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Ab initio model for the chlorophyll-lutein exciton coupling in the LHCII complex
摘要： 2A_g^- state of lutein plays a crucial role in photoprotection of higher plants. Due to its multiconfigurational nature, accurate description of this electronic state and respective transition properties is a formidable task. In this paper, applicability of various CASSCF and RASSCF formulations for description of the 2A_g^- state is discussed. It is shown that inclusion of the entire π-system of lutein into the active space is required for accurate calculation of transition properties. Exciton coupling in the chlorophyll-lutein dimer involved in non-photochemical quenching in the LHCII complex was calculated to provide a connection between pigment interactions and non-photochemical quenching regulation.
关键词： non-photochemical quenching,MCSCF,Xanthophyll,lutein,exciton coupling,LHCII
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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Graphene oxide-quenching-based fluorescence in situ hybridization (G-FISH) to detect RNA in tissue: Simple and fast tissue RNA diagnostics
摘要： FISH-based RNA detection in paraffin-embedded tissue can be challenging, with complicated procedures producing uncertain results and poor image quality. Here, we developed a robust RNA detection method based on graphene oxide (GO) quenching and recovery of fluorescence in situ hybridization (G-FISH) in formalin-fixed paraffin-embedded (FFPE) tissues. Using a fluorophore-labeled peptide nucleic acid (PNA) attached to GO, the endogenous long noncoding RNA BC1, the constitutive protein β-actin mRNA, and miR-124a and miR-21 could be detected in the cytoplasm of a normal mouse brain, primary cultured hippocampal neurons, an Alzheimer’s disease model mouse brain, and glioblastoma multiforme tumor tissues, respectively. Coding and non-coding RNAs, either long or short, could be detected in deparaffinized FFPE or frozen tissues, as well as in clear lipid-exchanged anatomically rigid imaging/immunostaining-compatible tissue hydrogel (CLARITY)-transparent brain tissues. The fluorescence recovered by G-FISH correlated highly with the amount of miR-21, as measured by quantitative real time RT-PCR. We propose G-FISH as a simple, fast, inexpensive, and sensitive method for RNA detection, with a very low background, which could be applied to a variety of research or diagnostic purposes.
关键词： glioblastoma multiforme tumor,tissue RNA diagnostics,Graphene oxide-quenching-based fluorescence in situ hybridization (G-FISH),Alzheimer’s disease,formalin-fixed paraffin-embedded (FFPE) tissue
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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A turn-on fluorescent probe for vitamin C based on the use of a silicon/CoOOH nanoparticle system
摘要： The authors describe a fluorometric method for the turn-on determination of vitamin C (ascorbic acid). The blue fluorescence of silicon nanoparticles (SiNPs; with excitation/emission maxima at 350/450 nm) is found to be quenched by CoOOH nanoparticles (NPs). In the presence of vitamin C, the CoOOH NPs are decomposed by a redox reaction between the diol group of vitamin C and CoOOH NPs. As a result, fluorescence recovers. On the basis of this finding, a fluorometric method was designed for the turn-on detection of vitamin C. Under optimal conditions, the method has a low detection limit (0.47 μM) and a linear response in the 0.5 μM to 20 μM a concentration range. It was successfully applied to the determination of vitamin C in spiked red grape and orange juice, and in vitamin C tablets.
关键词： Fluorescence Bturn-on^ strategy,Cobalt oxyhydroxide nanoparticles,Fluorometry,Stern-Volmer plot,Surface energy transfer,Redox reaction,Inner filter effect,Quenching,Silicon nanoparticles
更新于2025-09-23 15:23:52
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Structure variation and luminescence enhancement of BaLaMg(Sb, Nb)O6:Eu3+ double perovskite red phosphors based on composition modulation
摘要： A series of BaLaMgSb1-xNbxO6:Eu3+ double perovskite red phosphors was successfully obtained. X-ray diffraction and Rietveld refinement analyses were conducted to determine the phase information and the detailed structure parameters. The coordinate variations of both La3+/Eu3+ and Sb5+/Nb5+ were discussed to elucidate the influence of B-site ion doping on the lattice variation. Luminescence properties, excitation and emission spectra, were presented to show the advantages of doping with Nb5+ ion. Ultraviolet-vis diffuse reflectance spectra were performed to reveal the reason for the decreased emission intensity under the charge transfer band excitation. Moreover, band gap energy was estimated to clarify the relationship between the increased intensity (λex = 395 and 465 nm) and Nb5+ concentration. Intensity ratios of I(615)/I(590) were performed to show the symmetry variation of the lattice. Thermal quenching property was also investigated and the quenching mechanism was discussed in detail based on the ionization process.
关键词： White LED,Structure variation,Thermal quenching mechanism,Double perovskite
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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Luminescence quenching properties of Sr2Ga2GeO7: Pr3+ with and without traps participation
摘要： Thermal quenching has been extensively regarded as one of the most signi?cant challenges that limits the application of phosphors in today's world. Further e?ort is urgently required to understand the mechanism of thermal stability for achieving the improved performance of these phosphors. Sr2Ga2GeO7: Pr3+ has been synthesized by the conventional high temperature solid state reaction. A dominant green emitting is presented for the partial energy transition quenching process of the 3P0→3H4 emission. The defect states structure is improved via the introducing of co-solvents, and the thermal stability of 1D2→3H4 and 3P0→3H4 levels can be further adjusted. The intervalence charge transfer (IVCT) and traps are introduced to explain the luminescence quenching properties of Sr2Ga2GeO7: Pr3+. The synergy of various models will provide a new idea for improving the luminescence stability of phosphors in the future.
关键词： Partial energy transition,Thermal quenching,IVCT,Mechanism
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