Search Results (319)

Manganese(II) halide complexes with the general formula [MnX₂{(PhN=PPh₂)CH₂}], where X is bromine or iodine and (PhN=PPh₂)CH₂ is the bis-phosphanimine ligand 1,1′-methylenebis-(N,1,1-triphenylphosphanimine), were prepared and isolated. The structure of the two compounds was determined by single-crystal X-ray diffraction, revealing an approximately tetrahedral geometry at the metal centre. Unlike structurally comparable compounds containing phosphine oxides or related [O=P]-donors in the coordination sphere, which commonly show green emissions, solid samples of [MnBr₂{(PhN=PPh₂)CH₂}] and [MnI₂{(PhN=PPh₂)CH₂}] exhibited orange emissions upon irradiation with UV light. The emission spectra resulted excitation-independent. Superimposable steady-state luminescence spectra were collected for both compounds as powders and crystals suitable for X-ray diffraction. The excitation spectra and the ligand→metal antenna effect were affected by the coordinated halide, and only [MnBr₂{(PhN=PPh₂)CH₂}] showed bright luminescence under near-UV irradiation. Either ligand- or metal-centred transitions can account for the observed luminescence, and the luminescence decay curves were consistent with a multiplicity change from the excited to the ground state, with excited-state lifetimes in the range of hundreds of microseconds. Attempts to rationalize the unexpected luminescence were carried out based on DFT calculations. Full article

Organic light-emitting diodes (OLEDs) have the advantages of high efficiency and high color purity, which gives them great potential and application prospects in the field of display technology, and thus they have been of wide interest for scholars and industry. Due to their nature, when using the first generation of fluorescent materials, only 25% of the excitons are used, while the rest are wasted, meaning the device efficiency does not exceed 25%. The second generation of phosphorescent materials solves this problem by utilizing 25% singlet excitons while utilizing 75% triplet excitons, achieving 100% internal quantum efficiency. Therefore, a third generation of materials, namely Thermally Activated Delayed Fluorescence (TADF) materials, has been developed, and these are able to use the small singlet–triplet energy gap to allow excitons on the triplet state to upconvert back to the single state, which improves the utilization of triplet excitons. These TADF materials can also reach 100% maximum internal quantum efficiency, but they have many problems, such as low color purity and serious efficiency roll-off. Therefore, researchers have designed hyperfluorescent materials, which possess high efficiency, high color purity, and a long lifetime, showing tremendous potential and application prospects in the field of display technology. This report takes hyperfluorescent OLEDs as the entry point and the molecular design and luminescence mechanism of hyperfluorescent materials are reviewed, considering blue, green, red, and white light. Full article

The polar oxide Lithium Niobate Tantalate is probed using time-resolved luminescence spectroscopy with the goal of revealing an initial structural insight into the solid solution by analyzing the spectral properties and dynamics of radiatively decaying self-localization phenomena. A blue-green luminescence band can be induced by ultraviolet nanosecond laser pulses with a temperature-dependent intensity and spectral width, pointing to the radiative decay of optically generated self-trapped excitons as its origin, i.e., electron–hole pairs with strong coupling to either the NbO₆- or TaO₆-octahedra. The luminescence decay takes place in the microsecond time range and deviates significantly from a single exponential behavior, so the determined lifetime constants of up to ≈70 μs and stretching factors (1/3–1/5) are validated in more detail using alternative evaluation methods. We discuss our findings, considering the interplay of radiative and non-radiative decay channels, the transition from self-trapped to free excitons, and the presence of a structural disorder of the oxygen octahedra in the solid solutions. Overall, our results suggest self-trapped excitons as local probes for an initial structural elucidation and provide essential information about further experimental and theoretical studies on the atomic structure of Lithium Niobate Tantalate, but also for improving the crystal quality in the framework of applications in photonics and quantum optics. Full article

The photochemistry of transition metal complexes has been crucial for the development of many fundamental topics, as well as to pave the way for several important applications. However, in most cases, photoactive transition metal complexes involved precious metals, with luminescent ruthenium polypyridine complexes playing the dominant role. Developing photoactive species based on earth-abundant metals is highly important for fundamental and applicative reasons. Iron is one of the most abundant metals on Earth’s crust, so luminescent iron complexes are highly desired. The recent search for iron complexes with long-lived and luminescent excited states is here presented, including Fe(II) species with metal-to-ligand charge transfer (MLCT) excited states and Fe(III) species with luminescent ligand-to-metal charge transfer (LMCT) states. The excited-state equilibration approach to prolong the luminescence lifetimes of Fe(III) compounds in multichromophoric species is also discussed. This latter approach can increase the possibility of luminescent iron complexes being involved in bimolecular processes as well as in photoinduced electron and energy transfer at interfaces, which is relevant for many applications. Full article

Calcium phosphates are one of the main materials used in biomedicine for bone regeneration purposes. To improve the properties of biocompatible β-Ca₃(PO₄)₂, doping by bioactive, antibacterial is actively used, as well as luminescent ions. Co-doped phosphates Ca_8−xSr_xZnEu(PO₄)₇ with a β-Ca₃(PO₄)₂ (β-TCP)-type structure were synthesized through solid-state synthesis. The β-TCP-type structure was confirmed using X-ray powder diffraction and FTIR spectroscopy. Photoluminescence data, including excitation and emission spectra, decay curves, lifetime values and quantum yields, were collected for all samples. Ca_8−xSr_xZnEu(PO₄)₇ phosphates exhibit strong red-emission due to 4f-4f transitions of Eu³⁺ ions in disordered oxygen surrounding, with quantum yields reaching 54%. The phosphates demonstrated biocompatibility through MTT assay, with successful differentiation of aMSCs into the osteogenic lineage. Antibacterial activity was tested against four bacteria (E. coli, S. aureus, P. aeruginosa, and E. faecalis) and a fungus (C. albicans). It was found that the samples demonstrated antibacterial properties. The growth of E. coli and E. faecalis is significant inhibited by Ca_8−xSr_xZnEu(PO₄)₇ samples with 0 ≤ x ≤ 6.0. Analysis of mixed salt solubility using Eu³⁺ ions as a fluorescent probe showed that increasing Sr²⁺ concentration in Ca_8−xSr_xZnEu(PO₄)₇ delays both β-TCP phase resorption and HAP phase precipitation. These results demonstrate the potential of Ca_8−xSr_xZnEu(PO₄)₇ phosphates for bioimaging and bone healing control. Full article

The osmium(II) polypyridyl complex [Os(tpy)(pydppn)]²⁺ (tpy = 2,2′:6′,2″-terpyridine; pydppn = 3-(pyrid-2′-yl)-4,5,9,16-tetraaza-dibenzo[a,c]naphthacene) was synthesized and characterized to evaluate the effect of an extended planar π-system on photophysical properties and DNA interactions. This complex represents the π-expanded analog of the previously studied [Os(tpy)(pydppz)]²⁺ system. Electrochemical studies revealed a reversible Os(II)/Os(III) oxidation at +0.99 V vs. SCE and five ligand-centered reductions, generally less negative than those of the smaller pydppz analog, consistent with enhanced electron-accepting ability. In acetonitrile, the complex exhibits UV absorption bands at 328 and 473 nm and near-infrared emission at 840 nm, assigned to a long-lived ³MLCT state (τ = 110 ns, Φ = 0.02). Upon titration with calf-thymus DNA, [Os(tpy)(pydppn)]²⁺ shows a pronounced light-switch effect, hypochromism, red-shifted MLCT bands, induced circular dichroism, and an increase in DNA melting temperature (ΔT_m = 8.9 ± 0.5 °C), consistent with intercalative binding. Viscometric titrations further support intercalation, with a binding constant K_B ≈ 1.2 × 10⁶ M⁻¹. Transient absorption spectroscopy indicates that DNA binding prolongs the excited-state lifetime and modifies vibrational relaxation pathways. These results highlight how π-system extension in Os(II) complexes modulates photophysical behavior and DNA affinity, offering insights for the rational design of NIR-emitting, DNA-targeted luminescent probes and potential phototherapeutic agents. Full article

The chemical identity of oxygen species plays a decisive role in determining the optical stability of halide perovskite QD films. Here, real-time in situ spectroscopic monitoring, together with steady-state and time-resolved photoluminescence measurements, is utilized to differentiate the effects of molecular oxygen and plasma-activated oxygen species on CsPbBr₃ QD films. The films maintain nearly unchanged emission intensity, spectral profile, and carrier lifetimes when stored in vacuum or exposed to molecular O₂ even under UV illumination, demonstrating that neutral O₂ exhibits minimal reactivity toward the [PbBr₆]⁴⁻ framework. In contrast, oxygen plasma generates highly reactive atomic and ionic oxygen species that induce rapid and spatially heterogeneous photoluminescence quenching. This degradation is attributed to Br⁻ extraction, Br-vacancy formation, and subsequent Pb–O bond generation, which collectively introduce deep trap states and enhance nonradiative recombination. These findings clearly indicate that reactive oxygen species rather than molecular O₂ are the dominant driver of oxygen-induced luminescence degradation, providing mechanistic insight and offering processing guidelines for the reliable integration of perovskite nanomaterials in optoelectronic devices. Full article

Zero-dimensional (0D) tin halide perovskites have emerged as promising luminescent materials owing to their broadband emission, high quantum yield, and negligible self-absorption. Yet, their luminescence efficiency and stability remain insufficient for practical optoelectronic applications. Here, Sb³⁺ dopants are introduced into Cs₄SnBr₆ through a water-assisted wet ball milling strategy, resulting in bright and thermally robust emission. The doped materials exhibit pronounced self-trapped exciton (STE) luminescence centered at 525 nm with a broad full width at half maximum of 110 nm, a large Stokes shift of approximately ~1.3 eV, and a photoluminescence lifetime of ~0.8 µs. Remarkably, Sb³⁺ incorporation boosts the photoluminescence quantum yield (PLQY) up to 64% at room temperature while simultaneously improving thermal stability. Correlated spectroscopic analyses reveal that the Sb³⁺-induced lattice distortion of the [SnBr₆]⁴⁻ octahedra strengthens electron–phonon interactions and elevates the STE binding energy, thereby stabilizing the excited states and suppressing nonradiative losses. Full article

In this work, Sm³⁺-activated lead phosphate glass has been studied using spectroscopic methods. Based on absorption spectrum measurements, the oscillator strengths for Sm³⁺ ions were determined and compared to those calculated from the Judd–Ofelt theory. This procedure was applied to evaluate some radiative parameters (radiative transition rates, emission branching ratios, radiative lifetime) of Sm³⁺ ions in lead phosphate glass. Further luminescent studies indicate that lead phosphate glass doped with Sm³⁺ emits intense reddish-orange light due to ⁴G_5/2 ⟶ ⁶H_7/2 transition, for which several important spectroscopic parameters like emission linewidth and lifetime, quantum efficiency, peak stimulated emission cross-section, and figure of merit for laser gain were determined. The factors for Sm³⁺ ions in lead phosphate glass are as follows: η = 53%, FWHM = 10.5 nm, τ_exp = 1.925 ms, σ_em = 7.6 × 10⁻²² cm², σ_em × τ_exp = 14.6 × 10⁻²⁵ cm²s. The experimental and theoretical results suggest that samarium-doped lead phosphate glass can be successfully used as a reddish-orange-emitting component in photonic devices. Full article

In this work, we have synthesized a more acid-stable variant of the classic chromophore difluoro-Bodipy by substituting the difluoro ligands at boron with cyano groups. This dicyano-Bodipy variant allowed the in situ incorporation during the MOF formation under acidic conditions and was investigated for the first time as dye@MOF composites using both post-synthetic and in situ incorporation into the zirconium-based metal–organic frameworks (MOFs) UiO-66, MOF-808, DUT-67, and MIP-206. The successful incorporation of dicyano-Bodipy was confirmed by PXRD, N₂ sorption, digestion UV–Vis, and fluorescence spectroscopy. Depending on the incorporation method used, significant lower BET surface areas could be determined. The luminescence properties of the resulting dicyano-Bodipy@MOF composites from the in situ incorporation had up to almost eight-fold extended photoluminescent lifetimes of 9.0 ns, compared to the neat dye in its solid state with 1.2 ns, which suggests the formation of a solid solution in which the incorporated Bodipy is protected from external influences within a well-defined MOF pore. The quantum yield could be enhanced to as high as 77% through post-synthetic incorporation into the MOF DUT-67, compared to the neat dye in its solid state, with 9%. Full article

Room-temperature phosphorescence (RTP) materials with photo-responsive properties have attracted increasing attention for applications in smart luminescent switches, optical logic control, and multidimensional information storage. Compared to other external stimuli, light offers the advantages of non-contact control, high spatiotemporal resolution, and excellent programmability, making it an ideal strategy for reversible and dynamic modulation of RTP. This review summarizes recent advances in light-triggered RTP systems coupled with photochromism. From a structural design perspective, we discuss strategies to integrate photochromic and RTP units within a single material system, covering photoisomerizable molecules, metal–organic complexes, organic–inorganic hybrids, and purely organic radicals. These materials demonstrate unique advantages in fields such as information encryption, bioimaging, and light-controlled upconversion. Finally, future design directions and challenges are proposed, aiming toward high-security, long-lifetime, and multi-channel collaborative luminescent systems. Full article

Alpha-synuclein (αsyn) misfolding and aggregation underlie several neurodegenerative disorders, including Parkinson’s disease. Early oligomeric intermediates are particularly toxic yet remain challenging to detect and characterize within cellular systems. Here, we employed the luminescent conjugated oligothiophene h-FTAA to investigate early aggregation events of human wildtype (huWT) and A53T-mutated αsyn (huA53T) both in vitro and in HEK293 cells stably expressing native human-αsyn. Comparative fibrillation assays revealed that h-FTAA detected αsyn aggregation with higher sensitivity and earlier onset than Thioflavin T, with the A53T variant displaying accelerated fibrillation. HEK293 cells stably expressing huWT- or huA53T-αsyn were exposed to respective pre-formed fibrils (PFFs), assessed via immunocytochemistry, h-FTAA staining, spectral emission profiling, and fluorescence lifetime imaging microscopy (FLIM). Notably, huA53T PFFs promoted earlier aggregation patterns and yielded narrower fluorescence lifetime distributions compared with huWT PFFs. Spectral imaging showed h-FTAA emission maxima (~550–580 nm) red-shifted and broadened in cells along with variable lifetimes (0.68–0.87 ns), indicating heterogeneous aggregate conformations influenced by cellular milieu. These findings demonstrate that h-FTAA is useful for distinguishing early αsyn conformers in living systems and, together with stable αsyn-expressing HEK293 cells, offers a platform for probing early αsyn morphotypes. Taken together, this opens for further discovery of biomarkers and drugs that can interfere with αsyn aggregation. Full article

A novel long-lasting luminescent composite material based on the (Ca,Sr)-Al-O system was synthesized using a solution combustion method. (Ca,Sr)₃Al₂O₆ is the primary phase, with SrAl₂O₄ as a controllable secondary phase. Compared to conventional single-phase SrAl₂O₄ phosphors, the introduction of a calcium-rich hexaaluminate matrix creates additional defects and a specific trap distribution at the composite interface, significantly improving carrier storage and release efficiency. Eu²⁺ + Nd³⁺ synergistic doping enables precise control of the trap depth and number. Under 365 nm excitation, Eu²⁺ emission is located at ~515 nm, with Nd³⁺ acting as an effective trap center. Under optimal firing conditions at 700 °C (Eu²⁺ = 0.02, Nd³⁺ = 0.003), the afterglow lifetime exceeds 30 s. Furthermore, The (Ca,Sr)₃Al₂O₆ host stabilizes the lattice and optimizes defect states, while synergizing with the SrAl₂O₄ secondary phase to improve the afterglow performance. This composite phosphor exhibits excellent dual-mode anti-counterfeiting properties: long-lasting green emission under 365 nm excitation and transient blue-violet emission under 254 nm excitation. Based on this, a screen-printing ink was prepared using the phosphor and ethanol + PVB, enabling high-resolution QR code printing. Pattern recognition and code verification can be performed both in the UV on and off states, demonstrating its great potential in high-security anti-counterfeiting applications. Compared to traditional single-phase SrAl₂O₄ systems, this study for the first time constructed a composite trap engineering of the (Ca,Sr)₃Al₂O₆ primary phase and the SrAl₂O₄ secondary phase, achieving the integration of dual-mode anti-counterfeiting functionality with a high-resolution QR code fluorescent ink. Full article

Precise remote temperature sensing at the micro- and nanoscale is a growing necessity in modern science and technology. We report a series of luminescent tris-acetylacetonate lanthanide complexes, Ln(acac)₃(H₂O)₂ (Ln = Eu (1Eu), Tb (1Tb), Yb (1Yb)); acac⁻ = acetylacetonate), operating as self-referenced thermometers in the 290–350 K range, both in the solid state and when embedded in hybrid nanoparticles. Among the investigated systems, the Eu³⁺ complex exhibits excellent lifetime-based thermometric performance, achieving a maximum relative sensitivity (S_rmax) of 2.9%·K⁻¹ at 340 K with a temperature uncertainty (δT) as low as 0.02 K and an average temperature uncertainty ($\overline{\delta T}$) of 0.5 K, placing it among the most effective ratiometric lanthanide-based luminescent thermometers reported to date. The Yb³⁺ analog enables intensity-based thermometry in the near-infrared domain with a good sensitivity S_rmax = 0.5%·K⁻¹ at 293 K, δT = 0.5 K at 303 K, and $\overline{\delta T}$ = 1.6 K. These molecular thermometers were further incorporated into the shell of Prussian Blue@SiO₂ core–shell nanoparticles. Among the resulting hybrids, PB@SiO₂-acac/(1Tb/1Eu) (with a Tb/Eu ratio of 2/8) stood out by enabling ratiometric temperature sensing based on the Eu³⁺⁵D₀ → ⁷F₂ lifetime, with satisfactory parameters (S_rmax = 0.9%·K⁻¹, δT = 0.21 K at 303 K, and $\overline{\delta T}$ = 1.1 K). These results highlight the potential of simple coordination complexes and their nanohybrids for advanced luminescent thermometry applications. Full article

In this study, a novel carbon quantum dots-functionalized UiO-66 composite was successfully prepared via the post-synthetic modification method and further developed into a ratiometric fluorescent probe for detecting uric acid. The composite demonstrates excellent structural and luminescent stability under challenging environmental conditions. As a ratiometric fluorescent probe, its recognition principle relies on the ratio of response signals from two different fluorescent emission centers in the composite. In the presence of uric acid, the fluorescence emission intensity at 430 nm from CDs did not change significantly. However, the fluorescence intensity at 545 nm from Tb³⁺ ions decreased remarkably. This material was evaluated for its capacity to sense urinary components and was shown to specifically recognize uric acid over a wide concentration range (0~5 × 10⁻³ M). Moreover, it exhibited strong resistance to interference and high sensitivity in uric acid detection. The detection limit (LOD) was determined to be 0.102 μM through quantitative analysis. The sensing mechanism was validated through spectral overlap and fluorescence lifetime analysis, which can be attributed to the fluorescence resonance energy transfer (FRET) process. This ratiometric fluorescent probe provides an efficient and reliable strategy for detecting the biomarker uric acid. Full article