Kubelka-Munk Theory Research Articles

Measurement and modeling of polarized reflectance factor on rough coating materials using a goniometer instrument

The study of spectral polarization characteristics of different materials is benefit to improve the abilities of object recognition and polarization remote sensing applications. Most of studies focus on the degree of polarization of the material, the polarized reflectance factor is rarely reported. In this study, we measure the spectral polarized reflectance factor of typical rough coating materials (green and black paint) in the range of 400–900 nm. The polarization reflectance characteristics of coating materials have been analyzed based on the measured data sets and the polarization mechanism. Moreover, a polarized reflectance parameter model is built with the basic of the Kubelka-Munk theory, and the optimal model parameters are fitted by the genetic algorithm. The analyses indicate that our measured polarized reflectance factors of the rough coating samples are spectrally neutral, and the distribution of the polarized reflectance factor is obviously anisotropic. The polarized reflectance parameter model provides good fits to the measurements, which confirms the validity and reliability of the modeling, and can precisely describe the polarization reflectance behaviors of rough coating materials. We also found that contrast between the rough coating samples and typical natural background in polarized reflectance factor is much greater than in degree of linear polarization in visible and near-infrared bands, which suggests that it is more helpful to distinguish the objects in natural environment by using the polarized reflectance factor indicator. The study has a great potential for object identification and polarization scene modeling.

A low temperature synthesis of Ag2S nanostructures and their structural, morphological, optical, dielectric and electrical studies: An effect of SDS surfactant concentration

Nanostructures of Silver sulfide (Ag2S) possess wide range of applications as infrared detectors, resistance-switches and nonvolatile memory devices. Hence, the authors aim is to synthesize the Ag2S nanostructures using facile chemical route at low temperature (i.e. ~ 65°) with different concentrations (i.e. from 0 to 1 g) of sodium dodecyl sulfate (SDS) surfactants for such applications. High crystallinity and single phase was proved by X-ray diffraction and EDX analyses as there was no peak due to impurity was seen. The crystallite size was estimated and found in range of 39–44 nm. SEM analysis showed the homogeneous nanoparticles formation is all samples and the size was obtained in range of 40–60 nm for Ag2S samples prepared with 0, 0.1, 0.25 g SDS, however at higher SDS concentrations the size was found in range of 30–50 nm. Diffused reflectance spectra were measured for all samples and Kubelka-Munk theory is applied to estimate the energy gap which is found in range of 1–1.04 eV. The refractive index was also estimated in the range of 1.7–2 in 200–1200 nm wavelength region. The prepared nanoparticles possess high dielectric constant and electrical conductivity.

Preparation of La doped ZnO ceramic nanostructures by electrospinning–calcination method: Effect of La3+ doping on optical and photocatalytic properties

Ceramic nanostructures of ZnO doped with La3+ ions (0.02%, 1%, 2% and 4%) were prepared by electrospinning-calcination method. Polyvinylpyrrolidone (PVP) was used as an additional polymer to promote the electrospinning. And, the intermediate electrospun products were processed thermically at 700 °C for 3 h. The produced materials were characterized morphologically and structurally by using scanning/transmission electron microscopy (SEM/TEM) and X-ray diffraction (XRD). The XRD patterns showed the successful incorporation of La ions in the hexagonal wurtzite structure of ZnO. Optical band gaps of these ceramic nanostructures were estimated from reflectance data using Kubelka-Munk theory and were found to vary from 2.589 to 2.889 eV, depending on La3+ doping concentration. Photoluminescence spectra of undoped/doped ZnO with different contents of La3+ ion were investigated. The decay curves for the La3+ ion doped ZnO nanostructures were measured and the average lifetime was found to increase from 2.69 to 2.80 ns when La3+ content increased from 0 to 4%. The photocatalytic activity of doped products (ZnO:La) was investigated by using Congo-Red dye as a probe molecule for degradation under UV-light. Maximal color removal efficiency (97.63%) was observed experimentally for ZnO doped with 2% La3+ in dosage of 0.283 g/L. Finally, the recovered catalyst was thermally activated at 700 °C (1 h) and then successfully reused for the dye photodegradation.

Semi-Empirical Soil Organic Matter Retrieval Model With Spectral Reflectance

Rapid and accurate monitoring of soil organic matter (SOM) content is of great significance for precision fertilization of farmland. However, the SOM retrieval models are mainly established by statistical methods, which have limited application scope and incomplete theoretical foundation. Moreover, the accuracy of the SOM retrieval models remains raised. In this paper, for the first time, a semi-empirical SOM content retrieval model is constructed, which has certain theoretical basis, strong applicability and higher accuracy than before. Based on the Kubelka-Munk (KM) theory, the SOM retrieval model with the absorption coefficient k and scattering coefficient s related to SOM (r = k/s) is derived. The validity and reliability of the model are confirmed with validation set (n = 26) including three sorts of soils. Results show that the model can estimate SOM content in different sorts of soils with high prediction accuracy and good prediction ability (root mean square errors of prediction (RMSEP), coefficients of determination (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and relative percentage deviation (RPD) values of 0.18%, 89.9% and 3.2, respectively) in the range of 552-950nm. The model provides an innovative method for predicting SOM content.

Determination of the optical properties of Intralipid 20% over a broadband spectrum

The aim of this study is to characterize the optical properties of Intralipid20% using two methods modified Kubelka-Munk model and Mie theory and to test the applicability of a modified Kubelka-Munk model with a single integrating sphere system over a wide wavelength range 470 – 725nm. Scattering coefficients which estimated by these two methods were matched and the absorption effect was observed and quantified. Finally, the imaginary part of the refractive index was estimated besides scattering, absorption and anisotropy coefficients. Full Text: PDF ReferencesB.W. Pogue, and M.S. Patterson, "Review of tissue simulating phantoms for optical spectroscopy, imaging and dosimetry", J. Biomed. Opt. 11, 4(2006). CrossRef J. Hwang, C. Ramella-Roman, and R. Nordstrom, "Introduction: Feature Issue on Phantoms for the Performance Evaluation and Validation of Optical Medical Imaging Devices", Biomed. Opt. Express. 3, 6(2012). CrossRef P. Ninni, F. Martelli, and G. Zaccanti, "Intralipid: towards a diffusive reference standard for optical tissue phantoms", Phys. Med. Biol 56, 2(2011). CrossRef S. Flock, S. Jacques, B. Wilson, W. Star, and J.C. van Gemert, "Optical properties of intralipid: A phantom medium for light propagation studies", Lasers. Surg. Med 4, 12(1992). CrossRef R. Michels, F. Foschum, and A. Kienle, "Optical properties of fat emulsions", Opt. Express. 16, 8(2008). CrossRef L. Spinelli et al. "Calibration of scattering and absorption properties of a liquid diffusive medium at NIR wavelengths. Time-resolved method", Opt. Express. 15, 11(2007). CrossRef L. Spinelli et al. "Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink", Biomed. Opt. Express. 5, 7(2014). CrossRef H. van Staveren, C. Moes, J. van Marle, S. Prahl, and J. van Gemert, "Light scattering in lntralipid-10% in the wavelength range of 400–1100 nm", Appl. Opt. 30, 31(1991). CrossRef B. Wilson, M. Patterson, and S. Flock, "Indirect versus direct techniques for the measurement of the optical properties of tissues", Photochem. Photobiol. 46, 5(1987). CrossRef H. Soleimanzad, H. Gurden, and F. Pain, "Optical properties of mice skull bone in the 455- to 705-nm range", J. Biomed. Opt. 22, 1(2017). CrossRef C. Holmer et al. "Optical properties of adenocarcinoma and squamous cell carcinoma of the gastroesophageal junction", J. Biomed. Opt. 12, 1(2007). CrossRef S. Thennadil, "Relationship between the Kubelka–Munk scattering and radiative transfer coefficients", OSA. 25, 7(2008). CrossRef L. Yang, and B. Kruse, "Qualifying the arguments used in the derivation of the revised Kubelka–Munk theory: reply", OSA. 21, 10(2004). CrossRef W. Vargas, and G. Niklasson, "Applicability conditions of the Kubelka–Munk theory", Appl. Opt. 36, 22(1997). CrossRef A. Krainov, A. Mokeeva, E. Segeeva, P. Agrba, and M. Kirillin, "Optical properties of mouse biotissues and their optical phantoms", Opt. Spec. 115, 2(2013). CrossRef H.C. van de Hulst, Light Scattering by Small Particles. (New York, Dover Publication 1981). CrossRef C. Matzler, Matlab Functions for Mie Scattering and Absorption. (Bern, Bern university 2002). DirectLink C. Matzler, Matlab Functions for Mie Scattering and Absorption, version 2 (Bern, Bern university 2002). DirectLink G. Segelstein, The complex refractive index of water [dissertation]. (Kansas, university of Missouri-Kansas city 1981). DirectLink A. Shahin, and W. Bachir, Pol. J. Med. Phys. Eng. 21, 4(2017). CrossRef

A novel approach to prepare one-pot Fe/PPy nanocomposite and evaluation of its microwave, magnetic, and optical performance

The aim of this study was preparation of Fe/Fe2O3/Fe3O4 (Fe)/polypyrrole (PPy) nanocomposite using reductive method and investigation of its microwave absorbing properties using polymethylmethacrylate (PMMA) medium. Firstly, PPy was prepared by an oxidative polymerization method with Fe3+ as a doping agent. Next, the Fe/PPy nanocomposite was formed by in situ reduction of Fe2+ and remained Fe3+ with adding sodium borohydride in the solution under an inert nitrogen atmosphere. Finally, PPy and Fe/PPy nanostructures were separately suspended within the PMMA matrix to examine their microwave absorbing characteristics. The prepared PPy and Fe/PPy nanostructures were studied using the Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), and field emission scanning electron microscopy (FE-SEM). The diffuse reflection spectroscopy (DRS) analysis presented a 1.79 eV band gap for the Fe/PPy nanocomposite based on the Kubelka–Munk theory. The vibrating sample magnetometer (VSM) revealed that magnetic properties were reinforced in the Fe/PPy nanocomposite. According to the results obtained by vector network analyzer (VNA), the maximum reflection loss of Fe/PPy/PMMA nanocomposite was −76.02 dB at 8.96 GHz with a thickness of 3.2 mm, absorbing all of the x-band frequency more than 12.72 dB with a thickness of 2.8 mm. Interestingly, the Fe/PPy/PMMA nanocomposite demonstrated a bandwidth >3.4 GHz more than 10 dB from 2.2 to 3.2 mm at the x-band frequency.

Facile low temperature synthesis and characterization of bismuth molybdate (Bi2MoO6) nanostructures: An effect surfactant concentration

Bismuth molybdates are found to be very fascinating materials due to their inimitable characteristics along with other budding requests like: ion conductors, acousto-optics, photo-conductors, sensors, photocatalyst etc. Owing to their exceptional applications, we aimed to synthesized the nanostructures of bismuth molybdate with different concentrations of CTAB as surfactant. Final products were subsequently dried and annealed at 550 °C for 2 h. X-ray diffraction and FT-Raman study confirm the single phase of α-Bi2Mo3O12 predominantly. The purity of synthesized product was further confirmed from EDX and SEM mapping analyses. The crystallite size estimated from Scherer rule are found in range of 21 nm to 30 nm and dislocation density and strain is found of the order of 10−3. Morphological analysis was carried out with the help of SEM and indicates the variation in shape and size due to different concentrations of CTAB. The morphology of nanoparticles is spherical of size in range of 30 to 50 nm. SEM images also approved mesoporous nanostructure formation in all samples. The energy gap values evaluated from Kubelka-Munk theory are found to be reduced from 2.979 to 2.713 eV due to increase of CTAB concentration that leads to increase in particle size. With increasing the CTAB concentration from 0.1 g to 1 g the dielectric permittivity was found to be enhanced from 24 to 32. Furthermore, the electrical conductivity is also increased with frequency and follow the universal frequency power law. Synthesized homogeneous spherical nanoparticles and improved characteristics, mesoporous nature and low energy gap makes them favorable in photocatalytic applications.

The effects of nanoporous Fe2O3 synthesized via mechano-thermal process on electrical and optical properties of zinc oxide

This study was performed to investigate the effects of nanoporous hematite (Fe2O3) the electrical and optical properties on zinc oxide. Zinc oxide powder was commercially obtained. The nanoporous hematite with iron core was prepared using a specific method including ball milling and annealing processes. The particle size of the nanoporous hematite was determined to be 40–50 nm using an electron microscope. The electrical conductivity values of pure ZnO and the composites with 1% Fe2O3, 3% Fe2O3, and 5% Fe2O3 were obtained to be 6.55 × 10−5, 5.35 × 10−4, 3.79 × 10−4 and 1.29 × 10−4 S/cm, respectively. The nanoporous Fe2O3 with iron core increases the electrical conductivity of the ZnO-nanoporous:Fe2O3 composites. The optical band gap (Eg) values of the composites were determined by the Kubelka-Munk theory based on the diffused reflectance. As the nanoporous Fe2O3 content is increased, the Eg values of the composites are decreased. The obtained results indicate that the electrical and optical properties of the ZnO semiconductor is improved with the nanoporous Fe2O3.

Calculation method of a random beard fibrogram based on the derived Kubelka–Munk theory

The random beard image method is a newly developed fiber length measurement method with the advantages of speed, reliability and low cost. This paper proposed the methods of acquiring an accurate and stable fibrogram from the transmission image with the random beard image method based on the derived Kubelka–Munk theory. In the dual-beard preparation process, the optical properties of the short fiber region in the beard were changed by the napping effect. To solve this problem, an imitating experiment with five types of wool fibers was designed to obtain the optical coefficient of the maximum value of the fibrograms of 1.03. To eliminate the random error of the sample, the symmetry principle was adopted to determine the start line of the dual-fibrogram, and the weighted smoothing average fibrogram from two dual-beards is used as the final fibrogram. In addition, upon testing 20 types of wool fiber samples by the random beard image method and the international standard instrument Almeter100, the waviness coefficient of 1.10 was determined. A Z-test and Bland–Altman plot were also applied to verify the accuracy and repeatability of the random beard image method. The results show that under the significance level α = 0.05, the accuracy and the repeatability of the two methods are at the same level. This method sets the foundation for measuring the fiber length distribution parameters, especially the short fiber content.

Nonlinear Unmixing of Hyperspectral Datasets for the Study of Painted Works of Art.

Nonlinear unmixing of hyperspectral reflectance data is one of the key problems in quantitative imaging of painted works of art. The approach presented is to interrogate a hyperspectral image cube by first decomposing it into a set of reflectance curves representing pure basis pigments and second to estimate the scattering and absorption coefficients of each pigment in a given pixel to produce estimates of the component fractions. This two-step algorithm uses a deep neural network to qualitatively identify the constituent pigments in any unknown spectrum and, based on the pigment(s) present and Kubelka-Munk theory to estimate the pigment concentration on a per-pixel basis. Using hyperspectral data acquired on a set of mock-up paintings and a well-characterized illuminated folio from the 15th century, the performance of the proposed algorithm is demonstrated for pigment recognition and quantitative estimation of concentration.

Optimized Structural and Colorimetrical Modeling of Yarn-Dyed Woven Fabrics Based on the Kubelka-Munk Theory

Optimized Structural and Colorimetrical Modeling of Yarn-Dyed Woven Fabrics Based on the Kubelka-Munk Theory

Phosphor modeling based on fluorescent radiative transfer equation.

The behaviors of the light propagation in the phosphor play a vital role in determining the optical performance of the phosphor-converted light-emitting diodes (pc-LEDs). In this paper, we presented a general model based on the radiative transfer equation integrated with fluorescence (FRTE) to describe the overall light propagating properties in the phosphor layer in terms of light absorption, strong forward scattering, and fluorescence. The model was established by accounting for general boundary conditions including the LED Lambertian incidence, the diffuse reflection at the substrate/reflector, and the Fresnel reflection at the phosphor-air interface. The spectral element method (SEM) was extended to numerically solve FRTE. The radiant intensity at any location and direction of blue and yellow light was iteratively calculated, in which case the angular properties could be further evaluated. The model was validated by comparing the light extraction efficiency (LEE) and angular correlated color temperature (CCT) calculated by the presented model with the experimental results. Good agreements were achieved between model predictions and measurements with the corresponding maximum deviation of 4.9% and 3.7% for LEE and CCT, respectively. We also conducted a comparison between our model and the previous Kubelka-Munk (KM) theory. It has been revealed that the KM theory may overestimate the phosphor heating due to lacking of the blue light scattering effect.

Discovery of the Linear Region of Near Infrared Diffuse Reflectance Spectra Using the Kubelka-Munk Theory.

Particle size is of great importance for the quantitative model of the NIR diffuse reflectance. In this paper, the effect of sample particle size on the measurement of harpagoside in Radix Scrophulariae powder by near infrared diffuse (NIR) reflectance spectroscopy was explored. High-performance liquid chromatography (HPLC) was employed as a reference method to construct the quantitative particle size model. Several spectral preprocessing methods were compared, and particle size models obtained by different preprocessing methods for establishing the partial least-squares (PLS) models of harpagoside. Data showed that the particle size distribution of 125–150 μm for Radix Scrophulariae exhibited the best prediction ability with = 0.9513, RMSEP = 0.1029 mg·g−1, and RPD = 4.78. For the hybrid granularity calibration model, the particle size distribution of 90–180 μm exhibited the best prediction ability with = 0.8919, RMSEP = 0.1632 mg·g−1, and RPD = 3.09. Furthermore, the Kubelka-Munk theory was used to relate the absorption coefficient k (concentration-dependent) and scatter coefficient s (particle size-dependent). The scatter coefficient s was calculated based on the Kubelka-Munk theory to study the changes of s after being mathematically preprocessed. A linear relationship was observed between k/s and absorption A within a certain range and the value for k/s was >4. According to this relationship, the model was more accurately constructed with the particle size distribution of 90–180 μm when s was kept constant or in a small linear region. This region provided a good reference for the linear modeling of diffuse reflectance spectroscopy. To establish a diffuse reflectance NIR model, further accurate assessment should be obtained in advance for a precise linear model.

New insights into structural and magnetic properties of Ce doped ZnO nanoparticles

Cerium doped ZnO nanoparticles were successfully prepared by the co-precipitation method using cerium sulphate as dopant precursor. The effect of cerium doping on the structural, morphological and optical properties of the obtained nanoparticles were investigated. X-ray diffraction and EDX analyses indicated that the cerium doped ZnO nanoparticles retained the hexagonal wurtzite structure of ZnO and the cerium ions were incorporated into the ZnO lattice. TEM images showed the average diameter of cerium doped ZnO nanoparticles (30–60 nm). The absorption spectra were determined from the reflectance spectra using the Kubelka-Munk theory and the band gap energy was found to decrease as the Ce doping level increased. Ce doped ZnO nanoparticles exhibited an intense UV emission at about 380 nm, and a blue emission at 400–500 nm due to surface defects. Room temperature ferromagnetism was found in these samples associated with Ce3+ ion doping and oxygen vacancies.

Reconstructing Van Gogh\u2019s palette to determine the optical characteristics of his paints

The colors of Field with Irises near Arles, painted by Van Gogh in Arles in 1888, have changed considerably. To get an idea of how this painting, as well as other works by Van Gogh, looked shortly after their production, the Revigo (Re-assessing Vincent van Gogh’s colors) research project was initiated. The aim of this project was to digitally visualize the original colors of paintings and drawings by Vincent van Gogh, using scientific methods backed by expert judgement where required. We adopted an experimental art technological approach and physically reconstructed Van Gogh’s full palette of oil paints, closely matching those he used to paint Field with Irises near Arles. Sixteen different paints were reconstructed, among which the most light-sensitive pigments and linseed oil, which is prone to yellowing, were produced according to 19th century practice. The resulting pigments and oils were chemically analyzed and compared to those used by Van Gogh. The ones that resembled his paints the most were used in the paint reconstructions. Other pigments were either obtained from the Cultural Heritage Agency’s collection of historical pigments, or purchased from Kremer Pigmente. The reconstructed paints were subsequently used to calculate the absorption K and scattering S parameters of the individual paints. Using Kubelka–Munk theory, these optical parameters could in turn be used to determine the color of paint mixtures. We applied this method successfully to digitally visualize the original colors of Field with Irises near Arles. Moreover, the set of optical parameters presented here can similarly be applied to calculate digital visualizations of other paintings by Van Gogh and his contemporaries.

Electrochemical, photoluminescence and EPR studies of Fe3+ doped nano Forsterite: Effect of doping on tetra and octahedral sites

For the first time we report on, structural, electrochemical, optical and electron paramagnetic resonance (EPR) properties of Mg2SiO4:Fe3+ nanomaterial synthesized by low temperature (350 °C) solution combustion method. Cyclic voltammetry and electrochemical impedance analysis were carried out to investigate the conduction efficiency and charge transfer resistance of Fe3+ doped Mg2SiO4. The Kubelka–Munk theory was used to calculate the bandgap of the prepared nanomaterial by analysing the diffuse reflectance spectra. Photoluminescence properties were studied by exciting the samples at 375 nm wavelength which results in yellow emission and applicable for warm white light emitting devices. The quantum efficiency of the optimized sample was found to be 46%. The decay curve analysis were carried out for the optimized (3 mol%) sample was found to be 6.4 ms. The EPR spectra were recorded at RT in X-band for Fe3+ (1 & 11 mol%) doped Mg2SiO4.

In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

The extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (&lt;5 wt %) lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe3O4. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible light using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe2O3 increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe+2.57 for the catalyst with no lanthana and Fe+2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe+2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe+2.57. The findings of this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. The paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities.

Interdisciplinary approach to develop a disposable real time monitoring tool for the cleaning of graphic artworks. Application on “le Nozze di Psiche”

Disposable non-invasive and compatible real time monitoring tool was developed in order to follow the cleaning process of paper artwork directly in situ. This tool was based on a biocompatible cleaning hydrogel coupled with flow electrochemical diagnostic tool, suitable to verify in situ and in a simple way the assessment of degradation of artwork and the efficiency of cleaning process. In this paper, the results obtained by applying this tool on a great format artwork with a lining as support, “Le Nozze di Psiche”, engraved by Diana Scultori, printed in 1613, are reported. This opera was affected by a structural and chromatic deterioration due to a strong oxidative degradation. Such deterioration was probably accelerated by the adhesive (a mixture of starch paste and animal glue) used in a previous lining intervention. In this case, the cleaning agents used are rigid hydrogels of Gellan gum, modified with hydrolytic enzymes. By using the flow sampling system, all materials removed by the gel was carried up to a thin layer cell containing a selective electrochemical biosensors, suitable to monitor both treatments, the cleaning process and the removal of lining. These were monitored, allowing understanding when both processes were completed, thus avoiding lengthy and unnecessary cleaning applications. The effectiveness of cleaning with Gellan gel was assessed quantitatively by using non-invasive optical reflectance spectroscopy by a portable instrumentation, elaborating data with an improved version of the Kubelka-Munk theory in order to recover the absorption coefficient of the cellulose fibers of “Le Nozze di Psiche”. The concentration of oxidized groups acting as chromophores was obtained by comparing the experimental optical absorption spectra to those simulated computationally by using TDDFT-based calculations. By following the cleaning with Gellan gel the results indicate a large decrease of the concentration of degradation product of cellulose. Moreover, chromatographic analysis were carried out in order to evaluate the amount of acid compound, produced during the aging and present on the graphic artwork, using the Gellan gel after cleaning step. The results obtained from the restoration of “Le Nozze di Psiche” have allowed the restorers to evaluate innovative methods for cleaning treatment of paper artworks with a highly specialized scientific-diagnostic approach.

Effect of the synthesis conditions on the structural, morphological and optical properties of Bi2Te2.7Se0.3 nanoparticles

Beside their promising utility as thermoelectric generators, Bi2Te3 and related compounds have several applications in electronic and optoelectronic devices. In this work, Bi2Te2.7Se0.3 nanoparticles (NPs) were successfully prepared via physical vapor deposition technique at different conditions of flow rate and temperature. The x-ray diffraction patterns show that, the NPs crystallize in a rhombohedral crystal structure with preferable growth along the (015) plane. Field-emission scanning electron microscope (FE-SEM) investigation shows that the NPs size depends significantly on the synthesis conditions of flow rate and temperature where it decreases with the decrease in the former or with the increase in the later. The effect of deposition conditions on the final morphology can be interpreted through the accompanied variation in the concentration of the gaseous precursors in the hot zone. The optical properties were studied using Kubelka-Munk theory. Optical band gaps of 0.52, 0.58, 0.53 eV were determined for the samples synthesized under different conditions.

Quantitative coating thickness determination using a coefficient-independent hyperspectral scattering model

BackgroundHyperspectral imaging is a technique that enables the mapping of spectral signatures across a surface. It is most commonly used for surface chemical mapping in fields as diverse as satellite remote sensing, biomedical imaging and heritage science. Existing models, such as the Kubelka-Munk theory and the Lambert-Beer law also relate layer thickness with absorption, and in the case of the Kubelka-Munk theory scattering, however they are not able to fully describe the complex behavior of the light-layer interaction.MethodsThis paper describes a new approach for hyperspectral imaging, the mapping of coating surface thickness using a coefficient-independent scattering model. The approach taken in this paper is to model the absorption and scattering behavior using a developed coefficient-independent model, calibrated using reference sample thickness measurements performed with optical coherence tomography.ResultsThe results show that this new model, by considering the spectral variation that can be recorded by the hyperspectral imaging camera, is able to measure coatings of 250 μm thickness with an accuracy of 11 μm in a fast and repeatable way.ConclusionsThe new coefficient-independent scattering model presented can successfully measure the thickness of coatings from hyperspectral imaging data.