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We synthesized Eu3+-doped CsY2F7 and RbY2F7 nanoparticles (orthorhombic crystal structure, Pnna space group, No. 52) by the microwave-assisted solvothermal technique and investigated the influence of reaction temperature and fluoride ion concentration on the particles’ phase and crystal structure. Fluoride ions were added in excess of the stoichiometric amount to achieve the orthorhombic phase for CsY2F7 and to convert the cubic RbY3F10 to the orthorhombic RbY2F7. Mild synthesis conditions yielded nanoparticles with crystallites ranging in size from 19 to 37 nm and a combination of spherical, rod-like, and hexagonal shapes. Nanoparticles emit a strong orange and red light when excited into the Eu3+ 5L6 level, which is centered around 390 nm. The strongest emission peak is around 612 nm, which comes from the 5D0→7F2 electronic transitions. Emission intensity dependence on Eu3+ concentration revealed that nanoparticles can be heavily doped with Eu3+, up to 25 % with respect to Y3+. Emission decay measurements provided values of excited state lifetimes of 6.2 ms for the Cs(Y0.75Eu0.25)2F7 and 6.0 ms for the Rb(Y0.75Eu0.25)2F7.

Luminescent Eu3+-doped SrF2 nanoparticles were synthesized using microwave-assisted synthesis. Their surfaces were modified either by polyethylene glycol or mercaptopropionic acid to enhance their dispersibility in aqueous media and colloidal formation. X-ray diffraction analysis confirmed single-phase cubic structure in both types of hydrophilic-modified Sr0.9Eu0.1F2 luminescent powders. The average crystallite size of nanoparticles is found to be ∼13 nm. Scanning electron microscopy of the representative PEG2000-modified sample revealed that particles form agglomerates composed of densely packed nanoparticles. The microstructure at a local level was investigated by transmission electron microscopy showing the presence of sphere-like nanoparticles with an average particle size of 12.5 nm and 14 nm for PEG-modified and MPA-modified Sr0.9Eu0.1F2, respectively. Both PEG2000 and MPA-modified Sr0.9Eu0.1F2 water dispersions show strong red Eu3+ emission under 405 nm excitation that is quenched in the presence of the primary NP fertilizer, ammonium dihydrogen phosphate, NH4H2PO4. The limit of detection was calculated to be ∼19 mM for both hydrophilic-modified Sr0.9Eu0.1F2 luminescent nanoparticles.

We report on overcoming the sensitivity limit of Boltzmann's thermometers by utilization of seven thermalized Dy3+ excited states in the Lu1.5Y1·5Al5O12 host. Emission spectra recorded from room temperature to 938 K show transitions originating from seven 4F9/2, 4I15/2, 4G11/2, 4I13/2, 4M21/2, 4K17/2, and 4F7/2 excited levels to the 6H15/2 ground state. We introduce the multi-cascade LIR (McLIR) by extending the conventional, two-thermalized level Boltzmann-type LIR to seven thermalized levels. This approach provides higher energy differences between thermalized levels which results in five times larger sensitivity than in the conventional LIR. Considering energy differences between Dy3+ excited states of 1043, 2464, 4331, and 5089 cm−1, the luminescence thermometry with McLIR provided 0.35, 0.84, 1.47, 1.73% K−1 relative sensitivities at 650 K, respectively, in four different LIR combinations. The validity of the McLIR method and the effectiveness of thermalizations between levels is confirmed with the good theoretical fit of experimental data.

A series of La1−xGa0.99O3:Cr0.01, Ndx phosphors (where x = 0.005, 0.01, 0.02) for luminescence thermometry was synthesised by the solid-state method, structurally characterised using powder X-ray diffraction data, and investigated by ambient and variable-temperature optical measurements. The design principle relies on the use of a combination of transition metal and rare earth activator ions such that the excitation and emission wavelengths fall within the near infra-red spectral region, notably in the ‘first biological window’ that is attractive for potential in vivo applications. The photoluminescence spectra of the compounds feature the characteristic 2E phosphorescence of Cr3+ at 729 nm and the 4F3/2 → 4I9/2 emission of Nd3+ around 890 nm. The Nd3+ emission is quenched at a higher rate than that of Cr3+ with increasing temperature. Thermometric analysis by monitoring the luminescence intensity ratio (LIR) between the emissions of Cr3+ and Nd3+ from 300 K to 650 K shows a quasi-Boltzmann trend, with a maximum relative sensitivity of ∼2% K−1, high absolute sensitivity values over this entire temperature range, excellent temperature resolution of 0.04 K at room temperature, and high stability.

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 first biological window (650–950 nm) is the area within the NIR spectrum able to penetrate skin more effectively than shorter wavelengths.1 The TM3+, Ln3+ activator combination has attracted attention due excitation/emission within this wavelength range.2 In this investigation, a series of La1-xGa0.99O3: Cr0.01, Ndx phosphors (where x = 0.005, 0.01, 0.02) were synthesised by conventional solid-state methods and structurally characterised by Rietveld refinement of a structural model and powder diffraction data.3 Room temperature photoluminescence was undertaken with excitation spectra of both the Cr3+ and the Nd3+ showing energy transfer to the other emission centre alongside showing the characteristic Cr3+ broadbands, and sharp Nd3+ line excitations. Emission spectra showed both the Cr3+ 2E sharp peak at 729 nm, and the Nd3+ 4I3/2  4I9/2 emission of Nd3+ ca. 890 nm. Variable temperature thermometric analysis was undertaken, with the La1-xGa0.99O3: Cr0.01, Ndx (x = 0.02) sample exhibiting the emissions from the Cr3+ and Nd3+ centres at comparable intensities. Monitoring by luminescence intensity ratio (LIR) showed Cr3+ emission being quenched slower than Nd3+ emission. The phosphor produced a relative sensitivity of ~2.0% K-1 at 300 K, high absolute sensitivity, and a temperature resolution of 0.04 K at 300 K.

The introduction of additional functionalities to materials is exceptionally important as it opens new applications for them. Aluminum, one of the most abundant and important materials, is coated with luminescent Sm2+-doped γ-aluminium oxide to impart thermometric functionality. Considering the potential industrial applications, two of the most widely used aluminum alloys, 6061 and 7075, are also coated. For this purpose, plasma electrolytic oxidation (PEO), an effective technique for producing hard ceramic coatings on various metal surfaces, is used. It is shown that thermometric coatings can be produced on aluminum in one-step process by adding the raw precursor to the electrolyte. The valence reduction of Ln3+ to Ln2+ is achieved during the PEO process. The intense and broad (orange to deep red) emission from the coating shows supersensitivity to temperature changes over the 100–648 K range. The temperature is obtained from the coating emission using i) the emission intensity ratio method, ii) emission lifetime, and iii) emission band position with sensitivities of 4.8% K−1, 1.2% K−1, and 8 cm−1 K−1, respectively. Several applications would benefit from the thermometric coating's excellent temperature resolution of 0.04 K and the choice of three temperature read-outs that facilitate the coating's use in different luminescence thermometry setups. © 2021 Wiley-VCH GmbH

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.

The Judd-Ofelt model, already verified for the luminescence intensity ratio (also called fluorescence intensity ratio, FIR) thermometry from the emission spectra, is modified and tested for the dual-excited single band luminescence thermometry. The adapted model has been tested on Lu2O3:Eu3+, with a 99.9% match of the temperature invariant parameter to the experimental value. The absolute sensitivity obtained experimentally and predicted by the model are almost indistinguishable. The model is proven to be adequate for inaugural phosphor quality evaluation, as it can reveal the approximate figures of merit of luminescence thermometry solely from the single emission spectrum.

When activated by Dy3+, Na0.25K0.25Bi0.50TiO3 (NKBT), piezoelectric powders show strong luminescence in the blue and yellow spectral range. Emissions of this material can be effectively utilized for both luminescence intensity ratio and lifetime-based readouts of temperature. Photoluminescence measurements over a temperature range of 293–483 K show that the luminescence intensity ratio temperature readout has maximal relative sensitivity of 1.93% K−1 at 380 K, while the relative sensitivity of the lifetime temperature readout reaches 1.1% K−1 at 480 K. For this study, materials were synthesized by a solid-state reaction using TiO2, Bi2O3, Na2CO3, K2CO3 and Dy2O3 as precursors. X-ray diffraction measurements showed that the NKBT sample crystallized in the A-site substituted distorted perovskite rhombohedral structure (R3c symmetry). The photoluminescence spectra showed characteristic emission bands of Dy3+ ions centered at 457 nm (4I15/2 → 6H15/2), 478 nm (4F9/2 → 6H15/2), 574 nm (4F9/2 → 6H13/2) and 663 nm (4F9/2 → 6H11/2). The ratio of emissions from 4F9/2 and 4I15/2 excited states to the 6H15/2 ground state was used as a luminescence intensity ratio indicator of temperature, while the decay of emission from 4F9/2 → 6H13/2 transition was used as a lifetime indicator of temperature. CIE coordinates x = 0.326 and y = 0.361 calculated from room temperature emission spectra show the perspective of this material for use in white light emission devices.

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.

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. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Honey is a frequent target of adulteration through inappropriate production practices and origin mislabelling. Current methods for the detection of adulterated honey are time and labor consuming, require highly skilled personnel, and lengthy sample preparation. Fluorescence spectroscopy overcomes such drawbacks, as it is fast and noncontact and requires minimal sample preparation. In this paper, the application of fluorescence spectroscopy coupled with statistical tools for the detection of adulterated honey is demonstrated. For this purpose, fluorescence excitation-emission matrices were measured for 99 samples of different types of natural honey and 15 adulterated honey samples (in 3 technical replicas for each sample). Statistical t -test showed that significant differences between fluorescence of natural and adulterated honey samples exist in 5 spectral regions: (1) excitation: 240–265 nm, emission: 370–495 nm; (2) excitation: 280–320 nm, emission: 390–470 nm; (3) excitation: 260–285 nm, emission: 320–370 nm; (4) excitation: 310–360 nm, emission: 370–470 nm; and (5) excitation: 375–435 nm, emission: 440–520 nm, in which majority of fluorescence comes from the aromatic amino acids, phenolic compounds, and fluorescent Maillard reaction products. Principal component analysis confirmed these findings and showed that 90% of variance in fluorescence is accumulated in the first two principal components, which can be used for the discrimination of fake honey samples. The classification of honey from fluorescence data is demonstrated with a linear discriminant analysis (LDA). When subjected to LDA, total fluorescence intensities of selected spectral regions provided classification of honey (natural or adulterated) with 100% accuracy. In addition, it is demonstrated that intensities of honey emissions in each of these spectral regions may serve as criteria for the discrimination between natural and fake honey.

The interaction of partially reduced graphene oxide (prGO) and Huh7.5.1 liver cancer cells was investigated by means of DUV fluorescence bioimaging. The prGO sample was obtained by the reduction (to a certain extent) of the initially prepared graphene oxide (GO) nanosheets with hydrazine. The fluorescence of the GO nanosheets increases with time of the reduction due to a change in ratio of the sp2 and sp3 carbon sites and the prGO sample was extracted from the dispersion after 6 min, when the intensity of the fluorescence reached its maximum. The reduction process was left to proceed further to saturation until highly reduced graphene oxide (denoted here as rGO) was obtained. GO, prGO and rGO samples were investigated by structural (scanning electron microscopy (SEM), scanning transmission electron microscopy coupled with energy dispersive spectrometry (STEM-EDS)) and spectroscopic (UV-vis, photoluminescence (PL), Raman) methods. After that, Huh7.5.1 cells were incubated with GO, prGO and rGO nanosheets and used in bioimaging studies, which were performed on DISCO beamline of synchrotron SOLEIL. It was found that the prGO significantly enhanced the fluorescence of the cells and increased the intensity of the signal by ~2.5 times. Time-lapse fluorescence microscopy experiments showed that fluorescence dynamics strongly depends on the type of nanosheets used. The obtained prGO nanostructure can be easily conjugated with aromatic ring containing drugs, which opens a possibility for its applications in fluorescence microscopy monitored drug delivery. © 2018 IOP Publishing Ltd.

This paper presents parallel factor analysis (PARAFAC) of fluorescence of cereal flours. Excitation emission matrices (EEMs) 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. EEMs 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 EEMs 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. (C) 2017 Elsevier Ltd. All rights reserved.

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 2 mm 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 2.8-3.0 mm. 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 2 mm. (C) 2015 Elsevier B.V. All rights reserved.

In this study, the thermal behavior of modified urea-formaldehyde (UF) resin with nanosilica (nano-SiO2), wood flour (WF), and their mixture of SiO2/WF was investigated. Five modified UF hybrid composite materials with 0.8 F/U ratio with different filler were synthesized using the same procedure. The thermal behavior of materials was studied using nonisothermal thermogravimetric analysis, differential thermal gravimetry (DTG), and differential thermal analysis and supported by data from infrared spectroscopy. The shift of DTG peaks to a high temperature indicates the increase in thermal stability of modified UF resin with hybrid SiO2/WF fillers, which is confirmed by the data obtained from the Fourier transform infrared spectroscopic study. It was estimated that the UF/WF samples based on nano-SiO2 have better thermal stability.

The paper presents the results of the experimental and theoretical study of 3,3-disulfopropyl-5,5-dichlorothiacyanine sodium salt (TC) adsorption and J-aggregation on the surface of citrate-capped silver nano particles (AgNPs) with an average particle size 10 nm. Various nanospectroscopy techniques such as UV-vis, TEM, AFM, DLS, zeta potential, and fluorescence measurements were carried out in order to characterize the hybrid system. Besides this, a set of simple density functional theory calculations (DFT) was performed and this suggested that TC dye, from the thermodynamical point of view, most likely interacted with AgNPs via oxygen atom from SO3- groups. The methods, which considered AgNPs as the macromolecule with several binding sites and TC dye as the ligand, were applied for the analysis of saturation curves constructed from the fluorescence data to obtain the binding constant (K-a = 1.5 x 10(6) M-1) and the average number of TC dye molecules bonded per AgNP (similar to 330). Moreover, TC fluorescence was quenched in the presence of AgNPs on the concentration dependent manner, yielding the linear Stern-Volmer relation accounting for both static and dynamic quenching with the quenching constant K-sv = 2.5 x 10(8) M-1. Kinetic measurements of J-aggregation as the dependence of AgNPs/TC concentration ratio confirmed that the J-aggregation occurred via a two-step process, the first of them being the initial adsorption of dye on AgNPs surface, followed by dye molecules rearrangement and the consecutive growth of TC aggregate layers.

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. (c) 2014 Elsevier Ltd. All rights reserved.

Optiĉka spektroskopija i imidţing tehnike mogu biti korisne za ranu dijagnostiku kancera. U ovoj tezi, razlike u luminescentnim odgovorima pigmentnih lezija (melanoma i nevusa) i po svemu sudeći nepigmentne koţe ljudi su analizirane sinhronom luminescentnom spektroskopijom. Merenja su izvršena u opsegu eksitacione talasne duţine od 330 do 545 nm i sinhronom intervalu od 30 do 120 nm, da bi se dobili osnovni i trodimenzionalni sinhroni luminescentni spektri (3DTSLS) za svaki uzorak. Normalna koţa, nevus i melanom se razlikuju u naĉinu na koji fluoresciraju, i te razlike su više naglašene u sinhronim fluorescentnim spektrima nego u klasiĉnim emisionim i eksitacionim spektrima. Razlike u fluorescentnim karakteristikama pigmentnih lezija i zdrave koţe potiĉu od razliĉitih koncentracija endogenih fluorofora i hromofora. Analizom glavnih komponenata i linearnom diskriminantnom analizom sinhronih spektara izmerenih za razliĉite sinhrone intervale pokazano je da je najveća razlika izmeĊu grupa uzoraka dobijena za sinhroni interval 70 nm. Ovi spektri su zatim korišćeni za pravljenje klasifikacionih modela diskriminantnom analizom parcijalno najmanjih kvadrata. Testiranjem uspešnosti ovih modela krivom operativnih karakteristika pokazano je da su oni optimalni, sa maksimalnom vrednošću od jedan za površinu ispod krive operativnih karakteristika za detekciju melanoma. Za testiranje primenjivosti pomenutih tehnika korišćene su veštaĉke neuronske mreţe. U ovu svrhu, samoorganizujuće mape (SOM) i višeslojni perceptron (MLP) su obuĉene na osnovu luminescentnih podataka, a zatim je izvršeno grupisanje uzoraka tkiva. Pokazano je da su obe mreţe SOM i MLP dale dobre rezultate sa stopom uspešnosti klasifikacije uzoraka tkiva od 96% i 98%. Drugi deo eksperimentalnog rada u ovoj tezi se sastojao od merenja difuzno refleksionih spektara koţe volontera na dve regije tela, ĉelu i šaci, u cilju analize svojstava boje koţe na objektivan naĉin. Dobijeni spektri su analizirani korišćenjem anal, Novel optical spectroscopy and imaging methods could be valuable in the early detection of cancer. Differences in the luminescence responses of pigmented skin lesions (melanomas and nevi) and apparently non-pigmented human skin were analyzed using synchronous luminescence spectroscopy in this thesis. Measurements were performed in the excitation range of 330-545 nm, with synchronous interval varyng from 30-120 nm to obtain ordinary and three-dimensional total synchronous luminescence spectra (3DTSLS) of each specimen. Normal skin, nevi and melanomas differ in the way they fluorescence, and these differences are more distinct in the syncronous 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 concentracions 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 recevier operating characteristic curves showed they performed well, with a maximum value of one for the area under the curve for melanoma detection. To test applicability of the presented techniques artificial neural networks were used. For this purpose self organizing maps (SOM) and multi layer feed-forward neural network (MLP) were trained with luminescence data and then used for tissue specimen clustering. It was shown that both SOM and MLP gave promising results with 96 to 98% success tissue classification rate. Second part of experimental work in this thesis were measurements of diffuse reflectance spectra from skin sites located on a forehead and top of a hand of healthy volunteers in order to

In recent years, the potential of Fourier-transform infrared spectroscopy coupled with different chemometric tools in food analysis has been established. This technique is rapid, low cost, and reliable and requires little sample preparation. In this work, 130 Serbian unifloral honey samples (linden, acacia, and sunflower types) were analyzed using attenuated total reflectance infrared spectroscopy (ATR-IR). For each spectrum, 64 scans were recorded in wavenumbers between 4000 and 500 cm(-1) and at a spectral resolution of 4 cm(-1). These spectra were analyzed using principal component analysis (PCA), and calculated principal components were then used for support vector machine (SVM) training. In this way, the pattern-recognition tool is obtained for building a classification model for determining the botanical origin of honey. The PCA was used to analyze results and to see if the separation between groups of different types of honeys exists. Using the SVM, the classification model was built and classification errors were acquired. It has been observed that this technique is adequate for determining the botanical origin of honey with a success rate of 98.6%. Based on these results, it can be concluded that this technique offers many possibilities for future rapid qualitative analysis of honey.

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.

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.

Opalized white tuff (OWT) with 40 mu m average particle size and 39.3m(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 theOWT is poorly dispersed in the rubber matrix. According to that, the lower interactions betweenOWT 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.

Over the years various optical spectroscopic techniques have been widely used as diagnostic tools in the discrimination of many types of malignant diseases. Recently, synchronous fluorescent spectroscopy (SFS) coupled with chemometrics has been applied in cancer diagnostics. The SFS method involves simultaneous scanning of both emission and excitation wavelengths while keeping the interval of wavelengths (constant-wavelength mode) or frequencies (constant-energy mode) between them constant. This method is fast, relatively inexpensive, sensitive and non-invasive. Total synchronous fluorescence spectra of normal skin, nevus and melanoma samples were used as input for training of artificial neural networks. Two different types of artificial neural networks were trained, the self-organizing map and the feed-forward neural network. Histopathology results of investigated skin samples were used as the gold standard for network output. Based on the obtained classification success rate of neural networks, we concluded that both networks provided high sensitivity with classification errors between 2 and 4%.

We report on a new synthetic route for synthesis of Sm3+ doped TiO2 nanocrystals by shape transformation of hydrothermally treated titania nanotubes in the presence of Sm3+ ions. Shape and size of Sm3+ doped TiO2 nanocrystals were characterized by transmission electron microscopy. An average size of polyhedral nanocrystals mainly of square/rectangular shape varied between 12 and 14 nm. X-ray diffraction analysis of resultant powder revealed the anatase crystal phase of Sm3+ doped TiO2 nanocrystals independently of the amount of dopant. Room-temperature photoluminescence observed in the orange-red spectral region, which is associated with (4)G(5/2)- GT H-6(J) (J=5/2, 7/2 and 9/2) f-f transitions of the Sm3+ in the 4f(5) configuration after band-to-band excitation, confirmed energy transfer in Sm3+ doped TiO2 nanocrystals. (C) 2013 Elsevier B.V. All rights reserved.

We report on a new approach toward synthesis of Sm3+ doped TiO2 and Ni2+ doped TiO2 nanocrystals by shape transformation of hydrothermally treated titania nanotubes in the presence of Sm3+ or Ni2+ ions. The percentage ratio of Sm3+ (or Ni2+) to Ti4+ ions in doped nanocrystals was determined using ICP atomic emission spectroscopy. The XRD patterns revealed the homogeneous anatase crystal phase of both 0.4 at% Sm3+ doped TiO2 and 0.12 at% Ni2+ doped TiO2 nanoparticles. An average size of polyhedral Sm3+ doped TiO2 nanocrystals was between 12 and 14 nm. In the orange-red spectral region, room temperature photoluminescence signals associated with 4 G5/2 →6 HJ (J = 5/2, 7/2 and 9/2) transitions of Sm3+ was observed in Sm3+ doped TiO2 nanocrystals. Optically transparent film made of 0.12 at% Ni2+ doped TiO2 nanoparticles showed room temperature ferromagnetic ordering. The coercive field was found to be HC ~ 80 Oe.

Synchronous fluorescence spectroscopy, a technique that measures both the absorption and the emission properties of a sample in a single measurement, was used for the analysis and classification of intact cereal flours (wheat, corn, rye, buckwheat, rice, and barley). Total synchronous fluorescence spectra recorded in constant wavelength mode show clear differences in the emission spectra of different flours due to variances in intrinsic fluorophore concentrations and their microenvironments. Principal component analysis, cluster analysis, and partial least squares discriminant analysis are used to assess the ability of synchronous fluorescence measurements to differentiate and classify intact samples of different flour types. The flour specimens were obtained directly from a market in Belgrade and had different expiration dates to provide a more representative set of samples. The results of the current analysis suggest that chemometric methods applied on synchronous fluorescence data can discriminate and classify flour types and that the best results are achieved using a combination of synchronous fluorescence measurements at synchronous intervals of 7 and 20 nm. The quality of results, the high speed of measurements, and the avoidance of extensive sample preparation make synchronous fluorescence spectroscopy a promising technique for cereal research.

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.

In this work we explored the possibility of obtaining nanocrystalline (Y0.5Lu0.5)(2)O-3 powders, doped with europium and co-doped with praseodium, employing polymer complex solution synthesis. Polyethylene glycol, with average molecular weight 200, served both as a fuel and dispersing medium for nanocrystals formation. We investigated structure, morphology, luminescence emission and decay characteristics of obtained powders and how different concentrations of Pr co-dopant affect theirs optical characteristics. (C) 2009 Elsevier Ltd. All rights reserved.

Supervised self-organizing map, a type of artificial neural network, is applied for classification of human breast tissue samples utilizing data obtained from fluorescence landscape measurements. Female breast tissue samples were taken soon after the surgical resection, identified and stored at -80 degrees C until fluorescence measurements. From fluorescence landscapes obtained in UV-VIS region spectral features showing statistically significant differences between malignant and normal samples are identified and further quantified to serve as a training input to neural network. Additional set of samples was used as a test group input to trained network in order to evaluate performance of proposed optical biopsy method. Classification sensitivity of 83.9% and specificity of 88.9% are found.

The synthesis of nanophosphors for various applications and the improvement of their working parameters constitute one of the most topical problems of nowadays technology. Zinc-silicate has been extensively used as host material for phosphors in cathode ray tubes, and nowadays for phosphors in electroluminescent devices. In this work we present novel synthesis procedure for obtaining Zn2SiO4:Eu3+ powder, based on the combination of standard sol-gel and modified combustion method. Influence of preparation conditions on the structure and morphology are analyzed using X-ray diffraction and scanning electron microscopy. Luminescence properties of Eu3+ are investigated with fluorescence emission and lifetime measurements. (C) 2009 Elsevier B.V. All rights reserved.

Investigation done on Y(2)SiO(5) nanoparticles doped with Eu(3+) ions obtained with the alkoxy sol-gel route is presented in this paper. We investigate the optical and thermal properties of obtained material during the conversion of the gel into nanocrystalline form. Fourier transform infrared spectroscopy and fluorescence spectroscopy of Eu(3+) ions are used for the optical characterizations, while thermal analysis is done with thermogravimetric-differential thermal analysis technique. Material exhibits characteristic luminescence emission of the trivalent europium ion.