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Fluorescence and absorption studies of DNA-Pd(II) complex interaction: Synthesis, spectroanalytical investigations and biological activities
摘要： Novel palladium(II) complexes (7a–7e) of substituted quinoline derivatives were synthesized. The complexes were characterized using various techniques such as thermogravimetric analysis (TGA), elemental analysis, conductance measurement, mass, absorption, infra‐red (IR), 1H NMR, 13C NMR and energy‐dispersive X‐ray spectroscopy (EDX). Complexes for herring sperm DNA (HS DNA) binding were explored and absorption titration and the binding constant (Kb) as well as Gibb's free energy were evaluated. Complex 7d exhibited the highest binding constant, therefore the thermodynamic parameters of 7d at different temperatures were evaluated. To support the results of the absorption titration, fluorescence titration, viscosity measurement and molecular docking studies were performed. The fluorescence quenching data as evaluated from Stern–Volmer equation were used to calculate KSV, K f and the number of binding sites. The results of all these studies were in good agreement with the absorption study. DNA electrophoretic mobility was performed to explore the possible application of metal complexes as artificial metallonucleases. The antibacterial activity of the complexes was accessed against different pathogenic bacteria and cytotoxicity was measured using brine shrimp and S. pombe.
关键词： Stern–Volmer equation,absorption titration,thermodynamic parameters,cytotoxicity,fluorescence quenching,artificial metallonuclease
更新于2025-09-23 15:23:52
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Synthesis and fluorescence studies of selected N-aryl-2-aminoquinolines: Effect of hydrogen bonding, substituents and ESIPT on their fluorescence quantum yields
摘要： N-aryl-2-aminoquinolines have been widely synthesised and used in biological applications. However, their luminescence properties have not been studied in detail. Herein a series of N-aryl-2-aminoquinolines was synthesised from substitution reaction between 2-chloroquinoline and anilines with different substituent groups gave sufficient yield from 72–90%. The fluorescence behaviour was investigated in toluene, ethyl acetate and ethanol. The result shows that fluorescence quantum yield of N-aryl-2-aminoquinolines was the highest in toluene, followed by in ethyl acetate and the lowest in ethanol. Quenched emission observed in ethanol is caused by site-specific fluorophore-solvent hydrogen bonding interactions, inducing deactivation of the quinolinyl ring system. The bell-shaped Hammett plot of various substituted compounds suggested that both strong electron donating and electron withdrawing groups caused significant quenching in the fluorescence quantum yields. Therefore, most types of substituent groups on the phenyl moiety, hydrogen bonding between the fluorophore and solvent, and excited-state intramolecular proton transfer (ESIPT) were found as crucial contributors to fluorescence quenching of N-aryl-2-aminoquinolines.
关键词： Substituent effects,ESIPT,Hydrogen bonding,N-aryl-2-aminoquinolines,Fluorescence quenching
更新于2025-09-23 15:23:52
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A magnetic and carbon dot based molecularly imprinted composite for fluorometric detection of 2,4,6-trinitrophenol
摘要： A magnetic molecularly imprinted composite was prepared by reverse microemulsion using carbon dots (CDs), Fe3O4 as the co-nucleus, and a molecularly imprinted polymer (MIP; with 2,4,6-trinitrophenol as the template) acting as recognition sites. The composite of type CD/Fe3O4@MIPs was characterized by transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), zeta potentiometric analysis, X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The results showed that the composite MIP has a spherical shape with average diameter of 200 nm. They also showed that the composite contains core-shell structures with several Fe3O4 nanoparticles and CDs embedded in each of the microsphere. The composite can extract 2,4,6-trinitrophenol (TNP) and has an imprinting factor of 3.6. It has high selectivity and sensitivity for TNP which acts as a quencher of the fluorescence of the CDs (with excitation/emission maxima at 370/470 nm). The limit of detection of this fluorometric TNP assay is 0.5 nM. The method was successfully applied to the determination of TNP in spiked tap water and river water samples, and recoveries ranged from 89.4% to 108.5% (with an RSD of <6%).
关键词： Fluorescence quenching,Fe3O4 nanoparticles,Stern-Volmer plot,Environmental pollutants,Reverse microemulsion method,Selective recognition,Molecularly imprinting
更新于2025-09-23 15:23:52
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Identification performance of two luminescent lanthanide–organic frameworks
摘要： By the reaction of organic ligands, 2-(3,4-dimethylphenyl)-1H-imidazole-4,5-dicarboxylic acid (H3DMPhIDC) and terephthalic acid (H2DCB) with Eu3+ or Tb3+ ions, respectively, two luminescent metal-organic frameworks (MOFs) [Ln(H2DMPhIDC)(DCB)]n [Ln = Eu (1); Tb (2)] have been constructed. Both MOFs 1 and 2 are isostructural and show two-dimensional structures, which were fully characterized by single crystal X-ray diffraction, elemental analysis, and infrared spectroscopy. Both MOFs have excellent thermal and water stability, and indicate characteristic lanthanide metallic luminescence. Importantly, they can significantly recognize Fe3+ cation in aqoues solutions. Their sensing mechanisms have been suggested according to structural analyses, PXRD data and UV-Vis determinations.
关键词： recognition,crystal structure,luminescent MOFs,fluorescence quenching
更新于2025-09-23 15:23:52
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Novel ELISA based on fluorescent quenching of DNA-stabilized silver nanoclusters for detecting E. coli O157:H7
摘要： Escherichia coli O157:H7 (E. coli O157:H7) is a potential threat to human health; thus, a rapid and sensitive method for detecting it is necessary. We designed a single-stranded DNA that contained an appended block and anchoring block. The appended block acted as a scaffold to prepare fluorescent Ag nanoclusters (AgNCs). The anchoring block contained Poly A, which bound with the surface of gold nanoparticles to quench the fluorescence of AgNCs. An interesting ELISA approach for detecting E. coli O157:H7 was established via fluorescent quenching of DNA-stabilized AgNCs by using a sandwich complex. The changes in fluorescence intensity of AgNCs were used to quantitatively detect E. coli O157:H7. The sensitivity for detecting E. coli O157:H7 reached 1.905 × 10^3 CFU/mL with a good linear range. Compared with conventional ELISA, the sensitivity of this technique increased by 30-fold. Moreover, this method demonstrated specificity and reproducibility and could be used in food samples.
关键词： Fluorescence quenching,Ag nanoclusters,Escherichia coli O157:H7,Gold nanoparticles
更新于2025-09-23 15:23:52
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Heterobimetallic (Fe <sup>II</sup> /Pt <sup>II</sup> )-Based Supramolecular Coordination Complexes Using 1,1′-Ferrocene Dicarboxylate: Self-Assembly and Interaction with Carbon Dots
摘要： The synthesis and characterization of a new pyrazine-based ditopic organoplatinum(II) complex having a bite angle of 180° is reported. The facile and efficient syntheses are described of three discrete neutral Fe(II)/Pt(II) heterobimetallic SCCs with Pt(II) acceptor clips of different binding angles, 0, 120, and 180°. These new SCCs were characterized by multinuclear NMR and mass spectrometry. Electrochemical response of these ferrocene containing self-assembled ensembles was studied using cyclic voltammetry. The diplatinum acceptor organometallic clips significantly quench the fluorescence of highly emitting carbon quantum dots (CD), while the self-assembled macrocycles tend to nullify the quenching effect of the organometallic clips. Interestingly, the inefficient quenching of CD fluorescence by these SCCs was found to be directly related to the angular disposition of the binding sites in the Pt(II) based organometallic clips.
关键词： carbon dots,heterobimetallic,electrochemical response,self-assembly,supramolecular coordination complexes,fluorescence quenching,ferrocene
更新于2025-09-23 15:23:52
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Photoinduced electron transfer in non-covalent free-base octaethylporphyrin and 2-nitrofluorene donor-acceptor system: A combined experimental and quantum chemical study
摘要： Photosynthetic reaction center functions through non-covalent incorporation into a well-defined transmembrane proteins. In the context of exploring photoinduced electron transfer (PET) in non-covalent donor-acceptor systems, we have investigated electron transfer from free-base octaethylporphyrin (OEP) donor to 2-nitrofluorene (2NF) acceptor in acetonitrile (ACN), a polar solvent. Steady-state and time-resolved emission spectroscopic studies in conjunction with density functional theory (DFT) calculations were employed to explore the electron transfer process. Quenching of the fluorescence emission intensity as well as fluorescence lifetime of the OEP upon excitation at the Q band of OEP at 300 K, is attributed to the PET from OEP to 2NF. Our DFT [wB97XD functional and 6-31G (d,p) basis set] calculations also support the interaction between donor and acceptor and also reveals the co-facial π-π interaction energy of ?24.6 kcal/mol with intermolecular distance b4 ?. Our results are expected to shed light on PET in non-covalent donor acceptor systems.
关键词： Marcus theory,Photoinduced electron transfer,Octaethylporphyrin,Second-order bimolecular fluorescence quenching constant,2-Nitrofluorene,DFT study by wB97XD/6-31G(d,p),Time-resolved emission spectroscopy
更新于2025-09-23 15:22:29
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A Signal-On Fluorosensor Based on Quench-Release Principle for Sensitive Detection of Antibiotic Rapamycin
摘要： An antibiotic rapamycin is one of the most commonly used immunosuppressive drugs, and also implicated for its anti-cancer activity. Hence, the determination of its blood level after organ transplantation or tumor treatment is of great concern in medicine. Although there are several rapamycin detection methods, many of them have limited sensitivity, and/or need complicated procedures and long assay time. As a novel fluorescent biosensor for rapamycin, here we propose “Q’-body”, which works on the fluorescence quench-release principle inspired by the antibody-based quenchbody (Q-body) technology. We constructed rapamycin Q’-bodies by linking the two interacting domains FKBP12 and FRB, whose association is triggered by rapamycin. The fusion proteins were each incorporated position-specifically with one of fluorescence dyes ATTO520, tetramethylrhodamine, or ATTO590 using a cell-free translation system. As a result, rapid rapamycin dose-dependent fluorescence increase derived of Q’-bodies was observed, especially for those with ATTO520 with a lowest detection limit of 0.65 nM, which indicates its utility as a novel fluorescent biosensor for rapamycin.
关键词： rapamycin,fluorescent biosensor,fluorescence quenching,photoinduced electron transfer,antibiotics
更新于2025-09-23 15:22:29
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Bonded-luminescent foam based on europium complexes as a reversible copper (II) ions sensor in pure water
摘要： Developing novel lanthanide complexes to rapidly and reliably sensing Cu2+ ions in pure water is highly challenging. Here, a series long luminescence lifetime luminescent Eu-complex polyurethane foams (Eu-PUFs) porous material by simple one-step co-polycondensation reaction has been successfully assembled. The photoluminescence (PL) results indicated that the pure red emission from Eu3+ ions is selectively quenched upon addition of Cu2+ ions, and barely any interference by other metal ions in pure water, thus making Eu-PUFs as a potential Cu2+ ions sensing material. The original luminescent intensity of Eu3+ ions located 617nm can be recovered about 84% by washing of ethylenediaminetetraacetic acid (EDTA) there times, indicating the sensing ability of Eu-PUFs is highly reversible. Due to the probe molecules Eu (TTA)3 ? Phen-NH2 was bonded into Eu-PUFs through covalent bond linker, so the Eu-PUFs sensors can be utilized to detection of Cu2+ ions in pure water multiple times (more than 20 times) without much effect on the sensitivity, and the limitation of detection (LOD) for Cu2+ in pure water is as low as 0.28 μM. All above mentioned results revealed these Eu-PUFs are excellent and potential Cu2+ ions sensing material in pure water and will be widely used in analytical and biological application fields.
关键词： copper (II) ions detection,fluorescence quenching,Europium complexes,Bonded-luminescent foam
更新于2025-09-23 15:22:29
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Determination of cochineal and erythrosine in cherries in syrup in the presence of quenching effect by means of excitation-emission fluorescence data and three-way PARAFAC decomposition
摘要： The simultaneous determination of two food colorants (cochineal (E-120) and erythrosine (E-127)) was achieved by means of excitation-emission fluorescence matrices and three-way PARAFAC decomposition together with the use of a calibration set that contained binary mixtures of both analytes. In the measured conditions, the amount of cochineal present in the sample affected the fluorescence signal of erythrosine since cochineal caused a quenching effect in the fluorescence of the other food additive. However, the signal of cochineal was not affected by the presence of erythrosine. A calibration line for erythrosine was built for each different concentration level of cochineal. The slopes of these regressions were different depending on the amount of quencher, whereas the intercepts were statistically equal to 0 at a 95% confidence level. The quantification of erythrosine was possible using the regression 'amount of cochineal' versus 'the slope of the calibration line for erythrosine'. Using this procedure, the mean of the absolute values of the relative errors in prediction for mixtures of both colorants were 5.86% (n = 10) for cochineal and 4.17% (n = 10) for erythrosine. Both analytes were unequivocally identified by the correlation between the pure spectra and the PARAFAC excitation and emission spectral loadings. Pitted cherries in syrup were analyzed. Cochineal and erythrosine were detected in those cherries at a concentration of 185.05 mg kg?1 and 10.76 mg kg?1, respectively. These concentration values were statistically equal to the ones obtained with a HPLC/DAD method.
关键词： Erythrosine,Cochineal,PARAFAC,Excitation-emission fluorescence,Quenching effect,Cherries
更新于2025-09-23 15:22:29