Light Emission Research Articles

Ambipolar Charge Injection and Bright Light Emission in Hybrid Oxide/Polymer Transistors Doped with Poly(9‐Vinylcarbazole) Based Polyelectrolytes (Adv. Mater. Technol. 20/2024)

Ambipolar Charge Injection and Bright Light Emission in Hybrid Oxide/Polymer Transistors Doped with Poly(9‐Vinylcarbazole) Based Polyelectrolytes (Adv. Mater. Technol. 20/2024)

Alpha sensing, NIR to green light emission in Er3+ doped PbWO4 nanoparticles with modification of calcination atmosphere

In this study, various concentrations (0.5, 1, and 1.5 at%) of Er3+ PbWO4 nanoparticles (PWO: Er NPs) were prepared using a co-precipitation procedure, and the effect of the calcination atmosphere (air and argon) on the luminescence properties and scintillation responses were investigated. Different characterization analyses were carried out to study the structural and optical characteristics of prepared samples. We found evidence of the transformation of the PWO Scheelite structure into a non-centered group, which effectively influences the symmetry properties of the structure and subsequently its luminescence and sensing properties. Both Ar atmosphere and Er concentration contribute to the distortion of the scheelite structure and the symmetry breaking. However, with increasing dopant concentrations, the lattice becomes more homogeneously distorted, causing the structure to re-symmetrize and, as a result, the intensity of luminescence increases, particularly magnetic dipolar (MD) transitions that correspond to NIR emission. The ideal conditions are given when the impurity percentage reaches 1.5 at%, in the Ar atmosphere. Our PWO: Er (1.5 at%-Ar) sample had a maximum count rate of 1388 and 2082 and detection efficiency of 0.216 and 0.170 cps/Bq under 241Am sources with 0.22 and 0.26 μc activities, respectively. By exceeding the efficiency of the commercial ZnS(Ag), it showed promising potential for practical applications in future optoelectronic domains.

Characteristics of light emission and wear behaviour of a reinforced composite material made of basalt and jute for optimum parameters

Characteristics of light emission and wear behaviour of a reinforced composite material made of basalt and jute for optimum parameters

Polarized and Directional Electroluminescence from Organic Light‐Emitting Devices by Using a Bifunctional Meta‐Electrode

AbstractOrganic light‐emitting devices (OLEDs) with polarized and directional emission are highly desired for their promising applications in optical imaging, optical communication, and immersive visual technologies. Existing implementation methods based on free space bulk optical elements suffer from significant power loss, limiting their practical applications. Here, a bifunctional meta‐electrode is proposed by integrating a metasurface consisting of Ag periodic corrugations onto the indium tin oxide (ITO) anode to simultaneously realize the functions of charge carrier injection and photon management in the OLEDs. Highly polarized and directional light emission is demonstrated while maintaining a high device efficiency using the meta‐electrode. The electroluminescence with a polarization extinction ratio of 5 is achieved by judiciously engineering the polarization‐dependent Purcell factor of the resonant cavity constructed by the meta‐electrode. Meanwhile, the directional light emission with a divergence angle of 10° can be obtained by the efficient out‐coupling of surface plasmon‐polariton mode. The light beam can be collimated in one direction by using 1D nanogratings and in two directions by using 2D nanopillars, respectively.

Modulation of photoluminescence properties of transition metal dichalcogenides through temperature and Au/Ag nanoparticles

Abstract Transition metal dichalcogenides (TMDCs) attract significant attention because of their remarkable optical properties. Nowadays, the light emission efficiency of TMDCs is still inferior. Temperature and plasma resonance effects can be important approaches in the modulation of their luminescence performance. Here, multilayer WSe2 and monolayer MoSe2 were synthesized. Under the temperature control system, two photoluminescence (PL) peaks are observed from multilayer WSe2. The higher-energy PL peak results from K-Γ indirect band gap transition, which is then demonstrated by the first principle calculation. Otherwise, PL enhancement is realized on monolayer MoSe2 decorated with Au nanoparticles. The PL of WS2 is inhibited by hybridization with Ag nanoparticles.

Computational insights into the photophysical processes of an acylhydrazone fluorescent probe based on conical intersection and sensing mechanism for Al3+ detection

Al3+ detection is crucial for food safety, environmental monitoring, and biological assays. This work investigated the fluorescent properties of the probe VN62 and its sensing mechanism for the detection of Al3+ ion in detail. The ground- and excited-state properties such as isomerization geometries and absorption spectra, as well as the photophysical processes of transitions in PES have been studied. There are few fluorescent S1 states (PT*, TICT) of the VN62 molecule, and the conical intersections (CIs) have key importance in the fluorescent process. By comparing the radiative rate (kr) and the rate of transition to CI, we deduce that these fluorescent states are lack of stability for light emission. Therefore, the fluorescence of probe alone can be quenched by CI pathways. After coordination with Al3+, the CI pathways will be suppressed, resulting in enhanced fluorescence. This sensing mechanism is different from the previously proposed mechanisms, such as the dark state of TICT or ESIPT. We anticipate that our research would shed some light on the design of turn-on sensors.

Opalescence and Fluorescence of 46 Resin-Based Composites Exposed to Ultraviolet Light

Identifying the boundary between the tooth and the resin-based composite (RBC) is difficult when replacing restorations. Ultraviolet (UV) light has been reported to assist the viewer by causing the RBC to fluoresce. Using a laboratory-grade fiberoptic spectrometer, 46 RBCs were exposed to UV light from the Woodpecker O-Star curing light. The opalescence and fluorescence were measured relative to a human tooth that contained just dentin and a tooth that contained both enamel and dentin. After these quantitative measurements, 10 RBCs with large differences in light emittance were compared qualitatively to assess their brightness when exposed to UV light compared to the dentin specimen and the specimen containing both enamel and dentin. It was found that, when exposed to UV light, some of the RBCs were less bright compared to the two samples of teeth used for comparison, but most were brighter; some were up to six times brighter. The filler appears to affect the opalescence peaks, while the resin appears to affect the fluorescence peaks. It was concluded that because RBCs emit very different levels of opalescence and fluorescence, UV light from the Woodpecker O-Star cannot be relied upon to detect all brands of RBC on the tooth. The opalescence and fluorescence can also be used to detect changes in the formulation of the RBC.

Accurate Crystal Structure Prediction of New 2D Hybrid Organic-Inorganic Perovskites.

Low-dimensional hybrid organic-inorganic perovskites (HOIPs) are promising electronically active materials for light absorption and emission. The design space of HOIPs is extremely large, as a variety of organic cations can be combined with different inorganic frameworks. This not only allows for tunable electronic and mechanical properties but also necessitates the development of new tools for in silico high throughput analysis of candidate materials. In this work, we present an accurate, efficient, and widely applicable machine learning interatomic potential (MLIP) trained on 86 diverse experimentally reported HOIP materials. This MLIP was tested on 73 experimentally reported perovskite compositions and achieves a high accuracy, relative to density functional theory (DFT). We also introduce a novel random structure search algorithm designed for the crystal structure prediction of 2D HOIPs. The combination of MLIP and the structure search algorithm reliably recovers the crystal structure of 14 known 2D perovskites by specifying only the organic molecule and inorganic cation/halide. Performing this crystal structure search with ab initio methods would be computationally prohibitive but is relatively inexpensive with the MLIP. Finally, the developed procedure is used to predict the structure of a totally new HOIP with cation (cis-1,3-cyclohexanediamine). Subsequently, the new compound was synthesized and characterized, which matches the predicted structure, confirming the accuracy of our method. This capability will enable the efficient and accurate screening of thousands of combinations of organic cations and inorganic layers for further investigation.

Optical characterization of GaN:Eu microcrystals grown by the ammonothermal method

Eu-doped gallium nitride (GaN:Eu) microcrystals with a wurtzite crystal structure were synthesized using the ammonothermal method. The Eu concentration of GaN:Eu microcrystals estimated by glow discharge mass spectrometry (GDMS) was 5.8 × 1020 atoms/cm3. The morphology of GaN:Eu microcrystals was characterized by scanning electron microscopy (SEM). The exposed crystal faces of GaN:Eu microcrystals were identified as {10−10}, {10−11}, (000−1), and (0001), respectively. The photoluminescence excitation (PLE), photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra of GaN:Eu microcrystals revealed two luminescent sites of Eu3+ ions, designated as Eu0 and Eu1. The Eu0 was excited in the range of 300 nm to 420 nm, resulting in the observation of four characteristic luminescence peaks at 599 nm (5D0-7F1), 620 nm (5D0-7F2), 632 nm (5D1-7F4), and 663 nm (5D0-7F3). The Eu1 was associated with O2- ions and emitted light at specific excitation wavelengths. The main luminescence peak of the Eu1 was located at 614 nm, accompanied with characteristic peaks at 578 nm, 591 nm, and 698 nm. In view of the distinct luminescence properties of the Eu0 and the Eu1, the energy transfer processes of two luminescence sites were proposed.

Chemical sensors: From fundamentals to the future—A review

<p>Chemical sensors bridge the gap between the chemical and electrical/optical domains, offering a powerful tool for analyzing our environment. These ingenious devices, with detection limits reaching parts-per-billion (ppb) for some analytes, rely on interactions between a specific material and the target molecule. This interaction, which can involve changes in electrical current, light emission, or mass, is translated into a measurable signal. This review delves into the core working principles of various sensor types, highlighting their diverse applications. From environmental monitoring (tracking air and water pollutants at concentrations as low as 10 ppb) to medical diagnostics (detecting biomarkers for early disease identification), chemical sensors play a crucial role in shaping a safer and healthier future. Recent advancements, such as miniaturization and integration with nanomaterials, promise even greater sensitivity, portability, and affordability, paving the way for a new era of sensor-driven innovation. This review article explores these advancements and their potential impact on various fields, inspiring further development and exploration of this transformative technology.</p>

Harvesting the tuning mechanism of strategic polychrome and white light emission in NapH dye based on excited state intermolecular proton transfer

Organic white light emitting (WLE) materials have sparked a research boom due to their promising applications in display devices, artificial lighting, and molecular sensors. However, the complex luminescence mechanism of full-spectra emitting materials has limited the development of white light materials with high stability and reproducibility. In this study, building on the full-spectra luminescent naphthimide dye (NapH) introduced by Xu et al., (Chin. Chem. Lett. 35(2024), 108348), we report the solvent-sensitive excited state proton transfer (ESPT) properties and white light emission mechanism in NapH. Our theoretical research results show that the ESPT process of NapH molecule is hindered in the low-polar solvent tetrahydrofuran (THF), so only the blue fluorescence from the Enol* is observed in the experiment. In contrast, in polar solvents such as water (H2O) and methanol (MeOH), the formation of strong intermolecular hydrogen bonds successfully initiates the ESPT process, leading to the dual fluorescence observed in experiments, with blue emission from the Enol* and red emission from the Nap anion. In essence, different solvent environments can adjust several emission colors. Furthermore, we theoretically verify that the optimal white light emission can be achieved when the mixed solvent ratio of dimethyl sulfoxide (DMSO) and dioxane (DIOX) is 5:5, which aligns well with experimental results. More importantly, we elucidate the specific WLE mechanism from multiple perspectives, including potential energy curves and electron spectra. Our work not only displays the interaction models of NapH molecule in various solvents, but also reveals the underlying luminescence mechanism, thus providing a valuable theoretical reference for the development and advancement of new white light materials.

In Vivo Lifetime Imaging of the Internal O2 Dynamics in Corals with near-Infrared-Emitting Sensor Nanoparticles.

Mapping of O2 with luminescent sensors within intact animals is challenging due to attenuation of excitation and emission light caused by tissue absorption and scattering as well as interfering background fluorescence. Here we show the application of luminescent O2 sensor nanoparticles (∼50-70 nm) composed of the O2 indicator platinum(II) tetra(4-fluoro)phenyltetrabenzoporphyrin (PtTPTBPF) immobilized in poly(methyl methacrylate-co-methacrylic acid) (PMMA-MA). We injected the sensor nanoparticles into the gastrovascular system of intact colony fractions of reef-building tropical corals that harbor photosynthetic microalgae in their tissues. The sensor nanoparticles are excited by red LED light (617 nm) and emit in the near-infrared (780 nm), which enhances the transmission of excitation and emission light through biological materials. This enabled us to map the internal O2 concentration via time-domain luminescence lifetime imaging through the outer tissue layers across several coral polyps in flowing seawater. After injection, nanoparticles dispersed within the coral tissue for several hours. While luminescence intensity imaging showed some local aggregation of sensor particles, lifetime imaging showed a more homogeneous O2 distribution across a larger area of the coral colony. Local stimulation of symbiont photosynthesis in corals induced oxygenation of illuminated tissue areas and formation of lateral O2 gradients toward surrounding respiring tissues, which were dissipated rapidly after the onset of darkness. Such measurements are key to improving our understanding of how corals regulate their internal chemical microenvironment and metabolic activity, and how they are affected by environmental stress such as ocean warming, acidification, and deoxygenation. Our experimental approach can also be adapted for in vivo O2 imaging in other natural systems such as biofilms, plant and animal tissues, as well as in organoids and other cell constructs, where imaging internal O2 conditions are relevant and challenging due to high optical density and background fluorescence.

Spatiotemporally modulated full-polarized light emission for multiplexed optical encryption

Spatiotemporal control of full freedoms of polarized light emission is crucial in multiplexed optical computing, encryption and communication. Although recent advancements have been made in active emission or passive conversion of polarized light through solution-processed nanomaterials or metasurfaces, these design paths usually encounter limitations, such as small polarization degrees, low light utilization efficiency, limited polarization states, and lack of spatiotemporal control. Here, we addressed these challenges by integrating the spatiotemporal modulation of the LED device, the precise control and efficient polarization emission through nanomaterial assembly, and the programmable patterning/positioning using 3D printing. We achieved an extremely high degree of polarization for both linearly and circularly polarized emission from ultrathin inorganic nanowires and quantum nanorods thanks to the shear-force-induced alignment effect during the protruding of printing filaments. Real-time polarization modulation covering the entire Poincaré sphere can be conveniently obtained through the programming of the on-off state of each LED pixel. Further, the output polarization states can be encoded by an ordered chiral plasmonic film. Our device provides an excellent platform for multiplexing spatiotemporal polarization information, enabling visible light communication with an exceptionally elevated level of physical layer security and multifunctional encrypted displays that can encode both 2D and 3D information.

Light Emission from the Sidewall Region Dominates the Spectral Broadening of InGaN-Based Red Micro-LEDs

Light Emission from the Sidewall Region Dominates the Spectral Broadening of InGaN-Based Red Micro-LEDs

Composite Nanostructures for the Production of White Light.

In this work, two different composite nanostructures, YAG:Ce and Ga0.9In0.1N, were prepared by the Urea Glass Route method and tested for the production of white light. The first composite was prepared by synthetizing the Ga0.9In0.1N nanoparticles in the presence of YAG:Ce nanoparticles. The second one was prepared by synthetizing YAG:Ce nanoparticles in the presence of Ga0.9In0.1N nanoparticles. These systems can be useful for the production of white light. X-ray Diffraction and Transmission and Scanning Electron Microscopies (TEM and SEM) were used to evaluate their structural and morphological properties. Excitation and emission spectra, the quantum yield and colour of the emitted light were acquired to evaluate the optical properties of the systems.

An innovative approach towards decolorization of tint and enhancing the optical & physical properties of high iron Na2O–CaO–SiO2 glass by co-doping with Ce4+/Nd3+: An experimental and comparative study

The aim of the research is to manufacture the colourless high iron Na2O–CaO–SiO2 glass with natural local raw materials with high iron content. Chemical and physical decolorizer like CeO2 and Nd2O3 were used in oxidation conditions by maintaining the redox of the melt. The maximum transmittance of colourless glass obtained at 546–562 nm is 91 % with a thickness of 6.5 mm. The addition of polyvalent ions Nd2O3/CeO2 decreases the optical band gap (Eg) and Urbach energy (ΔE) which results in resistance against solarization. Additionally, it also decreases the structural disorder results in high young & shear modulus. Lack of O–H in glass facilitates to retain more Si–O–Si in the glass matrices which enhances the down conversion luminance intensity of Nd3+ from 4I9/2 to 4F5/2 and improves the Far-IR behavior of the glass. Chromaticity diagram revealed that the doped glass has CI value 5416K which is closes to white light emission 5500k. Due to the presences of the Nd2O3/CeO2 and antimony oxide the Refractive index (ng), density (ρ), molar volume (V) and molecular weight of the glass increases. Maintaining the redox of the glass melt and Fe2+/Fe3+ ratio with the chemical and physical decolorizer will help to decolourize the Na2O–CaO–SiO2 glasses with the Fe2O3 content up to 0.3 % with the same methodology.

Controllable multicolored optical glass-ceramics based on nanostructure strategies and dopants

Novel functional materials that integrate multiple tunable luminescence modes hold significant scientific and application potential. In this study, nanostructure strategies were employed to fabricate a series of microcrystalline glasses doped with rare-earth and transition-metal ions. The crystallization behavior of the nanocrystals (NCs) was revealed through high-resolution transmission electron microscopy (HRTEM), and the photoluminescence spectra of the samples were systematically investigated, demonstrating the achievement of independent and efficient visible light emission. With the further addition of the dopant Mn2+, it can occupy different sites to generate efficient energy transfer for ions, effectively improve the luminous efficiency, and changing the Mn2+ concentration can achieve a wide tunable color gamut. In addition, by exciting the glass samples with different excitation light sources, tunable emission of both red and blue was achieved. The results demonstrated the significant potential of the experimental samples as new multifunctional materials for optical dynamic anti-counterfeiting applications.

Simultaneous Triboelectric and Mechanoluminescence Sensing Toward Self‐Powered Applications

AbstractSimultaneous phenomena of triboelectricity and mechanoluminescence (ML) acquire vital insights into the mechanics of charge separation and recombination, as well as the relationship between mechanical stress and light emission. In the present work, polydimethylsiloxane (PDMS) and ZnS:Cu particle‐based composites are fabricated, which have good ML characteristics and can generate electricity via contact electrification. ML, in conjunction with a triboelectric nanogenerator (TENG), contributes by producing power from mechanical operations while also giving vital visual input in the form of light emission. This dual capability improves user awareness and efficiency in a variety of applications, making mechanical systems and wearable devices easier to monitor and optimize. To accomplish this, a single‐electrode mode silver (Ag) nanowires embedded PDMS‐ZnS: Cu‐based TENG device is developed and achieved an electrical output of 60 V, 395 nA, and 15 nC by using a linear motor. Furthermore, the combined ML and TENG device is employed in various cases of safety monitoring. This integration provides self‐powered devices that detect mechanical stress, delivering real‐time warnings and illumination signals for increased safety and communication in demanding conditions such as SOS signaling, underwater driving, deep mining, and sports.

Wearable quantum dots organic light-emitting diodes patch for high-power near infra-red photomedicene with real-time wavelength control

Wearable photomedical application fields, such as photobiomodulation (PBM), and photoplethysmography (PPG) sensors using organic light-emitting diodes (OLEDs), are promising and attractive due to their flexibility, surface light emission, and ability to apply to various free-form (attachable or implantable) healthcare platforms. However, to maximize the impact on wearable photomedical applications, their spectrum needs to be freely tunable in real-time, and expanded into the near-infrared (NIR) wavelengths which are difficult to achieve in conventional electroluminescent OLED. In this study, we introduce the wavelength selective quantum dots high-power parallel-stacked OLED (QD-OLED) patch. Several NIR QD-OLEDs with 630, 700, and 730 nm peak wavlength were optimized by the high-power (> 100 mW·cm−2 at 6.3 V) parallel-stacked blue OLED with a 465 nm emission peak.The NIR QD-OLED patch platform with multi-functional blue reflective NIR-enhanced (> 60 %) encapsulation film (6 x 10−6 g·m−2·day−1), capable of real-time wavelength control, achieved a high-output NIR power density (>23.28 mW·cm−2). Using this NIR QD-OLED patch, PPG bio-signals were successfully measured. Additionally, this NIR QD-OLED demonstrated that it can increase the proliferation of dermal papilla cells by up to 131 % through NIR wavelength control, thereby optimizing the hair growth effect.

Electroluminescent and photoluminescent light-emitting diodes from carbon dots and device architecture optimization.

Light emission from carbon dots (CDs) is of great interest in both electroluminescence and photoluminescence. Herein, we construct electroluminescent and photoluminescent light-emitting diodes (LEDs) from emitters of CDs. The electroluminescent LED with host-guest-doped dual emissive layers (EMLs) of [poly(9-vinylcarbazole) (PVK)-CDs] × 2 gives satisfactory electro-optical properties, with maximum luminance of 560 cd m-2 at 16 V, luminous efficiency of 0.183 cd A-1, power efficiency of 0.082 lm W-1, and external quantum efficiency of 0.25%, which are superior to the counterparts with single-EML of CDs, single-EML of [PVK-CDs], and triple-EMLs of [PVK-CDs] × 3. These enhanced properties are rationally ascribed to optimization of the device architecture, carrier balance improvement, and reduction in concentration-induced quenching. The electroluminescent LEDs also show color evolution from PVK to CDs, and/or to the PVK/CDs interface, with increasing driving voltages, owing to incomplete energy transfer from PVK to CDs. Highly efficient photoluminescent LEDs with 365- and 395-nm UV excitation are demonstrated. With a CDs : polyvinyl pyrrolidone ratio of 1 : 3, the 365-nm excited photoluminescent LED gives a maximum luminance of 512 347 cd m-2 with a power efficiency of 25.2 lm W-1, while the 395-nm excited photoluminescent device gives a maximum luminance of 670 954 cd m-2 with a power efficiency of 22.0 lm W-1, with both showing yellow emission. Our experiments provide some new ideas for broadening CD applications and advancing LEDs.