LSC's, TFLSCs of just several 100 nm thick require much higher Cr3+ concentration to achieve 40% absorption which can enable several 10's of W/m2 LSC power efficiencies. Our transmission measurements on a Cr2O3 film with a thickness gradient result in an absorption cross section at 460 nm of 1.3 ± 0.7 × 10−19 cm2 showing that the TFLSC absorption requirement can be fulfilled provided that the Cr3+ concentration is in the order of 1022 ions/cm3. The Y:Al ratio of the YAlO host in our films ranged between 0.5 and 3.5, thereby including the monoclinic (Y4Al2O9), perovskite (YAlO3) and garnet (Y3Al5O12) stoichiometry's on a single film. Position dependent XRD, EDX, excitation, emission and lifetime measurements of Cr3+ and Nd3+ show that the unique gradient film sputtering method is able to characterize thin films as a function of host composition and doping concentration. Energy transfer between Cr3+ and Nd3+ in co-doped YAlO films is concluded from Cr3+ excitation bands observed while monitoring Nd3+ emission and from the matching of the rise-time of Nd3+ 1340 nm emission (4F3/2 ->4I11/2) and the decay time of Cr3+ 840 nm emission (4T2 ->4A2). Nd3+ lifetime systematically decreases from 0.24 to 0.05 ms with increasing Cr3+ concentration in Y3Al5-xCrxO12:Nd (0.05 < x < 2). The constraints of heavily doped Cr3+ thin films for enabling adequate absorption and energy transfer to Nd3+ in TFLSC applications are the subjects of the discussion.

Link between shape dependent lifetimes and thermal escape in quantum dots and rings

Understanding the optical emission characteristics of semiconductor nanostructures is important when determining their device applicability. Their emission depends on the material and its geometry, but also depends on other processes such as thermal escape from the nanostructure. Although it is widely accepted that scattering involving longitudinal optical phonons is the key process in thermal escape, it remains unclear why some quantum structures thermally emit excitons while others emit uncorrelated electron-hole pairs or single charge carriers. To investigate this phenomenon, we theoretically determine the energy levels and temperature- lifetime relationships of quantum dots and rings. We find that replicating the observed temperature dependence of the exciton lifetime requires both an eigenspectrum and a thermal escape mechanism which are geometry dependent. This suggests that geometry may be a significant factor in determining the dominant thermal escape process in quantum structures. Published by the American Physical Society 2024

Differences in Photophysical Properties and Photochemistry of Ru(II)-Terpyridine Complexes of CH3CN and Pyridine.

A series of 22 Ru(II) complexes of the type [Ru(tpy)(L)(L')]n+, where tpy is the tridentate ligand 2,2';6,2″-terpyridine, L represents bidentate ligands with varying electron-donating ability, and L' is acetonitrile (1a-11a) or pyridine (1b-11b), were investigated. The dissociation of acetonitrile occurs from the 3MLCT state in 1a-11a, such that it does not require the population of a 3LF state. Electrochemistry and spectroscopic data demonstrate that the ground states of these series do not differ significantly. Franck-Condon line-shape analysis of the 77 K emission data shows no significant differences between the emitting 3MLCT states in both series. Arrhenius analysis of the temperature dependence of 3MLCT lifetimes shows that the energy barrier (Ea) to thermally populating a 3LF state from a lower energy 3MLCT state is significantly higher in the pyridine than in the CH3CN series, consistent with the photostability of complexes 1b-11b, which do not undergo pyridine photodissociation under our experimental conditions. Importantly, these results demonstrate that ligand photodissociation of pyridine in 1b-11b does not take place directly from the 3MLCT state, as is the case for 1a-11a. These findings have potential impact on the rational design of complexes for a number of applications, including photochemotherapy, dye-sensitized solar cells, and photocatalysis.

Bunch lifetime analysis based on the injection interval at SuperKEKB

We study the bunch lifetime dependence on the bunch position at the SuperKEKB main ring. The bunch lifetime ratio is evaluated from the injection interval. The lifetime imbalance is observed between the forward and backward of the bunch train at the positron ring. It becomes larger when the beam current becomes larger. The luminosity dependence on the RF-bucket spacing can be explained with the lifetime dependency which we determined in this analysis. The result indicates the existence of the unknown phenomenon which varies the Touschek lifetime with the RF-bucket spacing in the electron ring.

Impact of excitation pulse width on the upconversion luminescence lifetime of NaYF4:Yb3+,Er3+ nanoparticles.

The upconversion luminescence (UCL) lifetime has a wide range of applications, serving as a critical parameter for optimizing the performance of upconversion nanoparticles (UCNPs) in various fields. It is crucial to understand that this lifetime does not directly correlate with the decay time of the emission level; rather, it represents a compilation of all the physical phenomena taking place in the upconversion process. To delve deeper into this, we analyzed the dependence of the UCL lifetime on the excitation pulse width for β-NaYF4:Yb3+,Er3+ nanoparticles. The results revealed a significant increase in the UCL lifetime with both the excitation pulse width and the excitation intensity. The laser fluence was identified as the parameter governing the UCL decay dynamics. We showcased the universality of the pulse-width-dependent UCL lifetime phenomenon by employing UCNPs of various sizes, surface coatings, host matrices, Yb3+ and Er3+ ratios, and dispersing UCNPs in different solvents. Theoretical explanations for the experimental findings were derived through a rate equation analysis. Finally, we discussed the implications of these results in UCNP-FRET (Förster resonance energy transfer)-based applications.

Small molecule interactions with biomacromolecules: selective sensing of human serum albumin by a hexanuclear manganese complex - photophysical and biological studies.

A covalently bonded hexanuclear neutral complex, [Mn6(μ3-O)2(3-MeO-salox)6(OAc)2(H2O)4] (1), has been synthesized and characterized by single crystal X-ray diffraction analysis along with IR and HRMS studies. Complex 1 has been found to selectively interact with human serum albumin (HSA), a model transport protein. The interaction of 1 with HSA was investigated by monitoring the change in the absorbance value of HSA at λ = 280 nm with increasing concentration of 1. Likewise, fluorescence titrations were carried out under two conditions: (i) titration of a 5 μM solution of complex 1 with the gradual addition of HSA, showing a ∼9-fold fluorescence intensity enhancement at 424 nm, upon excitation at 300 nm; and (ii) upon excitation at 295 nm, titration of 5 μM HSA solution with the incremental addition of complex 1, showing a quenching of fluorescence intensity at 334 nm, with simultaneous development of a new emission band at 424 nm. A linear form of the Stern-Volmer equation gives KSV = 9.77 × 104 M-1 and the Benesi-Hildebrand plot yields the binding constant as KBH = 1.98 × 105 M-1 at 298 K. The thermodynamic parameters, ΔS°, ΔH°, and ΔG°, were estimated by using the van't Hoff relationship which infer the major contribution of hydrophobic interactions between HSA and 1. It was observed that quenching of HSA emission arises mainly through a dynamic quenching mechanism as indicated by the dependence of average lifetime 〈τ〉 on the concentration of 1. The changes in the CD (circular dichroism) spectral pattern of HSA in the presence of 1 clearly establish the variation of HSA secondary structure on interaction with 1. The most probable interaction region in HSA for 1 was determined from molecular docking studies which establish the preferential trapping of 1 in the subdomain IIA of site I in HSA and substantiated by the results of site-specific marker studies. Complex 1 was further evaluated for its antiproliferative effects in lung cancer A549 cells, which strictly inhibits the growth of the cells in both 2D and 3D mammospheres, indicating its potential application as an anticancer drug.

Carrier lifetime dependence on temperature and proton irradiation in 4H-SiC device: an experimental law

Carrier lifetime dependence on temperature and proton irradiation in 4H-SiC device: an experimental law

Electron transfer and energy exchange between a covalent organic framework and CuFeS2 nanoparticles.

CuFeS2 is a prominent chalcogenide that possesses similar optical properties and a significantly lower cost, compared to gold. Additionally, covalent organic frameworks are a class of materials at the forefront of current research, mainly used as photoactive components and porous absorbers. Hence, in this work, hydrophilic CuFeS2 particles are coupled with multi-functional covalent organic frameworks through ionic bonding to produce a hybrid material with unique and optimized properties. To render the CuFeS2 particles negatively charged and dispersible in water, we coated them with sodium dodecyl sulfonate, shifting the surface plasmon resonance of the nanoparticles from 472 to 492 nm. When they are electrostatically assembled with the positively charged COFs, an S-scheme is formed and the fluorescence of the hybrid materials is highly quenched, with the electron transfer happening from the networks to the nanoparticles and a simultaneous energy exchange which is dependent on the emission wavelength. Through detailed fluorescence spectroscopy, time-resolved measurements and Stern-Volmer analysis, we identified an efficient emission quenching that differs from the bulk to the exfoliated hybrid system, while detailed electron microscopy studies demonstrated the strong interaction between the two components. The quenching mechanisms and the on or off surface resonance dependent lifetime could be applied to photocatalytic and photovoltaic applications.

Dynamic multivariate quantile inactivity time and applications in investigation of a treatment effect

&lt;p&gt;To investigate potentially dependent lifetimes, it is necessary to extend the $ \alpha $-quantile inactivity time to bivariate and multivariate frameworks. To extend this measure to a dynamic multivariate framework, all possible trajectories at time $ t $ are considered. The behavior of the extended $ \alpha $-quantile of inactivity time was investigated in relation to the corresponding multivariate hazard rate function. The $ \alpha $-quantile of the inactivity order is defined and discussed for the multivariate case. The difference between the two bivariate $ \alpha $-quantile functions of inactivity, which is an important measure for studying the effect of treatment on lifespan, was also investigated. This measure was used to analyze the effect of laser treatment on the delay of blindness. Two bootstrap approaches were implemented to construct confidence bounds for the difference measure.&lt;/p&gt;

Phonon anharmonicity and the pressure dependence of phonon lifetime for solid nitromethane by ab initio calculations

Phonon anharmonicity is important for energy transfer in energetic materials. Here we have investigated the vibrational anharmonicity including phonon lifetime, mode Grüneisen parameters and lattice thermal conductivity of solid nitromethane using first-principles calculations combining Boltzmann transport equation theory. The calculated structural and vibrational properties of solid nitromethane agree well with experimental results. It’s found that the CN stretching mode among all phonons has the longest lifetime with 99.3 ps at ambient condition. It’s worth noting that this would allow the vibrational energy to reside in this mode for a long time, leading to the formation of “hot” chemical bond and further its rapture. This is consistent with the previous report that the breakage of CN bond may be the initial reaction in nitromethane. The results also show the lifetimes of internal modes are generally higher than those of lattice modes. And the mode Grüneisen parameters indicate that the lattice modes are much more sensitive to the volume change than internal modes. Moreover, the lattice thermal conductivity of solid nitromethane shows obvious anisotropy. Finally, the influence of hydrostatic pressure on the phonon lifetime of solid nitromethane was also calculated and discussed.

Realizing Fluorescence Blinking in Monolayer MoSe2 with the Formation of 1D/2D Heterostructure

AbstractThe understanding and manipulating of photoluminescence blinking is essential in nano‐photonics and related device applications. The formation of mixed‐dimensional semiconductor heterostructures provides an important platform for the generation of blinking phenomena, which can be utilized to realize quantum emission properties of the heterostructures that are beyond the pure single material. Here, one‐dimensional (1D)/two‐dimensional (2D) heterostructures consisting of MoSe2 monolayer and a single CsPbBr3 perovskite nanowire are constructed. By studying the photoluminescence (PL) intensity time trajectory and lifetime, MoSe2 in heterostructure exhibits fluorescent blinking behavior, which has a negative correlation relation with the PL blinking in CsPbBr3 nanowire due to its super‐trap states. The excitation power dependent blinking and PL lifetime measurements of the heterostructure, as well as the low‐temperature PL spectroscopy, are performed to conclude that the bright state of MoSe2 in heterostructure is due to the suppressed interfacial charge transfer. In addition, MoSe2/hBN/PVK heterostructure is prepared and investigated, showing no blinking phenomena due to the dominated energy transfer process. This study not only provides a deeper understanding of interfacial charge transfer process in 1D/2D heterostructure, but also offers guidance for the design of photonic device with extended functionality.

On the optical properties of gallium based garnet phosphors according to Ca2Ln1-xCexZr2Ga3O12 (with Ln = Y, La, Gd, Lu)

Several samples of a gallium based garnet phosphor activated by cerium were investigated and reported upon in this work. Firstly, a solid solution corresponding to Ca2Lu1-xCexZr2Ga3O12 (x = 0.001–0.1), in which a doping level of 1 atom-% was revealed as the optimal activator concentration for high efficiency. Secondly, a range of samples according to the general composition Ca2(Y,La,Gd,Lu)0.99Ce0.01Zr2Ga3O12 was investigated to study the effect of different non emitting lanthanide ions on the optical properties. For this work various polycrystalline samples were synthesized and investigated by X-ray powder diffraction to determine the phase purity of the prepared samples. Fluorescence properties were examined employing excitation, emission, and diffuse reflectance spectroscopy. Temperature dependent emission spectra and fluorescent lifetimes were investigated to gain insight into the thermal quenching behaviour. From the spectroscopic investigation it was confirmed that the crystal field splitting of the cerium 5di components is strongly influenced by the size of the non-emitting lanthanide ion and the molar concentration of cerium. The change in crystal field splitting consequently shaped the excitation and emission wavelengths. Additionally, T1/2 values were determined from temperature dependent emission spectra and found to be between 230 and 250 K. Furthermore, luminescent lifetimes were calculated from pulsed laser excited decay curves. On the basis of the spectroscopy results potential applications of these phosphors are discussed.

Spectral (in)dependence of nonequilibrium charge carriers lifetime and density of states distribution in the vicinity of the band gap edge in F8BT polymer

Photoelectric properties of the F8BT polymer are investigated by the Constant photocurrent method (CPM) based on the photocurrent spectra Δjph(hν) and absorption spectra αCPM(hν). The negligibly weak dependence of charge carriers lifetime on the photon energy is found for hν = 2.2–2.7 eV. The peculiarities of the absorption spectra and the photoconductivity spectra are revealed to be determined mainly by the Gaussian distribution of the density of states (DOS). The density of trap states in the F8BT polymer thin films in the exponential DOS is estimated to be 103 times higher than in the Gaussian DOS.

The Perception of Spectacles Use Among the General Population in Ha'il Region, Saudi Arabia: A Cross-Sectional Study.

The study aims to assess the perception of optical spectacles use among the Ha'il region population in Saudi Arabia. A cross-sectional survey was distributed via various social media applications to the residents of the Ha'il region. An online questionnaire was designed and included informed consent and questions assessing the participants' perceptions about wearing eyeglasses, contact lenses, and general eye health. 32.4% of the participants think that long-term eyeglasses wearing worsens vision, and 43% think eyeglasses wearing improves vision. 75.2% believe that long-term use of glasses could cause lifetime dependency on eyeglasses. Regarding contact lenses, 45.9% believe that long-term wearing worsens vision, and 24.1% think long-term wearing of contact lenses improves vision. 60% think long-term use of lenses causes lifetime dependency on those contact lenses. Our results highlighted the misconceptions among the study population regarding wearing prescribed eyeglasses and contact lenses. Thus, education programs and media are warranted to correct the misconceptions about spectacles and raise the awareness about refractive errors and treatment options.