Lanthanide‐doped vanadate thin films offer (i) a promising platform for luminescence‐based noncontact temperature sensing; (ii) ratiometric/self‐referencing absolute measurements; (iii) exceptional ...repeatability and reversibility for multirun uses and a long life cycle; (iv) 2% K−1 maximum temperature sensitivity (among the highest recorded for inorganic nanothermometers); (v) a temperature resolution greater than 0.5 K; and (vi) the potential for high‐resolution 2D temperature mapping.
•Botanical origin of honey can be obtained from PARAFAC analyses of fluorescence EEM.•Method provides detection of fake honey samples with 100% sensitivity and specificity.•Fluorescence of phenolic ...and Maillard reaction compounds shows the largest variance.
Fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) and Partial least squares Discriminant Analysis (PLS DA) were used for characterization and classification of honey. Excitation emission spectra were obtained for 95 honey samples of different botanical origin (acacia, sunflower, linden, meadow, and fake honey) by recording emission from 270 to 640nm with excitation in the range of 240–500nm. The number of fluorophores present in honey, excitation and emission spectra of each fluorophore, and their relative concentration are determined using a six-component PARAFAC model. Emissions from phenolic compounds and Maillard reaction products exhibited the largest difference among classes of honey of different botanical origin. The PLS DA classification model, constructed from PARAFAC model scores, detected fake honey samples with 100% sensitivity and specificity. Honey samples were also classified using PLS DA with errors of 0.5% for linden, 10% for acacia, and about 20% for both sunflower and meadow mix.
Synthesis of Eu(3+)- and Er(3+)/Yb(3+)-doped GdVO4 nanoparticles in reverse micelles and their multifunctional luminescence properties are presented. Using cyclohexane, Triton X-100, and n-pentanol ...as the oil, surfactant, and co-surfactant, respectively, crystalline nanoparticles with ~4 nm diameter are prepared at low temperatures. The particle size assessed using transmission electron microscopy is similar to the crystallite size obtained from X-ray diffraction measurements, suggesting that each particle comprises a single crystallite. Eu(3+)-doped GdVO4 nanoparticles emit red light through downconversion upon UV excitation. Er(3+)/Yb(3+)-doped GdVO4 nanoparticles exhibit several functions; apart from the downconversion of UV radiation into visible green light, they act as upconvertors, transforming near-infrared excitation (980 nm) into visible green light. The ratio of green emissions from (2)H11/2 → (2)I15/2 and (4)S3/2 → (4)I15/2 transitions is temperature dependent and can be used for nanoscale temperature sensing with near-infrared excitation. The relative sensor sensitivity is 1.11%K(-1), which is among the highest sensitivities recorded for upconversion-luminescence-based thermometers.
Abstract The present study compared the photothermal anticancer activity of near-infrared (NIR)-excited graphene nanoparticles and carbon nanotubes (CNT). Despite lower NIR-absorbing capacity, ...suspension of polyvinylpyrrolidone-coated graphene sheets exposed to NIR radiation (808 nm, 2 W/cm2 ) generated more heat than DNA or sodium dodecylbenzenesulfonate-solubilized single-wall CNT under the same conditions. Accordingly, graphene nanoparticles performed significantly better than CNT in inducing photothermal death of U251 human glioma cells in vitro. The superior photothermal sensitivity of graphene sheets could be largely explained by their better dispersivity, which has been supported by a simple calculation taking into account thermodynamic, optical and geometrical properties of the two type of carbon nanoparticles. The mechanisms of graphene-mediated photothermal killing of cancer cells apparently involved oxidative stress and mitochondrial membrane depolarization resulting in mixed apoptotic and necrotic cell death characterized by caspase activation/DNA fragmentation and cell membrane damage, respectively.
•EEM spectra of cereal flours are measured and modelled by PARAFAC.•PARAFAC provided excitation and emission spectra of dominant flour fluorophores.•PLS-DA using PARAFAC scores is used for ...classification of flours.
This paper presents parallel factor analysis (PARAFAC) of fluorescence of cereal flours. Excitation-emission matrices (EEM’s) of different cereal flours (wheat, corn, rye, rice, oat, spelt, barley and buckwheat) were measured in a front-face configuration over the ultraviolet–visible spectral range. EEM’s showed that flours strongly fluoresce in two spectral regions, where amino acids, tocopherols, pyridoxine and 4-aminobenzoic acid show intense emissions. 4-component PARAFAC was used to model flour fluorescence and to decompose EEM’s into excitation and emission spectra of each component. PARAFAC also provided relative concentrations of these components. The largest differences between flours were found in the concentration levels of the first and third component. Finally, variations in concentrations of PARAFAC modelled components were analysed in relation to the botanical origin of flour samples.
Abstract
Judd–Ofelt theory is a cornerstone of lanthanides’ spectroscopy given that it describes 4f
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emissions and absorptions of lanthanide ions using only three intensity parameters. A ...self-referenced technique for computing Judd–Ofelt intensity parameters from the excitation spectra of Eu
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-activated luminescent materials is presented in this study along with an explanation of the parametrisation procedure and free user-friendly web application. It uses the integrated intensities of the
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transitions in the excitation spectrum for estimation and the integrated intensity of the
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magnetic dipole transition for calibration. This approach facilitates an effortless derivation of the Ω
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intensity parameter, which is challenging to compute precisely by Krupke’s parametrisation of the emission spectrum and, therefore, often omitted in published research papers. Compared to the parametrisation of absorption spectra, the described method is more accurate, can be applied to any material form, and requires a single excitation spectrum.
In this paper we will be presenting JOES (Judd-Ofelt from Emission Spectra), an application software for calculation of the Judd-Ofelt intensity parameters and derived quantities from the emission ...spectra of Eu3+ doped materials. The program is written to be user friendly and it requires no previous experience in the field of study. This Free and Open-Source program written in JAVA, works on Windows, Linux and MAC OS operating systems. Program has been tested on three europium doped oxides with good luminescent properties: TiO2:Eu3+, ZrO2:Eu3+ and Nb2O5:Eu3+. We wish to give to the researchers this theoretical tool which can make the calculations easier, faster and more reliable.
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Defect-fluorite structured Eu3+-doped Y2Sn2O7 nanoparticles (30–40 nm) were successfully prepared through a facile co-precipitation method without any organic additives or templates followed by ...calcination in air. Luminescent properties of the as-prepared Y2-xEuxSn2O7 (0.02 ≤ x ≤ 0.6) nanophosphors were fully characterized from an experimental and theoretical point of view (excitation, emission, lifetime, critical concentration, temperature-dependent luminescence and thermal stability, type of interactions and the Judd-Ofelt analysis). The nanophosphors showed relatively sharp excitation bands from 360 to 530 nm and exhibited characteristic emission bands with the most intensive emission centered at 612 nm. In addition, Gd1.98Eu0.02Sn2O7 and Lu1.98Eu0.02Sn2O7 samples were prepared in order to study how substitution of RE3+ (Y3+ with Gd3+ and Lu3+ ions) influences on luminescent properties of RE1.98Eu0.02Sn2O7 and thermal stability of their luminescence. In order to understand better luminescent properties, the Judd–Ofelt analysis was applied to all the synthesized powders. The highest value of quantum efficiency, ~96%, was estimated for Lu1.98Eu0.02Sn2O7. To assess potential application in high-power LEDs, the temperature-dependent emission spectra of Y1.98Eu0.02Sn2O7, Gd1.98Eu0.02Sn2O7 and Lu1.98Eu0.02Sn2O7 nanophosphors were studied.
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•Eu3+-doped Y2Sn2O7, Gd2Sn2O7, Lu2Sn2O7 samples were prepared by co-precipitation method.•An average size of all synthesized samples were ranging from 30 to 40 nm.•The highest value of quantum efficiency (QE~96%) was obtained for Lu1.98Eu0.02Sn2O7.•The color coordinates of studied samples are close to commercial red phosphor.•Samples showed good thermal stability in the range of operating WLED temperatures.
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