Light Emission Research Articles

Status of dual-readout calorimetry for future high-energy physics experiments

Future experiments at high energy e + e - colliders will focus on extremely precise Standard Model measurements. Among the most important physics benchmarks, there is the capability to resolve the Higgs decays into W or Z pairs, in their completely hadronic decay modes (4 jets in the final state), only based on the invariant mass of the jet pair coming from decay of the on-shell boson. This translates into a relative energy resolution target of 30%/√E, well beyond current detector performances. Dual-readout calorimetry is a technique which aims to improve the energy resolution, for single hadrons and hadronic jets, exploiting the information produced by two different physical processes, namely scintillation and Čerenkov light emission. The IDEA detector, whose concept has been included in both the FCC and CEPC Conceptual Design Reports, is based on a dual-readout fibre calorimeter with independent fibre readout exploiting Silicon PhotoMultipliers (SiPMs). The individual SiPM information will be beneficial for a highly granular calorimeter design, opening up to advanced reconstruction techniques such as Particle Flow and a variety of neural network algorithms.In this paper the status of calorimeter prototypes that have been developed to demonstrate the feasibility of the dual-readout method in association with the high granularity feature is illustrated. The specific choice for the design of each prototype is presented, together with the performances achieved at high-energy test beams or through simulations.

Interaction of atmospheric pressure helium plasma jet with non-planar substrates: path selectivity of surface ionization wave

Most surfaces treated by atmospheric pressure plasma jets (APPJs) in practical applications are notably three-dimensional. However, non-planar surfaces exhibit a diverse array of geometries, such as variations in curvature, roughness, and texture, complicating the prediction of surface ionization waves (SIWs) propagation behavior across varied surface shapes, in the absence of sufficient experimental data. In this study, we made measurements of APPJ interactions with the non-planar substrates using the spatio-temporal resolved image method. Non-planar substrates encompassed wavy surfaces, arrayed hemispheres, and randomly textured raised surfaces. We tracked the morphology and velocity of SIW propagation over these surfaces. The results indicate that the SIW propagation on non-planar surfaces is significantly influenced by surface geometry and displays path selectivity, i.e. the SIW tends to propagate along valleys. The average propagation velocity of the SIW increases with the increasing radius of the wavy surface, as well as with the increased height of the arrayed hemispheres. This is attributable to the surface geometry constraining the dispersion of the SIW, causing it to concentrate and propagate in a singular direction. Moreover, the surface geometry markedly affects the distribution of the plasma treatment area, with the plasma inclined to enter valleys (where the light emission is significantly stronger than that of peaks) and to closely adhere to hemispherical surfaces. These patterns suggest a potential positive impact on treating skin surfaces such as pores, reducing bacteria in wrinkles, and addressing pimples.

Simulating X-Ray Reverberation in the Ultraviolet-emitting Regions of Active Galactic Nuclei Accretion Disks with Three-dimensional Multifrequency Radiation Magnetohydrodynamic Simulations

Active galactic nuclei (AGN) light curves observed with different wave bands show that the variability in longer wavelength bands lags the variability in shorter wavelength bands. Measuring these lags, or reverberation mapping, is used to measure the radial temperature profile and extent of AGN disks, typically with a reprocessing model that assumes X-rays are the main driver of the variability in other wavelength bands. To demonstrate how this reprocessing works with realistic accretion disk structures, we use 3D local shearing box multifrequency radiation magnetohydrodynamic simulations to model the UV-emitting region of an AGN disk, which is unstable to the magnetorotational instability and convection. At the same time, we inject hard X-rays (>1 keV) into the simulation box to study the effects of X-ray irradiation on the local properties of the turbulence and the resulting variability of the emitted UV light curve. We find that disk turbulence is sufficient to drive intrinsic variability in emitted UV light curves and that a damped random walk model is a good fit to this UV light curve for timescales >5 days. Meanwhile, X-ray irradiation has negligible impact on the power spectrum of the emitted UV light curve. Furthermore, the injected X-ray and emitted UV light curves are only correlated if there is X-ray variability on timescales >1 day, in which case we find a correlation coefficient r = 0.34. These results suggest that if the opacity for hard X-rays is scattering dominated as in the standard disk model, hard X-rays are not the main driver of reverberation signals.

In-situ synthesis of CdS and Ag2S quantum dots in poly(diallyldimethylammonium chloride) gels

In this study, we proposed a hybridization method for polymer and quantum dots (QDs) by directly forming QDs in polymer gel; this method was completely different from conventional methods such as mixing and encapsulation. QDs were fabricated by reacting metal ions in solution with sulfide ions adsorbed in a gel made from poly(diallyldimethylammonium chloride) (PDADMAC), a cationic polymer. CdS and Ag2S QDs were successfully fabricated in PDADMAC gel for in situ synthesis, and visible light (534 nm) and NIR (1070 nm) emissions were observed in PDADMAC gel containing CdS and Ag2S QDs, respectively. We also discussed the formation mechanism of QDs in the gel considering the mesh size of polymer networks in PDADMAC gel.

Front Cover: Light‐up the white light emission in microscale with a superior deep‐blue AIE fiber as wave‐guiding source

Front Cover: Light‐up the white light emission in microscale with a superior deep‐blue AIE fiber as wave‐guiding source

Synthesisation of Photo-Mechanoluminescence Crystal of Europium Dibenzoylmethide Triethylamine (EuD4TEA) with Different Solvent

EuD4TEA crystals have a few fascinating properties, such as photoluminescence and mechanoluminescence. Both phenomena occur when external excitation is performed on EuD4TEA crystals. Photoluminescence is excited by external light radiation, whereas mechanoluminescence is stimulated by an external mechanical force applied to it. EuD4TEA has easily been prepared only by standard crystallisation using dibenzoylmethane, europium nitrate hexahydrate, and triethylamine. This research mainly focused on the solvent for the synthesis of EuD4TEA crystals. The solvents used were ethanol and acetone. Acetone has the main credit for producing much higher-quality EuD4TEA crystals in certain aspects. Acetone-based end products are larger and have higher light emission under excitation.

A novel halide hybrid white light emitter with remarkable structural and emission stability

Addressing the issues of self-absorption effect among different components in traditional white light-emitting diodes (WLEDs) and the high cost associated with rare earth elements, we propose the potential utility of zero-dimensional organic–inorganic metal halide hybrids (0D OIMHs) in white WLEDs fabrication. In this study, we synthesized a novel 0D OIMH, (C5N2H14)ZnCl4, characterized by broadband white light emission. The (C5N2H14)ZnCl4 crystal features a short ultraviolet cutoff situated at 190 nm and emits cold white light with a Color Rendering Index (CRI) of 73 under an excitation wavelength of 260 nm. Furthermore, (C5N2H14)ZnCl4 demonstrates exceptional structural and emission stability in an air atmosphere over a span of three months.

Enhanced thermal stability and luminous properties of Dy3+/Tm3+/Eu3+ doped glass ceramics containing Sr4Bi(PO4)3O crystalline phases based on back energy transfer

White light emitting and optical temperature sensing materials with high thermal stability have broad market development prospects. The use of substrates with excellent thermal stability is a common idea to improve thermal stability, while the modulation of dopants to enhance thermal stability has been less studied. Therefore, in this work, Tm3+/Dy3+/Eu3+ doped transparent glass ceramics containing Sr4Bi(PO4)3O crystalline-phase were prepared by melt-crystallization method to achieve warm white light emission and optical temperature sensing with good thermal stability. Since the Tm3+-Dy3+ doped samples can only achieve cold white light emission, warm white light emission is obtained by adding Eu3+, which can emit red light. The application scenario of the material is expanded. The luminous intensities of Tm3+, Dy3+, and Eu3+ were 109.4 %, 89.1 %, and 70.7 % of those at room temperature, at 473 K. The increase in the emission intensity of Tm3+ was explained by the presence of back energy transfer (BET) from Dy3+ and Eu3+ to Tm3+. The chromaticity shift (Δε) of the samples was 2.43 × 10−4 and the luminescent colour was stable. The absolute sensitivity of the material can reach 0.69 K−1 at 473 K, and the relative sensitivity of the material can reach 1.60 % K−1 at 293 K. This work provides new ideas for the study of improving the thermal stability of materials.

Green innovation: cool white light emission from inorganic ZnS nanoparticles with tunable structural and optical properties

Green innovation: cool white light emission from inorganic ZnS nanoparticles with tunable structural and optical properties

Optical Properties of Gd2O3 with Silver doped Zinc Borate Glasses

Glasses with chemical composition ZnO-B2O3-Gd2O3-Ag2O were prepared using melt quenching method. The synthesized glass was characterized using X-ray diffraction method. The densities of these glasses were measured using the Archimedes method, and the corresponding molar volumes were calculated using the corresponding formula. Absorption spectra were recorded using a UV-visible spectrometer. The energy bandgap was investigated using the Tauc’s diagram. The variation of band gap energy in relation to Gd2O3 concentration has been discussed. Study the structure and functional groups of the prepared samples were studied using FTIR spectra. Emission and excitation spectra were recorded using a luminescence spectrometer. Photoluminescence spectra provides stable blue light emission in rich in Gd2+ ions glass, Color coordination has also been decided using CIE chromaticity diagram and showing that blue emission was observed in all samples with slightly different positions.

Red–Green–Blue Light Emission from Composition Tunable Semiconductor Micro‐Tripods

AbstractMicro/nanoscale lasers that span the entire visible spectrum, especially those in red, green, and blue colors, are not only essential for a variety of optical devices but also have important applications in visible color communication, multi‐color fluorescence sensing, and wavelength division multiplexing. Despite the great efforts made to achieve multi‐color lasing using a variety of approaches, on‐chip white light emission and even red, green, and blue multi‐color lasers still suffer from considerable challenges in micro‐nano structures. Here, CdSxSe1−x, CdS, and ZnS micro‐tripod structures are successfully prepared using chemical vapor deposition approaches. The micro‐photoluminescence (µ‐PL) spectra and PL‐mapping of these micro‐tripods reveal various emissions at 630, 508, and 460 nm, respectively. Additionally, white‐light emissions based on these composition‐tunable tripods are realized through an end‐coupling structure system. Moreover, room‐temperature modes tunable lasers are observed clearly from three legs of these micro‐tripods, with a low threshold of ≈48.39 µJ cm−2 and a high quality factor of 1227.3. The realization of micro‐tripods‐based lasers may provide an innovative way for highly integrated photonic circuits and communications.

Overcoming Challenges in OLED Technology for Lighting Solutions

In academic research, OLEDs have exhibited rapid evolution thanks to the development of innovative materials, new device architectures, and optimized fabrication methods, achieving high performance in recent years. The numerous advantages that increasingly distinguish them from traditional light sources, such as a large and customizable emission area, color tunability, flexibility, and transparency, have positioned them as a promising candidate for various applications in the lighting market, including the residential, automotive, industrial, and agricultural sectors. However, despite these promising attributes, the widespread industrial production of OLEDs encounters significant challenges. Key considerations center around efficiency and lifetime. In the present review, after introducing the theoretical basis of OLEDs and summarizing the main performance developments in the industrial field, three crucial aspects enabling OLEDs to establish a competitive advantage in terms of performance and versatility are critically discussed: the quality and stability of the emitted light, with a specific focus on white light and its tunability; the transparency of both electrodes for the development of fully transparent and integrable devices; and the uniformity of emission over a large area.

PyDAP: Automated dental OPG beam area measurement using python and raspberry Pi camera

IntroductionThis study investigates if inexpensive computer hardware, open-source computer vision and a phosphor screen from disused CR (computed radiography) Cassette can be used to quantitatively assess beam shape and area. Materials and MethodsThe phosphor screen was affixed to a Carestream CS 8100 dental OPG system and the camera was mounted above the X-ray tube. Videos were acquired of the green light emissions during the tomographic irradiation. Images of a chessboard pattern, attached to the detector were used to correct for camera angulation and provide image pixel size calibration. K-Means colour clustering was used to define beam area. The effect of light conditions on beam dimension measurement was also investigated. The beam width measurement from optimised methodology was compared with that determined from dose calibrated GAFChromicTM XR-SP2film. ResultsVideos in dark conditions provided the most reproducible results. FW20M gained from initial sampling matched that obtained using the GAFChromicTM film within the errors of the measurements,6.41 ± 0.09 mm FW20M from this methodology,compared with FW20M (full width at 20 % of maximum) 6.4 ± 0.1 mm from film. The height and area were 126 ± 0.22 mm and 807 ± 11 mm2 respectively. The chess pattern imaging provided a robust means of perspective correction and pixel calibration. There is potential for this methodology to be employed using any digital camera, provided the camera acquisition settings remain constant, the sensor pixels are square, and the camera position is fixed. ConclusionThe potential of this low-cost open-source method of beam area measurement using computer vision is thus proven.

Two-Coordinate Thermally Activated Delayed Fluorescence Coinage Metal Complexes: Molecular Design, Photophysical Characters, and Device Application.

Since the emergence of the first green light emission from a fluorescent thin-film organic light emitting diode (OLED) in the mid-1980s, a global consumer market for OLED displays has flourished over the past few decades. This growth can primarily be attributed to the development of noble metal phosphorescent emitters that facilitated remarkable gains in electrical conversion efficiency, a broadened color gamut, and vibrant image quality for OLED displays. Despite these achievements, the limited abundance of noble metals in the Earth's crust has spurred ongoing efforts to discover cost-effective electroluminescent materials. One particularly promising avenue is the exploration of thermally activated delayed fluorescence (TADF), a mechanism with the potential to fully harness excitons in OLEDs. Recently, investigations have unveiled TADF in a series of two-coordinate coinage metal (Cu, Ag, and Au) complexes. These organometallic TADF materials exhibit distinctive behavior in comparison to their organic counterparts. They offer benefits such as tunable emissive colors, short TADF emission lifetimes, high luminescent quantum yields, and reasonable stability. Impressively, both vacuum-deposited and solution-processed OLEDs incorporating these materials have achieved outstanding performance. This review encompasses various facets on two-coordinate TADF coinage metal complexes, including molecular design, photophysical characterizations, elucidation of structure-property relationships, and OLED applications.

Unveiling Polymorphs and Polytypes of the 2D Layered Semiconducting Gallium Monosulfide

AbstractPolymorphism is gaining attention among van der Waals layered materials. In the case of gallium monosulfide, a hexagonal phase has predominantly been reported. Here the successful growth of rhombohedral gallium sulfide (GaS) with space group on sapphire substrates using chemical vapor deposition (CVD) is presented. Crystallographic analysis reveals that the CVD GaS has preferred 𝑐‐axis orientation, low microstrain and moderate mosaicity. A combined approach of X‐ray diffraction, Raman spectroscopy and photoluminescence measurements with first principles calculations is used to determine phononic and photonic properties of the rhombohedral GaS with direct band gap of 2.55 eV and near‐blue light emission at room temperature. These results pave the way to novel applications in optoelectronics and photonics, particularly for development of efficient light‐emitting devices such as LEDs or lasers, quantum dots, photodetectors, and integrated photonic circuits.

Controlling the helicity of light by electrical magnetization switching.

Controlling the intensity of emitted light and charge current is the basis of transferring and processing information1. By contrast, robust information storage and magnetic random-access memories are implemented using the spin of the carrier and the associated magnetization in ferromagnets2. The missing link between the respective disciplines of photonics, electronics and spintronics is to modulate the circular polarization of the emitted light, rather than its intensity, by electrically controlled magnetization. Here we demonstrate that this missing link is established at room temperature and zero applied magnetic field in light-emitting diodes2-7, through the transfer of angular momentum between photons, electrons and ferromagnets. With spin-orbit torque8-11, a charge current generates also a spin current to electrically switch the magnetization. This switching determines the spin orientation of injected carriers into semiconductors, in which the transfer of angular momentum from the electron spin to photon controls the circular polarization of the emitted light2. The spin-photon conversion with the nonvolatile control of magnetization opens paths to seamlessly integrate information transfer, processing and storage. Our results provide substantial advances towards electrically controlled ultrafast modulation of circular polarization and spin injection with magnetization dynamics for the next-generation information and communication technology12, including space-light data transfer. The same operating principle in scaled-down structures or using two-dimensional materials will enable transformative opportunities for quantum information processing with spin-controlled single-photon sources, as well as for implementing spin-dependent time-resolved spectroscopies.

Developing an Automated Spectrophotometer with RGB LED and Light Sensor Using Arduino Microcontroller

This research used RGB LED (Red Green Blue Light Emission Diode), LDR (Light Dependent Resistant) sensors, 3D printed sampling cartridge, and Arduino Mega to create a spectrophotometer with automation software to select wavelength, calculate calibration parameters, and report the concentration of the materials being studied. Spectrophotometers are finding applications across many fields, including clinical laboratories, pharmaceuticals, molecular biology, biochemistry, and even the medical realm. This study assembled an Arduino mega system coupled with software for the automatic selection of best-fit color light, calibration curve, and actual concentration interpolation processes. Dilution solutions from multiple chemical materials were evaluated to examine their linearity of calibration curves. Our study demonstrated that the tested chemical samples revealed a significant regression coefficient of up to 0.9945 for serial dilution solutions. Relative concentrations were measured with remarkable precision, exhibiting less than 5.0 % error compared to a commercial spectrophotometer. These findings highlight the viability of the RGB spectrophotometer and emphasize its potential with the promise of further refinement in development.

White-light clusteroluminescence of poly(β-hydroxyvinyl N-substituted carbamate)s via through-space interactions

White-light-emitting polymers have attracted considerable attention in the fields of solid-state lighting and flexible displays. However, achieving white light emission from single-component polymers, particularly in clusteroluminescence (CL) polymers, remains a significant challenge. Herein, we synthesize three non-conjugated luminescent poly(β-hydroxyvinyl N-substituted carbamate)s (PHNCs): PHNCs-C with steric cyclohexyl groups, PHNCs-E with side hydroxyethyl groups, and PHNCs-H with flexible n-hexyl carbon chains. All PHNCs show excitation-independent emission, which transitions to excitation-dependent emission as the excitation wavelengths increase. It is proposed that these emissions originate from the π*→n transition of carbamate in hydroxyurethane and CL of hydroxyurethane, respectively. PHNCs-C exhibits the strongest CL and possesses the highest quantum yield (17.9 %) in solution, a performance that surpasses both PHNCs-E and PHNCs-H. This finding implies that a rigid structure can enhance and stabilize the through-space interactions (TSIs) of hydroxyurethane groups, resulting in a wide cluster-size distribution and white-light emission. Theoretical calculations corroborate these experimental results, further revealing that TSIs occur between the oxygen atoms of hydroxyurethane groups, namely, through-space n-n interactions of oxygen atoms. This work not only provides valuable insights into the nature of CL and TSIs, but also offers a novel approach to preparing single-component white-light-emitting CL polymers.

High sensitivity of whitlockite-type phosphor toward optical thermometric

Whitlockite-type structure phosphors have been widely studied due to their adjustable chemical composition and abundant crystal location. Whitlockite-type phosphors can be doped with rare earth elements to achieve the emission of warm white light. White light-emitting diodes (w-LEDs) have become increasingly popular and play a significant role in many applications, such as Biosensing and fluorescent labeling. In this work, The Ca2.6K0.2La0.2(PO4)2(CKLP) whitlockite-type phosphors co-doped with Dy3+ and Sm3+ were entered via a high-temperature solid-phase reaction. Their crystal structure, luminescence characteristics, and temperature sensitivity were explored in detail. Through doping Dy3+ and Sm3+, can obtain white light and warm white light. As the concentration of Sm3+ increased, their lifetime decreased from 0.483 ms to 0.059 ms, confirming interionic energy transfer in the host. The CKLP: 0.06Dy3+, 0.06Sm3+ phosphor prepared by Fluorescence Intensity Ratio (FIR) technology has suitable temperature sensing performance. Its relative sensitivity (Sr) and complete sensitivity (Sa) are high up to 4.48 × 10−3 k−1 and 1.021%K−1 at 298 K. The results show that CKLP: Dy3+ and Sm3+ phosphors used in w-LEDs and display devices will present excellent application potential in new optical thermometry.

The Advent of Bodipy-based Chemosensors for Sensing Fluoride Ions: A Literature Review.

The detection of fluoride ions in water and other sources is crucial because they can harm human health if they exceed the safe limit of 1-1.5 ppm. BODIPY (boron dipyrromethene) dyes are promising fluorophores for chemosensors, and their design and modification have attracted a lot of attention. Their advantages include visible light excitation and emission, high molar absorption coefficients (ε) and fluorescence quantum yields [ϕ (λ)], and flexible scaffold manipulation for various applications. In this article, we review the progress of BODIPY-based sensors for fluoride ions from the early 2000s to the present. We focus on the different scaffold modifications of the sensors and their corresponding responses, as well as the underlying photophysical mechanisms and potential uses of each sensor.