Luminescence最新文献

To date, most luminescence studies on MOF-76 have focused on tetragonal Tb³⁺-doped and Tb³⁺/Eu³⁺ co-doped systems. In this work, MOF-76(Gd, Dy) and MOF-76(Gd, Tb, Dy, Eu) were synthesised for the first time and subsequently subjected to hydrothermal annealing in the presence of polyvinylpyrrolidone (PVP) as a dispersant. Annealing induced a tetragonal → monoclinic phase transition in MOF-76 and transformed the morphology from rods into highly crystalline, transparent nanosheets. As a result, the emission intensity of annealed MOF-76(Gd_0.98, Dy_0.02) increased by approximately 25-fold and its photoluminescence quantum yield (PLQY) improved from 2.33% to 18.60%. These enhancements enabled the combination of hydrothermal annealing with a lanthanide co-doping strategy to achieve precisely tunable, highly luminescent colours in the multi-doped MOF-76(Gd, Tb, Dy, Eu) system. In the annealed materials (aMOFs), efficient Tb³⁺ → Dy³⁺ and Dy³⁺ → Eu³⁺ energy transfer pathways were identified. Owing to their high luminescence and colour tunability, the resulting materials demonstrated practical applicability in colour-tunable fluorescent anti-counterfeiting and, when combined with N-CDs@starch, in white-light-emitting LED devices.

Thermal luminescence stability is a key challenge in developing luminescent materials for various applications. Photoluminescent properties of two red-emitting complexes, [Eu (PHT)₃·H₂O] and [Eu (PHT)₃], were studied. Infrared spectroscopy demonstrated characteristic ν_as (COO⁻) and ν_s (COO⁻) bands of coordinated carboxylates. Photoluminescence confirms an effective ligand to metal energy transfer in the [Eu (PHT)₃⸱H₂O] and [Eu (PHT)₃] complexes, resulting in the characteristic Eu³⁺ ion transitions corresponding to ⁵D₀ → ⁷F_J (J = 0–4). Luminescence lifetime (τ), Absolute Quantum Yield (Ф), and quantum efficiency (η) revealed an increase of nonradiative deactivation channels in the [Eu (PHT)₃⸱H₂O] complex due to the presence of O–H oscillators when compared to the [Eu (PHT)₃] complex. Photometric analysis placed both complexes in close agreement with NTSC red coordinates (x = 0.67, y = 0.33), and full color-purity values above 93%. The temperature-dependent luminescence of the [Eu (PHT)₃] complex exhibited thermal stability up to 423 K, maintaining a signal of 70%. In contrast, the initial intensity of the [Eu (PHT)₃·H₂O] complex increases up to 50% in the 393–413 K range, causing intensity variations and reduced reproducibility suggested by the presence of the water molecule. These results indicate that the anhydrous [Eu (PHT)₃] complex is an efficient red-emitting phosphor for optoelectronic devices.

The naphthalene carbohydrazide colorimetric and fluorimetric chemosensor (E)-N′-(4-(diethylamino)-2-hydroxybenzylidene)-1-naphthohydrazide (MKG-12) was designed, synthesized and evaluated for cation sensing via excited state intermolecular proton transfer (ESIPT) mechanism. The chemosensor MKG-12 shows a high sensitivity and selectivity to Al³⁺ ion detection in 10% aq.-DMSO solution (HEPES buffer, pH 7.4) with a 1:1 binding stoichiometry. The emission intensity of chemosensor MKG-12 was selectively enhanced by Al³⁺ ion, and an observable change in colour from colourless to fluorescent green was observed. Chemosensor MKG-12 shows limit of detection 8.79 × 10⁻⁸ μM and K_abs = 1.32  $��\times �$ 10⁴ M⁻¹ and K_em = 3.08  $��\times �$ 10⁴ M⁻¹ binding constant with Al³⁺ ion. Further, the interaction between the chemosensor MKG-12 and the Al³⁺ ion was supported by mass spectroscopy and DFT. Additionally, the chemosensor MKG-12 has been utilized as a small colorimetric kit for Al³⁺ ion on paper test strips and is also accomplished for detection of Al³⁺ ion in real water samples from different sources. Chemosensor MKG-12 was constructed as INHIBIT logic gate based on reversibility behaviour with EDTA.

In this work, the series of sol–gel materials doped with Nd³⁺ ions were synthesized and further transformed into nano-glass-ceramics containing LaF₃:Nd³⁺ nanocrystals via controlled heat treatment, carried out at 700°C and 900°C. The structural characterization of materials obtained at different temperature conditions was performed using x-ray diffraction analysis (XRD), revealing a crystallization of the fluoride nanophase. The examination of luminescent properties included analysis of PLE and PL spectra recorded using different excitation wavelengths. The characteristic emission bands of Nd³⁺ ions within near-infrared (NIR) spectral scope were observed for all fabricated samples. Furthermore, the luminescence decay curves of the ⁴F_3/2 state of Nd³⁺ were registered. It has been demonstrated that samples annealed at a higher temperature level (900°C) exhibited more intense NIR luminescence bands and longer lifetimes of the ⁴F_3/2 excited state, compared with the series fabricated at 700°C. Indeed, the luminescence lifetimes noted for materials annealed at 700°C ranged from 141 to 772 μs, whereas those obtained for materials heat-treated at 900°C ranged from 213 to 862 μs. Based on the obtained results, it was concluded that the Nd³⁺ ions were partially incorporated into LaF₃ nanocrystals, thus the fabricated sol–gel materials are promising candidates for the NIR luminescence applications.

The monitoring of alkaline phosphatase (ALP) activity and pyrophosphate (PPi) concentration is critical for assessing phosphorus dynamics and eutrophication in aquatic ecosystems. However, on-site, rapid detection of these dual targets in complex water matrices remains a challenge. In this work, a nitrogen-doped carbon dots (N-CDs)-Eu³⁺-tetracycline (TC)-based ratiometric fluorescence probe was constructed for turn “off–on” determination of PPi and ALP based on the strong binding interaction between PPi and Eu³⁺ and PPi hydrolyzed by ALP. In the N-CDs-Eu³⁺-TC system, with the addition of PPi, PPi could replace the N-CDs to form the PPi-Eu³⁺-TC multicomplex, and N-CDs were released, resulting in the fluorescence quenching of Eu³⁺ and fluorescence recovery of N-CDs. ALP could hydrolyze PPi to PO₄³⁻, which could destroy the PPi-Eu³⁺-TC multicomplex and form the N-CDs-Eu³⁺-TC multicomplex again, and the fluorescence of Eu³⁺ at 617 nm was recovered. The N-CDs-Eu³⁺-TC-based ratiometric fluorescent probe possesses a quick fluorescence response, obvious fluorescence color variance, and excellent selectivity and sensitivity with LOD of 40 nM for PPi and 0.03 U/L for ALP. The proposed probe was successfully applied for the detection of PPi and ALP in the actual environmental water samples or serum samples.

This review focuses on the application of o-phthaldehyde analogs as isoindole-forming probes for the sensitive fluorescence determination of biomedical and pharmaceutical compounds. Isoindole formation has been used effectively for the fluorescence detection of a wide range of analytes, including aliphatic and aromatic primary amines, amino acids, some proteins, thiols, cyanides, and others. Such derivatization is flexible and can be tailored for the analysis of different classes of compounds using techniques such as direct spectrofluorimetry, HPLC, and capillary electrophoresis. Most of the isoindole formation reactions proceeded rapidly at room temperature and yielded highly fluorescent products without the generation of interfering by-products. Several alternative reagents for the formation of isoindoles have also emerged; however, o-phthaldehyde is still the most commonly used reagent. The advantages and potential applications of these alternatives were discussed. Overall, this review will enlighten researchers on the development and applicability of o-phthaldehyde analogs based on isoindole formation in quantitative analysis and detection of biomolecular targets.

A simple, cost-effective, reproducible, highly sensitive, and green spectrofluorimetric technique for sitagliptin phosphate estimation has been established in its pure form and commercial formulation. The native fluorescence of sitagliptin was enhanced by inhibiting photoinduced electron transfer through optimization of medium pH. The highest fluorescence intensity of sitagliptin was observed at 296 and 583 nm after excitation at 265 nm, using 0.50-M acetic acid. The method exhibited a wide linearity range (0.30–4.00 μg/mL) with high correlation coefficient values of 0.9998 at both 296 and 583 nm, limits of detection of 0.09 and 0.10 μg/mL, and the limits of quantitation of 0.27 and 0.29 μg/mL, respectively. The guidelines of ICH have been applied for validation of the proposed method. The obtained results have been compared with the previous reported methods. The developed fluorimetric protocol demonstrated high accuracy and excellent precision for estimation of sitagliptin in commercial tablets. Furthermore, the method was confirmed to be environmentally friendly using AGREE, GAPI, Analytical Eco-Scale, MA, and AGSA tools. As a conclusion, the proposed fluorimetric protocol is highly suitable for the quality control of sitagliptin phosphate.

High concentrations of silver ions can lead to adverse effects on the skin, digestive system, nervous system, and other bodily functions at high concentrations. Therefore, it is crucial to monitor their concentration in water. This study has identified sulfur and nitrogen codoped carbon dots (S,N-CDs), which achieved optimal fluorescent performance with a fluorescence quantum yield as high as 37.9%. The amino (-NH₂) and mercapto (-SH) groups on the surface of S,N-CDs, which contain lone pair electrons, readily coordinate with silver ions to form complexes. Furthermore, a strong linear relationship is observed within the concentration range of 0.001–450 μM, making this method suitable for detecting silver ion concentrations. This study presents a cost-effective, easy-to-prepare, efficient, and selective fluorescent sensor for detecting silver ion concentrations, with potential applications in monitoring silver ions in water.

A D-A-D-type fluorescent molecular probe 4 has been designed and synthesized. The solvatochromic and photophysical properties of probe 4 were studied in different solvent systems. Probe 4, upon interaction with different classes of ions in a partial aqueous medium, showed sensitivity for Cu²⁺ and CN⁻ ions in which the intensity of the probe due to the intramolecular charge transfer (ICT) process diminished upon formation of a stable complex, 4.Cu²⁺ and deprotonation of –OH functions, respectively. Job's plot analysis revealed a 1:1 (Cu²⁺) and 1:2 (CN⁻) stoichiometry. Probe 4 displayed a naked eye–sensitive fluorescence response to detect both ions in solution with different rates of reaction and a limit of detection in the nanomolar range. The electrodynamic properties of the probe displayed redox behavior upon interaction with both ions. The variation in the ICT process was further assessed by the density functional theory (DFT) method. The probe has been utilized to detect the ions on test paper strips and in real water samples with a good recovery percentage. Also, probe 4 was successfully applied to estimate the Cu²⁺ ion concentration in natural grass extract solution. The molecular probe showed good applicability in on-site detection of both ions using a smartphone-based RGB analysis technique.