Search Results (1,664)

The synthesis, characterization, and equilibrium studies of complexes of selected lanthanide ions Eu(III), Gd(III), and Tb(III) with the ligand 1,3-bis(3-bromo-5-chlorosalicylideneamino)-2-propanol (H₃L) are reported. It was found that in the solid state, the complexes with the formulas [Eu(H₃L)₂(NO₃)₃], [Gd(H₃L)₂(NO₃)₃], and [Tb(H₃L)₂(NO₃)₃] are formed. In solution, complexes with stoichiometries of Ln(III):H₃L 1:1 and 1:2 were obtained. The ligand H₃L was isolated in crystalline form, and its molecular structure and conformation were determined by single-crystal X-ray diffraction analysis. The compounds were further characterized by elemental analysis, infrared spectroscopy, ¹H NMR, ¹³C NMR techniques, and mass spectrometry (ESI), confirming the formation of the Schiff base group. Stability constants of the complexes in solution were determined using potentiometric titration, providing insights into the metal-ligand binding equilibria. In addition, the spectroscopic properties of the ligand and its lanthanide(III) ion complexes were investigated by UV-Vis spectroscopy, which confirmed ligand-to-metal charge transfer interactions, as well as by luminescence measurements. The luminescence studies revealed inefficient energy transfer in [Eu(H₃L)₂(NO₃)₃] complexes, while no transfer was observed in [Tb(H₃L)₂(NO₃)₃] systems at any pH value. This behavior is attributed to the large energy gap between the ligand triplet state and the lowest resonant levels of the studied lanthanide ions. Full article

Organic–inorganic hybrid metal halides (OIMHs) have attracted widespread attention due to their unique chemical properties, excellent electronic performance, and low-cost fabrication processes. These hybrid materials impose fewer size constraints on the organic components, providing an exciting platform for the molecular-level design of new materials and functionalities. In this review, we discuss the latest progress in OIMHs. Specifically, we summarize recent advances in their structures, synthetic strategies, and luminescence mechanisms, and highlight their applications in light-emitting diodes (LEDs), information encryption and anti-counterfeiting, sensors, and X-ray imaging. Finally, we discuss the challenges related to structural design, mechanistic understanding, and stability, along with perspectives on future opportunities for OIMHs. 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

Fine powders of erbium niobate-tantalates ErNb_xTa_1−xO₄ (x = 0; 0.1; 0.3; 0.5; 0.7; 0.9; 1) have been synthesized by the liquid-phase method in this study. Ceramic samples have been prepared using conventional sintering from these powders. Rietveld refinement of XRD patterns of polycrystals determined the phase composition and clarified the parameters of the phase structure of ErNb_xTa_1−xO₄ solid solutions depending on the Nb/Ta ratio. The morphological features of the microstructure of erbium niobate-tantalate ceramics have been studied. Their mechanical properties, strength characteristics (Young’s modulus, microhardness) and critical stress intensity factor of the first kind K_IC have been estimated. The photoluminescent properties of ceramic solid solutions of erbium niobate-tantalates depending on the composition have been studied. Dark and photoinduced toxicity of finely dispersed ErNbO₄ powders have been studied in relation to Gram-positive, Gram-negative and spore-forming microorganisms. The best indicators of antibacterial activity of ErNbO₄ have been demonstrated in relation to Gram-positive cells of Micrococcus sp. The discovered properties open up the possibility of not only traditional use as functional materials, but also the use of these materials for disinfection of surfaces, water and biological tissues. Full article

In the search for new materials to open up creative pathways for industry and research, modification is one of the best methods to implement. Developing materials with high sensitivity and selectivity for specific applications, such as ion sensing, remains a significant challenge. This work aims to introduce a novel metal–organic framework (MOF) derived from the well-established 2-amino-[1,1′-biphenyl]-4,4′-dicarboxylic acid MOF by modifying its structure to enhance its properties and applications. A luminescent 2-naphthyl moiety was attached to the amino group of the linker to form the new luminescent Al-based MOF Al-BP-Naph with a surface area of 456 m² g⁻¹ and a pore volume of 0.55 cm³ g⁻¹. Al-BP-Naph showed high selectivity towards Fe³⁺ sensing due to the overlapping absorption and excitation spectra of both Fe³⁺ and MOF. The MOF demonstrated a detection limit of approximately 6 × 10⁻⁶ mol L⁻¹ with a limit of quantification of about 19 × 10⁻⁶ mol L⁻¹ and a very fast response time (less than 10 s). It also had a Stern–Volmer constant of approximately 0.09 × 10⁵ L mol⁻¹, distinguishing it from other ions. Our work contributes to the expanding repertoire of functional materials with promising applications in sensing technologies, offering a novel MOF with superior properties for iron(III) ion detection. 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

The present study investigates the luminescent behaviour of sol–gel derived Y₂SiO₅ powders doped with Eu³⁺ ions, subjected to spark plasma sintering. The sintering process induces the partial reduction of Eu³⁺ to Eu²⁺, and the phenomenon is strongly dependent on the holding time within the SPS chamber. The luminescent properties are tunable via the initial Eu concentration, holding time and excitation wavelength, resulting in a wide range of emission colours from red (Eu³⁺) at 220 nm excitation to blue (Eu²⁺) at 365 nm, and mixed colours at 257 nm. Moreover, the Eu³⁺/Eu²⁺ redox process is reversible. Overall, the results demonstrate that SPS conditions can be exploited to modulate the valence state of luminescent centres, which is reversible by oxidation under ambient conditions, enabling controlled modulation of the optical properties. 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

YVO₄ based phosphors have aroused extensive interest in the field of optoelectronics due to their good chemical stability and unique luminescence properties. However, commercialization of YVO₄ phosphors requires high luminescence intensity, enhanced conversion efficiency, and a wide excitation spectrum. In this work, Eu³⁺, Ba²⁺, Bi³⁺ co-doped YVO₄ was prepared by the sol–gel method. The XRD of YVO₄: 5%Eu³⁺, 5%Ba²⁺, 0.5%Bi³⁺ phosphor analysis confirms the pure tetragonal phase, with a fairly large size of approximately 100 nm for the optimal composition. And the SEM and TEM revealed well-dispersed spherical nanoparticles with sizes of 100–120 nm. The introduction of Ba²⁺ ions enhanced the luminescence intensity, while the incorporation of Bi³⁺ ions improved the excitation width of the phosphor. The resulting YVO₄: 5%Eu³⁺, 5%Ba²⁺, 0.5%Bi³⁺ phosphor exhibited a 1.39-times broader excitation bandwidth and a 2.72-times greater luminescence intensity at 618 nm compared to the benchmark YVO₄: 5% Eu³⁺ sample. Additionally, the transmittance of the films in the 350 nm to 800 nm region exceeded 85%. The YVO₄: 5%Eu³⁺, 5%Ba²⁺, 0.5%Bi³⁺ film effectively absorbed ultraviolet light and converted it to red emission, enabling potential applications in solar cell window layers, dye-sensitized cell luminescence layers, and solar cell packaging glass. Full article

Lead-free perovskite variants have emerged as promising candidates due to their self-trapped exciton emission. However, in ASnX₃ systems, facile oxidation of Sn(II) to Sn(IV) yields A₂SnCl₆ vacancy-ordered derivatives. Paradoxically, despite possessing a direct bandgap, these variants exhibit diminished photoluminescence (PL). Doping engineering thus becomes essential for precise optical tailoring of A₂SnX₆ materials. Herein, through integrated first-principles calculations and spectroscopic analysis, we elucidate the luminescence mechanism in Te⁴⁺-doped (NH₄)₂SnCl₆ lead-free perovskites. Density functional theory, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) confirm Te⁴⁺ substitution at Sn sites via favorable chemical potentials. Spectral interrogations, including absorption and emission profiles, reveal that the intense emission originates from the triplet STE recombination (³P₁ → ¹S₀) of Te centers. Temperature-dependent PL spectra further demonstrate strong electron–phonon coupling that induces symmetry-breaking distortions to stabilize STEs. Complementary electronic band structure and molecular orbital calculations unveil the underlying photophysical pathway. Leveraging these distinct thermal responses of PL intensity and peak position, 0.5%Te:(NH₄)₂SnCl₆ emerges as a highly promising candidate for non-contact, dual-parameter optical thermometry over an ultra-broad range (100–400 K). This work provides fundamental insights into the exciton dynamics and thermal engineering of optical properties in this material system, establishing its significant potential for advanced temperature-sensing applications. Full article

Mg₂TiO₄:Mn⁴⁺ (MTO:Mn⁴⁺) red phosphor has important applications in areas such as red LEDs and forensic science, but the preparation of MTO:Mn⁴⁺ through the solid-state reaction method requires a high sintering temperature. Herein, MTO:Mn⁴⁺ red phosphor was synthesized using the solid-state reaction method with LiCl flux, and its crystallographic structure and photoluminescence properties were studied to determine the influence of experimental parameters like the amount of fluxing agent added and sintering temperature in producing a bright red phosphor suitable for LEDs. The experimental results showed that samples with added LiCl could form pure MTO after sintering at 950 °C, whereas those without LiCl still contained a mixture of MTO and MgTiO₃, even when sintered at 1400 °C. The optimal performance was achieved with a sample doped with 0.2 mol% Mn⁴⁺, synthesized using 50 wt% LiCl flux and sintered at 950 °C for 12 h. This sample exhibited a broad excitation band and a narrow red emission band peaking at 662 nm, confirming its excellent luminescence properties. Furthermore, a prototype red LED fabricated with a 377 nm chip and MTO:0.2% Mn⁴⁺ phosphor achieved photoelectric conversion efficiency of 78.5% at a 100 mA drive current, confirming its viability for high-performance red LED manufacturing. Full article

Gallium Nitride (GaN) is a wide-bandgap semiconductor that has revolutionized optoelectronic applications, enabling blue/white light-emitting devices and high-power electronics. Point defects in GaN strongly influence its optical and electronic properties, producing both beneficial and detrimental effects. This review provides a comprehensive update on the current understanding of point defects in GaN and their impact on photoluminescence (PL). Since our earlier review (Reshchikov and Morkoç, J. Appl. Phys. 2005, 97, 061301), substantial progress has been made in this field. PL bands associated with major intrinsic and extrinsic defects in GaN are now much better understood, and several defects in undoped GaN (arising from unintentional impurities or specific growth conditions) have been identified. Notably, the long-debated origin of the yellow luminescence band in GaN has been resolved, and the roles of Ga and N vacancies in the optical properties of GaN have been revised. Zero-phonon lines have been discovered for several defects. Key parameters, such as electron- and hole-capture coefficients, phonon energies, electron–phonon coupling strength, thermodynamic charge transition levels, and the presence of excited states, have been determined or refined. Despite these advances, several puzzles associated with PL remain unsolved, highlighting areas for future investigation. Full article

Metal–organic compounds, and especially those containing well-known antioxidant natural flavonoids (Chrysin, Chr) and metal ions (Ti(IV)), attract keen interest for their potential biological activity nutritionally and pharmacologically. To that end, chemical reactivity profiling in binary/ternary systems was investigated synthetically, revealing unique structural correlations between mononuclear (Ti(IV)-Chr) and tetranuclear assemblies (Ti(IV)-Chr-phen). Chemical profiling involved physicochemical characterization through elemental analysis, FT-IR, UV–Visible, 1D-2D NMR, ESI-MS spectrometry, solid-state luminescence, and X-ray crystallography, with theoretical work on intra(inter)molecular interactions of 3D assemblies pursued through Hirshfeld analysis and BVS calculations. An in-depth study of their chemical reactivity shed light onto specific structural properties in the solid-state and in solution, while concurrently exemplifying quenching behavior due to their distinct flavonoid pattern. In the framework of biological activity, the materials were investigated for their antibacterial properties toward Gram(−)-E. coli and Gram(+)-S. aureus, exhibiting an enhanced effect compared to the free ligand and metal ion. Further investigation of BSA denaturation revealed strong anti-inflammatory properties compared to Chr and Diclofenac, an anti-inflammatory agent. Finally, in vitro studies using physiological and cancer cell lines, including breast (MCF10A, MCF7) and lung tissues (MRC-5, A549), formulated a structure–tissue relation reactivity profile, thus justifying their potential as future metallodrugs. Full article

Europium mononuclear complexes are able to form organic molecular crystals by aggregation of molecules through non-covalent bonding interactions. These crystals have many unique optical properties. However, this kind of crystal still faces some difficulties and challenges in the process of research and application, such as the high difficulty of synthesis and purification, and the difficulty of spectral property modulation. In this work, an europium-containing rare-earth molecular crystal material [Eu(BA)₄(pip)], was prepared via a solvothermal method. It is characterized by low melting point, low polarity, stable structure, high luminescence intensity, and has the potential for the preparation of quantum optical devices. After that, optimized the structure of the molecular crystals by petroleum ether solvent. Through the recrystallization process, a uniform and continuous film was formed, which resulted with a more regular surface morphology, and the changes in the optimized crystal structure had an effect on the europium ion electron-leap energy level, the fluorescence emission spectra also showed higher fluorescence resolving ratio. This study particular emphasis on enhancing the quality of [Eu(BA)₄(pip)] molecular crystals and investigating their impact on their spectral properties. Full article

A para-substituted 1,10-phenanthroline ligand, 2-(4-methylphenoxy)-1,10-phenanthroline (L24), was synthesized and structurally characterized. Complexes with Eu³⁺, Tb³⁺, Sm³⁺, and Dy³⁺ were obtained in a 2:1 ligand-to-metal ratio and analyzed using single-crystal x-ray diffraction, photoluminescence spectroscopy, and TD-DFT calculations. Coordination via the phenanthroline nitrogen atoms, combined with steric asymmetry from the para-methylphenoxy group, induces low-symmetry environments favorable for electric-dipole transitions. Excited-state lifetimes reached 2.12 ms (Eu³⁺) and 1.12 ms (Tb³⁺), with quantum yields of 42% and 68%, respectively. The triplet-state energy of L24 (22,741 cm⁻¹) aligns well with emissive levels of Eu³⁺ and Tb³⁺, consistent with Latva’s criterion. Fluorescence titrations indicated positively cooperative complexation, with association constants ranging from 0.60 to 1.67. Stark splitting and high ⁵D₀ → ⁷F₂/⁷F₁ intensity ratios (R₂ = 6.25) confirm the asymmetric coordination field. The para-methylphenoxy substituent appears sufficient to lower coordination symmetry and strengthen electric-dipole transitions, offering a controlled route to enhance photoluminescence in Eu³⁺ and Tb³⁺ complexes. Full article