Excitation Intensity Research Articles

Excellent irradiation stability of Ce3+-doped Na5Lu9-xGdxF32 glass-ceramics scintillator for X-ray imaging

Scintillators, owing to their exceptional ability to convert high-energy ionizing radiation into visible light, are the core component of X-ray radiography. However, conventional single-crystal scintillators are inadequate to satisfy the modern social and scientific demands. So, the development of novel scintillator materials is imminent. Herein, a series of Na5Lu9-xGdxF32:Ce3+ glass-ceramics (GCs) scintillators were elaborated by an exercisable and low-cost method. Benefiting from the proper introduction of Al powder and Gd3+, as well as the crystallization of Na5Lu9-xGdxF32 nanocrystal (NCs) after heat treatment, luminescence excited by ultraviolet and X-ray of the sample is enhanced significantly. The integrated X-ray excited luminescence intensity of the representative sample can reach up to 128% of that of Bi4Ge3O12. More importantly, the sample has excellent irradiation stability that is almost undamaged even exposed to high-energy X-ray radiation. Finally, satisfactory X-ray imaging based on the resultant sample was realized. The spatial resolution is as high as 14 lp mm−1, which exceeds that of many novel perovskite scintillators. Thus, this investigation promotes the development of low-cost, stable and high-performing Ce3+-activated GCs scintillators.

Localization and interaction of interlayer excitons in MoSe2/WSe2 heterobilayers

Transition metal dichalcogenide (TMD) heterobilayers provide a versatile platform to explore unique excitonic physics via the properties of the constituent TMDs and external stimuli. Interlayer excitons (IXs) can form in TMD heterobilayers as delocalized or localized states. However, the localization of IX in different types of potential traps, the emergence of biexcitons in the high-excitation regime, and the impact of potential traps on biexciton formation have remained elusive. In our work, we observe two types of potential traps in a MoSe2/WSe2 heterobilayer, which result in significantly different emission behavior of IXs at different temperatures. We identify the origin of these traps as localized defect states and the moiré potential of the TMD heterobilayer. Furthermore, with strong excitation intensity, a superlinear emission behavior indicates the emergence of interlayer biexcitons, whose formation peaks at a specific temperature. Our work elucidates the different excitation and temperature regimes required for the formation of both localized and delocalized IX and biexcitons and, thus, contributes to a better understanding and application of the rich exciton physics in TMD heterostructures.

High‐Performance NIR Emission in Chromium‐Doped Garnet Phosphors Enabled by Structure and Excitation Regulation

AbstractThe burgeoning phosphor‐converted near‐infrared light‐emitting diodes (pc‐NIR LEDs) have important applications in special illumination and spectroscopy analysis. However, the development of efficient NIR‐emitting phosphors with high performance is still a challenge. In this work, a chemical unit co‐substitution strategy is proposed to realize the excitation transition regulation and successfully achieve high‐performance NIR luminescence in Ca3‐yNayMg1‐ySb2‐xAl2+yO12: xCr3+ (0 ≤ x ≤ 0.05, 0 ≤ y ≤ 1) garnet‐type solid solution phosphors. Through the excitation transition modulation from the 4A2 ground state to the 4T1(4P) and 4T1(4F) excitation state, the excitation intensity at the blue light region is largely enhanced by 25.6 times. Moreover, the NIR‐emitting efficiency and thermal stability are improved, with the optimal luminescence internal quantum efficiency of 90.6% and thermal stability of 97%@423 K, without any flux‐assisted sintering or reduction atmosphere protection. The structure regulation induced small Stokes shift, weak electron‐phonon coupling effect, and decreased non‐radiative transition are responsible for the excellent NIR‐emitting performance. Finally, the NIR pc‐LED is fabricated with photoelectric efficiencies of 18.7%@100 mA and NIR output powers of 63 mW@100 mA, presenting potential applications in nondestructive internal defect detection, veins imaging, and night vision surveillance.

Novel Color Converters for High Brightness Laser‐Driven Projection Display: Transparent Ceramics–Glass Ceramics Film Composite

AbstractLaser‐driven projection display puts forward urgent demand for color converter materials to simultaneously achieve balanced‐spectrum properties and strong heat dissipation. Herein, this work develops a novel optofunctional composite by coupling Y3Al5O12:Ce3+ transparent ceramics (TC) with CaAlSiN3:Eu2+ phosphor‐in‐glass film (PiGF) for the first time. Remarkably, this new material architecture design enables a balance between the spectrum properties and heat dissipation ability, and can yield high‐quality white light with brightness of over 2500 lm, luminous efficacy (LE) of over 200 lm W−1, correlated color temperature (CCT) of 3700–4100 K, and improved color rendering index (CRI) of 60–70. Furthermore, the PiGF@TC‐converted laser projection system is also successfully designed, showing natural and real color restoration. Additionally, the combined action of thermal quenching and optical excitation intensity quenching is confirmed for the luminescence saturation upon high‐power blue laser driven. The main mechanism of optical quenching is identified to be energy upconversion dominated by second‐order nonlinear processes. The findings described here suggest a step toward developing the admirable laser‐driven color converters for next‐generation lighting sources.

Genesis of temperature-driven red-shift of charge transfer band edge for Sm3+-doped vanadate self-activated phosphor

The temperature-driven redshift of the charge transfer band (CTB) exhibits promising potential for optical temperature sensing as well as for the design of anti-thermal quenching phosphors. Therefore, it is essential to investigate the displacement mechanism in detail. In this contribution, we created LiCa2.95MV3O12:5%Sm3+ (M = Mg/Zn) phosphors with considerably red-shifted CTB edges upon temperature stimulation and outstanding anti-thermal quenching behavior. To investigate this unusual behavior, gaussian fitting was performed on the excitation spectra and emission spectra at different temperatures to investigate the redshift mechanism. By averaging the peak energy of the lowest excitation and emission peaks, the zero phonon line (Ezp) indicating the electronic energy level location of the charge transfer state (CTS) shows a downward trend is obtained. As well as the energy reduction of the 1A2(1T1)-1B1(1T2) and 1E(1T1)-1B1(1T2) absorption bands in the [VO4]3− group is observed. Therefore, the drop in the CTS electronic energy level is the dominant factor in the temperature-driven CTB redshift. Based on the redshift phenomenon and anti-thermal quenching phenomenon of CTB, the phosphor exhibited exceptional optical temperature measurement performance in all three thermometry modes of excitation intensity ratio (EIR), International Committee on Illumination (CIE) color coordinates, and fluorescence intensity ratio (FIR), demonstrating its broad application prospects in the field of optical temperature sensing as well as guiding the design of anti-thermal quenching phosphors.

Importance of evaluating the excitation intensity dependence of the temperature-dependent luminescence: Impact on optical thermometry and anti-thermal quenching performance

Afterglow materials exhibit distinct temperature-dependent luminescence compared to general optical materials due to the presence of extra unique energy transfer paths from traps to luminescent centers. These paths include: 1) energy transfer through the conduction band (CB), and 2) energy transfer via quantum tunneling channels to various energy levels. These have a notable impact on both the overall intensity and the relative intensity of emission at different temperatures, which is often unintentionally overlooked. To investigate the influence of these additional paths on temperature-dependent luminescence, we employed a simple yet effective method of varying the excitation light intensity in Y2CaSnGa4O12:Pr3+, an afterglow material. And the influences on optical thermometer and anti-thermal quenching performance were illustrated comprehensively. We ultimately arrived at some interesting and widespread conclusions: 1) The performance of fluorescence intensity ratio (FIR) thermometry, which relies on excitation intensity, can be stabilized by avoiding the presence of charging traps. The high sensitivity of the afterglow intensity ratio (AIR)-based thermometry, which does not require an external light source, may be closely associated with the quantum tunneling process. 2) The performance of trap-assisted anti-thermal quenching is excitation intensity-dependent. We elucidated the specific contribution of traps that had previously been unaccounted for in earlier reports.

Plasmon-enhanced circular dichroism spectroscopy of chiral drug solutions.

We investigate the potential of surface plasmon polaritons at noble metal interfaces for surface-enhanced chiroptical sensing of dilute chiral drug solutions with nl volume. The high quality factor of surface plasmon resonances in both Otto and Kretschmann configurations enables the enhancement of circular dichroism differenatial absorption thanks to the large near-field intensity of such plasmonic excitations. Furthermore, the subwavelength confinement of surface plasmon polaritons is key to attain chiroptical sensitivity to small amounts of drug volumes placed around ≃100 nm by the metal surface. Our calculations focus on reparixin, a pharmaceutical molecule currently used in clinical studies for patients with community-acquired pneumonia, including COVID-19 and acute respiratory distress syndrome. Considering realistic dilute solutions of reparixin dissolved in water with concentration ≤5 mg/ml and nl volume, we find a circular-dichroism differential absorption enhancement factor of the order ≃20 and chirality-induced polarization distortion upon surface plasmon polariton excitation. Our results are relevant for the development of innovative chiroptical sensors capable of measuring the enantiomeric imbalance of chiral drug solutions with nl volume.

All-fiber photoacoustic system for large-area nondestructive testing

Nondestructive testing (NDT) is of paramount importance in ensuring the safe operation of equipment. Among various NDT techniques, ultrasonic NDT has garnered widespread attention due to its high sensitivity, fast speed, and accurate defect location. Photoacoustic NDT, a burgeoning field in ultrasonic NDT, is particularly attractive due to its immunity to electromagnetic interference. However, existing photoacoustic NDT systems suffer from inadequate excitation intensity and complex ultrasonic signal characteristics, impeding large-area NDT and accurate crack visualization. In this study, we present an all-fiber photoacoustic system for large-area NDT. To address the issues, we have developed a photoacoustic generator unit that can be optimized and controlled to generate stronger ultrasonic signals. Furthermore, we have employed mode decomposition to simplify the detected ultrasonic signals by mitigating the acoustic impedance mismatch-induced mode mixing problem in the system. As a result, the technology allows for large-area crack monitoring of up to 50*50 cm2 with an improved resolution of 1 mm. The present technology paves the way for high-resolution equipment crack monitoring with substantially enhanced accuracy in various environments.

Phase-sensitive analysis of a two-color infrared photodetector using photoreflectance spectroscopy

The phase diagrams of photoreflectance spectra were investigated for an InGaAs two-color infrared photodetector. The diagrams for a high excitation intensity revealed that the spectrum is multi-component. The origin of these components was investigated, and the photoreflectance spectra and phase diagrams were also measured for an angle-polished version at different depths. With the help of the polished sample, the variation of the phase delay angles and the trapping time constants was tracked for different depths. Additionally, the polished version enables us to find a confirmation for the origins of the multi-component nature of the whole phase diagram. It can be concluded that when the phase delays or time constants of various components are very close, more attention should be paid to interfering with the phase-sensitive investigations of layered materials. As a main result, the consistency of the phase delay with interface trap densities was confirmed qualitatively. Using a reciprocal space map of the sample, this result can be a piece of experimental evidence for a correlation between the photoreflectance time constant and trap densities in the junctions. This non-contact method enables the characterization of layered devices, offering a valuable tool for achieving high-performance devices.

Preparation of smart glue using strontium aluminate and polylactic acid oligomer grafted Arabic gum

An intelligent nanocomposite adhesive was developed to streamline the manufacturing process for long-lasting photoluminescent and hydrophobic consumer goods. The photoluminescent adhesive composite continued to emit light for up to 120 min after being exposed to darkness. Using lanthanide-activated strontium aluminate (LaSA) nanoparticles (NPs; 5–11 nm) homogeneously immobilized in the eco-friendly polylactic acid oligomer grafted Arabic gum (PLA/AG), a light-transmitting nanocomposite adhesive agent was created. The produced adhesives at various LaSA NPs concentrations exhibited excitation intensity at 365 nm and an emission wavelength at 518 nm. Afterglow phosphorescence or fluorescence was seen in the emission spectra, depending on the LaSA ratio. The photochromic effect was observed as the adhesive film switch color from translucent to green in the presence of ultraviolet light and greenish-yellow in the absence of light. The LaSA nanoparticles embedded in the polylactic acid oligomer grafted Arabic gum matrix improved the nanocomposite hydrophobicity and scratch resistance. Both of durability and photostability of the LaSA@PLA/AG nanocomposite were found to be exceptional. This work verified the viability of mass producing photoluminescent adhesive for a variety of smart uses such as smart windows, smart packaging, and safety directional signs in buildings.

Principal-Internal Joint Resonance of an Axially Moving Beam with Elastic Constraints and Excited by Current-Carrying Wires

Principal-internal joint resonance of an axially moving beam with elastic constraints is investigated, where the beam is located in magnetic field excited by current-carrying wires. Based on the magnetoelasticity theory and Hamilton principle, the nonlinear magneto-elastic vibration equations are derived. The displacement function is obtained by the elastic constraint boundary condition, and then the equation is discretized into 2-DOF ordinary differential equations using the Galerkin integral method. The method of multiple scales is employed for obtaining the amplitude–frequency response equations with coupling of the first two vibration modes. Through examples, amplitudes varying with frequency tuning parameter, axial velocity, current intensity, and external excitation force are exhibited. Results indicate that as current intensity increases, electromagnetic damping increases and the amplitude decreases; As external excitation force increases and axial velocity decreases respectively, the amplitude increases and the system changes from single periodic motion to quasi-periodic motion and then to single periodic motion; The lower-order modes are always dominant when the principle-internal resonance occurs.

Excitation of exchange spin waves in the transition layer of the two-layer ferrite-ferrite structure

The possibility of intense excitation of exchange spin waves in a tangentially magnetized two-layer epitaxial film of iron yttrium garnet is demonstrated. The waves are excited in a thin transition layer at the interface between the ferrite layers, propagate into the doped layer with reduced magnetization, and reflect from its opposite surface. In continuous excitation mode, they can be observed as a series of spin wave resonance peaks. Mathematical processing of the measured frequencies of resonance peaks allows for the calculation of the magnetization profile of the doped layer and the modeling of the excitation and propagation processes of exchange spin waves. The proposed methodology of mathematical processing can be applied for non-destructive control of the layered structure of epitaxial ferrite structures.

Tuning LSPR of Thermal Spike-Induced Shape-Engineered Au Nanoparticles Embedded in Si3N4 Thin-Film Matrix for SERS Applications.

While gold nanoparticles (Au NPs) are widely used as surface-enhanced Raman spectroscopy (SERS) substrates, their agglomeration and dynamic movement under laser irradiation result in the major drawback in SERS applications, viz., the repeatability of SERS signals. We tune the optical and structural properties of size- and shape-modified Au NPs embedded in a thin silicon nitride (Si3N4) matrix by intense electronic excitation with swift heavy ion (SHI) irradiation with the aim of overcoming this classical SERS disadvantage. We demonstrate the shape evolution of a single layer of Au NPs inserted between amorphous Si3N4 thin films under fluences of 120 MeV Au9+ ions ranging between 1 × 1011 and 1 × 1013 ions cm-2. This shape modification results in the gradual blue shift of the localized surface plasmon resonance (LSPR) dip until 1 × 1012 ions/cm2 and then a sudden diminishment at 1 × 1013 ions/cm2. Finite domain time difference (FDTD) simulations further justify our experimental optical spectra. The dynamical NP aggregation and dissolution, in addition to NP elongation and deformation at different fluences, are noted from 2D grazing incidence small-angle X-ray scattering (GISAXS) profiles, as well as cross-sectional transmission electron microscopy (X-TEM). The systematic shape evolution of metal NPs embedded in the insulating matrix is shown to be due to thermal spike-induced localized melting and a localized pressure hike upon SHI irradiation. Utilizing this specific control over the characteristics of Au NPs, viz., shape, size, interparticle gap, and corresponding optical response via SHI irradiation, we demonstrate their applications as very stable SERS substrates, where the separation between NPs and analyte does not alter under laser illumination. Thus, these irradiated SERS active substrates with controlled NP size and gap provide the optimal conditions for creating localized electromagnetic hotspots that amplify the SERS signals, which do not alter with time or laser exposure. We found that the film irradiated with 1 × 1011 exhibits the highest SERS intensity due to its optimal NP size distribution and shape. Thus, not only our study provides a SERS substrate for stable and repeatable signals but also the understanding depicted here opens new research avenues in designing SERS substrates, photovoltaics, optoelectronic devices, etc. with ion beam irradiation.

Effects of confining pressure and pore pressure on multipole borehole acoustic field in fluid-saturated porous media

In-situ stress is a common stress in the exploration and development of oil reservoirs. Therefore, it is of great significance to study the propagation characteristics of borehole acoustic waves in fluid-saturated porous media under stress. Based on the acoustoelastic theory of fluid-saturated porous media, the field equation of fluid-saturated porous media under the conditions of confining pressure and pore pressure and the acoustic field formula of multipole source excitation in open hole are given. The influences of pore pressure and confining pressure on guided waves of multipole borehole acoustic field in fluid-saturated porous media are investigated. The numerical results show that the phase velocity and excitation intensity of guided wave increase significantly under the confining pressure. For a given confining pressure, the phase velocity of the guided wave decreases with pore pressure increasing. The excitation intensity of guided wave increases at low frequency and then decreases at high frequency with pore pressure increasing, except for that of Stoneley wave which decreases in the whole frequency range. These results will help us get an insight into the influences of confining pressure and pore pressure on the acoustic field of multipole source in borehole around fluid-saturated porous media.

Cooperative luminescence of Yb3+ ions in multisite YAM crystal

A series of Yb3+-doped yttrium aluminum monoclinic Y4Al2O9 (Yb:YAM) single crystals with Yb3+ ion concentrations of 0.1, 1, 5 and 10 at.% was grown by means of micro pulling down method. Blue emission was observed in Yb3+ activated YAM crystals under infrared site-selective laser excitation. Through the excitation and emission spectra, decay time measurements and excitation intensity dependence the process responsible for this anti-Stokes emission was assigned to the cooperative deexcitation of two Yb3+ ions. The results show that at 10% Yb3+ dopant concentration investigated system could be considered as single-site system in which cooperative luminescence is dominated by the energetically lowest Yb3+ site. Theoretical cooperative emission spectrum and the cooperative luminescence rate of Yb3+:YAM were calculated.

The universal luminescence behavior of three-level system

The universal luminescence behavior of three-level system is studied. Through theoretical analysis, the population of each energy level under different pump powers could be obtained. Further, the power decay rate coefficient (kD) was proposed and analyzed. The kD represents the effect of the excitation pump power on the decay process of S2, and it is universal available either under weak or intense excitation powers. Besides, the population of S2 could be described by the ratio of kD to the total decay rate. The above analysis could be verified through the experiment.

Dual-excitation carbon dots-based lateral flow visual sensing device for ratiometric determination and discrimination of tetracyclines in food

Excessive releasing of tetracyclines in the nature has constituted a major threat to ecosystem. Therefore, it is crucial to develop an accurate and convenient on-site analysis device for tetracyclines. Herein, we construct a neoteric dual-excitation carbon dots (DE-CDs) through microwave radiation and establish an excitation-based ratiometric approach for quantitative tetracyclines determination. The ratio of different excitation intensities under the same emission wavelength changes linearly in response to tetracyclines concentration. As a proof of feasibility, we choose doxycycline (DOX) as the analysis model. It shows a low detection limit (LOD) of 61 nM in a wide concentration range of 0.061–80 µM, suggesting that this sensor is conducive to application potential in tetracyclines determination of food products. Moreover, considering the differentiated overlap between tetracyclines absorbance and DE-CDs excitations, the discrimination of tetracyclines is realized in the form of mixtures. Significantly, combining with the DE-CDs, RGB (Red, Green and Blue) analysis and 3D printing technologies, we construct a miniaturized visual sensing device with low LOD and achieve the discrimination of TCs based on RGB variations, showing a great opportunity for industrial production of pollutant monitoring sensors in resource-constrained areas.

ZARURIY MUDOFAA CHEGARASIDAN CHETGA CHIQIB VA KUCHLI RUHIY HAYAJONLANISH HOLATIDA QASDDAN ODAM O‘LDIRISHNING FARQLI JIHATLARI

This article analyzes the different aspects of intentional homicide in a state of intense emotional excitement and beyond the bounds of necessary defense. This article focuses on two situations. First, jealousy is a concept that applies not only to the relationship between husband and wife but also to the relationship between people in a wider circle, and the feeling of jealousy is also between parents and children or other relatives, or between an engaged boyfriend and girlfriend. or opinions about the possibility of it occurring between those who love each other have also been analyzed. Continuing in the article, scholars who think about jealousy in the second place try to associate this concept with betrayal or infidelity. However, it is appropriate to take into account that infidelity between a couple can be done not only by betrayal but also by hugging or expressing love to another person, and thirdly, there are many situations that cause jealousy. In addition, when qualifying the act with Article 98 of the Criminal Code, he also explained the expediency of paying attention to the sudden and sharp occurrence of a state of strong emotional excitement caused by jealousy.

A DNA‐Stabilized Ag1812+ Cluster with Excitation‐Intensity‐Dependent Dual Emission

AbstractDNA‐stabilized silver nanoclusters (DNA‐AgNCs) are easily tunable emitters with intriguing photophysical properties. Here, a DNA‐AgNC with dual emission in the red and near‐infrared (NIR) regions is presented. Mass spectrometry data showed that two DNA strands stabilize 18 silver atoms with a nanocluster charge of 12+. Besides determining the composition and charge of DNA2[Ag18]12+, steady‐state and time‐resolved methods were applied to characterize the picosecond red fluorescence and the relatively intense microsecond‐lived NIR luminescence. During this process, the luminescence‐to‐fluorescence ratio was found to be excitation‐intensity‐dependent. This peculiar feature is very rare for molecular emitters and allows the use of DNA2[Ag18]12+ as a nanoscale excitation intensity probe. For this purpose, calibration curves were constructed using three different approaches based either on steady‐state or time‐resolved emission measurements. The results showed that processes like thermally activated delayed fluorescence (TADF) or photon upconversion through triplet‐triplet annihilation (TTA) could be excluded for DNA2[Ag18]12+. We, therefore, speculate that the ratiometric excitation intensity response could be the result of optically activated delayed fluorescence.

A DNA-Stabilized Ag18 12+ Cluster with Excitation-Intensity-Dependent Dual Emission.

DNA-stabilized silver nanoclusters (DNA-AgNCs) are easily tunable emitters with intriguing photophysical properties. Here, a DNA-AgNC with dual emission in the red and near-infrared (NIR) regions is presented. Mass spectrometry data showed that two DNA strands stabilize 18 silver atoms with a nanocluster charge of 12+. Besides determining the composition and charge of DNA2 [Ag18 ]12+ , steady-state and time-resolved methods were applied to characterize the picosecond red fluorescence and the relatively intense microsecond-lived NIR luminescence. During this process, the luminescence-to-fluorescence ratio was found to be excitation-intensity-dependent. This peculiar feature is very rare for molecular emitters and allows the use of DNA2 [Ag18 ]12+ as a nanoscale excitation intensity probe. For this purpose, calibration curves were constructed using three different approaches based either on steady-state or time-resolved emission measurements. The results showed that processes like thermally activated delayed fluorescence (TADF) or photon upconversion through triplet-triplet annihilation (TTA) could be excluded for DNA2 [Ag18 ]12+ . We, therefore, speculate that the ratiometric excitation intensity response could be the result of optically activated delayed fluorescence.