A promising way to improve the performance of luminescent materials is to combine them with noble metal nanoparticles. Herein, a set of silver/europium-doped lanthanum orthophosphate ...(Ag/La0.95Eu0.05PO4) nanostructures with different concentrations of silver nanoparticles were prepared and investigated. The presented overlap between the strongest europium (Eu3+) excitation line and the broad silver nanoparticle surface plasmon resonance makes the combination prospective for coupling. X-ray powder diffraction confirmed the monoclinic monazite structure. The transmission electron microscopy revealed particles with a rod-like shape and ~4 aspect ratio. Photoluminescence spectra show characteristic Eu3+ ion red emission. One of the requirements for an enhanced luminescence effect is the precise control of the distance between the noble metal nanoparticles and the emitter ion. The distance is indirectly varied throughout the change of Ag nanoparticle concentration in the La0.95Eu0.05PO4 host. The emission intensity increases with the increase in Ag nanoparticles up to 0.6 mol %, after which the luminescence decreases due to the nanoparticles’ close packing and aggregation leading to the displacement of La0.95Eu0.05PO4 from the vicinity of the metal particles and reabsorption of the emitted light. The emission intensity of La0.95Eu0.05PO4 increases more than three times when the Eu3+ excitation is supported by the localized surface plasmon resonance in the Ag/La0.95Eu0.05PO4 nanostructures.
Concentrations of toxic elements (lead, cadmium, mercury, and arsenic) were measured in water, sediment, and four commercial fish species (
Cyprinus carpio
,
Hypophthalmichthys molitrix
,
Silurus ...glanis
, and
Esox lucius
) and their tissues (muscle, liver, and kidney) from Saničani Lake, Bosnia and Herzegovina. The concentration of toxic elements was measured by atomic absorption spectrometry. Toxic element concentrations were significantly affected by the fish species and tissues sampled. The lead was the most heavily deposited element in lake sediments and waters. The highest concentrations of Pb and Cd were in the kidney in all four fish species. Concentrations of Hg and As were higher in the muscle than in the kidney and liver in all four fish species. The toxic element concentrations in all examined tissues were significantly higher in
Silurus glanis
and
Esox lucius
than in the other fish species examined. Concentrations of all tested elements were present in the fish muscle at different levels, but these levels were under the maximum levels allowed by the European Union and FAO/WHO. Accordingly, fish meat from this lake is acceptable for human consumption.
This study was aimed at the investigation into the influence of polyphenols on fermented sausages produced with and without nitrite addition, during storage which lasted for 280 days. Three types of ...sausages were produced and formed the three experimental groups: C – the control – sausages of usual composition containing nitrites; N+P - sausages with nitrites and polyphenols; and P - nitrite-free sausages with added polyphenols. The proximate chemical composition of all groups was in the range with that of dry fermented sausages. P sausages contained 0.3 mg nitrites per kg, while C and N+P contained 54.8 mg/kg and 52.2 mg/kg, respectively. Polyphenol-enriched sausages had significantly lower peroxide and TBARS values than C sausages. In all sausages lactic acid bacteria counts reached 8.9-9.9 log cfu/g, but decreased during storage to 4.3-4.8 log cfu/g at the end of the storage period.
counts remained stable: 3.5-3.9 log cfu/g. In P and N+P sausages a significantly lower number of
was observed than in the control. The lightness of C and P sausages was similar (L=50.2 and L=49.5, respectively), while N+P sausages were darker (L=42.5). C and N+P sausages had similar redness (a*=14.5 and a*=13.2, respectively) and yellowness (b*=5.9 and b*=6.4, respectively), but the values which correspond to redness and yellowness were lower in P sausages (a*=8.0 and b*=4.6). Sensory characteristics of all products were found to be very similar. The flavour of polyphenol-enriched sausages was considered to be better. The most dominant polyphenol in sausages was kaempferol-3-O-glucoside followed by quercetin, luteolin-7-O-glucoside, catechin and syringic acid. Nitrite-free polyphenol-enriched sausages reached the same shelf life as conventional sausages containing nitrites did, which is a promising result implying that polyphenols might be used as natural preservatives and nitrite substitutes. Simultaneous use of nitrite and polyphenols is questionable due to their interactions which should be further studied.
Eu3+-doped YxLu1−xNbO4 (x = 0, 0.25, 0.5, 0.75, 1) were prepared by the solid-state reaction method. YNbO4:Eu3+ and LuNbO4:Eu3+ crystallize as beta-Fergusonite (SG no. 15) in 1–10 μm diameter ...particles. Photoluminescence emission spectra show a slight linear variation of emission energies and intensities with the solid-solution composition in terms of Y/Lu content. The energy difference between Stark sublevels of 5D0→7F1 emission increases, while the asymmetry ratio decreases with the composition. From the dispersion relations of pure YNbO4 and LuNbO4, the refractive index values for each concentration and emission wavelength are estimated. The Ω2 Judd–Ofelt parameter shows a linear increase from 6.75 to 7.48 × 10−20 cm2 from x = 0 to 1, respectively, and Ω4 from 2.69 to 2.95 × 10−20 cm2. The lowest non-radiative deexcitation rate was observed with x = 1, and thus LuNbO4:Eu3+ is more efficient phosphor than YNbO4:Eu3+.
The physicochemical parameters (free acidity, moisture content, sucrose content, hydroxymethylfurfural, reducing sugars, electrical conductivity, diastase activity and water-insoluble content), ...elements (Cu, Fe, Zn, Mn, Cr, Co, Ni, Se, K, Na, Ca, Mg) and heavy metal/metalloid concentrations (Cd, Hg, Pb and As) of 84 honeys (linden, multifloral, honeydew and acacia) from Serbia, were analyzed using ICP-MS. Concerning the physicochemical parameters, all tested honeys were found to meet European Legislation (EC Directive 2001/110). Potassium was the major element, ranging between 943.9 ± 538.6 mg/kg and 2563 ± 1817 mg/kg. Statistical analysis showed significant differences in the concentrations of Zn, Mn, Co and Na between the honeys. Selenium and Hg levels were below the limits of detection. Positive correlations were found between electrical conductivity and most of the elements. The present study showed that Serbian honey examined were of good quality according to its physicochemical parameters and met safety criteria concerning the concentrations of Cd, Hg, Pb and As.
MgTiO
nanoparticles doped with Mn
, with homogeneous size ranging about 63.1 ± 9.8 nm, were synthesized by a molten salt assisted sol gel method. These nanoparticles have been investigated as optical ...thermal sensors. The luminescence of tetravalent manganese ion in octahedral environment within the perovskite host presents drastic variations with temperature. Three different thermometry approaches have been proposed and characterized. Two luminescence intensity ratios are studied. Firstly between the two R-lines of Mn
emission at low temperature (-250 °C and -90 °C) with a maximal sensitivity of 0.9% °C
, but also secondly between
E →
A
(R-line) and the
T
→
A
transitions. This allows studying the temperature variation within a larger temperature range (-200 °C to 50 °C) with a sensitivity between 0.6% °C
and 1.2% °C
over this range. The last proposed method is the study of the lifetime variation
temperature. The effective lifetime value corresponds to a combination of transitions from two excited energy levels of the tetravalent manganese (
E and
T
) in thermal equilibrium toward the fundamental
A
state. Since the more energetic transition (
T
→
A
) is spin-allowed, contrary to the
E →
A
one, the lifetime drastically decreases with the increase in temperature leading to an impressive high sensitivity value of 4.1% °C
at 4 °C and an exceptional temperature resolution of 0.025 °C. According to their optical features, MgTiO
:Mn
nanoparticles are indeed suitable candidates for the luminescence temperature probes at the nanoscale over several temperature ranges.
Sol-gel technique for the synthesis of anatase TiO2 at 420 °C produces nanocrystals of 10–20 nm in size with Ti4+ in crystal volume and Ti3+ at terminal planes of the crystal. The study of Li+ ...co-doping effects on the structure, morphology, absorption, and luminescence of Eu3+ activated TiO2 anatase nanocrystals is presented. Pure anatase structure is achieved up to 9 at.% Li, with significant improvement in crystallinity of europium doped anatase TiO2. The Li+ co-doping reduces the unit cell volume of the crystal, induces the blue shift of the absorption edge, lengthens the lifetime of Eu3+5D0 excited state, and improves the Eu3+ emission intensity up to 37.5%. Judd-Ofelt analysis of Eu3+ emission showed enhancement of quantum efficiency from 66.4% to 98.7% when TiO2:Eu3+ was co-doped with 9 at.% of Li.
•Li+ co-doped TiO2:Eu3+ luminescence nanocrystals synthesized by a sol-gel technique.•Blue-shift of an absorption edge in DRS spectra for the larger doping content of Li.•The enlargement of the asymmetry ratio and emission intensity of Eu3+ in TiO2.•The increase of the 5D0 lifetime and the internal quantum efficiency of Eu3+ emission.
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