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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
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Synthesis, Anticonvulsant and Binding Interaction Study of Novel Piperamides with Bovine Serum Albumin by Fluorescence Spectroscopy
摘要： A series of piperamides (PA) 8a-j were designed, synthesized and evaluated for their antimicrobial and anticonvulsant activity. Compounds 8a and 8h showed considerable antibacterial activity against B. subtilis with minimum inhibitory concentration (MIC) of 8 and 10 μg/mL, respectively. Compounds 8a and 8h showed advanced anticonvulsant activity as well as lower neurotoxicity than the reference drugs. The interaction between bovine serum albumin (BSA) and PA was investigated using fluorescence quenching and UV-vis absorption spectroscopy. Results showed that PA could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The binding constant and number of binding sites of PA with BSA were obtained. The binding distance was calculated based on Forster non-radiative energy transfer theory.
关键词： Anticonvulsant,bovine serum albumin,fluorescence quenching,piperamide
更新于2025-09-23 15:22:29
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Fluorescence Quenching-Based Mechanism for Determination of Hypochlorite by Coumarin-Derived Sensors
摘要： A fluorescence quenching-based mechanism for the determination of hypochlorite was proposed based on spectroscopic and chromatographic studies on the hypochlorite-sensing potency of three structurally similar and highly fluorescent coumarins. The mode of action was found to rely upon a chlorination of the coumarin-based probes resulting from their reaction with sodium hypochlorite. Importantly, the formation of chlorinated derivatives was accompanied by a linear decrease in the fluorescence intensities of the probes tested. The results obtained suggest the applicability of a coumarin-dependent hypochlorite recognition mechanism for the detection of, as well as for quantitative determination of, hypochlorite species in vitro.
关键词： fluorescence quenching,coumarin,hypochlorite sensing
更新于2025-09-23 15:22:29
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Photoluminescence Characteristics of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as New Orange-red Phosphors
摘要： A series of Sm3+-doped LnBWO6 (Ln=La, Gd and Y) phosphors with orange-red light emitting in pure phase were prepared by high temperature solid-state process. The crystal structure, photoluminescence properties, decay lifetimes and thermal stability properties of those as-prepared samples were investigated. Those phosphors can be efficiently excited by near-UV and blue light and emitted orange-red luminescence with color coordinates (0.622, 0.377). Among those LnBWO6 (Ln=La, Gd and Y) hosts, the emission intensities of Sm3+-doped LaBWO6 are the strongest ones. The optimum doping concentration and critical energy transfer distance of Sm3+ ions in LaBWO6 were determined. The fluorescence concentration quenching mechanism was attributed to the dipole-dipole interaction between the Sm3+ ions. The fluorescent thermal quenching studies showed Sm3+ doped LaBWO6 had high thermal-stable properties. The present work suggested that Sm3+-doped LnBWO6 (Ln=La, Gd and Y) as orange-red phosphors exhibited potential application in white LED.
关键词： red phosphors,concentration quenching,energy transfer,white LEDs,luminescent properties
更新于2025-09-23 15:22:29
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High-efficiency blue phosphorescent organic light-emitting devices with low efficiency roll-off at ultrahigh luminance by reduced the triplet-polaron quenching
摘要： High performance phosphorescent organic light-emitting devices (PhOLEDs) at high luminance are still a remaining problem needing to be solved, especially blue PhOLEDs. Here, 5-(5-9H-carbazol-9-yl) pyridin-2-yl)-8-(9H-carbazol-9-yl) -5H-pyrido [3, 2-b] indole (p2PCB2CZ) with excellent characteristics as host is designed to realize a novel host-guest system without hole trapping effect in blue PhOLEDs. The device in which p2PCB2CZ and Bis (3, 5-difluoro-2-(2-pyridyl) phenyl-(2-carboxypyridyl)iridium(III) (FIrpic) is used as host and guest, respectively, is proposed to improve the performances of blue PhOLEDs at high luminance, especially ultrahigh luminance (>30000 cd/m2). The maximum external quantum efficiency (EQE) of this type blue PhOLEDs is 19.2%, while the maximum EQE of reference blue PhOLEDs is 18.7 %. Nevertheless, the p2PCB2CZ-based devices exhibit significant advantage at high luminance, because its EQE still attains to 10.8% even when the luminance increases to 30000 cd/m2, which is 1.67 times that of the reference device. From measurements based on steady-state and time-resolved spectroscopy, the reduction of triplet-polaron quenching in p2PCB2CZ-based devices is proved to the main reason for improving the performances of blue PhOLEDs at high luminance.
关键词： Ultrahigh luminance,Efficiency roll-off,Blue PhOLED,Hole trapping,Triplet-polaron quenching.
更新于2025-09-23 15:22:29
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Near White Light Emission and Concentration Quenching of Calcium Titanate Doped with Dysprosium (III) Phosphors
摘要： This paper reports the preparation of CaTiO3 doped with various concentrations of Dysprosium (II) using solid state reaction technique. X-ray diffraction patterns of the sample were taken. Observed XRD pattern was matched using software match2!. The pattern was matched significantly with the crystallographic open database card (COD – 96-101-1212) which is a standard card for CaTiO3. This matching exhibited that, the prepared sample is cubic in structure with space group P m ? 3 m (221). Photoluminescence (PL) studies of the samples were also done. PL intensity was found increasing with increasing dopant concentration and maximum intensity was noted at 2.0 mol% concentration of Dy3+, thereafter concentration quenching occurred. Emission Peaks were centered at 483 nm (4F9/2?6H15/2) and 576 nm (4F9/2?6H13/2) respectively. For studying the concentration quenching, the critical distance for energy transfer and electric multipolar character were estimated. The value of multipolar character expressed that, the transition in emission spectra is a dipole – dipole (d-d) transition. Commission Internationale de l’éclairage (CIE) coordinates was found as (0.36, 0.39), which is near to white light. Colour Correlated Temperature (CCT) was 4489 K which was indicative of cool appearance of the light emitted.
关键词： White LED,Concentration quenching,Photoluminescence
更新于2025-09-23 15:22:29
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Fluorene – Triazine Conjugated Porous Organic Polymer Framework for Superamplified Sensing of Nitroaromatic Explosives
摘要： A porous organic polymer with fluorene and triazine units (PTF), was synthesised through a simple cost effective method. The material was well characterised by FT-IR, solid state 13C NMR and X-ray photoelectron spectroscopic studies. Absorption spectrum indicated the electronic coupling between the two units in the polymer backbone. Experiments proved high thermal and chemical stability, and porous nature of the material. Luminescence of PTF was quenched, on the addition of ppb level concentration of nitroaromatic compounds. This was attributed to the photo induced electron transfer from the electron rich polymer backbone to the electron deficient nitro aromatic compounds. The observed superamplification effect in the fluorescence quenching was studied extensively by a series of ground state absorption, steady state and time resolved fluorescence experiments. Finally, the superamplified quenching was successfully assigned to static quenching by quenching sphere of action model. High value of static quenching constant of the order of 3.9 × 103 M-1, for picric acid combined with detection limit as low as 89 ppb envisages PTF as an effective chemosensor for nitroaromatic explosives.
关键词： sphere of action model,porous polymer,fluorescence life-time,Stern-Volmer plot,cyanuric chloride,fluorescence quenching
更新于2025-09-23 15:21:21
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Photoinduced Electron Transfer in Carbon Dots with Long Wavelength Photoluminescence
摘要： Carbon dots have often been studied to investigate their unique optical properties such as excitation wavelength-independence emission. Carbon dots have also been shown to undergo electron transfer in different situations. This study endeavors to investigate the properties of carbon dots photoluminescence and electron transfer. Herein, the preparation and characterization of carbon dots which exhibit long wavelength photoluminescence has been reported. These carbon dots exhibit quenching when exposed to metal ions in proportion to the reduction potential of the metal, which experimental evidence has shown for the first time. This property of metal ion reduction potential-dependent quenching has been studied to show the collisional electron transfer from amine groups in carbon dots to the metal ions. Therefore, the photoluminescence in these carbon dots are directly related to organic functional groups on the surface of the carbon dots.
关键词： Quenching,Electron transfer,Photoluminescence,Carbon dots,Metal ions
更新于2025-09-23 15:21:21
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Ultrathin Y <sub/>2</sub> O <sub/>3</sub> :Eu <sup>3+</sup> nanodiscs: spectroscopic investigations and evidence for reduced concentration quenching
摘要： Here, we report the synthesis and spectral properties of ultrathin nanodiscs (NDs) of Y2O3:Eu3+. It was found that the NDs of Y2O3:Eu3+ with a thickness of about 1 nm can be fabricated in a reproducible, facile and self-assembling process, which does not depend on the Eu3+ concentration. The thickness and morphology of these NDs were determined with small angle x-ray scattering and transmission electron microscopy. We found that the crystal field in these nanoparticles deviates from both the cubic and monoclinic characteristics, albeit the shape of the 5D0 → 7FJ (J = 0, 1, 2) transitions shows some similarity with the transitions in the monoclinic material. The Raman spectra of the non-annealed NDs manifest various vibration modes of the oleic acid molecules, which are used to stabilise the NDs. The annealed NDs show two very weak Raman lines, which may be assigned to vibrational modes of Y2O3 NDs. The concentration quenching of the Eu3+ luminescence of the NDs before annealing is largely suppressed and might be explained in terms of a reduction of the phonon density of states.
关键词： nanodiscs,small angle x-ray scattering,europium-doped yttrium oxide,Raman spectroscopy,concentration quenching,transmission electron microscopy,luminescence
更新于2025-09-23 15:21:21
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Optical oxygen sensing by MPA-capped CdTe quantum dots immobilized in mesoporous silica
摘要： A novel nanocomposite luminescent material was prepared by taking advantage of the versatile wet impregnation method for the dispersion of CdTe quantum dots (QDs) into mesoporous silica host matrix and thus providing great interaction between oxygen and QDs, with potential application in an optical oxygen sensor. The optical/spectroscopic properties of the QDs suspended in aqueous media and incorporated in mesoporous silica were evaluated as a function of aging time, temperature variation and oxygen concentration. Luminescence quenching studies were carried out for both QDs suspended in solution and loaded into the silica matrix, in the presence of varying O2 concentration. By Stern-Volmer plot analysis, obtained at different temperatures, it was possible to verify the existence of two types of emission quenching mechanisms for CdTe QDs. After aging for 120 days at room temperature, the QDs in colloidal suspension displayed a small red-shifted emission, which was interpreted as a decreased bandgap energy owing to the increase in the nanocrystal size. In contrast, the emission spectrum of CdTe QDs loaded into the mesoporous SiO2 matrix remained unchanged after aging for the same time at ambient temperature. The presented results will contribute to the discernment of oxygen quenching mechanisms and chemical stability of optical sensors based on CdTe QDs.
关键词： oxygen sensors,mesoporous silica,Quantum Dots,CdTe,wet impregnation,fluorescence quenching
更新于2025-09-23 15:21:01