Radiative Transitions Research Articles

Convenient Size Analysis of Polystyrene Nanoplastics via Regulating the Radiative Transition Efficiency.

Developing a convenient method to efficiently determine the size of nanoplastics in the environment is urgent in terms of ecological or human health protection. In this work, a novel strategy for discriminating the size of polystyrene (PS)-based nanoplastics was reported via regulating the radiative transition efficiency of NH2-UIO-66 (NU) with benzoic acid (BA) as the auxiliary ligand. The elaborately doped BA capped the defect sites and triggered nonradiative transition efficiency of NU. As a result, the formed composite (denoted as BA-NU) was more sensitive to interaction among neighboring NU and nanoplastics. The interaction between particles limited the rotation and vibration of the benzene ring within the BA-NU molecule, thus increasing the BA-NU fluorescence. The sensitivity of BA-NU on nanoplastics was well controlled by manipulating the doping contents of BA, leading to precisely tunable physicochemical properties for this structure. Deriving from the exquisitely designed nanostructures, the composite of BA-NU was successfully used to discriminate different size PS as an ultrasensitive turn-on probe. This work highlights the possibility of boosting the detection performance by regulating the main structure with guest molecules at the molecular level.

Highly sensitive optical thermometer based on Li+-doped erbium ytterbium silicate films

This work provides a new material, Li+-doped erbium ytterbium silicate, with reliable and high temperature sensing sensitivity for optical thermometers. The Li+-doped erbium ytterbium silicate films were prepared by RF magnetron sputtering. The film shows strong green visible emission, which is related to the radiation transitions from thermally coupled energy levels 2H11/2, 4S3/2 to 4I15/2. Lithium doping reduces the field symmetry around erbium and improves the radiation transition efficiency, and Yb doping improves the pump light absorption. Lithium or ytterbium is advantageous to enhance up-conversion luminescence and temperature sensing sensitivity of erbium ions. Therefore, the temperature dependence of green up-conversion luminescence in the range of 80–460 K of the Li+-doped erbium ytterbium silicate films have been found to be a promising optical thermometer material with a high relative sensitivity of 16.9 % K−1, which is higher than the optimum value of other Er3+ materials. In addition, we have provided a preliminary temperature measurement scheme based on the Li+-doped erbium ytterbium silicate film.

Radiative transitions of χcJ→ ψγ and χbj→ Υγ

In the framework of instantaneous Bethe-Salpeter equation, according to the JPC of quarkonia, we find that their wave functions all contain multiple partial waves, rather than pure waves. In the radiative electromagnetic transitions χcJ→γψ and χbJ→γΥ (J = 0, 1, 2), the main wave of quarkonium gives the non-relativistic contribution, while other waves provide the relativistic corrections. Our results indicate that the relativistic effect of charmonium, especially highly excited states, is significant. Such as the relativistic effects of χcJ(2P) → γψ(1S) (J = 0, 1, 2) are {49.7%, 30.9%, 37.5%}, much larger than the corresponding {17.8%, 7.08%, 12.9%} of χbJ(2P) → γΥ(1S). The decay of χcJ(2P) → γψ can be used to distinguish between χc0(3860) and χc0(3915), which particle is the charmonium χc0(2P). Although our result of χc1(3872)→γψ(2S) is consistent with data, but the one of χc1(3872)→γψ(1S) is much larger than data, so whether χc1(3872) is the conventional χc1(2P) remains an open question. The undiscovered Υ(1D) and Υ(2D) have large production rates in decays of χb0(2P) → γΥ(1D) and χbJ(3P) → γΥ(2D) (J = 0, 1), respectively. To search for χbJ(3P) (J = 0, 1, 2), the most competitive channels are the decays χbJ(3P) → γΥ(3S). And the best way to find χb2(1F) is to search for the decay of χb2(1F) → γΥ(1D).

Role of the short-distance interaction in e+e−→γX(3872)

In this study, we analyze the cross-section data from the e+e−→γJ/ψω process to explore both short-distance and long-distance interactions for the radiative transition Y(4200)→γX(3872). We investigate the short-distance effects through the E1 transition among the cc¯ components, and the long-distance effects via hadronic loop diagrams. Our numerical analysis reveals that short-distance interactions play a significantly larger role in the radiative transition than that of the long-distance interactions. This finding underscores the importance of the compact cc¯ components in both the initial and the final states for accurately understanding the cross-section σ[e+e−→γJ/ψω]. Furthermore, with the help of relative branch ratio R we estimate the Γ[Y(4200)→γX(3872)] implied in the experimental study. Finally, we also discuss the possible existence of the ψ(4040) signal within the cross-section data. Published by the American Physical Society 2024

Room-temperature electroluminescence in the InAsSbP/InAs0.95Sb0.05/InAsSbP single quantum well

The electrical and luminescent characteristics of the heterostructure with a 20 nm-wide n-InAsSbP/n-InAs0.95Sb0.05/p-InAsSbP single quantum well, grown on an n-InAs substrate by the MOVPE method, have been studied. An intense room temperature electroluminescence (EL) with a maximum near the photon energy of 0.34 eV and a FWHM of 32 meV was discovered. It was established that the EL in such single quantum well has been emitted due to type I radiative transitions between the ground levels of electrons and holes both at forward and reverse bias. The characteristics of heterostructures with a single quantum well and the active region based on a bulk InAsSb layer of the same composition have been compared.

Structural, magnetic, and luminescent properties of NaGdF4:Nd3+@Fe3O4 nanocomposites

The diverse applications of nanomaterials, and their rapidly increasing demand, have spurred the development of novel multifunctional materials. As such, this study aimed to synthesize and characterize a magneto-luminescent nanocomposite, composed of magnetite and fluorescent quantum dots (NaGdF4:Nd3+@Fe3O4). Nanomaterial synthesis was accomplished through solvothermal and co-precipitation methods. Stable nanoparticles (NPs) with a zeta potential of -19.57 ± 0.42 mV, and a size of 4.55 ± 1.44 nm were obtained. The crystalline structure of the NPs, verified via x-ray diffraction, affirmed the hexagonal pattern of the NaGdF4:Nd3+NPs and the inverse spinel pattern of Fe3O4NPs. In the diffraction pattern of the NaGdF4:Nd3+@Fe3O4NPs, only the phase pertaining to the Fe3O4NPs was identified, indicating their influence on the nanocomposite. Magnetic measurements revealed the superparamagnetic behavior of the material. Photoluminescence spectra of NaGdF4:Nd3+and NaGdF4:Nd3+@Fe3O4NPs verified the luminescent emission around 1060 nm; a feature of the radiative transitions of Nd3+ions. Based on the assessed characteristics, the nanocomposite's multifunctionality was confirmed, positioning the material for potential use in various fields, such as biomedicine.

Linearly Arranged Multi‐π‐Stacked Structure for Efficient Through‐Space Charge‐Transfer Emitters

AbstractNoncovalent spatial interaction has become an intriguing and important tool for constructing optoelectronic molecules. In this study, we linearly attached three conjugated units in a multi π‐stacked manner by using just one trident bridge based on indeno[2,1‐b]fluorene. To achieve this structure, we improved the synthetic approach through double C−H activation, significantly simplifying the preparation process. Due to the proximity of the C10, C11, and C12 sites in indeno[2,1‐b]fluorene, we derived two novel donor|acceptor|donor (D|A|D) type molecules, 2DMB and 2DMFB, which exhibited closely packed intramolecular stacking, enabling efficient through‐space charge transfer. This molecular construction is particularly suitable for developing high‐performance thermally activated delayed fluorescence materials. With donor(s) and acceptor(s) constrained and separated within this spatially rigid structure, elevated radiative transition rates, and high photoluminescence quantum yields were achieved. Organic light‐emitting diodes incorporating 2DMB and 2DMFB demonstrated superior efficiency, achieving maximum external quantum efficiencies of 28.6 % and 16.2 %, respectively.

Linearly Arranged Multi-π-Stacked Structure for Efficient Through-Space Charge-Transfer Emitters.

Noncovalent spatial interaction has become an intriguing and important tool for constructing optoelectronic molecules. In this study, we linearly attached three conjugated units in a multi π-stacked manner by using just one trident bridge based on indeno[2,1-b]fluorene. To achieve this structure, we improved the synthetic approach through double C-H activation, significantly simplifying the preparation process. Due to the proximity of the C10, C11, and C12 sites in indeno[2,1-b]fluorene, we derived two novel donor|acceptor|donor (D|A|D) type molecules, 2DMB and 2DMFB, which exhibited closely packed intramolecular stacking, enabling efficient through-space charge transfer. This molecular construction is particularly suitable for developing high-performance thermally activated delayed fluorescence materials. With donor(s) and acceptor(s) constrained and separated within this spatially rigid structure, elevated radiative transition rates, and high photoluminescence quantum yields were achieved. Organic light-emitting diodes incorporating 2DMB and 2DMFB demonstrated superior efficiency, achieving maximum external quantum efficiencies of 28.6 % and 16.2 %, respectively.

Structure and photoluminescence properties of coordination compound [Eu2(o-MBA)6(phen)2] with high quantum yield

An europium(III) coordination binuclear compound [Eu2(o-MBA)6(phen)2] (o-MBA = ortho-methylbenzoate, phen = 1,10-phenantroline) has been synthesized and investigated by X-ray diffraction method, thermogravimetric analysis (TGA), infrared (IR) and photoluminescence (PL) spectroscopy. The single crystal X-Ray diffraction measurements show that the compound crystallizes in the triclinic centrosymmetric space group P-1. The PL excitation spectrum displays a broad band between 300 and 420 nm and a number of sharp transitions between 384 and 590 nm, which can be attributed to the Eu3+ 4f6 intra-shell excitation transitions. The complex exhibits characteristic narrow, metal-centred emission bands, which are determined by the radiative transitions of the Eu3+ ion, from the first excited non-degenerate 5D0 level to the 7FJ (J = 0–4) manifold. The compound shows intense hypersensitive transition 5D0→7F2 which dominates the PL emission spectrum. The dipole strengths of the transitions were determined from the emission spectra in terms of Judd-Ofelt (JO) intensity parameters Ωλ (λ = 2, 4). The high intensity bright-red emission of the complex can be attributed to highly polarizable ligands environment and the low site symmetry (Ci) around the lanthanide ions. We suppose that the J-mixing effect in the Eu(III) ions is responsible for enhanced peak maximum of the 5D0→7F0 transition.

Integrating Molecular Motions in Ternary Cocrystals for NIR‐II Photothermal Conversion

Organic photothermal conversion materials hold immense promise for various applications owing to their structural flexibility. Recent research has focused on enhancing near‐infrared (NIR) absorption and mitigating radiative transition processes. In this study, we have developed a viable approach to the design of photothermal conversion materials through the construction of ternary organic cocrystals, by introducing a third component as a molecular blocker and motion unit into a binary donor–acceptor system. Superstructural and photophysical properties of the ternary cocrystals were characterized using various spectroscopic techniques. The role of the molecular blocker in radical stabilization and photothermal conversion were demonstrated. Intriguingly, the motions of the entire pyrene molecules in the cocrystal have been observed by variable temperature single‐crystal X‐ray diffraction results. The excellent performance of ternary cocrystal as a photothermal material was validated through efficient NIR‐II photothermal and solar‐driven water evaporation experiments. The efficiency of water evaporation reached 88.7 %, with a corresponding evaporation rate of 1.29 kg m−2 h−1, representing excellent performance among pure organic small molecular photothermal conversion materials. Our research underscores the introduction of molecular blockers and motion units to stabilize radicals and produce outstanding photothermal conversion materials, offering new pathways for developing efficient and stable photothermal conversion materials.

Integrating Molecular Motions in Ternary Cocrystals for NIR-II Photothermal Conversion.

Organic photothermal conversion materials hold immense promise for various applications owing to their structural flexibility. Recent research has focused on enhancing near-infrared (NIR) absorption and mitigating radiative transition processes. In this study, we have developed a viable approach to the design of photothermal conversion materials through the construction of ternary organic cocrystals, by introducing a third component as a molecular blocker and motion unit into a binary donor-acceptor system. Superstructural and photophysical properties of the ternary cocrystals were characterized using various spectroscopic techniques. The role of the molecular blocker in radical stabilization and photothermal conversion was demonstrated. Intriguingly, the motions of the entire pyrene molecules in the cocrystal have been observed by the results of variable temperature single-crystal X-ray diffraction. The excellent performance of the ternary cocrystal as a photothermal material was validated through efficient NIR-II photothermal and solar-driven water evaporation experiments. The efficiency of water evaporation reached 88.7 %, with a corresponding evaporation rate of 1.29 kg m-2 h-1, representing excellent performance among pure organic small molecular photothermal conversion materials. Our research underscores the introduction of molecular blockers and motion units to stabilize radicals and produce outstanding photothermal conversion materials, offering new pathways for developing efficient and stable photothermal conversion materials.

Reactive magnetron deposition of YAG:Ce phosphor coatings in the metallic mode

The possibility of YAG:Ce3+ coatings phosphor formation by reactive magnetron deposition during sputtering of metal targets in an atmosphere of argon and oxygen activated by a radio-frequency source of inductively coupled plasma has been studied. The installation consists of three middle-frequency magnetrons with Y, Al and Ce targets with power of 1000, 1570 and 150 W, respectively. The (Y–Al–O):Ce coatings were deposited in metal and oxide sputtering modes of yttrium and aluminium targets. The coating deposition rate on the planetary rotating substrates in the metallic sputtering mode reaches of 0.67 nm/s. This is about an order of magnitude higher compared to the oxide sputtering mode and the method of radio-frequency magnetron sputtering of ceramic targets commonly used to deposit such coatings.Characterization of the elemental and phase composition of the coatings showed the YAG:Ce crystal structure formation during annealing both in air at 1100 °C and in a nitrogen atmosphere at 1200 °C. Cathodo- and photoluminescent spectroscopy was used for study of YAG:Ce thin films emission properties. The emission properties of YAG:Ce correspond to the radiation transition in Ce3+ ions. It was found that the intensity of both types of luminescence turned out to be slightly higher for samples annealed in air. It enhanced with increasing coating thickness in the considered range from 1.8 to 7.0 μm. The suggested approach could be potentially used for luminescent coatings formation with high level of the emission properties.

Bottomonia in quark-antiquark confining potential

This paper comprehensively explores bottomonia mass spectra and their decay properties by solving the non-relativistic Schrodinger wave equation numerically with an approximate quark-antiquark potential form. We also incorporate spin-dependent terms—spin-spin, spin-orbit, and tensor terms to remove mass degeneracy and to obtain excited states (nS, nP, nD, nF, n = 1, 2, 3, 4, 5) mass spectra. Using the Van Royen—Weisskopf formula, we investigate leptonic decay constants, di-leptonic, di-gamma, tri-gamma, di-gluon decay widths and incorporate first-order radiative corrections. We also computed radiative transition widths, which provide better insight into the non-perturbative aspects of QCD. The states ϒ(10750), ϒ(10860), ϒ(11020) are analyzed as pure states 33 D 1, 53 S 1 and 43 D 1, respectively. The present mass spectroscopy and decay properties results align with available experimental values and other theoretical predictions. Our results may provide better insight into upcoming experimental information in the near future.

M1 radiative and spin-nonflip ππ transitions of Bc states in the Cornell potential model

In this paper, we mainly predict the rates of M1 radiative and spin-nonflip ππ transitions of the Bc-meson under the nonrelativistic Cornell potential model with a screening potential effect. We employ the numerical wave function to determine the M1 radiative transition widths of Bc excited states and utilize the Kuang-Yan proposed method for the spin-nonflip ππ transitions among Bc states. Our theoretical results are valuable for studying the M1 radiative and spin-nonflip ππ transition processes of Bc states in experiments. Published by the American Physical Society 2024

Correlation between photoluminescence and radiative defects in silicon oxycarbide films due to the growth temperature effect

In this work, the effect of growth temperature (678–988 °C) on silicon oxycarbide (SiCxOy) samples obtained by hot filament chemical vapor deposition (HFCVD) is reported. The samples were deposited on silicon (Si) n-type (100) and quartz substrates for optical and structural studies. At a lower temperature (678 °C), silicon oxycarbide powders were formed on Si substrates due to the homogeneous reaction occurring in the gas phase. However, for temperatures between 804 and 988 °C, silicon oxycarbide films were formed on Si substrates. By changing the temperature from 678 to 988 °C, both carbon (C) concentration (21.2–17.7 wt.%) and the relative percentage of Si–C bond density (%RtSi-C = 11.34–3.47 %) decreased, as demonstrated by EDS and FTIR measurements, respectively. On the other hand, the content of relative Si–O–Si bonds located around 1060 cm−1 remained dominant in all cases, resulting in SiCxOy films with an amorphous SiOx-type structure. These films exhibited strong photoluminescence (PL) centered in the blue region (∼3 eV), where Si–NOVS radiative centers were preferentially responsible for PL emission. At a lower temperature (678 °C), the PL intensity decreased. The determination of optical bandgap energy (Eopt) using Tauc Plots coincided with the emission due to luminescent centers (∼3 and ∼2.7 eV) observed in PL, indicating that the radiative transitions were due to defects. The AFM measurements showed an increase in roughness from 5.01 to 16.20 nm as the growth temperature decreased, as expected according to SEM measurements.

Ultrafast Scintillator Based on Zirconium‐Doped Cesium Zinc Chloride Single Crystals and Their Charge Carrier Dynamics

AbstractScintillators have been widely used for high‐energy radiation imaging. It is in great demand and challenge to develop scintillator materials with fast decay time, high scintillation light yield, and low detection limit for high‐resolution imaging applications such as time‐of‐flight positron emission tomography. However, it is still a challenge to develop the ultrafast carrier dynamics to achieve 100% ultrafast decay time with high scintillation light yield. To meet the demand, a series of component‐tunable Cs2ZnCl4: x%Zr single crystals as promising ultrafast scintillators is successfully developed. With 8% of Zr‐dopant (Cs2ZnCl4: 8%Zr), the single crystal exhibits high light yield (28000 photons MeV−1) and low detection limit (51 nGy s−1) under X‐ray excitation. Photo‐induced transient absorption signals on sub‐nanosecond and nanosecond scales ensure almost 100% fast decay time (≈3 ns) in nanoseconds under γ‐ray excitation. In particular, the different radiative transition processes are achieved under ultraviolet and high‐energy radiation due to the tunable carrier dynamics from the shallow trapped state to the self‐trapped exciton (STE) state.

Enhanced terahertz radiation generated by intense laser interaction with a two-layer thin solid target

A terahertz radiation enhancing scheme, in which a linearly polarized weakly relativistic laser pulse irradiates a target consisting of two parallel thin-solid layers with a certain gap, is proposed and studied by using two-dimensional particle-in-cell simulations. The radiation is known to be produced by laser-produced hot electrons via mechanisms such as coherent transition radiation at the target surfaces. Under optimized conditions, the energy conversion efficiency of terahertz radiation can be as high as 3.3%, which is nearly 1.5 times higher than that obtained with a single-layer target with the same drive laser. This is mainly due to the enhanced hot electron generation with moderate energy via multiple reflections of the laser pulse between the two target layers. The radiation has two peaks close to 30° from the target surface, which are more collimated than that with the single-layer target. The dependence of the terahertz radiation on a variety of target parameters is given, which can control the terahertz spectrum and radiation efficiency and thus provide guidance for experimental investigations. Moreover, both the coherent transition radiation and antenna radiation models are applied to explain the angular distributions of the terahertz emission found in the simulations. Published by the American Physical Society 2024

Green’s functions in the presence of a bubble wall

Field theoretical tools are developed so that one can analyze quantum phenomena such as transition radiation that must have occurred during the Higgs condensate bubble expansion through plasma in the early universe. Integral representations of Bosonic and Fermionic propagators are presented for the case that particle masses are varied continuously during the passage through the bubble wall interface between symmetry-restored and symmetry-broken regions. The construction of propagators is based on the so-called eigenfunction expansion method associated with self-adjoint differential operators, developed by Weyl, Stone, Titchmarsh, Kodaira and several others. A novel method of field quantization in the presence of the bubble wall is proposed by using the spectral functions introduced in constructing the two-point Green’s functions.

Synthesis, optical properties, and applications of Eu3+, Na+-doped high-color-purity Sr3MgNb2O9 red phosphors for w-LEDs and the detection of latent fingerprints

A series of novel phosphors, doping Eu3+ and Na+ ions in the Sr3MgNb2O9 (SMNO) crystal lattice (SMNO:xEu3+, xNa+, x = 0.5–30 mol%), was successfully synthesized through high-temperature solid-state reaction. X-ray diffraction (XRD) analysis and Rietveld refinement confirmed the successful synthesis of SMNO:Eu3+, Na+. The phosphor belongs to the hexagonal crystal system and the P3¯m1 (No.164) space group. The bandgap energy of SMNO was calculated with Materials Studio and measured with the use of diffuse reflectance spectroscopy. The excitation spectrum of SMNO:Eu3+, Na+ displays multiple narrow absorption peaks in the violet-blue region as well as a charge transfer band (CTB) near 300 nm, exhibiting the highest peak at 394 nm. Four distinct characteristic peaks are observed in the emission spectrum of SMNO:Eu3+, Na+. Notably, the peak at 601 nm shows the highest emission intensity due to the radiative transition from 5D0→7F2. By varying doping concentrations, it was determined that an optimal concentration of 5 mol%Eu3+ resulted in phosphors, with high color purity exceeding 99 %. Concentration quenching is attributed to the nearest neighbor ions interaction. Furthermore, SMNO:Eu3+, Na+ exhibited good stability in 300–480 K, with luminescent intensity remaining 68.6 % at 420 K and 54.4 % at 480 K compared to room temperature (300 K). The internal quantum efficiency (IQE) of SMNO:5%Eu3+, 5 %Na+ is 65.0 %. Both red and white light-emitting diodes (LEDs) were prepared using SMNO:Eu3+, Na+. The chromaticity coordinates of w-LED were measured as (0.357, 0.376), correlating to a correlated color temperature (CCT) of 4685 K and exhibiting a good color rendering index (CRI, Ra = 88). Additionally, the latent fingerprint (LFP) development demonstrated clear visualization of Levels I-III characteristic structures of fingerprints when utilizing SMNO:Eu3+, Na+. These findings suggest promising applications for SMNO:Eu3+, Na+ in w-LED lighting and LFP development.

1,1,2,2-Tetra(4-carboxylphenyl)ethylene-Based Metal-Organic Gel as Aggregation-Induced Electrochemiluminescence Emitter for the Detection of Aflatoxin B1 Based on Nanosurface Energy Transfer.

In this Letter, a sensitive DNA sensing platform was developed using an indium-ion-coordinated 1,1,2,2-tetra(4-carboxylphenyl)ethylene (TPE) metal-organic gel (In-MOG) as an aggregation-induced electrochemiluminescence (AIECL) emitter and nanosurface energy transfer (NSET) as an efficient quenching strategy for detecting aflatoxin B1 (AFB1), the most dangerous food toxin. The coordination occurred in indium ions, and carboxyl groups restricted the internal rotation and vibration of TPE molecules, forcing them to release photons via radiative transitions. The quenchers of microfluidic-produced gold nanoparticles were embedded in a long-tailed triangular DNA structure, where the quenching phenomenon aligned with the theory of ECL-NSET under the overlap of spectra and appropriate donor-acceptor spacing. The proposed analytical method showed a sensitive ECL response to AFB1 in the wide concentration range of 0.50-200.00 ng/mL with a limit of detection of 0.17 ng/mL. Experimental results confirmed that constraining luminescent molecules using coordination and bonding to trigger the AIECL phenomenon was a promising method to prepare signal labels for the trace detection of food toxins.