Journal of Fluorescence最新文献

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.

Synozol Navy Blue poses severe ecological risks, necessitating advanced treatment approaches. Ni-Ag co-doped ZnO (Ni-Ag@ZnO) catalyst was synthesized via the sol-gel method and characterized using XRD, SEM-EDX, BET, UV-Vis, PL, and XPS. In contrast to previous research primarily focused on simple model dyes, this study demonstrates the effective degradation of Synozol Navy Blue, a highly resistant azo dye, utilizing Ni-Ag co-doped ZnO under visible light. Comprehensive characterization, including XPS analysis, offered valuable insights into the oxidation states and successful incorporation of Ni and Ag. Furthermore, scavenger studies, mineralization tests, and pH-dependent performance evaluations elucidated the mechanistic pathways and conditions that optimize photocatalytic activity. Ni-Ag doping reduced crystallite size from 35.4 to 29 nm and increased surface area from 1.89 to 2.54 m²/g, while narrowing the band gap from 3.42 to 3.28 eV. Photoluminescence confirmed reduced electron-hole recombination. Under optimized conditions of 75 mg/L dye concentration, 0.03 g/50 mL catalyst dosage, pH 2-, and 50-min contact time 10% Ni-Ag@ZnO doping ratio achieved 81% degradation efficiency under solar light irradiation, significantly outperforming pure ZnO. The process followed pseudo-first-order kinetics (k = 2 × 10⁻² min⁻¹) and attained 80% mineralization (TOC removal) in 60 min. Scavenging tests identified hydroxyl and superoxide radicals as the dominant reactive species, with IPA and BQ enhancing charge separation. These results establish 10% Ni-Ag@ZnO as a promising eco-friendly photocatalyst for wastewater remediation.

Trace-level nitrite detection is essential for environmental monitoring. We have developed a rapid, reagent-minimal method for the detection of trace amounts of nitrite. Our study focused on the spectral characteristics of the fluorescent probe 6-amino-1,3-naphthalenedisulfonic acid (ANDSA). We identified the fluorescence intensity at excitation and emission wavelengths of 278 nm and 465 nm, respectively, as the key indicator of nitrite quantification. This method, utilizing a 278 nm excitation wavelength, achieves high sensitivity for trace levels of nitrite. The incorporation of ultrasound assistance has reduced the detection time to 12 min. Through method optimization, only two reagents, sulfuric acid and potassium bromide, are required to form the ANDSA solution for sensitive nitrite detection. Nitrite addition reduces the fluorescence emission peak of ANDSA. In the nitrite concentration range of 0 to 3.2 µM, a strong exponential relationship exists between ANDSA's fluorescence response and nitrite concentration, conforming to the equation F₀/F = 0.94183 × e^(0.8766 C). The proposed method yields reliable results, with relative standard deviations ranging from 0.4% to 2.5% and recovery rates between 89.87% and 101.97% for real water samples. This method provides a highly sensitive solution for nitrite monitoring.

Meat adulteration poses significant challenges to public health and consumer trust, necessitating the development of effective detection methods. Isothermal nucleic acid amplification (NAA) techniques, such as loop-mediated isothermal amplification (LAMP) and polymerase spiral reaction (PSR), have emerged as rapid and cost-effective alternatives to conventional polymerase chain reaction (PCR). These techniques simplify infrastructure requirements and can enable naked-eye detection (NED) through visible color changes with specific dyes. This study highlights the potential and suitability of various dyes for the NED of IA-based meat adulteration detection. Intercalating dyes, such as SYBR Green I, bind to the amplified DNA and emit fluorescence. pH-sensitive dyes, including phenol red, neutral red, and xylenol orange, change color with pH shifts during amplification. Triphenylmethane dyes, such as crystal violet and malachite green, directly interact with DNA, showing no pH dependence. Intercalating dyes, such as SYBR Green I, achieve superior sensitivity, often reaching 10 fg of target DNA. Conversely, other dyes like Hydroxynaphthol blue and other pH-sensitive and pH-independent dyes provide slightly lesser sensitivity, typically ranging from 100 fg to 1 pg. Dye-based NED combined with IA offers advantages such as rapid results, high sensitivity and specificity, suitability for field testing, and potential integration into lab-on-chip systems. However, further research is required to optimize dye formulations, develop multiplex assays, enhance sample preparation for complex food matrices, and investigate novel isothermal methods and primer designs. Accurate standardization and validation of these techniques are crucial for their widespread adoption to ensure food safety and consumer trust in the meat industry.

In this study, we report a novel and practical tandem approach for synthesizing symmetric ketazines derived from the reaction of hydrazine hydrate and Acetophenone using nickel phosphate (NiP) as a heterogeneous nano-catalyst for the first time. The catalyst underwent comprehensive characterization using several techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, Ultraviolet-visible Spectroscopy (UV-Vis), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDS), X-ray diffraction (XRD), and N₂ adsorption-desorption isotherm using BET and BJH methods to define their structure and properties. The results demonstrate that the catalyst exhibited a high surface area of 266.10 m²/g and a heterogeneous nano- structure with high stability and reusability. The synthesized ketazines were analysed using Infrared Spectroscopy (IR) and Nuclear Magnetic Resonance (NMR) spectroscopy. Additionally, the fluorescence properties of the ketazines were tested under various conditions, such as different concentrations and solvents. Also, the same molecules were used in the detection of Fe²⁺ and Pb²⁺ ions in water. Notably, significant alterations in the fluorescence properties were observed.

The rational design of stable, earth-abundant quantum dots with tuneable electronic and optical properties is crucial for advancing sustainable optoelectronic and photocatalytic technologies. In this work, density functional theory (DFT) is employed to investigate pristine and 3d transition-metal (TM)-doped armchair hexagonal silicon carbide quantum dots (AH-SiC-QDs, Si₅₇C₅₇H₃₀). Structural analysis reveals that pristine AH-SiC-QDs exhibit high stability (5.612 eV), surpassing previously reported SiC- and AlN-based QDs. Upon TM incorporation, stability remains robust, with Ni-doping providing the strongest binding and Sc-doping the weakest. Electronic structure calculations show significant dopant-induced modifications in HOMO-LUMO distributions and bandgaps, where Ti- and Sc-doped systems achieve remarkable bandgap narrowing (1.056 and 0.919 eV), indicating strong hybridization between dopant and host states. Optical absorption studies demonstrate pronounced red-shifts into the visible and near-infrared regions, with Sc- and V-doped systems offering extended light-harvesting potential. Mulliken charge and natural bond orbital (NBO) analyses confirm strong donor-acceptor interactions, orbital rehybridization, and enhanced charge transfer, directly linking dopant chemistry to improved catalytic and optoelectronic behaviour. These findings establish TM-doped AH-SiC-QDs as versatile and highly tuneable platforms for next-generation photocatalysis and energy conversion applications.

Cancer remains a major global health challenge, requiring the development of novel therapeutic agents with high efficacy and minimal side effects. In this study, we designed and synthesised a series of hybrid molecules incorporating triazoles, Schiff bases and substituted aromatic motifs, targeting the key oncogenic proteins Bcl-2 and EGFR. The compounds were characterised using spectroscopic techniques and their physicochemical and computational insights were assessed using in silico tools. ADMET showed poor toxicity, Molecular docking studies revealed high binding affinities for both Bcl-2 (docking energies: -6.9 to -7.1 kcal/mol) and EGFR (-9.6 to -10.0 kcal/mol), with compound 5d showing the highest affinity. Molecular dynamics simulations confirmed the stability of the protein-ligand complexes over 200 ns, with RMSD, RMSF, Rg and SASA analyses confirming favourable binding interactions. The compounds showed excellent similarity to drugs, high gastrointestinal absorption and low risk of toxicity. These results suggest that the synthesised hybrids hold great promise as as potential dual-targeted anti-cancer agents warranting further experimental investigation.

In this study, we present a theoretical investigation of Graphene Quantum Dots (GQDs), a zero-dimensional derivative of two-dimensional graphene, as potential Förster Resonance Energy Transfer (FRET) probes. Using a cost-effective semi-empirical approach, we explore how surface functionalization with hydrogen (H), hydroxyl (-OH), and amino (-NH₂) groups systematically tunes the optical and electronic properties of GQDs. The passivation-dependent red-shifts observed in the emission spectra provide clear design rules for generating donor-acceptor pairs with strong spectral overlap. In particular, the yGQDs-rGQDs pair exhibits a Förster radius (R_o) of 6.47 nm, enabling efficient energy transfer over nanoscale distances. These results demonstrate that even simplified modeling can uncover fundamental trends in structure-property relationships of GQDs and predict their FRET performance with remarkable agreement to reported experimental spectra (< 5% error). Our findings highlight the potential of functionalized GQDs as versatile FRET probes and establish semi-empirical simulations as a practical screening tool for guiding the development of 2D material-derived fluorophores in biosensing and optoelectronic applications.

Structure-switching aptamers (SSAs) generate measurable signals through target-induced conformational changes, serving as sensitive molecular recognition elements. We developed a dual-fluorescence SSA for ochratoxin A (OTA) detection by inserting 2-aminopurine (2AP) into the OTA aptamer and hybridizing a complementary DNA (cDNA) strand at the 5' end. OTA binding induced the aptamer-cDNA duplex to form a G4, enhancing 2AP fluorescence at 370 nm. Together with the intrinsic fluorescence of OTA at 450 nm, this enabled ratiometric dual-fluorescence measurements without external quenchers or fluorophores. To elucidate the molecular mechanism, all-atom molecular dynamics (MD) simulations and spectroscopic experiments assessed the effects of cDNA hybridization sites and strand lengths on sensing performance. Simulations further examined OTA binding at various 2AP insertion sites. Apt@2AP-cDNA1, with cDNA hybridized to bases 1-12, exhibited a binding pattern closely resembling the original aptamer. Umbrella sampling simulations revealed similar binding affinities: 46.3 kJ/mol for Apt@2AP-cDNA1 and 43.2 kJ/mol for the original aptamer. Experimentally, Apt@2AP-cDNA1 converted to G-quadruplexes more efficiently than other designs. A ratiometric dual-fluorescence aptasensor using Apt@2AP-cDNA1 was developed, with a linear detection range of 10-800 nM, a detection limit of 5.9 nM. The dual-fluorescence ratiometric aptasensor has good selectivity and was proven effective for detecting OTA in beer samples.