Exploiting High-Energy Emissions of YAlO3:Dy3+ for Sensitivity Improvement of Ratiometric Luminescence Thermometry.

The sensitivity of luminescence thermometry is enhanced at high temperatures when using a three-level luminescence intensity ratio approach with Dy3+- activated yttrium aluminum perovskite. This material was synthesized via the Pechini method, and the structure was verified using X-ray diffraction analysis. The average crystallite size was calculated to be around 46 nm. The morphology was examined using scanning electron microscopy, which showed agglomerates composed of densely packed, elongated spherical particles, the majority of which were 80-100 nm in size. The temperature-dependent photoluminescence emission spectra (ex = 353 nm, 300-850 K) included Dy3+ emissions in blue (458 nm), blue (483 nm), and violet (430 nm, T 600 K). Luminescence intensity ratio, the most utilized temperature readout method in luminescent thermometry, was used as the testing method: a) using the intensity ratio of Dy3+ ions and 4I15/2→6H15/2/4F9/2→6H15/2 transitions; and b) employing the third, higher energy 4G11/2 thermalized level, i.e., using the intensity ratio of 4G11/2→6H15/2/4F9/2→6H15/2 transitions, thereby showing the relative sensitivities of 0.41% K-1 and 0.86% K-1 at 600 K, respectively. This more than doubles the increase in sensitivity and therefore demonstrates the method's usability at high temperatures, although the major limitation of the method is the chemical stability of the host material and the temperature at which the temperature quenching commences. Lastly, it must be noted that at 850 K, the emission intensities from the energetically higher levels were still increasing in YAP: Dy3+.

The Parallel Factor Analysis of Beer Fluorescence.

Fluorescence excitation-emission matrices were measured for 111 samples of different types of beer and studied by the parallel factor analysis (PARAFAC). The 5-component PARAFAC model was found to suitably describes the beer fluorescence, accounting for 99.4% of the fluorescence variance in the measured set of samples, and providing the completely resolved excitation and emission spectra of each component. The model was chosen based on a model's core consistency and split-half analysis. It is shown that beer fluorescence is the sum of fluorescence of aromatic amino acids (tryptophan, tyrosine, and phenylalanine), different forms of vitamin B, and phenolic compounds. Obtained PARAFAC model of beer fluorescence demonstrated the potential for the quantification and quality analysis of beer fluorophores and classification of different beer types.

Changes of Color and Fluorescence of Resin Composites Immersed in Beer.

OBJECTIVE: The aim of this study was to evaluate changes of color and fluorescence of resin based composite exposed to beer. MATERIALS AND METHODS: 84 samples (13 mm in diameter and 1.5 mm thick) of microhybrid composite Gradia DirectTM extra bleach white were immersed in 5 different beers (dark and light) or distilled water. Color and fluorescence were measured prior and after 1-, 7-, and 14-day immersion by Spectrophotometer Thermo Evolution 600 and Fluorolog-3-221 spectrofluorometer. RESULTS: Resin based composites changed color after immersion in beers of different types. Beers with higher optical absorption induced greater color changes. The fluorescence intensity of composites was decreased after immersion in beer, but the shape of fluorescence spectra was not changed. 14-day immersion in Bernard dark beer caused the greatest changes in optical properties of composite: ΔE*=9.0 and 57.6% reduced fluorescence. CONCLUSION: Dark and light beers changed optical properties of resin based composite. The color change come exclusively from the change of chroma. CLINICAL SIGNIFICANCE: To fully meet esthetic criteria when using dental materials in restoration it is crucial to match optical properties of teeth and dental restoration at the moment of placement, but also to keep the match over the time. Considering that staining in beer causes changes in color and fluorescence of composites and that discoloration is a frequent reason for replacement of composite restorations, the data and conclusions on discoloration of dental restorations caused by beer consumption should aid dental professionals when reaching for high esthetics of modern dentistry.(J Esthet Restor Dent 28:330-338, 2016).

Properties of vulcanized polyisoprene rubber composites filled with opalized white tuff and precipitated silica.

Opalized white tuff (OWT) with 40 µm average particle size and 39.3 m(2)/g specific surface area has been introduced into polyisoprene rubber (NR). Their reinforcing effects were evaluated by comparisons with those from precipitated silica (PSi). The cure characteristic, apparent activation energy of cross-link (E(ac)) and reversion (E(ar)), and mechanical properties of a variety of composites based on these rubbers were studied. This was done using vulcanization techniques, mechanical testing, and scanning electron microscopy (SEM). The results showed that OWT can greatly improve the vulcanizing process by shortening the time of optimum cure (t(c90)) and the scorch time (t(s2)) of cross-linked rubber composites, which improves production efficiency and operational security. The rubber composites filled with 50 phr of OWT were found to have good mechanical and elastomeric properties. The tensile strengths of the NR/OWT composites are close to those of NR/PSi composites, but the tear strength and modulus are not as good as the corresponding properties of those containing precipitated silica. Morphology results revealed that the OWT is poorly dispersed in the rubber matrix. According to that, the lower interactions between OWT and polyisoprene rubber macromolecules are obtained, but similar mechanical properties of NR/OWT (100/50) rubber composites compared with NR/PSi (100/50) rubber composites are resulted.

Support Vector Machine on fluorescence landscapes for breast cancer diagnostics.

Excitation-emission matrices (EEM) and total synchronous fluorescence spectra (SFS) of normal and malignant breast tissue specimens are measured in UV-VIS spectral region to serve as data inputs in development of Support Vector Machine (SVM) based breast cancer diagnostics tool. Various input data combinations are tested for classification accuracy using SVM prediction against histopathology findings to discover the best combination regarding diagnostics sensitivity and specificity. It is shown that with EEM data SVM provided 67% sensitivity and 62% specificity diagnostics. With SFS data SVM provided 100% sensitivity and specificity for a several input data combinations. Among these combinations those that require minimal data inputs are identified.

Na, K-ATPase as a Biological Target for Gold(III) Complexes: A Theoretical and Experimental Approach.

BACKGROUND: Gold-based complexes represent a new class of potential metallodrugs. Although their action mechanism is not entirely understood, it was shown that gold complexes inhibit some enzymes' activities. Among them, Na,K-ATPase is emerging as an essential target for various anticancer drugs. The functionalization of nanoparticles by gold(III) complexes could facilitate their delivery into the cells and enable the following of their distribution in the target tissues. OBJECTIVE: The paper presents an overview of Na,K-ATPase interaction with representative and structurally related cytotoxic gold(III) complexes. The results obtained by the employment of theoretical methods (DFT and docking studies) combined with the experimental approach involving a variety of nanotechnology-base techniques (UV/Vis, Raman and fluorescence spectroscopy, CD, AFM, DLS) are discussed. Detailed information was obtained on the enzyme's conformational and structural changes upon binding the gold(III) complexes. The experimentally determined reaction parameters (constants of dissociation and the reaction stoichiometry) were predicted theoretically. CONCLUSION: The presented results offer further support to the view that Na,K-ATPase may be a relevant biomolecular target for cytotoxic gold(III) compounds of medicinal interest.

Surface Plasmon Enhancement of Eu3+ Emission Intensity in LaPO4/Ag Nanoparticles.

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.

Comparison of Three Ratiometric Temperature Readings from the Er3+ Upconversion Emission.

The emission of Er3+ provides three combinations of emission bands suitable for ratiometric luminescence thermometry. Two combinations utilize ratios of visible emissions (2H11/2→4I15/2 at 523 nm/ 4S3/2→4I15/2 at 542 nm and 4F7/2→4I15/2 at 485 nm/ 4S3/2→4I15/2 at 545 nm), while emissions from the third combination are located in near-infrared, e.g., in the first biological window (2H11/2→4I13/2 at 793 nm/ 4S3/2→4I13/2 at 840 nm). Herein, we aimed to compare thermometric performances of these three different ratiometric readouts on account of their relative sensitivities, resolutions, and repeatability of measurements. For this aim, we prepared Yb3+,Er3+:YF3 nanopowders by oxide fluorination. The structure of the materials was confirmed by X-ray diffraction analysis and particle morphology was evaluated from FE-SEM measurements. Upconversion emission spectra were measured over the 293-473 K range upon excitation by 980 nm radiation. The obtained relative sensitivities on temperature for 523/542, 485/542, and 793/840 emission intensity ratios were 1.06 ± 0.02, 2.03 ± 0.23, and 0.98 ± 0.10%K-1 with temperature resolutions of 0.3, 0.7, and 1.8 K, respectively. The study showed that the higher relative temperature sensitivity does not necessarily lead to the more precise temperature measurement and better resolution, since it may be compromised by a larger uncertainty in measurement of low-intensity emission bands.

Characterization of cereal flours by fluorescence spectroscopy coupled with PARAFAC.

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.

Effects of a low-shrinkage methacrylate monomer and monoacylphosphine oxide photoinitiator on curing efficiency and mechanical properties of experimental resin-based composites.

This study investigated the degree of conversion, depth of cure, Vickers hardness, flexural strength, flexural modulus and volumetric shrinkage of experimental composite containing a low shrinkage monomer FIT-852 (FIT; Esstech Inc.) and photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO; Sigma Aldrich) compared to conventional composite containing Bisphenol A-glycidyl methacrylate (BisGMA) and camphorquinone-amine photoinitiator system. The degree of conversion was generally higher in FIT-based composites (45-64% range) than in BisGMA-based composites (34-58% range). Vickers hardness, flexural strength and modulus were higher in BisGMA-based composites. A polywave light-curing unit was generally more efficient in terms of conversion and hardness of experimental composites than a monowave unit. FIT-based composite containing TPO showed the depth of cure below 2mm irrespective of the curing light. The depth of cure of FIT-based composite containing CQ and BisGMA-based composites with either photoinitiator was in the range of 2.8-3.0mm. Volumetric shrinkage of FIT-based composite (0.9-5.7% range) was lower than that of BisGMA-based composite (2.2-12% range). FIT may be used as a shrinkage reducing monomer compatible with the conventional CQ-amine system as well as the alternative TPO photoinitiator. However, the depth of cure of FIT_TPO composite requires boosting to achieve clinically recommended thickness of 2mm.

Fluorescence spectroscopy coupled with PARAFAC and PLS DA for characterization and classification of honey.

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 640 nm with excitation in the range of 240-500 nm. 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.

Discrimination among melanoma, nevi, and normal skin by using synchronous luminescence spectroscopy.

Novel optical spectroscopy and imaging methods may be valuable in the early detection of cancer. This paper reports differences in the luminescence responses of pigmented skin lesions (melanomas and nevi) and apparently normal non-pigmented human skin, based on analyses of synchronous luminescence spectroscopy measurements. Measurements were performed in the excitation range of 330-545 nm, with synchronous intervals varying from 30-120 nm. Normal skin, nevi, and melanomas differ in the way they fluoresce, and these differences are more distinct in the synchronous fluorescence spectra than in the conventional emission and excitation spectra. The differences in the fluorescence characteristics of pigmented and normal skin samples were ascribed to differences in concentrations of endogenous fluorophores and chromophores. Principal component and linear discriminant analysis of the synchronous spectra measured at different synchronous intervals showed that the greatest variance among the sample groups was at the 70 nm interval spectra. These spectra were then used to create partial least squares discriminant analysis-based classification models. Evaluation of the quality of these models from the receiver operating characteristic curves showed they performed well, with a maximum value of 1 for the area under the curve for melanoma detection. Hence, synchronous luminescence spectroscopy coupled with statistical methods may be advantageous in the early detection of skin cancer.

Determination of the botanical origin of honey by front-face synchronous fluorescence spectroscopy.

Front-face synchronous fluorescence spectroscopy combined with chemometrics is used to classify honey samples according to their botanical origin. Synchronous fluorescence spectra of three monofloral (linden, sunflower, and acacia), polyfloral (meadow mix), and fake (fake acacia and linden) honey types (109 samples) were collected in an excitation range of 240-500 nm for synchronous wavelength intervals of 30-300 nm. Chemometric analysis of the gathered data included principal component analysis and partial least squares discriminant analysis. Mean cross-validated classification errors of 0.2 and 4.8% were found for a model that accounts only for monofloral samples and for a model that includes both the monofloral and polyfloral groups, respectively. The results demonstrate that single synchronous fluorescence spectra of different honeys differ significantly because of their distinct physical and chemical characteristics and provide sufficient data for the clear differentiation among honey groups. The spectra of fake honey samples showed pronounced differences from those of genuine honey, and these samples are easily recognized on the basis of their synchronous fluorescence spectra. The study demonstrated that this method is a valuable and promising technique for honey authentication.