Multifunctional Luminescent Materials Research Articles

Molecular engineering of thiophene- and pyrrole-fused core arylamine systems: Tuning redox properties, NIR spectral responsiveness and bacterial imaging applications

The thiophene- and pyrrole-fused heterocyclic compounds have garnered significant interest for their distinctive electron-rich characteristics and notable optoelectronic properties. However, the construction of high-performance systems within this class is of great challenge. Herein, we develop a series of novel dithieno[3,2-b:2′,3′-d] pyrrole (DTP) and tetrathieno[3,2-b:2′,3′-d] pyrrole (TTP) bridged arylamine compounds (DTP-C4, DTP-C12, DTP-C4-Fc, TTP-C4-OMe, TTP-C4, and TTP-C12) with varying carbon chain lengths. The pertinent experimental results reveal that this series of compounds undergo completely reversible multistep redox processes. Notably, TTP-bridged compounds TTP-C4 and TTP-C12 exhibit impressive multistep near-infrared (NIR) absorption alterations with notable color changes and electroluminescent behaviors, which are mainly attributed to the charge transfer transitions from terminal arylamine units to central bridges, as supported by theoretical calculations. Additionally, compound DTP-C4 demonstrates the ability to visually identify gram-positive and gram-negative bacteria. Therefore, this work suggests the promising electroresponsive nature of compounds TTP-C4 and TTP-C12, positioning them as excellent materials for various applications. It also provides a facile approach to constructing high-performance multifunctional luminescent materials, particularly those with strong and long-wavelength NIR absorption capabilities.

Blue-excitable orange-red-emitting M3Y(PO4)3:Pr3+ (M = Ba, Sr, Ca) phosphors for multifunctional applications

Research on multifunctional luminescent materials has become an emerging trend for new applications of optical sensing, monitoring, anticounterfeiting, lighting, etc. Herein, a library of Pr3+-doped M3Y(PO4)3 (M = Ba, Sr, Ca) phosphors was prepared for careful spectroscopic studies in potential lighting and optical temperature sensing applications. With the help of density functional theory calculation, diffuse reflectance spectra, and steady/dynamic photoluminescence spectra, the effects of alkaline earth metals on the fluorescence properties of M3Y(PO4)3:Pr3+ were studied systematically. Under the excitation of blue ∼ 445 nm, orangish-red fluorescence of approximately 602 nm was efficiently detected due to Pr3+ 1D2 → 3H4 transition, which becomes stronger by regulating alkaline-earth elements from Ba to Sr and to Ca. An optimized Ca3Y(PO4)3:0.7%Pr3+ sample was validated with excellent thermal stability 89%@423 K and further applied to fabricate a white light emitting diode by combining with commercial YAG:Ce3+ phosphors on a 445 nm blue chip. Specifically, CIE chromaticity coordinates (0.3510, 0.3650) and correlated color temperature (∼ 4838 K) were obtained for an obvious improvement. Moreover, optical thermometry properties of Ca3Y(PO4)3:0.7%Pr3+ were explored on basis of Pr3+ 3P0-3P1 thermally coupled energy levels. Their fluorescence intensity ratios following the Boltzmann equation could be operated over 298-598 K with superior relative sensitivity ∼ 0.87% K-1 at 298 K. These interesting results for multifunctional luminescence will greatly promote the development of novel Pr3+-doped luminescent materials as well as the related photoelectric devices.

Ultraviolet-B and Near-Infrared Dual-Band Luminescence in Bi3+/Bi2+ Codoped Persistent Phosphor for Optical Storage Application.

Discovering multifunctional luminescent materials to meet the demands of modern spectroscopy is of great significance. However, it is a standing challenge to enable multiple luminescence properties in a single material system via single metal ion doping. Here, we report the inherently Bi3+/Bi2+ codoped Ca3Ga2Ge3O12 persistent phosphor where Bi3+ is in situ reduced to Bi2+. This phosphor can act as an efficient multimodal luminescence material, which simultaneously exhibits long-lasting (>12 h) ultraviolet-B (UVB) and near-infrared (NIR) dual-band persistent luminescence after irradiation by 254 nm ultraviolet (UV) light. UVB and NIR afterglow are ascribed to the distinct Bi3+ and Bi2+ emitters, respectively, proven by comprehensive spectroscopic investigations including X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. Besides, this phosphor also exhibits exceptional photochromic features, accompanied by a rapid body color transformation from white to brown in response to 254 nm UV light within 60 s and excellent recovery capacity upon thermal or blue/white light stimulation. The combination of UVB persistent luminescence of Bi3+ and NIR afterglow of Bi2+ coupled with reversible white-to-brown photochromism phenomenon offers one type of promising multifunctional luminescence material, showing potential to be used for optical storage and anti-counterfeiting applications.

Luminescence properties of a green-emitting mechanoluminescent phosphor CaSrGa4O8:xTb3+ without pre-excitation.

In this study, both mechanoluminescence (ML) and long persistent luminescence (LPL) characteristics were first observed in CaSrGa4O8 doped with Tb3+ ions, which confirmed that CaSrGa4O8 is a high-quality host for luminescent material research. Notably, the samples show stronger mechanoluminescent intensity with increasing Tb3+ doping. Additionally, the introduction of Tb3+ led to a shift of the thermoluminescence peak towards higher temperatures and a substantial increase in its intensity, suggesting that Tb3+ doping enhances the overall trap concentration and introduces deeper trap energy levels. Presumably, the free carriers in the system recombine upon mechanical stimulation, releasing energy that is transferred to Tb3+ ions. Investigations into the intrinsic structure, matrix effects, and trap evolution of the material confirmed that deep and shallow traps are responsible for the observed ML and LPL phenomena, respectively. The elucidation of the unique luminescent properties of the material provides us with some guidance for the development of new multi-functional luminescent materials.

Lanthanide‐Containing Heteropolyoxomolybdate as Precursor to Porous Complex Oxides via Polymeric Micelle Assembly and Its Heterostructure with Carbon Dots for Anticounterfeiting Application

AbstractThe fabrication of porous complex oxides with intriguing opto‐functional properties remains a challenge that requires innovative synthetic strategies. In this work, a facile soft template method is developed based on stable micellar solutions formed with lanthanide‐containing heteropolyoxomolybdate and alkaline earth citrates as metal salt precursors and block copolymer as templates. The resulting structures exhibit an effective interfacial Förster resonance energy transfer (IFRET) between the porous CaMoO4:Eu3+ (CEMO) host and the embedded surface‐active carbon dots through the conjugated bonds between Ca2+/Mo6+ cations and the C═O functional groups. Such IFRET process extends of Eu3+ absorption band toward the UV and blue regions, enabling the proof‐of‐concept demonstration of multiresponsive anticounterfeiting codes. The study not only presents a new strategy to prepare porous lanthanide‐doped complex oxides but also provides a feasible way to achieve spectral regulation through interfacial interaction for multifunctional luminescent materials.

A Japan-Poland Collaboration for Coupling Molecular Nanomagnetism and Luminescent Thermometry.

This invited Team Profile was created by the Laboratory of Advanced Functional Materials (Tokoro Lab), Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba (Japan); the Multifunctional Luminescent Materials Group (Szymon Group, MLMG), Faculty of Chemistry, Jagiellonian University, Kraków (Poland); and the Solid State Physical Chemistry Group (Ohkoshi Lab), Department of Chemistry, School of Science, The University of Tokyo (Japan). They recently published an article on a bimetallic cyanido-bridged TbIII -CoIII framework exhibiting a desolvation-induced structural transformation providing high-symmetry trigonal-prismatic [TbIII (NC)6 ]3- complexes. This induces a strong magnetic anisotropy leading to single-molecule magnet behavior with an energy barrier of 854(26) K, which appears in the cryogenic temperatures range, together with the concomitant luminescent thermometry effect. "Desolvation-Induced Highly Symmetrical Terbium(III) Single-Molecule Magnet Exhibiting Luminescent Self-Monitoring of Temperature", J. Wang, J. J. Zakrzewski, M. Zychowicz, Y. Xin, H. Tokoro, S. Chorazy, S. Ohkoshi, Angew. Chem. Int. Ed. 2023, 62, e202306372.

A Japan–Poland Collaboration for Coupling Molecular Nanomagnetism and Luminescent Thermometry

AbstractThis invited Team Profile was created by the Laboratory of Advanced Functional Materials (Tokoro Lab), Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba (Japan); the Multifunctional Luminescent Materials Group (Szymon Group, MLMG), Faculty of Chemistry, Jagiellonian University, Kraków (Poland); and the Solid State Physical Chemistry Group (Ohkoshi Lab), Department of Chemistry, School of Science, The University of Tokyo (Japan). They recently published an article on a bimetallic cyanido‐bridged TbIII−CoIII framework exhibiting a desolvation‐induced structural transformation providing high‐symmetry trigonal‐prismatic [TbIII(NC)6]3− complexes. This induces a strong magnetic anisotropy leading to single‐molecule magnet behavior with an energy barrier of 854(26) K, which appears in the cryogenic temperatures range, together with the concomitant luminescent thermometry effect. “Desolvation‐Induced Highly Symmetrical Terbium(III) Single‐Molecule Magnet Exhibiting Luminescent Self‐Monitoring of Temperature”, J. Wang, J. J. Zakrzewski, M. Zychowicz, Y. Xin, H. Tokoro, S. Chorazy, S. Ohkoshi, Angew. Chem. Int. Ed. 2023, 62, e202306372.

Achieving TADF and RTP with Stimulus‐Responsiveness and Tunability from Phenothiazine‐Based Donor−Acceptor Molecules

AbstractResearch of thermally activated delayed fluorescence (TADF) and room‐temperature phosphorescence (RTP) materials is attractive owing to their extensive applications in various fields. However, achieving organic TADF and RTP materials, particularly those with stimulus‐responsiveness and tunability, is highly desirable but challenging and rarely reported. Herein, two easily synthesized organic molecules are reported with abnormal stimulus‐responsive switchable TADF and RTP effects, in which phenothiazine (PTZ) and benzo[b]phenothiazine (BPTZ) based donor−acceptor molecules PTZ‐DBQ and BPTZ‐DBQ show mechanical‐induced TADF in crystalline phase and photo‐responsive RTP in doping poly(methyl methacrylate) (PMMA) films. This is the first time tetracyclic BPTZ has been used as a donor in achieving TADF and RTP materials, and it is found that BPTZ‐DBQ exhibits remarkably better photophysical properties than PTZ‐DBQ. Systematic studies of experimental results and theoretical calculations indicate that the conformational heterogeneity plays an essential role in achieving mechanical‐induced TADF with mechanochromic luminescence (MCL) property. Embedding the organic phosphors into rigid polymer matrices effectively suppresses the molecular motion, thus turning on the RTP emission channel. The conversion of 3O2 to 1O2 under UV irradiation is mainly responsible for the photo‐induced process. These multifunctional luminescent materials have great potential applications in chemical sensors, information encryption, and anti‐counterfeiting.

Ultralong organic room-temperature phosphorescence, multiple stimulus responsiveness and high-level anti-counterfeiting based on multifunctional carbazolyl imidazolopyridine

Ultralong organic room-temperature phosphorescence materials induced by host−guest doping and the underlying mechanism have become the current research focus. Furthermore, high-level anti-counterfeiting and information encryption require multifunctional luminescent materials. Here, CzIP and L-CzIP with push−pull electronic system are successfully constructed by imidazopyridine units and commercial/self-made carbazole. The comparison experiment results indicate that trace isomer doping not only shows slight influence on crystal stacking and molecular space conformation but also significantly changes fluorescence and phosphorescence spectra and phosphorescence lifetime by boosting intersystem spin–orbit coupling. Non-radiative relaxation of CzIP and L-CzIP can be effectively inhibited by polymethyl methacrylate (PMMA) doping but not for crystallize. PMMA doping further confirms intrinsic phosphorescent characteristic of L-CzIP, whose room-temperature phosphorescence lifetime (84.83 ms) is close to that of CzIP (100.14 ms). Concentration-dependent fluorescent and phosphorescent emission and dynamic phosphorescent emission are also observed for CzIP in PMMA film. More importantly, a new aminopyridine/CzIP-doped system gives room-temperature phosphorescence lifetimes of 657.56 ms and afterglow lifetimes of 4 s. Notably, CzIP also shows high-contrast mechanochromism, selective response and differentiation to HCl, CF3COOH, and CH3COOH, and excellent detection capability to picric acid in aqueous medium and solid state. Finally, various anti-counterfeiting and encryption patterns are successfully constructed based on multifunction of CzIP. This work not only provides a multifunctional luminous material but also more importantly provides a theoretical basis and experimental guidance for designing novel ultralong organic room-temperature phosphorescence materials and achieving high-level anti-counterfeiting and encryption.

Mononuclear copper(Ⅰ) complexes with mechanochromic thermally activated delayed fluorescence behaviour based on switchable hydrogen bonds

Four neutral mononuclear copper(I) complexes (1–4) with formula of [(N^P)Cu(PPh3)2] (1–2) and [(N^P)Cu(Xantphos)] (3–4) based on NH–deprotonated (2–(1H–benzimidazole)phenyl) diphenylphosphine ligands (N^P) and phosphine ancillary ligands have been synthesized. The copper(I) complexes exhibit bright thermally activated delayed fluorescence at room temperature with photoluminescence quantum yield up to 43.5%. Upon grinding, the complexes display apparent bathochromic shift in the emission maxima of up to 50 nm (1). Meanwhile, the complexes display similar luminescence profiles to those of the origin samples exposed to CH3OH vapor. Single crystal X–ray and PXRD diffraction results demonstrate that the reversible mechanochromic luminescent (MCL) properties are ascribed to the transformation of crystalline and amorphous state dependent on the disruption and restoration of hydrogen bonds during external stimuli, which have been rarely observed in the copper(I)-based MCL materials hitherto. These findings clearly suggest that the introduction of switchable secondary interactions in mononuclear copper(I) complex is a large-scale synthesis strategy for multifunctional luminescent materials.

Multifunctional emitters with TADF, AIE, polymorphism and high-contrast multicolor mechanochromism: Efficient organic light-emitting diodes

Organic multifunctional luminescent materials have drawn growing attention due to their diverse emissive mechanism and potential application in luminescent field. Herein, a series of cyanobenzene-decorated dimethylacridine-quinoline conjugates is designed and synthesized, which exhibit thermally activated delayed fluorescence (TADF), aggregation-induced emission (AIE), polymorphism and multicolor mechanochromic luminescence (MCL) with high contrast beyond 75 nm. Significantly, structure-property investigations via the in-depth analysis of molecular conformations and three-dimensional supramolecular framework of the polymorphic crystals demonstrate that the diverse conformations and abundant noncovalent interactions have a predominant impact on aggregation-dependent TADF property and emission wavelength. The quasi-equatorial conformational electron-donating unit and quasi-planar structural electron-withdrawing segment in aggregation states of the emitter are beneficial for accelerating the rate of the reverse intersystem crossing, enhancing TADF character, and promoting the emission with a bathochromic shift. The organic light-emitting diodes (OLEDs) employing these emitters achieve good device performance with an external quantum efficiency (EQE) of 14.6%.

Exciplex-induced TADF, persistent RTP and ML in a host–guest doping system

A universal exciplex platform was reported to construct multifunctional luminescent materials, including thermally-activated delayed fluorescence (TADF), persistent room temperature phosphorescence (RTP) and mechanoluminescence (ML).

Full-color-tunable phosphorescence of antimony-doped lead halide single crystal

Although multiple emissive phosphors are of great fundamental interest and practical importance, it is still challenging to achieve full-color tunable luminescence in a single-component material. Herein, we present an antimony-doped lead halide single crystal (C10NH22)2PbBr4: Sb3+ with widely tunable red/green/blue/white luminescence. Extrinsic Sb3+ dopants provide host another active sites to capture photo-generated excitons, thus triggering blue/red dual emission. Moreover, a reversible thermal-induced phase transition transforms blue/red emission into green/red dual emission. Both two phases exhibit intriguing excitation-wavelength dependent emission, affording a whole color gamut covering the red-green-blue (RGB) color triangle on the CIE 1931 diagram. Experimental and theoretical calculation studies reveal two emitters work independently, which paves the way for the multimode optical control and promotes the development of multifunctional luminescent materials.

Bright Cyan‐Emissive Copper(I)‐Halide Single Crystals for Multi‐Functional Applications

AbstractAnti‐counterfeiting has become a serious issue around the global world; fluorescence‐based tags are praised for the low‐cost and facile decryption process. However, the high‐level anti‐counterfeiting application requires incorporating multifunctional luminescent materials with response to different excitation sources. Herein, a dimeric Cu(I)‐halide‐clusters‐assembled single‐crystal (AEP)2Cu2I6·2I·2H2O (AEP = N‐aminoethylpiperazinium) concerning a high down‐conversion photoluminescence quantum yield (PLQY) value of near unity is reported (λex = 305 nm), which can also be activated by the near‐infrared light and X‐ray. The ultrafast spectroscopy and density functional theory calculations reveal that the broad‐band emission originates from the recombination of self‐trapped excitons. Remarkably, the high PLQY and excellent attenuation capability for X‐ray confers an outstanding light yield of 55 650 photons MeV−1 to (AEP)2Cu2I6·2I·2H2O, which is 5.25 times higher than the standard bismuth germaniumoxide scintillator. Such multi‐light‐stimulus response endows (AEP)2Cu2I6·2I·2H2O with great application potential in anti‐counterfeiting, solid‐state lighting devices, and digital radiography.

Integrated Afterglow and Self-Trapped Exciton Emissions in Hybrid Metal Halides for Anti-Counterfeiting Applications.

0D hybrid metal halides (0D HMHs) are considered to be promising luminescent emitters. 0D HMHs commonly exhibit self-trapped exciton (STE) emissions originating from the inorganic metal halide anion units. Exploring and utilizing the emission features of the organic cation units in 0D HMHs is highly desired to enrich their optical properties as multifunctional luminescent materials. Here, tunable emissions from organic and inorganic units are successfully achieved in triphenylsulfonium (Ph3 S+ )-based 0D HMHs. Notably, integrated afterglow and STE emissions with adjustable intensities are obtained in (Ph3 S)2 Sn1- x Tex Cl6 (x= 0-1) via the delicate combination of [SnCl6 ]2- and [TeCl6 ]2- . Moreover, such a strategy can be readily extended to develop other HMH materials with intriguing optical properties. As a demonstration, 0D (Ph3 S)2 Zn1- x Mnx Cl4 (x= 0-1) are constructed to achieve integrated afterglow and Mn2+ d-d emissions with high efficiency. Consequently, these novel 0D HMHs with colorful afterglow and STE emissions are applied in multiple anti-counterfeiting applications.

Up/down-conversion luminescence of monoclinic Gd2O3:Er3+ nanoparticles prepared by laser ablation in liquid

Multifunctional luminescent materials are attracting attention nowadays. In this work, monoclinic Gd2O3:Er3+ nanoparticles, which possess up-conversion luminescence and down-conversion luminescence properties, were successfully synthesized by laser ablation in liquid (LAL) technique. Up-conversion luminescence and down-conversion luminescence of monoclinic Gd2O3:Er3+ nanoparticles were got under the excitation of 980 nm and 379 nm, respectively. In addition, tunable luminescence was got. Furthermore, the cytotoxicity of the nanoparticles is low and the fluorescence of the nanoparticles in cell is also strong enough. The results indicate that the Gd2O3:Er3+ nanoparticles synthesized by LAL technique are promising candidates for bio-imaging or other fields that require controllable fluorescence.

A multifunctional luminescent material based on quinoxaline and triphenylamine groups: polymorphism, mechanochromic luminescence, and applications in high-efficiency fluorescent OLEDs

TQT exhibits multifunctional luminescence characteristics, such as polymorphism and mechanochromic, with potential application in OLEDs. An extremely high photoluminescence quantum yield of 96.5% is achieved in CBP: TQT-G doped film.

Resonance-Enhanced Two-Photon Absorption and Optical Power Limiting Properties of Three-Dimensional Perylene Bisimide Derivatives.

Push-pull organic structures characterized by an intramolecular charge transfer (ICT) process and π-electron delocalization are potentially interesting luminescent materials. A series of three-dimensional o-carborane-containing perylene bisimide derivatives (PBIs) were synthesized, and their optical properties were systematically investigated to illustrate the stereo effect, especially on the two-photon absorption (2PA) and optical power limiting (OPL) properties. Open-aperture Z-scan curves showed that all four PBIs displayed strong and broad two-photon absorptivities based on the resonance-enhanced phenomenon. The maximum degenerate two-photon absorption cross section (δ2PA) increased with the number of PBI substituents. The derivative CB-PBI possessed a δ2PA value of ∼2400 GM at 650 nm, a significant enhancement in comparison with that of the parent PBI (∼719 GM), ascribed to the present stereo effect. When the aromatic-donating units changed from naphthyl and pyrenyl to PBI, the generated multidimensional intramolecular charge transfer (ICT) from the aromatic units to the o-carborane cage contributed to the 2PA processes. All of the fluorophores exhibited excellent optical power limiting (OPL) performances as well as a minimum limiting threshold of ∼4.98 mJ/cm2 for CB-PBI. These significant results not only allow us to get deep insight into the nature of the fundamental stereo effect and nonlinear optical (NLO) response involved but also guide us toward the design of new multifunctional luminescent materials.

Saccharin-derived multifunctional emitters featuring concurrently room temperature phosphorescence, thermally activated delayed fluorescence and aggregation-induced enhanced emission

Multifunctional luminescent materials simultaneously imparted with various emission properties are of great significance. To develop multifunctional luminescent materials, saccharin was introduced as a novel electron acceptor for the first time, resulting in three new luminogens, namely 6-Cz-Sac, 5-Cz-Sac, and DiCz-Sac. All the three luminogens exhibited aggregation-induced enhanced emission (AIEE) and ultralong room temperature phosphorescence (RTP) properties. An in-depth analysis on their stacking arrangements in single crystals reveals the abundant supramolecular interactions, with intermolecular hydrogen bonds resulting from the carbonyl and sulfone groups of saccharin unit. These close-distance intermolecular non-covalent interactions can effectively suppress the intramolecular motions and impede non-radiative decay channels, thus resulting in intense emission in aggregated states. Among the three emitters, the 5-Cz-Sac crystal showed more intermolecular non-covalent interactions through the planar carbazole units, compared with DiCz-Sac and 6-Cz-Sac, which leads to its excellent RTP properties with an ultralong lifetime of 664 ms. DiCz-Sac, with a multi-donor structure and the largest donor–acceptor twisted angles among the three emitters, exhibited thermally activated delayed fluorescence (TADF) characteristics in addition to AIEE and RTP. DiCz-Sac represents the first reported saccharin-based multifunctional luminogen concurrently exhibiting AIEE, RTP, and TADF. This work reveals that such a molecular design strategy is a promising platform for constructing multifunctional luminescent materials.

Tunable Dual-Mode MOF-Based Composite Fluorescent Materials: Stimuli-Responsive and Anti-counterfeiting Application

With the incessant improvement of requirements for optical anti-counterfeiting technology, it is essential to develop multifunctional luminescent materials with multiple models and adjustable lumin...