Luminescence Phenomena Research Articles

Growth, structure and optical characterization of new Pr3+-doped LaGaGe2O7 and LaGa0.6Al0.4Ge2O7 single crystals

In this work, a new crystal belonging to the germanate family: LaGaGe2O7 (or LGGO) doped with trivalent Praseodymium (Pr) ion is studied. We report the first single crystal growth of this material using the Czochralski method. The spectroscopic properties including absorption and emission cross-sections of praseodymium in this new matrix are measured, as well as the refractive index along the dielectric axes. This material exhibits very high emission cross sections of 38, 20, and 16 10−20 cm2 at 746 nm, 646 nm and 620 nm, respectively. Some persistent luminescence is observed in Pr:LGGO after UV irradiation at 254 nm. To reduce the phenomenon, the solid solution LaGa1-xAlxGe2O7 (0 ≤ x ≤ 1) is considered. Thermoluminescence experiments show that a substitution of 40 % of gallium by aluminium in the crystal structure allows to suppress this persistent luminescence phenomenon.

OSL and PTOSL of dosimetric materials: Observation of the luminescence after exposure to 90Sr+90Y source and LEDs in ultraviolet range

The study of luminescence phenomena by crystal-based radiation detectors is suitable for radiation dosimetry, once the light emitted by them enables the quantification of their deposited radiation energy. The light emission can be promoted when a material is illuminated with a certain wavelength and time interval, as in the optically stimulated luminescence (OSL) and photo-transferred OSL (PTOSL) processes. The objective of this work is to evaluate the OSL and PTOSL responses of commercial dosimeters (LiF:Mg,Ti, CaF2:Dy, CaF2:Mn and CaSO4:Dy) in order to study their luminescence and the possibility of use in radiation dosimetry with the PTOSL technique. OSL and PTOSL responses of LiF:Mg,Ti, CaF2:Dy, CaF2:Mn and CaSO4:Dy dosimeters, commercially sold as TLD-100, TLD-200, TLD-400 e TLD-900, respectively, by Thermo Fischer Scientific, were studied. The samples were irradiated with the 90Sr+90Y source of the TL/OSL reader system Risø, and the measurements were taken using the same system and blue LEDs. For the PTOSL signal, the dosimeters were irradiated, thermally treated and illuminated with LEDs with wavelengths between 265 nm and 420 nm. The most intense OSL signal occurred for TLD-100. Comparing the OSL and PTOSL results, it is possible to observe clearly the photo-transferred effect for TLD-100. For TLD-200 and TLD-400, no effects were noted. In the case of TLD-900, it presented a PTOSL signal in a small-scale when analyzing the curve integral.

One-step preparation and dual mode luminescence anti-counterfeiting application of LiYF4: Yb3+, Ho3+, Ce3+@ carbon quantum dot composite materials

In the field of fluorescent anti-counterfeiting, materials with single luminous mode are easy to be forged, which cannot meet the current anti-counterfeiting requirements. Currently reported bimodal light-emitting materials usually require multi-step and tedious synthesis steps. In this paper, LiYF4: Yb3+, Ho3+, Ce3+ upconversion micron particles (UCMPs)/carbon quantum dots (CDs) composite materials were prepared by one-step hydrothermal method, which greatly simplified the composite process of CDs and UCMPs. The upconversion wavelength (from green light to red light excited by 980 nm) can be achieved by changing the doping concentration of Ce3+ ions. Through the combination of CDs and UCMPs, an obvious dual mode luminescence phenomenon was achieved. Finally, screen printing was used to produce a clover pattern, which realized multi-color luminescence under 365 nm and 980 nm excitations respectively. The new fluorescence anti-counterfeiting composites, which uses simple and environmentally friendly one-step synthesis process, is expected to promote the development of fluorescence anti-counterfeiting field.

Pr3+-Doped Lithium Niobate and Sodium Niobate with Persistent Luminescence and Mechano-Luminescence Properties

In this research, a comprehensive series of Pr3+-doped lithium niobate and sodium niobate materials were obtained at different temperatures via solid-state sintering, and their structures and properties were compared. NaNbO3: 0.75% Pr3+ phosphors were synthesized by sintering at 1150 °C for 2 h and emitted red persistent luminescence for more than 1200 s, peaking at 612 nm under UV excitation, which was a typical long persistent luminescence phenomenon. Furthermore, the sample glowed when pressurized, and a red bright luminescence which lasted for several seconds was visible to the naked eye. This was a typical mechanical luminescence phenomenon of samples under mechanical stress, directly converting mechanical energy into light energy. It was determined that NaNbO3:Pr3+ and LiNbO3:Pr3+ both possess multimode luminescence. Owing to their red long persistent luminescence (LPL) and mechano-luminescence (ML) properties, Pr3+ phosphors can be employed in fields, such as display technologies, stress sensing, structural damage detection, and other complex applications.

Unveiling the influence of ambient lighting on stimulating ultraviolet luminescence of deep-trap phosphors

Glow-in-the-daylight is a fascinating luminescence phenomenon displayed by certain storage phosphors that emit ultraviolet light upon being stimulated by ambient lighting. In this study, we investigate the influence of indoor lighting on the glow-in-the-daylight emission of a co-doped garnet phosphor, Y3Al5O12:Pr3+,Eu3+, known for its deep trap that effectively retains energy. Our experimental results demonstrate an interesting observation that, following x-ray radiation at room temperature, this phosphor exhibits negligible persistent luminescence in darkness but emits intense ultraviolet light peaking at 318 nm under indoor lighting conditions. This emphasizes the crucial role played by ambient lighting in releasing stored energy. Our findings not only shed light on the influence of indoor illumination dose and spectral distribution on the persistently stimulated luminescence but also expand our exploration to various ultraviolet phosphors with deep traps, with the aim of uncovering novel materials applicable in glow-in-the-daylight scenarios.

Mechanistic Insights into the Bacterial Luciferase-based Bioluminescence Resonance Energy Transfer Luminescence: The Role of Protein Complex Dimer.

Bacterial bioluminescence holds significant potential in the realm of optical imaging due to the inherent advantages of bioluminescence and ease of operation. However, its practical utility is hindered by its low light intensity. The fusion of bacterial luciferase with a highly fluorescent protein has been demonstrated to significantly enhance autonomous luminescence. Nevertheless, the underlying mechanism behind this enhancement remains unclear, and there is a dearth of research investigating the mechanistic aspects of bioluminescence resonance energy transfer (BRET) luminescence, whether it occurs naturally or can be achieved through experimental means. In this study, we investigated the phenomenon of bacterial luciferase-based BRET luminescence employing a range of computational techniques, including structural modeling, molecular docking, molecular dynamics simulations, as well as combined quantum mechanics and molecular mechanics calculations. The theoretical findings suggest that the BRET luminescence occurs through resonance energy transfer between the excited bioluminophore and the ground chromophore within the protein complex dimer. The proposed mechanism of the protein complex dimer offers a microscopic understanding of the intriguing BRET phenomenon and has the potential to inspire further practical applications in the field of optical imaging.

Excited state lifetime of electron trapping centres in alkali feldspars

The development of the infrared photoluminescence (IRPL) signal enables the direct non-destructive probing of the trapped electron population in feldspars. Whilst IRPL offers new perspectives for luminescence dating, it also enables detailed, site-selective measurements of the dosimetric defects emitting IRPL at 880 nm (IRPL880) and 955 nm (IRPL955), allowing improved understanding of luminescence phenomena in feldspars.We perform time-resolved IRPL measurements to investigate the excited state lifetimes of IRPL880 and IRPL955 electron trapping centres in chemically and structurally different feldspars. We analyse the time-resolved off-time data with three exponentially decaying components. The contribution of the fast component (τ1) fitted to the IRPL880 data is minor and its lifetime is consistent with the switch off time of the 830 nm excitation laser. The two longer lifetimes (τ2 and τ3) dominate the IRPL880 and IRPL955 signals. The τ2 values range from 2 μs to 6 μs for IRPL880 and from 2 μs to 7 μs for IRPL955, whereas τ3 ranges from 7 μs to 25 μs for IRPL880 and from 8 μs to 22 μs for IRPL955, with an average cluster value of ∼20 μs. We observe a weak decreasing trend in τ3 lifetime with decreasing K-feldspar content. Systematic thermal depletion of the trapped electron population results in decreasing τ2 lifetimes with increasing preheat temperature, but a negligible change in τ3. We suggest that time-resolved-IRPL lifetimes not only reflect the exited state lifetime of the electron trapping centre, affected by excited-to-ground state transition as well as tunnelling, but also a direct recombination from the band-tail states. The long excited-state lifetime of the order of 20 ∼ μs (the average cluster value) allows for tunnelling induced recombination from the excited state, which is supported by the fact that reported lifetimes for time-resolved-IRSL (infra-red stimulated luminescence) are shorter than those of time-resolved-IRPL.

Aggregation‐Induced Emission (AIE) of Au(I)‐GSH Complexes is Activated by Optical Manipulation and Exhibits Surprising 780 nm Emission

AbstractAn optical manipulation method to activate the aggregation‐induced emission (AIE) of Au(I)‐glutathione (Au(I)‐GSH) complexes is presented. First, the well‐known AIE‐type Au(I)‐GSH complexes with a solid emission wavelength of 570 nm are synthesized. At the beginning of the focusing a 1064 nm continuous‐wave (CW) laser at the interface of Au(I)‐GSH complexes solution, its luminescence is hardly detectable. However, with the extension of the laser irradiation time, aggregate appears and rapidly grows, and strong luminescence is shown, indicating the activation of AIE of Au(I)‐GSH complexes through optical manipulation. Surprisingly, the emission peak is at 780 nm and no blue‐shift is observed with the emission intensity increases. The activated AIE emission wavelength by optical manipulation is longer than reported previously, which means that optical manipulation activates AIE in a unique manner. The switching on/off of the activation of AIE is arbitrarily controlled by changing the laser power. In this paper, the luminescence phenomenon and mechanism of AIE are discussed from the perspective of the movement limitation of Au(I)‐GSH complexes under optical manipulation. It is of significant importance for further insights into the luminescence of Au(I)‐GSH complexes and their future development.

Evaluating the potential of persistent luminescence in counteracting urban overheating

In recent years, the use of numerical simulations to model real atmospheric conditions over cities has become increasingly popular. One of the primary objectives of these models is to assess the efficacy of various strategies for mitigating the Urban Heat Island (UHI) phenomenon. At the same time, researchers have developed and studied new adaptive materials for building applications that aim to reduce buildings’ energy consumption and improve urban microclimate conditions, while performing radiative cooling. Among the new generation of passive cooling solutions, persistent luminescent (PL) materials have emerged as a cutting-edge option for energy-saving purposes, owing to their ability to reject the incident solar radiation through both reflection and light emission. Here, the Princeton Urban Canopy Model (PUCM) is used to evaluate the potential of an advanced PL roof coating to counteract urban overheating. The phenomenon of persistent luminescence is modeled for the first time, taking advantage of experimentally obtained parameters coming from previous studies. Results demonstrate how persistent luminescence can effectively mitigate surface overheating reducing the roof’s surface temperature and net shortwave radiation up to 1.15 °C and 35 W/m2 respectively, with consequent benefits to the overall energy balance of the envelope. Such results may be further increased with the optimization of PL materials for engineering solutions.

Photocatalytic functionalization of thin-layer membranes using a monomer truncation strategy.

We present the design and synthesis of two new organic polymer films making use of a liquid-liquid interfacial amine-acid chloride polymerization strategy. One of them was additionally functionalized in situ by the anchoring of N-phenyl-phenothiazine through a monomer truncation strategy, which endowed it with photocatalytic activity. This photoactive film displays interesting luminescence phenomena that were used for the oxidation of a variety of sulphides to their corresponding sulfoxides and reduction of aryl bromines.

Lattice dynamics and electron-phonon interaction in lead-free perovskite-inspired materials with unexpected broadband NIR emission

Air-stable and Sb/Bi-based perovskite-inspired materials are attractive substitutes for their Pb-based counterparts in optoelectronic applications. The attractive low-energy broadband luminescence phenomenon has been hotly investigated. However, understanding the physical mechanism behind it is still at an early stage. Herein, high-quality Cs3SbBiI9 crystals were synthesized and accompanied with reference Cs3Sb2I9 and Cs3Bi2I9. The reformed energy band structure can be confirmed by experiment and density functional theory (DFT) calculation. Unexpected broadband near-infrared (NIR) emission has been discovered and is explained by the nonexclusive self-trapped exciton (STE) and defect-induced emission models. Temperature- dependent Raman and PL spectra confirm the diminished Stokes shift and electron-phonon coupling effect in Sb-Bi alloyed crystals driven by the local broken-symmetry. This result provides a basic physical explanation for the controversial photo-physical process in defect-type Bi/Sb alloyed perovskite-inspired family and it will inspire a feasible way to design novel Pb-free perovskites.

Thermally Reversible Luminescence in Ferroelastic Phase Transition Materials

AbstractThe thermally reversible luminescent materials with information encryption are important and widely used in the information age. However, it is challenging to obtain such materials. In this work, a 0D In‐based hybrid compound [(CH3)3NCH2CHCH2]2InCl5 ((TAMAC)2InCl5) is synthesized and undergoes a high‐temperature ferroelastic phase transition with an Aizu notation of mmF2/m at 333 K. In the room temperature phase (RTP), it shows a weak blue glow with a photoluminescent quantum yield (PLQY) of 0.32% under the UV lamp at 365 nm. By using a metal ion doping strategy to improve the photophysical properties, a series of compounds is obtained: (TAMAC)2In1‐xCl5:xSb3+ (x = 0.1%,0.5%,1%, and 1.5%, x represents the actual amount) with the same ferroelastic phase transition as that found in (TAMAC)2InCl5. When x = 0.5%, the PLQY reaches 50.66% with the luminous color change from blue to orange. Interestingly, it is found that the orange luminescence of the doped materials can rapidly and reversibly quench and recover between heating and cooling cycles, where the thermally induced phase transition results in this thermally reversible luminescence phenomenon. This discovery reveals the mechanism of luminescence quenching and phase transition, and provides a new pathway for the construction of new thermal‐sensitive luminescent materials with information encryption.

Pr3+-Er3+ co-doped Ba3.75Gd0.833Nb10O30 glass-ceramics for tunable luminescence, optical anti-counterfeiting and temperature sensing

Pr3+-Er3+ co-activated glass-ceramics containing Ba3.75Gd0.833Nb10O30 crystalline phase were prepared as a multifunctional material. The optimum heat treatment condition was determined to be 750 °C/90 min, as this condition is most favorable for luminescence. As the Pr3+ concentration increases, the emissions of 3P0 and 1D2 energy levels show different trends, leading to a shift in luminescence from orange to yellow. With the introduction of Er3+, the co-doped sample achieves orange-yellow-green tunable luminescence. The 0.3%Pr3+-0.3%Er3+ co-doped sample exhibits alternating yellow-orange-green luminescence during continuous excitation in the range of 250–500 nm, which has potential applications in optical anti-counterfeiting. In the temperature interval of 298–458 K, the maximum temperature sensitivities based on the NTCLs of Pr3+ and Er3+ were 0.82 × 10−2 K−1 (Sa) and 1.40 % K−1 (Sr). Meanwhile, the thermal repeatability ratio is higher than 92.3 %, which proved that it is a potential temperature sensing material. In addition, the concentration quenching, energy transfer and luminescence phenomena involved were analyzed in depth and their mechanisms were explained.

High-temperature dynamic luminescence of MgGa2O4: Tb3+, Er3+ phosphors for advanced anti-counterfeiting and information encryption

Long persistent luminescence (LPL) anti-counterfeiting technology is widely used in optical information storage, information security, and anti-counterfeiting fields due to the advantages of non-interference with background light and high imaging resolution. However, the performance of most LPL materials is greatly compromised in harsh environments such as high temperature, which seriously affects the effectiveness of anti-counterfeiting measures due to the accelerated decay rate of LPL luminescence. In this work, we synthesized a series of MgGa2O4: Tb3+ (MGO: Tb3+), which possess stable crystal structure with obvious LPL properties above room temperature, and the optimum temperature is determined to be 423 K. Moreover, the additional introduction of Er3+ ions enhances the security of anti-counterfeiting, and the combination of photo-stimulated luminescence (PSL) and upconversion (UC) phenomena enables color tuning from red to orange to green by extending the 980 nm laser irradiation time. Finally, the anti-counterfeiting strategy utilizing MGO: Tb3+ and MGO: Tb3+, Er3+ possesses an extremely high level of security, making it an attractive performance for designing advanced anti-counterfeiting technology.

Polymorphism and Light-Driven Forward Movement of TPE Derivative Micro-Crystal due to ArH-pi Interactions Difference.

Aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) are two classes of opposite luminescence phenomena. It is almost impossible to show both AIE and ACQ effect simultaneously by the same molecule. However, here we report that a simple TPE derivative TAP-TPE grows into both AIE crystals and ACQ ones. It is found that equatorial, contact distance-longer and weak ArH-π interactions exist in AIE crystals while vertical, contact distance-shorter and strong ArH-π interactions appear in ACQ crystals. Theoretical calculation of electron density on the interaction atoms unveils that ACQ crystals have much larger change in electron density than AIE ones, suggesting that the intermolecular electron transfer aroused by the strong ArH-π hydrogen bonds leads to ACQ phenomenon. This result provides a new insight into the emission mechanism in aggregation state. Interestingly, due to the ArH-pi interactions difference, only one of five kinds of crystals shows rapid photochromism, and can act as multimode anti-counterfeiting materials. Very exceptionally, for the first time we find that the photochromic micrometric rod-like crystal even makes forward rolling movement as it repeatedly bends and straightens by responding to on and off of the ultraviolet light irradiation, displaying potential for photo-actuator and light-driven micro-vehicle.

The Correlation between Surface V-Shaped Defects and Local Breakdown Phenomena in GaN-Based LEDs

This paper investigates the intriguing impact of surface V-shaped defects on the electrical and optical characteristics of GaN-based LEDs, particularly under reverse bias conditions. These defects introduce unique luminescence phenomena, notably giant dot-like luminescence (GDL), and exert significant influence on device performance. The size of these V-shaped defects plays a critical role: larger defects generate more indium-rich regions at their base, resulting in elevated tensile stress. This heightened stress promotes carrier tunneling, increasing reverse leakage current and leads to GDL formation. However, even with multiple V-shaped defects present, localized failure predominantly occurs at the defect experiencing the highest tensile stress, substantially reducing the breakdown voltage. Micro-Raman analysis further reveals distinct Raman shifts and increased tensile stress in these regions. These findings underscore the complexity of V-shaped defects’ effects, highlighting their importance in GaN-based LED design and optimization. Recognizing their influence on electrical and optical properties can significantly impact device reliability and performance, particularly in reverse bias conditions.

Biological Auto(chemi)luminescence Imaging of Oxidative Processes in Human Skin.

Oxidative processes in all types of organisms cause the chemical formation of electronically excited species, with subsequent ultraweak photon emission termed biological auto(chemi)luminescence (BAL). Imaging this luminescence phenomenon using ultrasensitive devices could potentially enable monitoring of oxidative stress in optically accessible areas of the human body, such as skin. Although oxidative stress induced by UV light has been explored, for chemically induced stress, there is no in vivo-quantified imaging of oxidative processes in human skin using BAL under the controlled extent of oxidative stress conditions. Furthermore, the mechanisms and dynamics of BAL from the skin have not been fully explored. Here, we demonstrate that different degrees of chemically induced oxidative stress on the skin can be spatially resolved quantitatively through noninvasive label-free BAL imaging. Additionally, to gain insight into the underlying mechanisms, a minimal chemical model of skin based on a mixture of lipid, melanin, and water was developed and used to show that it can be used to reproduce essential features of the response of real skin to oxidative stress. Our results contribute to novel, noninvasive photonic label-free methods for quantitative sensing of oxidative processes and oxidative stress.

Observation of photoelectric-induced microplasma avalanche breakdown in AlGaN ultraviolet photodiode with separate absorption and multiplication structure

Amplification of weak ultraviolet signals has always been a challenging issue to design and fabricate high-performance ultraviolet photodetectors. Here, we observe a distinctive microplasma breakdown behavior in AlGaN-based ultraviolet avalanche photodiodes with artificial mesa architecture. At 107 V breakdown voltage, the photocurrent increases sharply whereas dark current intriguingly remains at the extremely low level of 0.1 nA as the applied voltage increases. Simultaneously, a significant blue luminescence phenomenon is observed at the mesa edge of photodiode at breakdown voltage, indicating the occurrence of microplasma breakdown. Ultimately, the microplasma avalanche photodiode achieves a record-high avalanche gain of 3 × 106 with light–dark current ratio readily exceeding 107. Kelvin probe force microscopy was employed to reveal the physical mechanism of localized avalanche breakdown induced by photoelectric effects and elaborate the microplasma discharge process, which is related to surface states. The unprecedented detection mode of photocurrent triggering avalanche events while remaining low dark current is anticipated to effectively shield the background noise and amplify ultraviolet signals. It is worth further research to explore its possibility on high-sensitivity ultraviolet photodetection.

Photoluminescence and solid-state LED application based on pH-sensitive carbon quantum dots

Carbon quantum dots (CQDs) have attracted great interest on account of their outstanding physicochemical properties. Herein we study the optical properties of the CQDs (diamond structure) and observe interesting phenomenon of concurrent multiband luminescence across the whole visible region. What is more, the CQDs exhibit emission-dependent excitation and high pH-sensitive. The surface structural and luminescence investigation in conjunction with density functional theory calculation reveal that C(O)O, C(O)NH2, and C(O)OH-related surface defects in these CQDs lead to observed luminescence. The calculation shows that stronger transitions between band edges of C(O)NH2-terminated CQDs leads to relatively strong photoluminescence in strong contrast with usually weak emission in oxygen terminated CQDs. Finally, the solid-state LED devices with different emission colors were fabricated based on the pH-sensitive properties of the CQDs.

Emerging Clusteroluminescence from Complexes between Carbonyl‐Based Polymers and Organic Base†

Comprehensive SummaryThe study of luminescence phenomena in non‐conjugated systems, namely clusteroluminescence, has gained significant attention for the development of advanced luminescent materials. While conventional strategies to manipulate the luminescent performances are based on complicated chemical reactions. In contrast, nature employs complexation to modulate luminescence, inspiring researchers to adopt an engineering approach for the construction of efficient clusteroluminogens. In this work, we explore the complexation‐ induced clusteroluminescence of carbonyl‐based polymers with nitrogen‐containing organic bases, exemplified by polyamide, polyester, polycarbonate, and poly(monothiocarbonate). The results demonstrate an increase in the intrinsic 440 nm emission of carbonyl groups and the emergence of new emission peaks upon complexation. The study proposes a through‐space n‧‧‧π complex mechanism, highlighting the potential of complexation as a strategy for modulating the clusteroluminescent properties of non‐conjugated systems. Further research is necessary to unravel underlying mechanisms, optimize cluster structures, and explore new materials for complexation, thereby advancing optoelectronics and photonics fields and enabling practical applications of clusteroluminescent materials.