Journal of Fluorescence最新文献

Dysprosium ion-doped Calcium Yttrium Tungstate (Ca₃Y₂WO₉) (CaYW) phosphors were synthesised via the solid-state reaction method. The undoped and doped phosphor samples were characterised by the x-ray diffraction (XRD) method. The diffraction peaks of the samples, sintered at 1100 °C, matched well with reported Ca₃R₂WO₉-type patterns [1, 2], confirming the tetragonal crystal system. Scanning electron microscopy (SEM) was utilised to study the surface morphology of the samples. Diffuse reflectance spectroscopy (DRS) measured the optical band gap values. CaYW: xDy phosphors, with different doping concentrations of Dy³⁺ (x = 1.0, 3.0, 5.0, 7.0, 9.0, and 11.0 mol%), were synthesised, and their photoluminescence (PL) spectra were studied. No noticeable peak shifting with Dy³⁺ incorporation was observed, indicating retention of the host lattice structure. The emission spectra revealed that the phosphors, when excited at 352 nm, showed intense emission at 575 nm (yellow light), corresponding to the transition ⁴F_9/2→⁶H_13/2. Concentration quenching occurred after 9.0 mol% of Dy³⁺ ions, and thus, the optimum phosphor sample is CaYW:9.0Dy³⁺. For the prepared phosphor, the Commission Internationale de l'éclairage (CIE) coordinates were evaluated and were found in the yellowish-white region with the coordinates of the optimum sample equals to 0.3654, 0.3972. Fourier transform-infrared (FT-IR) spectra were analysed to identify the functional groups present in the samples. Thermogravimetric analysis (TGA) and temperature dependent-photoluminescence (TD-PL) analysis were also done to study the samples in a thermal context. In conclusion, the results of the current study demonstrate that the Dy³⁺ ions-doped CaYW phosphors may have the potential to be utilised in white light-emitting diodes (w-LEDs).

The interaction of the monomer dyes Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide), Sbo((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]oxazol-3-ium iodide), Sil((E)-2-(4-(dimethylamino)styryl)-1,3,3-trimethyl-3 H-indolium perchlorate) and their homodimers Dbt-10, Dbo-10, Dil-10 with salmon DNA were studied using steady-state and time-resolved fluorescence spectroscopic methods. A significant increase in the quantum yield was observed for homodimer dyes upon binding to DNA. Quantum chemical calculations show the formation of the non-emissive TICT state in these dyes. The increase in fluorescence quantum yield upon dye binding to DNA is associated with the restriction of the dye fragments rotations relative to one another in the excited state. For these dyes, the binding constant (K_b) to DNA were determined. Binding affinity depends on molecular structure of studied dyes. It was found that the addition of NaCl to a DNA solution leads to the formation of H-aggregates on the nucleic acid surface. Theoretical modeling shows that monomer and homodimer dyes bind to DNA in the minor groove via hydrogen bonds, Van der Waals and hydrophobic forces, that are main factor in the interaction of probe molecules with nucleic acid.

Development fluorescence chemosensor for selectively detection of a particular analyte intriguing tuning environmental, biological and pharmaceutical applications. In this regard, a simple and cost-effective Schiff base molecular probe, namely, (E)-3-((thiazol-2-ylimino)methyl)-4 H-chromen-4-one (L) was designed. The molecular probe (L) was used to detect trace amounts of water in DMSO. Upon addition of water, to the DMSO solution of L, the fluorescence emission band decreased significantly, this phenomenon suggests that the quenching in fluorescence emission was attributed to the formation of aggregates, indicating characteristics of aggregation-caused quenching-emission (ACQE). On the other hand, the probe (L) was selectively sensing Zn²⁺ ions over other metal ions. The change in emission band (blue shifted ~ 68 nm) is due to supersession of photo-induced electron transfer (PET) and inhibition of -C = N isomerisation. Using the Benesi-Hilderbrand plot, the binding stoichiometry is found to be 1:1. Theoretical calculations (DFT and TDDFT) have been explored to find the binding mechanism of the formation of the complex. Using four clinical drug-resistant microorganisms, the disc diffusion technique was used to perform the antibacterial test of L and L-Zn²⁺. The highest ZOI of these is seen in B. subtilis and S. aureus, which had diameters of 13 mm and 15 mm in L-Zn²⁺ and 10 mm and 12 mm in L and lowest ZOI was found in E. coli and K. pneumoniae with 12 mm and 11 mm in L-Zn²⁺ and 8 mm and 6 mm in L. Even at the lowest dose in both samples, the MIC and MBC analyses verify that there is around 99.9% inhibition.

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.