Journal of Fluorescence最新文献

Tetracycline (TC) is a broad-spectrum antibiotic primarily used for the prevention and treatment of bacterial infections in humans and animals. However, excessive use of tetracycline can lead to accumulation in the body, posing risks to human health. In this study, nitrogen-doped fluorescent carbon quantum dots (N-CQDs) were synthesized using sucrose as the carbon source and ethylenediamine as the nitrogen source via a microwave method. N-CQDs were characterized using transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and ultraviolet-visible spectroscopy (UV-vis). The preparation conditions for N-CQDs were optimized, and the results showed that when glycerol was used as the solvent, the mass ratio of sucrose to ethylenediamine was 1:4, and the microwave power was 800 W, the fluorescence quantum yield of the synthesized N-CQDs reached 43.78%. Optimisation of the TC detection process indicated that at a reaction temperature of 50 °C, a reaction time of 20 min, and a buffer solution pH of 7, within a concentration range of 1.6 to 45 µmol/L, the linear regression equation for TC concentration versus N-CQDs fluorescence quenching degree is (F₀-F)/F₀ = 0.01042 c + 0.42759, with an R² value of 0.99344 and a detection limit of 45 nmol/L. Experiments were conducted to determine the recovery rate and precision of TC in milk samples. The results showed that the recovery rates ranged from 94% to 107%, while the precision (RSD) was within the range of 1% to 4%, indicating that the synthesized N-CQDs can sensitively and efficiently detect TC. In this study, nitrogen-doped fluorescent carbon quantum dots (N-CQDs) were synthesized using sucrose as the carbon source and ethylenediamine as the nitrogen source via a microwave method.

A series of dicyanodistyrylbenzene derivatives Dn with different length of alkyl chains (C_4 ~ 16) were synthesized to systematically study the effects of alkyl chains on the solid state optical properties, mechanofluorochromic (MFC) and liquid crystal (LC) behaviors. The photophysical properties, time resolved photoluminescence (TRPL), fourier transform infrared spectrometer (FTIR) and X-ray diffraction (XRD) were conducted to explore their MFC response. MFC was fundamentally governed by the switch of excited-state species instead of just XRD or fluorescent lifetime changes. Dn with intermediate alkyl lengths (C₈, C₁₂) show the most contrastive MFC properties. Meanwhile shorter alkyl chains (C₄, C₈) promote the reversibility. However, excessive length (C₁₂, C₁₆) diminishes this effect. The mesomorphic properties were studied by combining differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM) and small-angle X-ray diffraction (SAXD) measurements. Alkyl chains mediate a crystal-to-mesophase transition. Shorter chains (C₄) favor crystalline rigidity, and LC properties were observed in homologs with longer alkyl chains (C_8 - 16). Four phase transitions of melting, S_E to S_C, S_C to S_A phase, and finally clearing were displayed in sequence during heating process. Lamellar structures were adopted with alkyl length correlating to interlayer distance and affecting structure stability. Among them, D8 exhibited the widest mesophase range. These findings establish alkyl chains as multifunctional spacers that comprehensively control optical, mechanical and thermal responses via competing π-π and aliphatic interactions.

Theranostic agents, which integrate diagnostic and therapeutic capabilities into a single nanoscale architecture, offer substantial advantages over conventional approaches. In this study, the potential of functionalized two-dimensional Titanium Carbide (Ti₃C₂) MXene Quantum Dots (MQDs) was explored as multifunctional agents capable of Magnetic Resonance Imaging (MRI), Computed Tomography (CT), and Photothermal Therapy (PTT). MQDs inherently possess efficient photothermal properties, making them suitable for therapeutic applications. To enhance diagnostic performance, MQDs were functionalized with Gadolinium (Gd) using two different methods, imparting magnetic properties and a high effective atomic number (Z-number), which significantly improved MRI and CT contrast capabilities. The MQDs, synthesized via a facile one-step hydrothermal method, exhibited an average size of 3.4 ± 1 nm and demonstrated intrinsic photoluminescent properties, enabling an additional Photoluminescence Imaging (PLI) modality. Surface modification with Polyethylene Glycol (PEG) was employed to effectively mitigate Gd-associated cytotoxicity while concurrently enhancing cellular internalization of the MQDs confirmed with RD cell line. Subsequent red (630 nm) laser irradiation studies were done at max power of 550mW for 10 min maximum, results of which confirmed that Gd-functionalization did not compromised the intrinsic photothermal efficiency of MQDs; remarkably, it enhanced the photoluminescence emission intensity by approximately 85% compared to the unmodified MQDs. Finally, this study successfully demonstrates the feasibility and possibility of Gd-functionalized MQDs as robust single-component multimodal theranostic agents capable of simultaneous MRI, CT, and photoluminescent imaging, along with potent photothermal therapeutic efficacy.

A green-synthesized europium-based metal-organic framework (Eu-ATPA@3RhB) was developed for ratiometric fluorescence sensing of Cu²⁺. Under 245 nm excitation, Eu-ATPA@3RhB exhibits dual emission peaks at 435 nm and 588 nm. When Cu²⁺ is added, the fluorescence at 435 nm is quenched while that at 588 nm remains constant, enabling ratiometric detection based on the I₄₃₅/I₅₈₈ ratio. The method shows a linear range of 1-25 µM (R²=0.99) with a detection limit of 0.25 µM, outperforming drinking water standards. Density functional theory (DFT) calculations elucidate the interaction mechanism between Cu²⁺ and Eu-ATPA@3RhB. The Eu-ATPA@3RhB developed in this study showcases the advantages of green synthesis, simplicity, and swiftness, affirming its potential for Cu²⁺ detection in diverse environmental water samples.

The present work reports the synthesis of novel D-π-A chromophores based on the molecular architecture of triphenylamine (donor group), thiophene (conjugated bridge) and aryl-methanimine (acceptor group). The synthetic route for the target chromophores involved the condensation of 2-formyl-5-(4-(diphenylamino)styryl)thiophene (5) with the appropriate acceptor, either 4-cyanoaniline or 4-nitroaniline (TPAT-CN and TPAT-NO₂), respectively. The newly synthesized chromophores were characterized by absorption and fluorescence spectroscopy, as well as other spectral data. The absorption and emission spectra of the chromophores were recorded in DMSO and presented a good Stokes' shift ([Formula: see text] = 5505-5593 cm^-1). The FMOs patterns and energies, obtained from DFT calculations, for the solvated ground (S_o) and excited states (S₁) have been compared. Moreover, the in vitro cytotoxic activity of the chromophores has been examined against three human cancer cell lines and a human fibroblast line (WI38), using Sorafenib as a reference. The TPAT-CN chromophore displayed strong cytotoxic effectiveness towards HCT-116 and HepG2 cells (IC₅₀ = 6.25 ± 0.36 and 9.44 ± 0.05 µM), while the TPAT-NO₂ analogue exhibited moderate effectiveness across the investigated cancer cells. In addition, the VEGFR-2 kinase inhibition efficacy revealed that both chromophores effectively inhibited VEGFR-2 enzymatic activity in the sub-micromolar range, where TPAT-CN IC₅₀ = 0.53 ± 0.26 µM and TPAT-NO₂ IC₅₀ = 0.62 ± 0.11 µM. Finally, the molecular docking study was conducted against the VEGFR-2 receptor (PDB: 3WZE) and revealed promising binding affinity, superior Sorafenib.

A noble highly selective, sensitive and SmA mesogenic dipeptide-based Schiff base ligand (HL) was synthesized and characterized using various instrumental and analytical techniques. The Schiff base ligand functions as a potent fluorescent chemosensor for the dual detection of Cd²⁺ and Zn²⁺ metal ions with the detection limits of 2.02 nM and 2.68 nM, respectively. Job's plot analysis revealed 2:1 stoichiometric ratio between the probe and the metal ions, with binding constant value of 3.25 × 10⁶ M^- 1 for Zn²⁺ and 5.20 × 10⁶ M^- 1 for Cd²⁺. The probe showed reversibility nature over four cycles through alternate addition of Zn²⁺/ Cd²⁺ and EDTA, exhibiting distinct off-on-off fluorescence, enabling construction of three molecular logic gates. The probe effectively detected Zn²⁺ and Cd²⁺ in real water samples over a broad pH range. The DFT study of the Schiff base and its complexes with Zn²⁺ and Cd²⁺ were performed using LanL2DZ and 6-31G(d, p) basis set with the hybrid correlation B3LYP to ascertain the optimized geometry.

2,4-Dichlorophenoxyacetic acid (2,4-D) is a selective, low-volatility, systemic herbicide. It is used to control broadleaf weeds in certain crops, such as rice, corn, and wheat. The use of 2,4-D has become widespread in both the agricultural and industrial sectors, with the serious drawback that 2,4-D residues can contaminate food, soil, and groundwater sources. It has been classified as a group 2B carcinogen by the International Agency for Research on Cancer. This paper proposes the development of a new alternative methodology to traditional techniques for the control and monitoring of 2,4-D in natural water samples from agricultural areas surrounding the Quinto River in the province of San Luis. The herbicide was quantified directly, in the presence of the anionic surfactant SDS, the systems were filtered through blue band filter paper as a solid support, prior to determination by solid surface fluorescence (SSF) (λ_exc = 555 nm; λ_em = 580 nm). Under optimal working conditions, a detection limit and a quantification limit of 0.33 and 0.90 ng L^- 1, respectively, with a linearity range of 0.90 to 1.13 × 10³ ng L^- 1. The proposed methodology was applied to natural water samples from agricultural areas, adjacent to the Quinto River in the province of San Luis, representing an innovative alternative to conventional methods for 2,4-D monitoring. The concentrations found were near to 3 ng L^- 1. Additionally, among the advantages of the new method, it is important to highlight the generation of low volumes of waste, preserving the environment and thus contributing to some principles of green chemistry.

This study aimed to establish and validate a novel detection method that combines padlock probe technology with fluorescence quantitative PCR (qPCR) for the rapid and specific detection of the SARS-CoV-2 Omicron S371L mutation in the spike protein. Padlock probes and amplification primers were designed and synthesized based on the Omicron S371L mutation site. The probe was designed to anneal with high specificity to the mutation, allowing ligase-mediated circularization only in the presence of the target sequence. The circularized probe then served as a template for qPCR amplification. Assay optimization included probe concentration, ligation temperature, ligase concentration, and ligation time. Analytical sensitivity, specificity, and recovery performance were systematically evaluated. Finally, the method was validated using 30 clinical samples, with results compared to Sanger sequencing. The optimal assay conditions were identified as a padlock probe concentration of 10 nM, ligase at 0.2 U/µL, ligation carried out at 65 °C for 30 min, and 10 µL of the ligated product used for subsequent qPCR amplification. Under these parameters, the assay achieved a limit of detection of 5.78 fM and demonstrated strong linearity (R² = 0.9669). Specificity testing showed clear differentiation between the mutant template and single-, double-, or triple-base mismatches. In performance evaluations, recovery rates ranged from 89.7% to 108.0% in both PBS and urine samples. For clinical validation, the method showed complete agreement with Sanger sequencing results, yielding positive and negative predictive values of 100%. In summary, the padlock probe-based qPCR assay developed in this study offers a fast and reliable approach for detecting the Omicron S371L mutation in SARS-CoV-2. Because the method bypasses the reverse transcription step that is typically required for RNA targets, it simplifies the workflow without compromising accuracy. These features suggest that the assay could be well suited for broader clinical application, particularly in large-scale screening of emerging SARS-CoV-2 variants.

In automated recycling systems, accurately sorting mixed-material waste remains a significant challenge, particularly when materials such as wood, metals, and polymers exhibit similar visual appearances. White polyamide polymer is widely used in industrial components due to its durability and chemical resistance, yet its recovery from waste streams is often hindered by optical similarities to light-colored wood and oxidized or coated metals. This study presents a dual imaging approach that combines laser-induced fluorescence (LIF) using ultraviolet excitation with hyperspectral imaging (HSI) of diffuse reflectance under broadband illumination (400-1000 nm). The fluorescence experiments revealed that the white polyamide polymer exhibited a strong significant wavelength at approximately 740 nm, distinctly separating it from wood and metal, alongside a less prominent secondary response at 443 nm. However, in the visible range from about 480 to 630 nm, the fluorescence responses of wood and polymer substantially overlapped, underscoring the importance of targeting the near-infrared (NIR) emission for effective polymer discrimination. Complementary diffuse reflectance HSI data analyzed through histogram techniques identified optimal wavelengths near 480 nm and 840 nm that enhanced contrast between the polymer, wood, and metal, guiding the design of simplified multispectral systems. This dual-modality imaging strategy integrates molecular fluorescence sensitivity with detailed reflectance profiling to achieve improved material discrimination, paving the way for practical, automated sorting solutions. The insights gained also support the future development of conventional aerial camera systems equipped with optimized filters and illumination sources to monitor and manage polymer waste accumulation on larger environmental scales.

A simple, cost-effective, accurate, and sensitive spectrophotometric method has been developed for the determination of fluometuron in environmental samples. The method is based on the formation of a metal complex between fluometuron and Fe(III), exhibiting maximum absorbance at 347 nm. The calibration curve followed Beer's law in the concentration range of 0.25-5.0 µg mL^- 1, with a correlation coefficient (R²) of 0.997, indicating excellent linearity. The method demonstrated a limit of detection (LOD) of 0.0787 µg mL^- 1 and a limit of quantification (LOQ) of 0.238 µg mL^- 1. Recovery studies performed on spiked environmental matrices showed high accuracy, with percent recoveries ranging from 82.12 ± 2.95% to 97.80 ± 6.11%. The developed method was successfully applied to the analysis of fluometuron in real samples, including tap water, canal water, pond water, and soil, confirming its reliability for routine environmental monitoring.