Dual Emission Research Articles

Facile preparation, mechanochromic luminescence and excitation wavelength-dependent emission of tetra(1H-benzo[d]imidazol-2-yl)ethene Zn(II) complexes and their applications.

Nowadays, benzimidazole and its derivatives are widely assembled into multifunctional materials with various properties such as mechanochromism, photochromism, thermochromism and electrochromism. Herein, two novel zinc(II) coordination compounds, [Zn2(L2)Br4]·2H2O (1) and [Zn2(L2)Cl4]·2H2O (2) (L2 = tetra(1H-benzo[d]imidazol-2-yl)ethene), have been constructed via one-pot facile synthesis from bis(1H-benzo[d]imidazol-2-yl)methane (L1) and zinc(II) salts. The ligand L2 with a CC double bond was in situ formed by C-C coupling of two sp3-C atoms of L1 in solvothermal synthesis, which provides a new strategy to generate the conjugation system conveniently. Impressively, complex 1 shows distinct fluorescence and phosphorescence dual emission due to the heavy atom effect of bromide ions. Complexes 1 and 2 exhibit high-contrast mechanochromic luminescence properties due to the transformation from a crystalline state to an amorphous state. In addition, they also exhibited excitation wavelength-dependent luminescence in crystalline states and DMF systems. As the excitation wavelength increased, their luminescence color in DMF solution changed significantly from blue to yellow. Theoretical calculations show that the complexes have multiple emission centers due to the locally excited nature and intramolecular charge transfer. Due to their excellent excitation wavelength-dependent luminescence properties, PMMA films based on complexes 1 and 2 were prepared and could be applied in anti-counterfeiting and UV protection.

MUSEQuBES: Unveiling Cosmic Web Filaments at z ≈ 3.6 through Dual Absorption and Emission Line Analysis

Abstract According to modern cosmological models, galaxies are embedded within cosmic filaments, which supply a continuous flow of pristine gas, fueling star formation and driving their evolution. However, due to their low density, the direct detection of diffuse gas in cosmic filaments remains elusive. Here, we report the discovery of an extremely metal-poor ([X/H] ≈ −3.7), low-density ( log 10 n H / cm − 3 ≈ −4, corresponding to an overdensity of ≈5) partial Lyman limit system (pLLS) at z ≈ 3.577 along the quasar sightline Q1317–0507, probing cosmic filaments. Additionally, two other low-metallicity ([X/H] ≲ −2) absorption systems are detected at similar redshifts, one of which is also a pLLS. Very Large Telescope (VLT) MUSE observations reveal a significant overdensity of Lyα emitters (LAEs) associated with these absorbers. The spatial distribution of the LAEs strongly suggests the presence of an underlying filamentary structure. This is further supported by the detection of a large Lyα-emitting nebula with a surface brightness of ≥ 1 0 − 19 erg cm − 2 s − 1 arcsec − 2 , with a maximum projected linear size of ≈260 pkpc extending along the LAEs. This is the first detection of giant Lyα emission tracing cosmic filaments, linked to normal galaxies and likely powered by in situ recombination.

Mn-Mn Dimers Induced Multimode Emitters in Mn2+-Activated AZn4(PO4)3 (A = K, Rb, and Cs) with Unique [Zn4PO12] Chains and [ZnOn] Groups.

Mn2+-doped luminescent materials play a significant role in a variety of fields, including modern lighting, displays, and imaging. Mn2+ exhibits a broad and adjustable emission, hinging on the local environment of the crystal field and the interaction of the 3d5 electrons. However, it is still a challenge to realize the precise control of the emission of Mn2+ ions due to site-prior occupation in a specific lattice. Here, the formation of Mn-Mn dimers is proposed to be an effective strategy to design a novel red emission. Multimode emitters in Mn2+-activated AZn4(PO4)3 (A = K, Rb, and Cs) with unique [Zn4PO12] chains and [ZnOn] groups are observed to achieve regular green and unusual red emissions. KZn4(PO4)3:Mn2+ shows broad dual emissions at 542 and 608 nm, attributed to [MnO4] and [Mn2O7] dimers, respectively. While K is replaced with Rb and Cs, the Zn ions form [ZnO4] tetrahedra and [ZnO5] octahedra. RbZn4(PO4)3:Mn2+ exhibits a broad red emission at 618 nm, ascribing to [Mn2O7] and [Mn2O8] dimers. CsZn4(PO4)3:Mn2+ also displays a broad orange-red emission at 608-620 nm with increasing doping levels, deriving from energy transfer from [MnO5] to [Mn2O7] and [Mn2O8] dimers. This work provides a framework for creating novel red emissions from Mn2+-doped luminescent materials.

A Dynamic Metal‐Organic Radical Emission System

AbstractDeveloping new organic radical emission systems and regulating their luminescence properties presents a significant challenge. Herein, we build dynamic and multi‐emission band radical luminescence systems by co‐assembling inorganic metal salts with carbonyl compounds in ionic liquids. After the assembling, dual‐band, and excitation wavelength‐dependent emission was observed upon ultraviolet light irradiation, one emission band originates from carbonyl radical after light irradiation, the other band from the ligand‐metal charge transfer (LMCT) state, which benefits from the charge transfer from the radicals to the metal salts. The dual emission centers also introduce excitation wavelength‐dependent properties for the molecules. In addition, three‐band emission covering the visible and near‐infrared regions can be shown when two or three kinds of metal ions are simultaneously doped into the radical system driven by the ligand‐metal‐metal charge transfer (LMMCT). Interestingly, visible light can quickly quench the radical emission of systems, thus realizing a dynamic luminescence. The LMMCT effect and strong supramolecular interactions significantly improve the photoluminescence quantum yield by up to 67.2 %. Moreover, such materials can be successfully used for detecting radioactive metal ions and information encryption. This study develops a platform for manufacturing various metal‐organic radical emission systems with diverse properties.

Dual-Emissive Iridium(III) Complex with Aggregation-Induced Emission: Mechanistic Insights into Electron Transfer for Enhanced Hypoxia Detection in 3D Tumor Models.

Accurate oxygen detection and measurement of its concentration is vital in biological and industrial applications, necessitating highly sensitive and reliable sensors. Optical sensors, valued for their real-time monitoring, nondestructive analysis, and exceptional sensitivity, are particularly suited for precise oxygen measurements. Here, we report a dual-emissive iridium(III) complex, IrNPh2, featuring "aggregation-induced emission" (AIE) properties and used for sensitive oxygen sensing. IrNPh2 exhibits dual emissions at 450 and 515 nm, with 515 nm triplet-state emission demonstrating remarkable oxygen sensitivity due to its long-lived excited state (12.12 μs) and high quantum yield (68%). Stern-Volmer analysis reveals a notable quenching constant (Ksv = 12.44%-1) and an ultralow detection limit of 0.0397%, emphasizing its superior performance. The oxygen quenching mechanism is driven by electron transfer (ET), supported by computational studies showing the lowest-unoccupied molecular orbital (LUMO) alignment of IrNPh2 with the πg* orbitals of triplet oxygen, leading to superoxide radical (O2•-) formation. Electron paramagnetic resonance (EPR) studies further confirm this pathway. Biological evaluations using a three-dimensional (3D) U87-MG glioma spheroid model highlight the ability of IrNPh2 to detect hypoxic regions, with significant fluorescence enhancement under hypoxia and minimal cytotoxicity (>80% viability at 100 μM). With high sensitivity, low detection limits, and biocompatibility, IrNPh2 emerges as a promising candidate for oxygen sensing in environmental and biomedical applications, especially tumor hypoxia detection.

Deciphering the Photophysical Properties of Nonplanar Heterocyclic Compounds in Different Polarity Environments.

Nonplanar (butterfly-shaped) phenothiazine (PTZ) and its derivative's (M-PTZ) photophysical and spectral properties have been tuned by varying the solvents and their polarity and investigated employing spectroscopic techniques such as UV-Vis, steady-state and time-resolved fluorescence, and TDDFT calculations. The UV-Vis absorption studies and TDDFT calculations reveal two distinct bands for both compounds: a strong π-π* transition at shorter wavelengths and a weaker n-π* transition, which displays a little bathochromic shift in polar solvents. The detailed emission studies reveal that such dual emission is a result of the photoinduced excited-state conjugation enhancement (ESCE) process. The band at a shorter wavelength corresponds to the locally excited (LE) state, while the longer wavelength band arises from the planarized excited state resulting from ESCE. With the increase in solvent polarity, the LE band is less affected, whereas strong positive solvatochromism is observed for the ESCE band. As the solvent polarity increases, the ESCE band demonstrates significant positive solvatochromism, while emission intensity decreases with higher solvent polarity, suggesting stabilization of the excited state. The biexponential decay of fluorescence lifetimes further corroborates the dual emission behavior of PTZ and M-PTZ. PTZ exhibits a higher photoluminescence quantum yield (PLQY) than that observed for M-PTZ, and the solvent viscosity influences the PLQY, indicating that nonradiative decay is activated during the planarization of the excited state, also known as excited-state conjugation enhancement. Furthermore, the (time-dependent) density functional theory (TD) DFT calculations performed to understand the geometrical parameters and the electronic transitions of these model molecules further corroborate experimental findings. These findings underscore the significant influence of solvent polarity and molecular structure on the dual emission and excited-state dynamics of PTZ and M-PTZ, which eventually hold substantial implications for advanced photophysical applications.

Red-Shifted and Enhanced Photoluminescence Emissions from Hydrogen-Bonded Multicomponent Nontraditional Luminogens.

Nontraditional luminogens (NTLs) without large π-conjugated aromatic structures have attracted a great deal of attention in recent years. Developing NTLs with red-shifted and enhanced emissions remains a great challenge. In this work, we developed a NTL composed of three components, i.e., polymaleic acid (PMA), arginine (Arg), and polyacrylamide (PAM), and investigated its photoluminescent behavior and mechanism. Compared with the single components and binary components, the PMA/Arg/PAM solid exhibited two red-shifted emission peaks at 510 and 562 nm and higher quantum yields. Structural characterizations demonstrated that hydrogen bonds formed between the nonconventional chromophores in PMA and Arg lead to more extended through-space conjugation and rigidified conformations, which is the fundamental reason for the red-shifted emission and higher quantum yield of the PMA/Arg/PAM solid. In addition, theoretical calculations proved that excited-state proton transfer occurs between the carboxyl groups of PMA and amino groups of Arg via photoexcitation, resulting in dual emissions in the PMA/Arg/PAM solid. This work provides a deeper understanding of the photoluminescence mechanism of NTLs based on multiple hydrogen bonds and is helpful in guiding the design of NTLs with red-shifted and enhanced emissions.

Dual Ratiometric Fluorescence Sensors Based on Chiral Carbon Dots for the Sensitive and Specific Detection of Arginine.

Arginine (Arg) is involved in tissue metabolism and regulates the immune function; thereby, achieving the detection of Arg is crucial for early diagnosis and treatment of diseases. Herein, dual ratiometric fluorescence sensors were prepared with the blue emission of levorotatory/dextrorotatory carbon dots (CDs) and the red emission of porphyrin (L/D-CDs-PP) for the sensitive and portable detection of Arg. Interestingly, L-CDs-PP and D-CDs-PP displayed not only the dual emission peaks at 493 and 650 nm but also different response modes to Arg; thus, they could serve as dual ratiometric fluorescence sensors to achieve the accurate and reliable detection of Arg, with the detection limit of 23.87 μM for L-CDs-PP and 2.39 μM for D-CDs-PP. Importantly, the solid-state sensors successfully achieved dual-mode visual and portable detection of Arg with the support of a smartphone platform. In addition, L-CDs-PP and D-CDs-PP exhibited excellent biocompatibility and cell imaging capabilities, and they could achieve the detection of Arg in cells and biological samples of urine and rat plasma. Therefore, the dual ratiometric fluorescence sensors exhibited broad application prospects in the fields of analytical sensing, biological imaging, and medical diagnosis.

Rationalization of the structural, electronic and photophysical properties of silver(I) halide n-picolylamine hybrid coordination polymers.

Hybrid coordination polimers based on AgX (with X = Cl, Br) and 2-, 3-, 4-picolylamine ligands, obtained by means of solvent-free methods, show peculiar luminescence properties that are strongly influenced by their structural motif, which in turn is defined by the adopted isomer of the ligand. A comprehensive study, combining photophysical methods and DFT calculations, allowed to rationalize the emissive behaviour of such hybrid coordination polymers in relation to their crystal structures and electronic properties. By means of luminescence measurements at variable temperatures, the nature of the emissive excited states and their deactivation dynamics was interpreted, revealing XMLCT transitions in the [(AgX)(2-pica)]n compounds, a TADF behaviour in the case of 3-pica derivatives, and a dual emission at room temperature for the [(AgX)(4-pica)]n family. The presence of low energy CC states, permitted by argentophilic interactions, is also considered in [(AgX)(2-pica)]n, whose structures are characterized by single/double inorganic chains, and in [(AgX)(4-pica)]n, where discrete dimeric Ag2X2 units are present. These findings open new avenues for the design and application of luminescent AgX-based hybrid materials.

Engineering Acid-Promoted Two-Photon Ratiometric Nanoprobes for Evaluating HClO in Lysosomes and Inflammatory Bowel Disease.

HClO is considered a potential contributing factor and biomarker of inflammatory bowel disease (IBD). Accurate monitoring of lysosomal HClO is important for further developing specific diagnostic and therapeutic schedules for IBD. However, only rare types of fluorescent probes have been reported for detecting HClO in IBD so far. Herein, an acid-promoted two-photon semiconducting polymer dot (Lyso-RS Pdot) with dual emission in green and red channels and dual-sensing sites is successfully fabricated with two newly designed polymers NADE-PSMA and PFNA-10TBT as precursors. The red conjugated polymer PFNA-10TBT with pH-inert and HClO-sensitive units is employed to evaluate the HClO concentration in turn-off fluorescence. Meanwhile, the amphiphilic green fluorescent polymer NADE-PSMA sensitive to pH and HClO is employed to evaluate the pH value or HClO concentration in turn-on fluorescence. The resultant Lyso-RS Pdots not only display satisfactory performances for detecting HClO and pH but also achieve accurate two-photon imaging of HClO in lysosomes and the colon of IBD mice based on the distinguished properties such as ratiometric signal output, acid-promoted signal amplification, ultrafast response, and two-photon excitation. The results demonstrate that the HClO level in IBD mice is elevated, and the fast early diagnosis of IBD can be achieved through fluorescence imaging by the proposed Lyso-RS Pdots. This work may provide some solid perspectives for fluorescent diagnosis of H+ and HClO-related diseases.

A ratiometric fluorescent probe with dual near infrared emission for in vivo ratio imaging of cysteine.

Accurately detecting cysteine (Cys) in vivo is crucial for diagnosing Cys-related diseases. A novel ratiometric fluorescent probe featuring dual near-infrared emission is developed in this study for the in vivo ratio imaging of Cys. The probe comprises a hemicyanine organic small-molecule dye (HCy-CYS) with specific Cys recognition capabilities covalently coupled with carbon dots (CDs) synthesized using glutathione (GSH) as the carbon source (GCDs), forming a unique composite nanofluorescent probe (GCDs@CYS). The probe undergoes a specific reaction with acrylate upon the addition of Cys, converting HCy-CYS to HCy-OH. Consequently, the GCD fluorescence intensity at 685nm gradually decreases, whereas that of HCy-OH at 720nm progressively increases, yielding a ratiometric fluorescence signal. Notably, both emission wavelengths of the probe exceed 650nm, thereby effectively mitigating the interference from background signals during cellular and in vivo imaging. Furthermore, the probe demonstrates high specificity for Cys, enabling its differentiation from homocysteine and GSH. The Cys concentration and fluorescence ratiometric intensity exhibit a strong linear correlation at 10-150μM with a detection limit of 0.95μM. These results indicate that the ratiometric fluorescent probe can serve as a valuable tool for monitoring Cys-related physiological or pathological processes.

Ratiometric luminescence detection of Bi(III) ions in water using a europium coordination polymer

A ratiometric luminescent probe for detecting Bi(III) in water using a functionalized Eu(III) coordination polymer was developed. The raw materials guanosine monophosphate (GMP), Eu(III), and 2,6-pyridine dicarboxylic acid (DPA) were used to synthesize the GMP-Eu-DPA polymer, which contained Eu(III) coordinated with GMP and DPA and gave red emission at a wavelength of 614 nm when excited at a wavelength of 282 nm. Adding Bi(III) decreased the intensity of luminescence of the GMP-Eu-DPA coordination polymer at 614 nm and caused a GMP–Bi complex that strongly luminesced at 373 nm under excitation at 282 nm to form. Under optimal conditions, the luminescence intensity ratio I 373/I 614 had a good linear relationship with the Bi(III) concentration in the range 1.0–230 μM, and the detection limit was low (0.6 μM). The dual emission reverse rate of change luminescent probe can eliminate environmental influences, making the proposed detection method highly selective. This method has been successfully used to detect Bi(III) in water samples.

High-Efficiency, Long-Lived, Multicolor Tunable Pure Organic Materials for Dual Fluorescent-Phosphorescent Emission at Room Temperature

High-Efficiency, Long-Lived, Multicolor Tunable Pure Organic Materials for Dual Fluorescent-Phosphorescent Emission at Room Temperature

Smartphone-assisted hydrogel sensing platform based on double emission carbon dots for portable on-site tetracycline detection.

Innovative double-emission carbon dots (DE-CDs) were synthesized via a one-step hydrothermal method using fennel and m-phenylenediamine (m-PD) as precursors. These DE-CDs exhibited dual emission wavelengths at 432 and 515nm under different excitations, making them highly versatile for fluorescence-based applications. The fluorescence of the DE-CDs was efficiently quenched by tetracycline (TC) through the inner filter effect (IFE), allowing for the construction of a sensitive dual-response fluorescent sensor. This sensor demonstrated a strong exponential correlation with TC concentrations in the range 0.99-118μM, achieving a low detection limit of 53.4nM, which is appropriate for environmental monitoring. To further enhance its practicality, a smartphone-integrated fluorescent hydrogel film sensing platform was developed. This portable and user-friendly system enabled rapid, on-site TC detection in water samples, combining high sensitivity with convenience for real-world applications. The integration of the DE-CD-based sensor into a hydrogel platform addressed the challenge of translating laboratory precision into field-ready tools. This study revealed the potential of DE-CDs as a robust and efficient solution for bridging the gap between laboratory-based analysis and portable, on-site environmental monitoring.

FRET-based Ratiometric Fluorescent Probes for Enzyme Detection: Current Insight

Over the decade many types of fluorescent sensors have been developed for detecting diverse types of analyte. The sensors developed using the phenomenon of fluorescence provide high sensitivity, selectivity, for the analyte that they are being developed for. This has led to a huge increase in development of sensors for biomarkers that are particularly of importance for early detection or diagnosis of life threatening diseases. In addition to the advantages of Fluorimetry there is continuous research going on to create sensors that are easy to construct, reproducible, cost and time efficient, along with maintaining sensitivity enough for accurate determination of the analyte of interest. As the research advanced, the dyes used as simple sensors were replaced with other molecules as a substrate for biomarker or other analyte sensing. Additionally, early scientists used single emission sensors for detection of analyte. Further, the single emission sensors were evolved to dual emission and then further advancement led to innovation of ratiometric sensors. These ratiometric sensors provide good internal standard referencing system which gives them good sensitivity as compared to other luminescent sensors. Through this review we aim to provide useful information on the subject of FRET, ratiometric fluorescence analysis, the types of materials used for developing the sensors and examples of biosensors used for enzyme detection.

Room-temperature phosphorescence and dual-emission behavior of simple biphenyl derivatives unlocked by intermolecular interactions with cyclic silver pyrazolate

Encapsulation of biphenyl derivatives between cyclic trinuclear silver(i) pyrazolate units unlocks room-temperature phosphorescence and dual emission in the solid state.

Enhanced Chromaticity and Dual Emission in Double-Site Mn4+-Activated KLiTiF6 Red Phosphor for Wide Color Gamut Displays

Mn4+-activated fluoride phosphors are pivotal for white LEDs due to their narrow-band red emission, which is essential for achieving wide color gamut displays. A red shift in the emission spectrum,...

Implementation of simultaneous ultraviolet/visible and x-ray absorption spectroscopy with microfluidics.

X-ray spectroscopies are uniquely poised to describe the geometric and electronic structure of metalloenzyme active sites under a wide variety of sample conditions. UV/Vis (ultraviolet/visible) spectroscopy is a similarly well-established technique that can identify and quantify catalytic intermediates. The work described here reports the first simultaneous collection of full in situ UV/Vis and high-energy resolution fluorescence detected x-ray absorption spectra. Implementation of a fiber optic UV/Vis spectrometer and parabolic mirror setup inside the dual array valence emission spectrometer allowing for simultaneous measurement of microfluidic flow and mixing samples at the Photon-In Photon-Out X-ray Spectroscopy beamline is described, and initial results on ferricyanide and a dilute iron protein are presented. In conjunction with advanced microfluidic mixing techniques, this will allow for the measurement and quantification of highly reactive catalytic intermediates at reaction-relevant temperatures on the millisecond timescale while avoiding potential complications induced by freeze quenching samples.

Cyclometalated Au(III) complexes with alkynylphosphine oxide ligands: synthesis and photophysical properties.

A series of cyclometalated Au(III) complexes [Au(C^N^C)(C2-L-P(O)Ph2)] with C^N^C = 2,6-diphenylpyridine and alkynylphosphine oxide ligands (L = no linker, Au1; phenyl, Au2; biphenyl, Au3; naphthyl, Au4; anthracenyl, Au5) were synthesized and fully characterized by spectroscopic methods and single crystal XRD analysis. The complexes obtained exhibit triplet (Au1-Au3) and dual (Au4, Au5) emissions in solution, in the solid phase and in the PMMA film, whose characteristics depend on the linker's nature of the alkynylphosphine oxide ligand. The description of electronic transitions responsible for energy absorption and emission in Au(III) complexes was made on the basis of a detailed analysis of the results of DFT calculations and has shown to involve ILCT, LLCT and MLCT transitions of singlet and triplet nature. It was demonstrated that packing in the crystal affects the solid-state emission of Au(III) complexes, which differs from that in solution. Based on DFT calculations for the supramolecular dimer for Au1, it was shown that this phenomenon is the result of packing of the complex molecules in the crystal.

Red-blue dual emission and enhanced luminescence of glass-ceramics containing Y2Sn2O7 for plant lighting

Red-blue dual emission and enhanced luminescence of glass-ceramics containing Y2Sn2O7 for plant lighting