Application Of Luminescent Materials Research Articles

Laminated dihydrazone Zn(II) coordination polymer with prospects for sensory and multifunctional biomedical applications

This study introduces a new laminated coordination polymer, {[Zn3(HL)2(H2O)6](SO4)2⋅1.5dmf·2.5H2O}n (1), synthesized through the direct interaction of ZnSO4·7H2O with dihydrazone Schiff base ligand (H2L = 2,6-diacetylpyridine bis(isonicotinoylhydrazone)) at room temperature. Comprehensive characterization of the compound, employing various methods (SCXRD, PXRD, IR, TGA) revealed different coordination surrounding of metal atoms and a combination of photoluminescent properties and biological activity. The polymeric layers are corrugated along the b-axis, mutually intertwined forming channels filled with outer sphere anions (SO42-) and solvent molecules (water and dmf). It was shown that solvent molecules have a decisive influence on the photoluminescent properties of the compound. The partial removal of water molecules leads to increased photoluminescence, the intensity of which doubles compared to the synthesized crystals. Furthermore, the compound demonstrates robust antibacterial effects against four Gram+ positive and two Gram- negative bacteria. In addition, its impact on cell proliferation, both in cancerous and non-cancerous cells, reveals the compound's antiproliferative effect on breast cancer cells in vitro, coupled with biocompatibility with human fibroblasts. This multifaceted approach positions the synthesized polymer as a promising candidate with vast potential for applications in luminescent materials and biomedical research.

Revealing The Degradation Mechanism of (Sr,Ca)AlSiN3:Eu2+ Phosphor Aged Under Thermal‐Moisture‐Sulfur Conditions: A Combined Experimental and Ab Initio Study

AbstractMAlSiN3:Eu2+ (M = Ca, Sr) is commonly used in high‐power phosphor‐converted white‐light‐emitting diodes and laser diodes to promote their color‐rendering index. However, the wide application of this phosphor is limited by the degradation of its luminescent properties in high‐temperature, high‐humidity, and high‐sulfur‐content environment. Here, the degradation mechanism of the (Sr,Ca)AlSiN3:Eu2+ (SCASN) red phosphor under thermal‐moisture‐sulfur coupling conditions is investigated. Furthermore, by performing first‐principles calculations, the hydrolysis mechanism on an atomic scale is assessed. The adsorption energy (Eads) and charge transfer (ΔQ) results showed that H2O chemically adsorbed on the (0 1 0), (3 1 0), and (0 0 1) surfaces of the CaAlSiN3 (CASN) host lattice. The energy barrier for H2O dissociation is only 29.73 kJ mol−1 on the CASN (0 1 0) surface, indicating a high dissociation probability. The formation of NH3, Ca(OH)2, and CaAl2Si2O8 is confirmed by H+ tended to combine with surface N atoms, while OH− combined with the surface Al/Si or Ca atoms. Moreover, ab initio molecular dynamics simulations were performed to further understand the hydrolysis process. This work offers a guidance on the design and applications of luminescent materials in LED packages with higher reliability and stability requirements in harsh environment.

Regulating luminescence thermal quenching based on the synergistic effect of energy transfer and energy gap modulation.

Thermal quenching is the core challenge that hinders the application of luminescent materials. Herein, a synergistic mechanism involving energy transfer and energy gap modulation is proposed based on the local crystal field regulation around sensitizers. The substitution of coordination cation V5+/P5+ weakens the crystal field strength of the sensitizer Bi3+, and the weakening of crystal field splitting causes an increase in the 3P1 energy level, thus increasing its energy gap. Compared with the YVO4:Bi3+,Eu3+ phosphor, the thermal stability of the YV0.25P0.75O4:Bi3+,Eu3+ phosphor is significantly improved, and the relative emission intensity of Eu3+ continuously increases with heating and reaches 1.24 times the original intensity at 523 K and does not show a decreasing trend in the studied temperature range. The anti-thermal quenching performance is mainly attributed to the increasing thermal quenching activation energy (ΔE) of the sensitizer by energy gap modulation, which enhances the energy transfer to compensate thermal quenching. Based on the thermal quenching characteristics of the materials, an optical thermometer is designed. The maximum relative sensitivity (Sr) and absolute sensitivity (Sa) are as high as 1.74% K-1 and 0.59 K-1, respectively, and the minimum temperature resolution reaches 0.288 K. The synergistic effect between energy gap modulation of the sensitizer and energy transfer enables the regulation of thermal quenching. Thus, this study provides a new strategy for exploiting high-performance luminescent materials.

Crystal structure and thermally enhanced photoluminescence in Eu(III) coordination polymers self-assembled from p-nitrobenzoic acid

Luminescent thermal quenching is a very troublesome thing for the practical application of luminescent materials, but also is a very common phenomenon. In theory, artificially reducing the number of quenching group around the luminescent lanthanide ion can effectively enhance the luminescence of lanthanide luminescent materials. In this paper, {[Eu2(NBA)6(H2O)4]∙H2O}n [Eu-NBA, NBA = p-nitrobenzoic acid] coordination polymers containing abundant coordination and interstitial water molecules were synthesized via hydrothermal methods. The chemical composition, crystal structures, and thermal stability of Eu-NBA coordination polymers were systemically investigated by Frontier-transfer infrared (FTIR) spectra, single-crystal X-ray diffraction and thermogravimetric analysis. X-ray diffraction analysis results revealed that Eu-NBA coordination polymers were crystallized into one-dimensional (1D) chain structures, where the adjacent Eu3+ ions were linked together by bidentate and/or tetradentate bridging carboxylate groups of the NBA ligands. The temperature-dependent photoluminescence spectra revealed that the shape and intensity of the luminescence spectra strongly depended on the coordination environment around Eu3+, and significant luminescent thermal enhancement was observed. These experimental results provided useful theoretical support for further understanding of the luminescence enhancement mechanism of lanthanide coordination polymers.

Synthesis of Naphthalimide Derivatives and Their Luminescence upon Complexation with Cucurbit[n]uril Hosts.

A series of naphthalimide derivatives are synthesized and their binding behavior upon complexation with cucurbit[n]urils (CB[n]s) has been investigated. With a heavy atom (bromine) on the naphthalimide core, 4-bromo-1,8-naphthalimide derivatives 1-4 show short room-temperature phosphorescence (RTP) lifetimes with low quantum yields. Their RTP properties are significantly enhanced in the presence of CB[8] or CB[10] both in aqueous solution and solid state owing to the efficient suppression of nonradiative decay and isolation of quenching factors by the rigid cavity of CB[n]. Without the bromine atom, 1,8-naphthalimide derivatives 5 and 6 show strong excimer emission upon complexation with CB[10] accompanied by fluorescence transition from blue to cyan. The fluorescence colors of 4-(dimethylamino)-1,8-naphthalimide derivatives 7 and 8 change from blue to white to yellow with the addition of CB[n]. This host-guest complexation strategy to modulate the luminescence of the luminophore would further broaden the application of luminescent materials.

Mild Synthesis of Polychlorinated Arenes for Efficient Organic Light‐emitting Diodes with Dual Thermally Activated Delayed Fluorescence

AbstractPolychlorinated (hetero)arenes have shown great promise for organic optoelectronics applications. However, the harsh synthetic routes for polychlorinated compounds and the possible luminescence quenching from the compact intermolecular π–π stacking induced by chlorine atoms limit their investigations and applications in luminescent materials. Herein, two isomeric polychlorinated polycyclic aromatic hydrocarbon (PAH) compounds JY‐1‐Cl and JY‐2‐Cl consisting of rigidified aryl ketones and amine are designed and synthesized under mild conditions through nucleophilic chlorination intermediated by an electron donor‐acceptor complex. Among them, as a result of the strong π–π interactions induced by chlorine atoms, JY‐2‐Cl exhibits bright monomer and dimer emissions with dual thermally activated delayed fluorescence (TADF) characters. Notably, compared with the non‐chlorinated compounds, a high photoluminescence quantum yield is maintained after introducing multiple chlorine atoms into JY‐2‐Cl. The first dual‐TADF organic light‐emitting diodes are also successfully fabricated with maximum external quantum efficiency as high as 29.1 % by employing JY‐2‐Cl as emitter. This work presents a new paradigm and synthesis of polychlorinated amine‐carbonyl PAHs and demonstrates the great potential of the chlorinated materials for luminescent applications.

Mild Synthesis of Polychlorinated Arenes for Efficient Organic Light-emitting Diodes with Dual Thermally Activated Delayed Fluorescence.

Polychlorinated (hetero)arenes have shown great promise for organic optoelectronics applications. However, the harsh synthesis of polychlorinated compounds and the possible luminescence quenching from the compact intermolecular π-π stacking induced by chlorine atoms limit their investigations and applications in luminescent materials. Herein, two isomeric polychlorinated polycyclic aromatic hydrocarbon (PAH) compounds JY-1-Cl and JY-2-Cl consisting of rigidified aryl ketones and amine are designed and synthesized under mild conditions through nucleophilic chlorination intermediated by electron donor-acceptor complex. Among them, due to the strong π-π interactions induced by chlorine atoms, JY-2-Cl exhibits bright monomer and dimer emissions with dual thermally activated delayed fluorescence (TADF) characters. Notably, in compared with the non-chlorinated compounds, high photoluminescence quantum yield is well maintained after introducing multiple chlorine atoms in JY-2-Cl. Eventually, the first dual-TADF organic light-emitting diodes are also successfully fabricated with maximum external quantum efficiency as high as 29.1% employing JY-2-Cl as emitter. This work presents a new paradigm and synthesis of polychlorinated amine-carbonyl PAHs and demonstrates the great potential of the chlorinated materials for luminescent applications.

Engineering Orthogonal Upconversion through Selective Excitation in a Single Nanoparticle

AbstractOrthogonal upconversion with color‐switchable emissions under different excitation conditions provides new chances to diverse frontier applications of luminescent materials. However, the previous orthogonal upconversion systems compulsorily require the precise control of spatial distributions of dopants and host compositions to avoid spectral cross‐talk, greatly limiting their synthesis and application. Herein, a conceptual design is presented to realize the orthogonal upconversion by selectively activating sensitizers and activators in nanostructure. In detail, the 915 nm laser, instead of the mostly used 980 nm, is adopted to activate the sensitizer Yb3+ because of the broad 2F5/2←2F7/2 absorption band; while it is non‐responsive to Er3+, consequently avoiding the spectral cross‐talk due to the simultaneous activation of both Er3+ and Yb3+ under 980 nm irradiation as shown in the previous works. Such a selective excitation strategy is able to realize the red/green, blue/red, and blue/green orthogonal upconversion in a single nanoparticle by simply altering the excitation wavelength from 915 to 1530 nm. More interestingly, it further allows for full‐color output by temporal control of the upconversion dynamics. The findings suggest a facile but effective approach to the design of smart luminescent materials, showing great potential in multi‐level anti‐counterfeiting, information security and biological applications.

Non-Covalent Dimer as Donor Chromophore for Constructing Artificial Light-Harvesting System in Water.

Dynamic emissive materials in aqueous media have received much attention owing to their ease of preparation, tunable luminescence and environmental friendliness. However, hydrophobic fluorophores usually suffer from aggregation-caused quenching in water. In this work, we constructed an artificial light-harvesting system by using a non-covalent aggregation-induced emission dimer as antenna and energy donor. The dimer is quadruple hydrogen bonded from a ureidopyrimidinone derivative (M) containing a tetraphenylethylene group. The dispersed nano-assemblies based on the dimer in aqueous media were fabricated with the help of surfactant. By loading a hydrophobic acceptor molecule DBT into the nano-assemblies, man-made light-harvesting nanoparticles were fabricated, showing considerable energy transfer efficiency and a relatively high antenna effect. Additionally, the fluorescence color of the system can be gradually tuned by varying the content of the acceptors. This study provides a general way for the construction of an aqueous light-harvesting system based on a supramolecular dimer, which is important for potential application in luminescent materials.

Pressure Effect on Self-Trapped Exciton and Dopant Energy Transfer in Neodymium-Doped CsPbBr3 Perovskite Nanocrystals

The CsPbBr3 nanocrystal is a highly attractive light emitter with outstanding monochromaticity and good thermal stability and has garnered tremendous interest in its application in luminescent materials and devices. Here, we propose a novel strategy to improve the luminescence intensity of CsPbBr3 nanocrystals by doping with Nd3+ ions and introducing pressure. Under high pressure, the CsPbBr3:Nd nanocrystals show an abnormal enhancement of the photoluminescence intensity from 0.19 to 0.34 GPa. The time-resolved photoluminescence measurements reveal that pressure facilitates the recombination of self-trapped excitons and suppresses the recombination of the Nd energy levels. This discovery shows that pressure can modulate the photoluminescence kinetics of CsPbBr3:Nd nanocrystals. This work deepens the understanding of the influence of high pressure on rare-earth-doped luminescent materials and provides insight to improve the capabilities of optical devices.

Stable Core–Shell Structure Nanocrystals of Cs4PbBr6-Zn(moi)2 Achieved by an In Situ Surface Reconstruction Strategy for Optical Anticounterfeiting

Zero-dimensional Cs4PbBr6 nanocrystals (NCs) possess attractive photoluminescence (PL) properties and feature facile chemical synthesis, making them promising for application in luminescent materials. However, Cs4PbBr6 remains sensitive to polar solvents and thermal stimuli because of soft ionic nature of Cs4PbBr6 and dynamic behavior of surface ligands. Herein, a strategy controlled by an in situ surface coordination reaction is developed to fabricate stable NCs with a Cs4PbBr6-Zn(moi)2 core-shell structure. It was found that the Cs4PbBr6 surface regulated by the use of 2-mercaptoimidazole (called moi) and the coordination between the -NH group of moi and Zn2+ is critical for the formation of Cs4PbBr6-Zn(moi)2 core-shell NCs. Meanwhile, the thickness of the Zn(moi)2 shell can be facilely controlled by the growth time because of the solubility of moi and Zn(OAc)2·2H2O in ethyl acetate. Compared to bare Cs4PbBr6, Cs4PbBr6-Zn(moi)2 NCs exhibited highly improved polar solvent resistance and thermal stability. By combining the sensitivity of Cs4PbBr6 and the stability of Cs4PbBr6-Zn(moi)2, we used two NCs as PL security inks to fabricate optical anticounterfeiting labels. Thus, the disposable or reusable optical anticounterfeiting label is achieved by changing the external dual-stimuli. This work provides a novel strategy to enhance the stability of Cs4PbBr6 and develop its potential interest for application in anticounterfeiting technologies.

Thermal Enhancement of Luminescence for Negative Thermal Expansion in Molecular Materials.

Overcoming thermal quenching is an essential issue in the practical application of luminescent materials. Herein, we found that negative thermal expansion (NTE) can achieve the thermal enhancement of luminescence in molecular materials based on three metal-organic frameworks CuX-bpy (X = Cl, Br, I; bpy = 4,4'-bipyridine). All complexes exhibit NTE on the c-axis, and the strongest NTE leads to a contraction of the Cu...Cu distance in CuCl-bpy, which further intensifies the luminescence emission. This phenomenon indicates the existence of thermally enhanced charge transfer. Moreover, the origin of the distinction in charge transfer attributed to the different valence states of the copper is investigated through the combined studies of X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and density functional theory calculations. This research provides a new approach to modulating the luminescence thermal enhancement by NTE.

Thermosensitive Microgels Containing AIEgens: Enhanced Luminescence and Distinctive Photochromism for Dynamic Anticounterfeiting.

The proposal of the aggregation-induced emission (AIE) effect shines a light on the practical application of luminescent materials. The AIE-active luminescence microgels (TPEC MGs) with photo-induced color-changing behavior were developed by integrating positively charged AIE luminogens (AIEgens) into the anionic network of microgels, where AIEgens of TPEC were obtained from the quaternization reaction between tetra-(4-pyridylphenyl)ethylene (TPE-4Py) and 7-(6-bromohexyloxy)-coumarin. The aqueous suspensions of TPEC MGs exhibit a significant AIE effect following the enhancement of quantum yield. In addition, further increase in fluorescence intensity and blueshift occur at elevated temperatures due to the collapse of microgels. The distinctive photochromic behavior of TPEC MGs was observed, which presents as the transition from orange-yellow to blue-green color under UV irradiation, which is different from TPEC in good organic solvents. The phenomenon of color changing can be ascribed to the competition between photodimerization of the coumarin part and photocyclization of TPE-4Py in TPEC. The photochromic TPEC MG aqueous suspensions can be conducted as aqueous microgel inks for information display, encryption, and dynamic anticounterfeiting.

Feasibility of Emission-Enhanced CsPbCl3 Quantum Dots Co-Doped with Mn2+ and Er3+ as Luminescent Downshifting Layers in Crystalline Silicon Solar Modules

In order to enhance the photoelectric conversion efficiencies of crystalline silicon (c-Si) solar cells, CsPbCl3 quantum dots (QDs) codoped with Mn2+ and Er3+ (CsPbCl3:Mn2+, Er3+ QDs) were mixed with ethylene–(vinyl acetate) (EVA) to form a film which was used as a luminescent down-shifting (LDS) layer. The LDS layer effectively improved the low utilization of near-ultraviolet light of c-Si solar cells. These CsPbCl3:Mn2+,Er3+ QDs were synthesized via a conventional high-temperature injection method. Mn2+ is the luminescence center, and the incorporation of Er3+ greatly enhances the luminescence intensity of Mn2+. The absolute photoluminescence quantum yield of the QDs dispersed in toluene reached 79.5% when the QDs were synthesized under the optimum conditions, that is, an injection temperature of 180 °C and Pb:Mn:Er preparation molar ratios of 6:4:4. The EVA film embedded with QDs at the optimum concentration (0.9 wt %) was used as an LDS layer for c-Si solar module. The short-circuit current (ISC) and the photoelectric conversion efficiency (η) were increased by 3.42% and 4.02%, respectively, owing to the LDS layer. Moreover, a luminescent solar concentrator (LSC) which was another application of luminescent materials was also demonstrated. For LSC, the relative changes in ISC and η by using the QDs-dispersed EVA film were +14.9% and +18.0%, respectively. These results indicate a feasible application of luminescent downshifting films in solar modules.

An efficient method to synthesize N/O, O-difluoroboron complexes from alkynes

A highly efficient redox- and step-economic method to synthesize N,O- and O,O-difluoroboron complexes from alkynes under aqueous condition with HBF4 as BF2 source has been developed. This strategy features good yields, broad substrate scope, mild reaction conditions, readily available starting materials and gram-scale synthesis. Significantly, these difluoroboron complexes present good fluorescence properties, indicating their potential applications in luminescent materials.

Nontraditional Luminescent Molecular Aggregates Encapsulated by Wormlike Silica Nanoparticles for Latent Fingerprint Detection.

The phenomenon of nontraditional luminescence has attracted wide attention and curiosity of researchers due to its inexplicable photoluminescence paradigm without aromatic or extended π-systems. The present work puts forward a neotype of a light-emitting nitrogenous small molecule, namely, N-stearoyl-hydroxyproline (L-C16-Hyp), which could emit weak light in aggregation states through the restriction mechanism of intramolecular motion, exhibiting properties comparable to those of AIEgens. Using these molecular aggregates as anionic surfactant micelles to incorporate within the silica matrix, we prepared fluorescent nanoparticles (FL-NPs) by a one-pot method for expedient visualization of latent fingerprints (LFPs). The FL-NPs exhibit an excitation range from 335 to 365 nm, resulting in nontraditional luminescence observed between 410 and 440 nm. The enhanced luminescent FL-NPs may derive from the collective entities or assemblies of restricted L-C16-Hyp, which can be reasonably explicated by an effect termed as cluster-triggered emission (CTE). Theoretical calculations demonstrated that this luminescence pattern belongs to partial charge transfer, which is mainly attributed to the close interaction between the tertiary amino and adjacent carboxyl in the L-C16-Hyp structure. Moreover, some merits of FL-NPs, such as wormlike nanomorphology, stable photophysical properties, low toxicity, great adhesion to multiple substrates, easy to get raw material, an inexpensive, simple process, and rapid detection without any further modification or assistance, provide the feasibility of efficacious LFP detection. Overall, this study will provide insights into the design and application of luminescent materials with unconventional groups.

Long Persistent Luminescence: A Road Map Toward Promising Future Developments in Energy and Environmental Science

In recent decades, research on persistent luminescence has led to new phosphors and promising performances. Efforts to improve the quality of phosphors’ afterglow have paved the way toward innovative solutions for many disciplines. However, there are few examples of the implementation of luminescent materials. In addition to providing a general background on persistent luminescence, the techniques used for its analysis, and its multidisciplinary potential in energy and environmental science, this article aims to explain the existing gap between the physical-chemical approach and the effective implementation of luminescent materials in larger-scale applications. It investigates engineering solutions in terms of the possible benefits of luminescence in lighting energy savings and passive cooling of urban surfaces. Finally, this article aims to reduce the abovementioned gap by suggesting what is most needed for the successful application of luminescent materials in the built environment.

Molecular design and application of luminescent materials composed of group 13 elements with an aggregation-induced emission property.

Complexation of π-conjugated ligands by metal or semimetal ions leads to the enhancement of the planarity and rigidity of π-conjugated systems. Boron, especially, has played a central role in the design of luminescent main-group complexes. However, these complexes still suffer the disadvantage of aggregation-caused quenching as well as typical organic fluorophores. It has recently been reported that some types of boron complexes exhibit the aggregation-induced emission (AIE) property. Moreover, AIE behavior from complexes and organometallic compounds composed of the other group 13 elements, such as aluminum and gallium, has emerged in this decade. These observations greatly encourage us to develop advanced functional materials based on the group 13 elements. Indeed, recent research has demonstrated that these classes of materials are potentially versatile scaffolds for constructing chromic luminophores, efficiently emissive π-conjugated polymers and so on. This review mainly describes AIE-active group 13 complexes with four-coordinate structures and their application as photo-functional materials. Proposed mechanisms of the origins of AIE behavior are briefly discussed.

Metal-catalyzed B-H acylmethylation of pyridylcarboranes: access to carborane-fused indoliziniums and quinoliziniums.

Metal-catalyzed mono-acylmethylation of pyridylcarboranes has been realized using α-carbonyl sulfoxonium ylides as a coupling partner. The reaction features high efficiency, excellent site-selectivity and good functional group tolerance. In the presence of pyridyl and enolizable acylmethyl groups, a post-coordination mode has been proposed and validated by in situ high resolution mass spectroscopy (HRMS) to rationalize the unique mono-substitution. Post-functionalization at the newly incorporated alkyl site provides additional utility of this method, including the construction of carborane-fused indoliziniums and quinoliziniums. We believe that these mono-alkylated carboranes, together with their post-functionalized derivatives, may find applications in luminescent materials and drug discovery in the near future.

A new resource-rich carbonate luminescent host KNa5Ca5(CO3)8: A case study activated by Eu3+ for red-phosphor purpose

Exploring and designing new luminescent host with rich resource is beneficial to reducing the cost and the large-scale application of luminescent materials. Herein, a series of novel Eu3+-activated KNa5Ca5(CO3)8 red-emitting phosphors with different Eu3+ concentrations were successfully synthesized under mild hydrothermal condition. XRD and SEM characterizations show that all as-prepared KNa5Ca5(CO3)8:Eu3+ samples crystallize in a hexagonal structure, P63mc (No.186) space group, and show monodispersed hexagonal sheet morphologies, within a side length interval about of 2–3 μm and a thickness of about 0.6 μm. Eu3+ doping within 6 mol% concentration has little influence on the crystal structure of the host, as indicated by XRD, and FT-IR results, but thermal stability changes as shown by the TG-DTA. KNa5Ca5(CO3)8 phosphors with different Eu3+ concentrations can emit red-light under effectively excitation by near-UV light. CIE chromaticity coordinates of all KNa5Ca5(CO3)8:Eu3+ phosphors were calculated to locate in red region, and CCT of each sample is the range from 2815 to 3650 K, very close to the tungsten lamp light. Besides, concentration quenching phenomenon appearing at 5 mol% is found to be the result of electric multipolar interaction of Eu3+ activators, and the decay lifetime is about 1.63 ms, which almost unchanges with Eu3+ doping concentration. Importantly, thermal quenching analysis reveals good thermal stability with thermal activation energy of about 0.216 eV. The results reported here demonstrate that KNa5Ca5(CO3)8 is a promising fluorescent host for LEDs applications.