Journal of Fluorescence最新文献

Detection of tumor biomarkers is critical for early cancer diagnosis and cancer therapeutic monitoring, but traditional methods often lack sufficient sensitivity and specificity, especially at low biomarker concentrations. To address this challenge, in this study a multiplex detection platform based on core-shell quantum dot-encoded silica microspheres was developed for highly sensitive, simultaneous detection of multiple tumor biomarkers in a single assay. The core-shell silica architecture provides a high surface area for bioconjugation, while embedded quantum dots (QDs) offer strong fluorescence, making them ideal labels. Carbon quantum dots (CQDs), which have low toxicity, superior biocompatibility, and high photostability, were used as reporter molecules instead of organic dyes. This choice improved detection sensitivity and reduced the detection system's environmental toxicity relative to traditional dye-based assays. After optimizing QD-silica conjugation and immunoassay conditions, the platform achieved highly sensitive multiplex detection of four tumor biomarkers (AFP, CEA, CA125, CA19-9) commonly used in early cancer screening. Results demonstrated specific detection of all four targets within a short time frame, with excellent stability and reproducibility. By enhancing sensitivity for these biomarkers and reducing assay toxicity while improving stability, this platform shows significant potential to greatly improve early cancer screening and cancer therapeutic monitoring in clinical practice.

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 Sm³⁺- doped NaCaBi₂(PO₄)₃ (NCBP: xSm³⁺, x = 0.02-0.14 mol) phosphors were synthesized via a conventional solid-state method. Phase purity, morphology and elemental composition were confirmed through PXRD data, FESEM images and EDAX analysis respectively. The Rietveld refinement analysis was performed and crystal structure was modelled using VESTA software. The optical energy band gap values were estimated from DRS measurements. Photoluminescence studies under 403 nm excitation revealed characteristic Sm³⁺ emissions at 563, 600, 647, and 707 nm (⁴G_5/2 → ⁶H_J).The emission intensity increased with Sm³⁺ concentration up to x = 0.08 mol, beyond which concentration quenching occurred due to non-radiative energy transfer predominantly through dipole-dipole interactions among Sm³⁺ ions. Lifetime measurements for the 600 nm emission revealed a systematic decrease in decay lifetime with increasing Sm³⁺ doping, supporting the observed quenching mechanism.The optimized composition (x = 0.08 mol) exhibited good thermal stability. The temperature dependent luminescence lifetime of the NCBP:0.08Sm³⁺ phosphor was measured under excitation at 403 nm and emission at 600 nm showed that the relative sensitivity is increasing from 0.21% °C^- 1 at 30 °C to 0.35% °C^- 1 at 210 °C. The CIE coordinates (0.590, 0.408) and low CCT (1647 K) confirmed efficient orange-red emission of the prepared sample. The internal quantum efficiency of the optimum phosphor was measured to be 33.32%. The calculated Judd-Ofelt intensity parameters confirm the low local symmetry and high covalency of the environment within the lattice, resulting in efficient radiative transitions. These results highlight the potential of NCBP: Sm³⁺ as a multifunctional phosphor for warm white solid-state lighting and temperature-sensing applications.

The hydrazide functional group is known for its specific recognition of peroxynitrite. Upon incorporation into rhodamine fluorophores, the resulting fluorescent probes have been widely used for the real-time tracking of peroxynitrite in biological systems. However, the lack of in-depth research on the fundamental reaction mechanism in peroxynitrite detection has limited the optimization of these probes. In this study, we developed two hydrazide-based peroxynitrite probes by linking hydrazine moiety to rhodamine and thio-rhodamine. The responsiveness of these probes toward peroxynitrite was also systematically investigated. Theoretical calculations indicate that the key mechanism of hydrazide-based probes in peroxynitrite detection lies in the reduced Gibbs free energy difference between the ring-open and ring-closed isomers of the oxidized intermediate, which thereby facilitates the ring-opening process. Overall, this study elucidates the reaction mechanism of hydrazide-based peroxynitrite probes from the perspective of Gibbs free energy, providing valuable insights for the rational design and optimization of rhodamine ring-opening probes.

A dual-responsive fluorescent chemosensor based on a 1,3,4-oxadiazole-linked bis-indole scaffold (FM) was developed for the selective and sensitive detection of 2,4,6-trinitrophenol (TNP) and iron ions (Fe³⁺ and Fe²⁺) in aqueous media. The probe exhibits strong photophysical properties, including a prominent emission at 438 nm and a large Stokes shift of 79 nm. Upon interaction with TNP or iron ions, a significant fluorescence "turn-off" response and bathochromic shifts were observed, attributed to π-π stacking, hydrogen bonding, and coordination interactions. Job's plot analysis revealed a 2:3 binding stoichiometry for TNP and 1:1 for both iron species, indicating distinct recognition mechanisms. For TNP, a high Stern-Volmer quenching constant (K_sv = 113.98 × 10³ M⁻¹) and a low detection limit (LOD = 59 nM) were obtained, outperforming many previously reported sensors. The probe also demonstrated reliable detection of Fe³⁺ and Fe²⁺ ions with LOD values of 2.95 µM and 16.2 µM, respectively. The FM sensor exhibited excellent photostability, rapid response (< 30 s), and high selectivity in the presence of competing analytes. Furthermore, a paper-based detection platform was successfully fabricated, enabling rapid visual detection of TNP under UV and daylight. These results highlight FM as a promising fluorescent sensor for environmental and security-related applications involving nitroaromatic explosives and metal ions.

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.

The temperature-dependent photophysical behavior of Coumarins 6 (C6), 7 (C7), and 30 (C30) was systematically investigated in non-polar alkane solvents (n-heptane, cyclohexane and n-hexadecane) across 303-343 K. Using steady-state absorption and photoluminescence together with time-resolved fluorescence (TCSPC), we quantified emission maxima shifts, quantum yields (Φ), fluorescence lifetimes (τ) and derived first-order rate constants (k_f, k_nr) with propagated uncertainties. Small blue shifts in absorption and emission with heating indicate reduced solute-solvent stabilization. C6 in n-hexadecane showed increased radiative contribution at higher temperature, C7 exhibited high thermal robustness with minimal k_nr activation, and C30 was most sensitive to thermal activation in cyclohexane. Arrhenius analysis of lnk_nr versus 1/T yields activation energies in the range 0.3-5.7 kJ·mol⁻¹ (reported with standard errors). All Φ values were corrected for temperature-dependent refractive index (n(T)) and Förster-Hoffmann analysis lnk_nr vs. ln(η/T) confirms viscosity as a primary control parameter. These quantitative results clarify how solvent viscosity and molecular structure modulate LE-ICT balance and inform the design of thermally stable coumarin fluorophores for sensing and optoelectronic applications.

Schiff base tethered 1,2,3-triazole (TBT) having excellent optical properties were examined via fluorescence and UV-vis spectroscopy that revealed it to be a highly selective and sensitive Lead and Copper ions sensor. TBT exhibited colorimetric changes for the Cu²⁺ and Pb²⁺ ions in the solution form. The probe TBT exhibited ultra-low detection limit of 190 pM and 130 pM for the Cu²⁺ and Pb²⁺ ions respectively. The Job's plot analysis confirmed the 1:1 stoichiometry of TBT-Cu²⁺ and TBT-Pb²⁺ complexes and time dependent, pH titration, and the reversibility, mimicking INHIBIT logic gate, were also explored photo-physically. Moreover, TBT-Cu(II) and TBT-Pb(II) complexes were studied via DFT studies at the B3LYP/6-311G++(d, p)/LANL2DZ depicting their binding interactions that supplemented with their experimental FTIR and mass analysis. Furthermore, the practical utility of sensor TBT was validated in real water samples with exclusive Pb(II) and Cu(II) ions detection imminent potential in environmental and analytical applications.

Enhancing fluorescence image brightness is critical for improving the detection sensitivity in analytical applications. In this study, we evaluated the respective contributions of (i) the overlap between the photonic stop band (PSB) wavelength (λ_PSB) of a hydrogel-based inverse opal photonic crystal (IOPC) and the emission wavelength (λ_emi) of a fluorescent dye, and (ii) the pore diameter (d) of the IOPC, which governs the fluorophore loading capacity, to the overall fluorescence intensity. The overlap was selected by employing a consistent d and a specific dye, Alexa Fluor™ 488 (A488). Meanwhile, the variation in fluorescence intensity (I_fluor.) with respect to d was normalized, revealing that although d reached 90% of the value at which wavelength overlap occurred (d_overl.), I_fluor. increased to only 59%. However, when d increased to 110% and 125% of d_overl., I_fluor reached only 75.6% and 77.1%, respectively. This suggested that the overlap effect was the key factor contributing to the enhancement of the I_fluor. compared with the contribution from an increase in d. In addition, this result highlighted the potential application of the IOPC with an overlap between λ_PSB and λ_emi for the detection of Escherichia coli (E. coli). Although IOPC samples with d value reached 110% and 125% of d_overl were used, I_fluor. only reached 71.6% and 78.4%, respectively, of the value at which the overlap occurred. The limit of detection (LOD) and linear range were 10 cfu/mL and 10 ÷ 10⁵ cfu/mL (R² = 0.91), respectively. This indicated the potential application of the hydrogel IOPC exhibiting the overlap effect for analytical detection based on fluorescence imaging.

Carbon quantum dots (CQDs), a novel class of zero-dimensional carbon-based nanomaterials, have attracted widespread interest due to their remarkable optical, electronic, and chemical properties, such as tunable photoluminescence, excellent biocompatibility, high surface area, and environmental friendliness. In this study, we report a facile, efficient, and scalable synthesis route for CQDs via a one-pot hot injection technique. This method involves the controlled thermal decomposition of an organic carbon precursor in the presence of a high-boiling point solvent and a surface passivation agent, enabling the formation of well-dispersed, highly luminescent CQDs with uniform particle size distribution. The synthesized CQDs exhibit strong and stable photoluminescence emission, which can be attributed to their quantum confinement effect and abundant surface functional groups introduced during synthesis. To explore their potential in environmental applications, the photocatalytic activity of the CQDs was evaluated by monitoring the degradation of Indigo Carmine (IC), a commonly used but environmentally persistent dye, under ultraviolet (UV) irradiation. The CQDs demonstrated outstanding photocatalytic performance, achieving significant degradation efficiency within a short irradiation period. The enhanced photocatalytic behavior is attributed to their efficient light-harvesting capability, rapid charge separation, and generation of reactive oxygen species. Radical scavenging studies were also carried out to understand the mechanism behind photocatalytic degradation of IC dye using carbon dots. This study not only introduces a straightforward and reproducible method for synthesizing high-performance CQDs but also highlights their effectiveness as a standalone photocatalyst for dye degradation. The findings pave the way for the development of sustainable nanomaterials for advanced environmental remediation technologies.