Luminescence最新文献

Eurycoma longifolia Jack, commonly known as Tongkat Ali, is a medicinal herb traditionally valued for its aphrodisiac properties, with eurycomanone being its principal bioactive quassinoid. This study introduces a novel, cost-effective method for the sensitive detection of eurycomanone using nitrogen-doped carbon quantum dots (N-CQDs) as a fluorescent probe. The spectral characteristics of the probe were carefully analyzed using UV–vis and fluorescence spectrophotometric techniques, and the sensing mechanism was investigated through Stern–Volmer and thermodynamic studies, revealing a static quenching interaction. A Box–Behnken design of experiment was applied to optimize the sensing conditions including pH, incubation time, and probe concentration, ensuring high sensitivity and robustness. A reduced quadratic model was found significant (p value > 0.0001) with pH and N-CQDs concentration being the most influential factors. The method was rigorously validated following ICH guidelines displaying excellent linearity in the range of 0.25–6.0 μg/mL, high sensitivity (LOD 0.067 μg/mL), and high accuracy and precision (RSD < 1.5%). The proposed technique was successfully applied to the analysis of real Tongkat Ali samples, demonstrating its practical utility in herbal analysis. The results showed good agreement with reported chromatographic methods, positioning the technique as a promising alternative to conventional analytical methods.

Folic acid (FA) is a crucial B vitamin for cell formation and maintenance, and its deficiency can lead to severe health disorders, highlighting the importance for accurate FA detection. Chemiluminescence (CL) provides a highly sensitive analytical approach, characterized by simple instrumentation, high accuracy, and low background interference. However, traditional CL techniques are often limited by weak signal intensity and poor robustness. This study presents a novel CL system using well-defined fluorescent Cl, S, N co-doped carbon dots (ClSN-CDs) integrated into the H₂O₂-KBrO₃ system. Under acidic conditions, the synergistic effect of H₂O₂ and KBrO₃ induced ClSN-CDs to emit a strong CL signal, with the emitting species identified as excited-state ClSN-CDs. Trace amounts of FA significantly quenched the CL intensity of the ClSN-CDs-H₂O₂-KBrO₃ system, enabling rapid, sensitive, and selective FA detection. The system demonstrated a linear response to FA concentrations ranging from 0.02 to 1.0 μM, with a detection limit of 3.1 nM. Selectivity and recovery studies validated the system's robust analytical performance. Mechanistic investigations revealed that the CL reaction involved reactive oxygen species (ROS), and FA-mediated ROS consumption led to luminescence suppression.

Luminescence materials activated with rare-earth ions for use in optical thermometers and lighting have garnered increasing attention in recent times. In this work, the problem has been tried to resolve by preparing Ba₂ZnSi₂O₇: Dy³⁺phosphor. X-ray diffraction shows their structure as monoclinic which was further confirmed by Rietveld refinement techniques. Optical studies have been done to confirm their luminescence properties. Stimulated at 351 nm, the as-prepared phosphors show blue (469 nm) and yellow (577 nm) emissions. The ⁴F_9/2 ➔ ⁶H_J (J = 13/2, 15/2) transitions of Dy³⁺ ions are responsible for these emissions, and they were also utilized to optimize the dopant concentration. The latter has two types of fluorescence intensity ratios and a type of excitation intensity ratio with maximum relative sensitivities of 2.05% K⁻¹ and 1.96% K⁻¹, respectively. Using an optimized phosphor, which exhibits good optical temperature measuring capabilities, a temperature measurement model was constructed using the fluorescence lifetime (FLT), with a maximum value of S_R = 5.42% K⁻¹. The generated Dy³⁺-doped Ba₂ZnSi₂O₇ phosphors can thus be a good option for UV-excitable warm lighting systems and noncontact optical thermometry measurements, in the light of every experimental finding.

A green hydrothermal method was used to synthesize luminol-based carbon dots (Lu-CDs) for chemiluminescence (CL) and fluorescence (FL) detection of nitrite ions in water samples. Lu-CDs were characterized by using different techniques. The morphology indicates a spherical shape and an amorphous crystalline structure. A reversed flow injection analysis (rFIA) CL detection method was developed based on the Lu-CDs-N-bromosuccinimide-NaOH system, where the CL signal was quenched by nitrite ions. For FL analysis, Lu-CDs exhibited blue fluorescence at 425 nm (quantum yield: 56.42%) upon 350 nm excitation, which was quenched by nitrite ions at pH 6.5. Reaction conditions and parameters were optimized for both methods. The CL and FL methods showed linearity for nitrite concentrations of 1.5–20.0 μg mL⁻¹ and 0.85–50.0 μg mL⁻¹, with detection limits of 0.75 and 0.55 μg mL⁻¹, respectively. Applicability was validated through tap and groundwater analysis, showing agreement with a standard spectrophotometric method (Student's t-test, F-test). The greenness of the developed methods was evaluated using the AGREE and GAPI tools, while their applicability was assessed with the BAGI tool, highlighting their eco-friendly and reliable nature for nitrite detection in water.

Phosphate (PO₄³⁻) ions play pivotal parts in the biological system as it provides key nutrients indispensable for sustaining life and also has vast applications in the industrial fields. However, surplus amount of PO₄³⁻ ion can be very hazardous and cause serious health issues in various aspects of life, which makes the targeted and precise identification of PO₄³⁻ ion essential. In this study, we have chosen an amino-imidazole-based probe, 2-(2-aminophenyl)-1H-benzimidazole (IMIDA), which undergoes distinct photophysical change, resulting in a significant violet to greenish fluorescence enhancement in the presence of PO₄³⁻ ion. The probe IMIDA exhibits excellent sensitivity, selectivity, and prompt response towards PO₄³⁻ ion having detection and quantification limit in the nM range, which makes it commendable for its monitoring. A handy paper strip and smartphone-based detection strategy are executed for the on-spot detection of PO₄³⁻ ion. The applicability of the probe is further illustrated by the detection of PO₄³⁻ ion in environmental conditions by using different water samples. Thus, the present study provides a robust, simple, and efficient scaffold for the detection of PO₄³⁻ ion, extending opportunities for advancement in environmental monitoring, industrial quality control, and biomedical diagnostics.

Fluorescence quenching, a process where the intensity of fluorescence is diminished by various molecular interactions, has emerged as a critical tool in drug discovery. This review delves into the underlying mechanisms of fluorescence quenching, including static and dynamic quenching, Förster resonance energy transfer (FRET), and photoinduced electron transfer (PET). Each mechanism offers unique insights into molecular interactions, binding affinities, and conformational changes of drug candidates, enabling researchers to dissect complex biological systems with precision. The application of fluorescence quenching in high-throughput screening (HTS) is particularly emphasized, highlighting its role in identifying lead compounds and optimizing drug–target interactions. Furthermore, the review explores the integration of advanced fluorescence techniques, such as time-resolved fluorescence and single-molecule spectroscopy, in elucidating the quenching phenomena at a molecular level. These techniques provide a deeper understanding of drug–receptor interactions, allosteric modulation, and protein dynamics, which are pivotal in the drug development pipeline. The potential of fluorescence quenching in probing the pharmacokinetics and pharmacodynamics of novel therapeutics is also discussed, underscoring its versatility and effectiveness. By offering a comprehensive analysis of fluorescence quenching mechanisms and their applications, this review aims to inform future drug discovery endeavors, fostering the development of more effective and targeted therapies.

Developing multifunctional probes capable of detecting two or more analytes under same test conditions is important for improving assay efficiency, simplifying experimental procedures, and providing more comprehensive analytical results in complex systems. This study employed 1,8-naphthalimide as a fluorescent group to design and synthesizes a naphthalimide-based Schiff base fluorescent probe, ANQ. In a CH₃CN/HEPES buffer solution with a volume ratio of 3:7, ANQ enabled the continuous and rapid detection of Cu²⁺ and cysteine under the same detection conditions. Of these, ANQ coordinated with Cu²⁺ in a 1:1 ratio, allowing for specific fluorescence “on–off” detection of Cu²⁺, with a complexation constant of 4.41 × 10⁴ M⁻¹ and a detection limit of 3.6 × 10⁻⁸ mol/L. In addition, under the same conditions, complex ANQ-Cu²⁺ had a fluorescence turn-on response to cysteine and was unaffected by other amino acids and glutathione, with a complexation constant of 5.2 × 10⁴ M⁻¹ and a limit of detection as low as 4.2 × 10⁻⁸ mol/L. Moreover, ANQ could be prepared as a test strip to detect copper ions, and ANQ-Cu²⁺ complex could be used to detect cysteine in milk, demonstrating excellent potential for practical applications.

The present work reports the preparation, characterization, and photoluminescence (PL) and thermoluminescence (TL) responses of Tb³⁺-doped Ba₃CdSi₂O₈ phosphors. X-ray diffraction analysis confirmed the consistency of the Tb³⁺-doped Ba₃CdSi₂O₈ samples with the PDF 00-028-0128 card structure. The TL glow curve of the material was examined at different dopant concentrations after irradiation with a ⁹⁰Sr/⁹⁰Y beta source. Among the samples, Ba₃CdSi₂O₈: 5% Tb³⁺ exhibited the highest TL intensity compared with the other concentrations. The glow curve deconvolution method was used to determine the number of peaks, trap structure, and kinetic parameters within the TL glow curve, yielding a figure of merit (FOM) value of 1.11. The PL spectra show that the 2.0%, 3.0%, 4.0%, 5.0%, and 6.0% mole Tb³⁺-doped Ba₃Cd (SiO₄)₂ phosphors capture excitation energy through the 4f-5d transitions of Tb³⁺ ions and emit light at 417, 440, 492, 552, 589, and 628 nm, corresponding to the 5D₃–7F₅, 5D₃–7F₄, 5D₄–7F₆, 5D₄–7F₅, 5D₄–7F₄, and 5D₄–7F₃ transitions, respectively.