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The characteristics of modern portable spectrometers based on photodetector arrays make it possible to create on their basis a new class of devices for operational control of the optical properties of various media. The introduction into the practice of diffuse reflectance spectroscopy with spatial resolution is hampered by the lack of an analysis of the influence of the width of the spectral region used and other sources of measurement uncertainty on the unambiguous determination of the optical properties of finely dispersed scattering materials. This article describes a method of determining the coefficient of local diffuse reflection and calculating the spectral parameters of the reduced scattering and absorption of radiation based on the differences in their shape, which are clearly manifested in a wide range of the spectrum. This allows the reduction in the determination of the desired spectral dependencies to the formation of a residual function that requires varying the values of only two parameters. A method for normalising the recorded spectral dependencies is described, which makes it possible to minimise the influence of the spectral characteristics of the equipment used on the recorded spectral–spatial profiles. Approbation of the method was carried out on examples of processing spectral–spatial diffuse reflection profiles of four samples of finely dispersed scattering structural materials, as well as diffuse reflection profiles of living tissue in the palm thenar region. The sources of uncertainty that affect the uniqueness of the obtained solutions are found, and solutions are proposed to minimise their influence on the desired spectral dependencies. The results obtained indicate the prospects of using the described method for creating equipment for non-destructive control of the optical properties of finely dispersed materials and media, including living tissues and food products.

The method of immersion optical clearing reduces light scattering in tissues, which improves the use of optical technologies in the practice of clinicians. In this work, we studied the optical and molecular diffusion properties of cat ovarian tissues in the follicular (F-ph) and luteal (L-ph) phases under the influence of glycerol using reflectance spectroscopy in a broad wavelength range from 200 to 800 nm. It was found that the reflectance and transmittance of the ovaries are significantly lower in the range from 200 to 600 nm than for longer wavelengths from 600 to 800 nm, and the efficiency of optical clearing is much lower for the ovaries in the luteal phase compared to the follicular phase. For shorter wavelengths, the following tissue transparency windows were observed: centered at 350 nm and wide (46 ± 5) nm, centered at 500 nm and wide (25 ± 7) nm for the F-ph state and with a center of 500 nm and a width of (21 ± 6) nm for the L-ph state. Using the free diffusion model, Fick’s law of molecular diffusion and the Bouguer–Beer–Lambert radiation attenuation law, the glycerol/tissue water diffusion coefficient was estimated as D = (1.9 ± 0.2)10−6 cm2/s for ovaries at F-ph state and D = (2.4 ± 0.2)10−6 cm2/s—in L-ph state, and the time of complete dehydration of ovarian samples, 0.8 mm thick, as 22.3 min in F-ph state and 17.7 min in L-ph state. The ability to determine the phase in which the ovaries are stated, follicular or luteal, is also important in cryopreservation, new reproductive technologies and ovarian implantation.

Understanding tumors and their microenvironment are essential for successful and accurate disease diagnosis. Tissue physiology and morphology are altered in tumors compared to healthy tissues, and there is a need to monitor tumors and their surrounding tissues, including blood vessels, non-invasively. This preliminary study utilizes a multimodal optical imaging system combining hyperspectral imaging (HSI) and threedimensional (3D) optical profilometry (OP) to capture hyperspectral images and surface shapes of subcutaneously grown murine tumor models. Hyperspectral images are corrected with 3D OP data and analyzed using the inverseadding doubling (IAD) method to extract tissue properties such as melanin volume fraction and oxygenation. Blood vessels are segmented using the B-COSFIRE algorithm from oxygenation maps. From 3D OP data, tumor volumes are calculated and compared to manual measurements using a vernier caliper. Results show that tumors can be distinguished from healthy tissue based on most extracted tissue parameters (p< 0.05). Furthermore, blood oxygenation is 50% higher within the blood vessels than in the surrounding tissue, and tumor volumes calculated using 3D OP agree within 26% with manual measurements using a vernier caliper. Results suggest that combining HSI and OP could provide relevant quantitative information about tumors and improve the disease diagnosis.

Three new tellurates, namely, K2BaPb0.62Ba0.38Te2O9 (1), Rb2BaPb0.7Ba0.3Te2O9 (2), and Ba2KLiTe2O9 (3), with hexagonal triple-perovskite structures have been designed via a cation substitution strategy. All three centrosymmetric compounds crystallize in the same hexagonal space group P63/mmc. In their structures, the [BTe2O9] (B = Pb/Ba for 1 and 2 and Li for 3) groups construct the final three-dimensional framework using face-sharing [Te2O9] dimmers and vertex-linked [BO6] linkages. Meanwhile, the theoretical calculations demonstrate the numerical differences of their birefringence. Thermal stability analysis and differential scanning calorimetry were performed, and UV-vis-NIR diffuse reflectance spectra and infrared spectra of the three title compounds were also characterized and analyzed.

The age of whole otoliths from barramundi (Lates calcarifer) obtained from the southern Gulf of Carpentaria were estimated using Fourier transform near-infrared (FT-NIR) spectroscopy. Otoliths from 1716 barramundi collected in 2006, 2009 and 2012–2015 were used in this study. Partial least-squares regression models (PLS-R) and multiple linear regression models (MLR) were developed from the diffuse reflectance spectra and the age was obtained from traditional sectioned otoliths. Calibration models were built up over consecutive years (2012–2015) by using a subset of the samples and used to predict the age of the remaining samples and samples from the following year. Results suggest that when seasonal (temporal) variability is incorporated into the calibration model, FT-NIR has the ability to predict barramundi age (validation R2 ranged from 0.73 to 0.78; RMSEP ranged from 6.92 to 7.64 months). The predicted age class was within 1 year of the reference age in over 96% of the samples. These models were also able to predict the age of otoliths from 2006 and 2009, which were retrieved from long-term storage (validation R2 ranged from 0.77 to 0.84; RMSEP ranged from 8.66 to 10.88 months). The results from this study have shown the potential for barramundi from the southern Gulf of Carpentaria to be aged quickly and accurately by using FT-NIR.

An integrated hardware–software approach was proposed to record the analytical response of sensor matrices exposed for a long time to liquid hydrocarbons and their vapors. A cell was designed and 3D-printed to detect hydrocarbons by photonic-crystal sensor matrices with computer recording and accumulation of the diffuse reflectance spectra with subsequent metrological signal processing. The low content of volatile organic compounds in the air of the working area was determined, and the obtained data agree well with the stages of the working cycle in paint and varnish production. The statistical significance of the changes in the analytical signal of the photonic-crystal sensor that were caused by the time variation of the concentration of hydrocarbons was confirmed.

Colorectal cancer (CRC) is the third most common type of cancer worldwide and the second most deadly. Recent research efforts have focused on developing non-invasive techniques for CRC detection. In this study, we evaluated the diagnostic capabilities of diffuse reflectance spectroscopy (DRS) for CRC detection by building 6 classification models based on support vector machines (SVMs). Our dataset consists of 2889 diffuse reflectance spectra collected from freshly excised ex vivo tissues of 47 patients over wavelengths ranging from 350 and 1919 nm with source-detector distances of 630-µm and 2500-µm to probe different depths. Quadratic SVMs were used and performance was evaluated using twofold cross-validation on 10 iterations of randomized training and test sets. We achieved (93.5 ± 2.4)% sensitivity, (94.0 ± 1.7)% specificity AUC by probing the superficial colorectal tissue and (96.1 ± 1.8)% sensitivity, (95.7 ± 0.6)% specificity AUC by sampling deeper tissue layers. To the best of our knowledge, this is the first DRS study to investigate the potential of probing deeper tissue layers using larger SDD probes for CRC detection in the luminal wall. The data analysis showed that using a broader spectrum and longer near-infrared wavelengths can improve the diagnostic accuracy of CRC as well as probing deeper tissue layers.

Two new selenite compounds Ca2Ni(HSeO3)2(SeO3)2 (CaNi) and Na2Cu(SeO3)2·2H2O (NaCu) were obtained by a hydrothermal method. Both compounds crystallize in the triclinic system of space group P1, featuring a selenite-bridged one-dimensional (1D) spin-chain structure running along the a-axis. Magnetic measurements indicate that CaNi undergoes a long-range antiferromagnetic order (LRO) at TN = ∼3.8 K, while NaCu does not exhibit a LRO down to 2 K but the onset of a short-range correlation at TM = ∼30 K. The intrachain exchange coupling J/kB = -2.59 K for CaNi and J/kB = -47.13 K for NaCu can be estimated by a fit using the 1D spin-chain model. The thermogravimetric analyses show that both compounds are stable below 130 °C. The UV-vis diffuse reflectance spectra indicate that the band gaps of CaNi and NaCu are 4.38 eV and 3.18 eV, respectively.

Metal chalcogenides play a critical role in the infrared (IR) nonlinear optical (NLO) field. However, Eu-based chalcogenide-type IR NLO materials are still scarce up to now. In this paper, two new quaternary Eu-based chalcogenides, EuHgGeSe4 and EuHgSnS4, containing the "NLO active groups" [HgQ4]6- (Q = S, Se) and [GeSe4]4-/[SnS4]4- were synthesized through traditional high-temperature solid-state reactions. They possess noncentrosymmetric structures, crystallizing in the Ama2 space group, and exhibit strong phase-matchable second-harmonic-generation (SHG) responses (3.1× and 1.77× that of AgGaS2 for EuHgGeSe4 and EuHgSnS4, respectively). Meanwhile, the optical band gaps of EuHgGeSe4 (1.97 eV) and EuHgSnS4 (2.14 eV) were determined from UV-vis-NIR diffuse reflectance spectra. Differential scanning calorimetry (DSC) analyses reveal the congruent-melting behavior of EuHgGeSe4. Furthermore, structural analysis and theoretical calculations verify the critical driving effects of [HgQ4]6- tetrahedra on the strong SHG activity. The overall results demonstrate that EuHgGeSe4 and EuHgSnS4 are potential IR NLO materials.

The layered perovskite (MA)2PbI2(SCN)2 (MA = CH3NH3+) is a member of an emerging series of compounds derived from hybrid organic-inorganic perovskites. Here, we successfully synthesized (MA)2PbI2-xBrx(SCN)2 (0 ≤ x < 1.6) by using a solid-state reaction. Despite smaller bromide substitution for iodine, 1% linear expansion along the a axis was observed at x ∼ 0.4 due to a change of the orientation of the SCN- anions. Diffuse reflectance spectra reveal that the optical band gap increases by the bromide substitution, which is supported by the DFT calculations. Curiously, bromine-rich compounds where x ≥ 0.8 are light sensitive, leading to partial decomposition after ∼24 h. This study demonstrates that the layered perovskite (MA)2PbI2(SCN)2 tolerates a wide range of bromide substitution toward tuning the band gap energy.

New iron(II) complexes with 2,6-bis(benzimidazol-2-yl)pyridine (L) and closo-borate(2–) anions—[FeL2][B10H10] ⋅ 2H2O and [FeL2][B12H12] ⋅ H2O—have been synthesized. The complexes have been characterized by static magnetic susceptibility measurements, electronic (diffuse reflectance spectra), IR, and EXAFS spectroscopy, and X-ray diffraction analysis. A study of the μeff(T) dependence in the temperature range 80–500 K has shown that the complexes exhibit a high-temperature spin crossover 1А1 ⇔ 5Т2.

The optical properties of silicon dioxide hollow particles with different size were investigated in UV/visible/near-IR region, as well as X-ray photoelectron spectra were analyzed. Synthesis of SiO2 hollow particles was carried out using a template method. It was established that hollow particle reflectance lower than bulk microparticles. Absorptance in the red and near infrared spectral ranges increases with decreasing size of hollow particles, but in the UV-region conversely. This is due to different absorption centers.

The diffuse reflectance spectra from green coniferous and deciduous leaves of trees and shrubs growing in Krasnodar region are compared with the diffuse reflectance spectra from green synthetic decorative and artificial leaves and various camouflage materials. It is proposed to use vegetation indices of “greenness” for the discrimination of coniferous and deciduous leaves of trees and shrubs from decorative and artificial materials by optical diffuse reflectance spectroscopy.

Well dispersed SnO2/ZnO composites with platelike shape were synthesized via a facile method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and UV–Vis diffuse reflectance spectra (UV–Vis DRS) were used to characterize the products. Photocatalytic activity of the as-prepared SnO2/ZnO composites was evaluated by degradation of persistent organic pollutant 2,4-dichlorophenol (2,4-DCP) in aqueous solution. Compared with pure ZnO, SnO2/ZnO composites show higher photocatalytic activity under simulated solar light irradiation. 2,4-DCP is almost completely degraded by SnO2/ZnO composite with molar ratio 1 : 3 within 3.5 h. Moreover, the SnO2/ZnO composites also show excellent circulation stability. The high performance of SnO2/ZnO is mainly attributed to the synergistic effect between SnO2 and ZnO.

In this study, we used machine learning techniques to reconstruct the wavelength dependence of the absorption coefficient of human normal and pathological colorectal mucosa tissues. Using only diffuse reflectance spectra from the ex vivo mucosa tissues as input to algorithms, several approaches were tried before obtaining good matching between the generated absorption coefficients and the ones previously calculated for the mucosa tissues from invasive experimental spectral measurements. Considering the optimized match for the results generated with the multilayer perceptron regression method, we were able to identify differentiated accumulation of lipofuscin in the absorption coefficient spectra of both mucosa tissues as we have done before with the corresponding results calculated directly from invasive measurements. Considering the random forest regressor algorithm, the estimated absorption coefficient spectra almost matched the ones previously calculated. By subtracting the absorption of lipofuscin from these spectra, we obtained similar hemoglobin ratios at 410/550 nm: 18.9-fold/9.3-fold for the healthy mucosa and 46.6-fold/24.2-fold for the pathological mucosa, while from direct calculations, those ratios were 19.7-fold/10.1-fold for the healthy mucosa and 33.1-fold/17.3-fold for the pathological mucosa. The higher values obtained in this study indicate a higher blood content in the pathological samples used to measure the diffuse reflectance spectra. In light of such accuracy and sensibility to the presence of hidden absorbers, with a different accumulation between healthy and pathological tissues, good perspectives become available to develop minimally invasive spectroscopy methods for in vivo early detection and monitoring of colorectal cancer.The application of machine learning methods to noninvasivelike diffuse reflectance spectra allowed us to reconstruct the absorption coefficient spectra of human healthy and pathological mucosa tissues from the colorectal wall. Consequently, we were able to obtain differentiated blood and pigment content in both tissues, which can be used for the development of new noninvasive diagnostic methods for colorectal cancer., The work of L. M. Oliveira was supported by the Portuguese Science Foundation (Grant No. FCT-UIDB/04730/2020). The work of V. V. Tuchin was supported by a grant of the Government of the Russian Federation (Registration No. 2020-220-08-2389).

In the original version of this article, the y-axis in Fig. 7b–f does not start from zero, and therefore, the x-axis cuts were not accurate. In the corrected version, the y-axis in Fig. 7 was corrected to start from zero. The corrected version of Fig. 7 and the caption is given below. The second sentence of the third paragraph in “Section 3.6 UV–Vis diffuse reflectance spectra” should now be read as “Table 1 shows the reduction in the bandgap energy value of Bi/BiOBr-20 to 2.36 eV compared to 2.85 eV for the pristine BiOBr.” Due to the above correction in the bandgap estimation, the corrected version of Table 1 is also given below.

Bi2O3 nanosheets (NSB) photocatalyst was fabricated via a very simple method of liquid precipitation. The as obtained products were characterized by SEM, N2 adsorption-desorption, XRD and UV-vis diffuse reflectance spectra. The results showed that NSB catalyst can beconsidered as set of nanosheets with an average thickness of 110 nm. NSB photocatalyst exhibited high surface area of 33.21 m2/g and high purity. In addition, NSB catalyst displayed excellent photocatalytic performance for the dye of rhodamine B (Rh B) under visible light due to the structure of sheet and high surface area.

Background Colorectal cancer is one of the most common malignancies worldwide. There is an urgent need for simple and fast methods to improve tumor detection in the diagnostic and intraoperative setting to avoid complications and provide objective information in distinguishing malignant and benign colorectal tissue. Optical spectroscopy methods have recently shown a great potential for this discrimination in different organs. Materials and methods In this pilot study, fluorescence emission spectra (excitation: 473 nm) and diffuse reflectance spectra (DRS) of normal and tumor tissues from resected colorectal cancer specimen were measured using fiber optical probes in an ex vivo setting, and the data were subjected to multivariate analysis. Results Substantial spectral differences were found in the fluorescence and DRS spectra of colorectal cancer tissue in comparison to benign tissue. The diagnostic potential of a multimode optical system combining both spectroscopic methods was investigated by mathematical combination. Compared with the individual techniques, a higher sensitivity of the joint DRS-fluorescence optical system in the discrimination between malignant and benign colorectal tissue could be observed. Conclusions In the pilot study presented herein, a quick and reliable method to differentiate malignant and benign colorectal tissue ex vivo with different spectroscopic techniques using spectral fiber probes could be established. Joint fluorescence and near-infrared spectroscopy had a higher sensitivity in tissue discrimination and showed to be a promising combination of two spectroscopic methods. Further studies using the synergic effect of fluorescence and DRS spectroscopy are needed to transfer these findings into the in vivo situation.

By using cation modulation strategy, a series of fluorooxoborates A3B3O3F6 (A = alkali and mixed alkali metal) were designed and successfully obtained via open high-temperature solid-state method for the first time, and single-crystal X-ray diffractions were used to determine their structures. The isolated B3O3F6 benzene-like ring structure in the title compounds is beneficial to obtain short ultraviolet absorption edge (

The paper is devoted to studying the effect of the specific surface area (SSA) of SiO2nanopowders (3 wt.%) added to BaSO4powders of a micron size on grain size distribution and diffuse reflectance spectra (ρλ) within the UV, visible, and near IR regions. Additionally, the authors have examined the spectra alteration (Δρλ) after irradiating with electrons (E=30 KeV). It has been established that mere mixing of the powders at a low concentration of nanoparticles leads to the post-irradiation decrease in the reflective power and to the subsequent increase in the reflectance coefficient stability.

BaSO4 powders demonstrate high reflecting capacity in the UV, visible, and near infrared regions of the spectrum and appear to be promising pigments for thermal control coatings of space vehicles and household paints. Their application in a wide range of fields is due to the constant impact of ionizing radiation. In the experiment under study, BaSO4 powders were heated in the atmosphere at T = 100, 400, and 800 °C for the purpose of increasing their radiation stability. It has been established that the highest resistance to accelerated electrons corresponds to the powders preheated at 400 °C. The reflecting capacity of BaSO4 powders after heating at 100 and 400 °C decreases insignificantly. Warming at 800 °C leads to a deterioration in both reflecting capacity and radiation stability compared with the initial powder.

In order to investigate the influence of Gd3+ doping on the photocatalytic activity of BiFeO3, BiFeO3 and BiFeO3:Gd3+ photocatalysts were fabricated by the sol-gel process. The phase, photocatalytic hydrogen production, microstructure, optical and photoelectrochemical properties of the fabricated photocatalysts were investigated. BiFeO3:Gd3+ photocatalyst has a larger ability for the hydrogen production in photocatalysis process than that of BiFeO3. The reason of the higher photocatalytic activity of BiFeO3:Gd3+ photocatalyst was revealed by the measurements of UV–Vis diffuse reflectance spectra, photocurrent curves and electrochemical impedance spectra. Moreover, the magnetic properties of BiFeO3 and BiFeO3:Gd3+ photocatalysts were also investigated to show the easy separation. These results in current work indicate that BiFeO3:Gd3+ is an excellent photocatalyst and has potential applications in photocatalytic hydrogen production.

Ba6Cu2GSn4S16 (G = Fe, Ni), and Sr6D2FeSn4S16 (D = Cu, Ag) were synthesized in an A-B-P-Q (A = Sr, Ba; B = Cu, Ag, Li; P = Sn, Ge; Q = S, Se, Te) system, through the introduction of the Fe and Ni atoms. The four compounds were found to be isostructural. They crystallize in space group I 4 3 d (no. 220) of the three-dimensional cubic structure. The structure is composed of SnS4 and (Cu|G)S4 by sharing corners with Ba2+ cations distributed in the channels of the Ba6Cu2GSn4S16 (G = Fe, Ni). The structure is composed of SnS4 and (D|Fe)S4 by sharing corners with Sr2+ cations distributed in the channels of the Sr6D2FeSn4S16 (D = Cu, Ag). The UV–vis diffuse reflectance spectra showed the Ba6Cu2FeSn4S16, Ba6Cu2NiSn4S16, Sr6Cu2FeSn4S16, and Sr6Ag2FeSn4S16 energy band gaps to be 1.20 eV, 0.82 eV, 1.53 eV and 1.87 eV, respectively.

Two new halogenated selenites, namely, Pb2Cd(SeO3)2X2 (X = Cl and Br), were synthesized via mild hydrothermal reactions. The isomorphic compounds crystallized in a noncentrosymmetric (NCS) and chiral space group. Their three-dimensional (3D) structures were formed by alternating undulated [Pb2(SeO3)X]∞+ cationic layers and flattened [Cd(SeO3)X]∞− anionic layers. Thermal analyses revealed that the compounds can remain stable up to 500 °C. The SHG efficiencies of Pb2Cd(SeO3)2X2 (X = Cl and Br) are much higher than those of commercial KDP (KH2PO4), and they are phase-matchable. UV-vis-NIR diffuse reflectance spectra revealed that the two compounds exhibited wide optical band gaps. The laser damage thresholds of Pb2Cd(SeO3)2X2 (X = Cl and Br) were measured to be about 38.5 and 35.7 times higher than that of AGS (AgGaS2). Their calculated birefringences were large enough to accomplish phase matching in SHG progression. The SHG density analyses disclosed that the lone pair electrons of the SeO3 and PbOnXm units made major contributions to their nonlinear efficiencies.

Two new tin(IV)-containing phosphate fluorides, K2SnPO4F3 and K6Sn(P2O7)2F2, have been obtained in a sealed system. Interestingly, K2SnPO4F3 and K6Sn(P2O7)2F2 are the first tin(IV)-containing phosphate fluorides in the K–Sn(IV)–P–O–F system. Both of them crystallize in the monoclinic space group P21/c; however, the 2D [SnPO4F3]∞ layer and isolated [Sn(P2O7)2F2] units can be found in K2SnPO4F3 and K6Sn(P2O7)2F2, respectively. A structural comparison indicates that K6Sn(P2O7)2F2 is the first inorganic tin(IV)-containing phosphate with an isolated Sn(IV)–P–O framework. Meanwhile, the structural evolution from KSnOPO4 to K2SnPO4F3 is discussed in detail. And the optical properties, including UV-Vis-NIR diffuse reflectance spectra and infrared spectra, are also reported. In addition, first-principle theoretical studies help us understand the electron structures of the title compounds.

A comprehensive data collection of authentic &ldquo, specialty&rdquo, or &ldquo, gourmet&rdquo, oils, namely cold-pressed industrial virgin oils, was performed. Eight different botanical species, i.e., Almond, Apricot, Avocado, Hazelnut, Mosqueta rose, Rosehip, Sunflower, and Walnut oils were studied plus Olive oil as the gold standard of cold-pressed virgin oils. Two different analytical approaches are proposed to rapidly verify the botanical species of the oil-based raw material. The first approach is based on a multivariate statistical analysis of conventional analytical data, namely their fatty acid composition. These data have been re-elaborated in a multivariate way by Principal Component Analysis (PCA) and classification methods. The second approach proposes a fast and non-destructive spectrophotometric analysis to determine the color of these oils to discriminate among different species. In this regard, the raw diffuse reflectance spectra (380&ndash, 780 nm) obtained by a UV-Vis spectrophotometer with an integrating sphere was considered and elaborated by chemometrics. This information was compared with the results obtained by the most common approach based on the CIELab parameters. A data fusion of chromatographic and spectral data was also investigated. Either fatty acid composition or color of these oils demonstrated to be two promising markers of their botanical authenticity.

Diffuse reflectance spectroscopy (DRS) has been widely used to interrogate the metabolic state and structure of several biological tissues with diagnostic purposes. The aim of this research is to compare the melanin content (melanosome volume fraction) of normal non-pigmented human skin sites versus skin sites containing tiny moles ranging from 1.2 mm to 2 mm diameter. The study was carried out in a group of ten volunteers presenting five different skin phototypes (I-V). Diffuse reflectance spectra of these sites were acquired with a USB 4000 fiber optic spectrometer and homemade optical probe consisting of two optical fibers separated 2.5 mm. In order to extract optical properties of skin sites containing tiny moles, a relative simple but novel skin model was proposed and used in combination with a slightly modified version of the inversion algorithm analyze2.m which is freely available. We found that melanin content ranges from 3.3 % to 29.2 % for the normal skin sites surrounding pigmented skin sites, while for skin sites with tiny moles melanin content varies from 7.6 % to 78.4 %. Our finding shows that for each volunteer the melanin content of pigmented areas is twice or more the melanin content of non-pigmented normal skin areas. In addition, we have evaluated the sensibility of the inverse extraction algorithm when the melanin content is varied while the remaining "guess parameters" (S, B, a, const) are kept constant. We have found that all the remaining parameters are strongly affected when the melanin content is changed.

This study describes parametric modeling of diffuse IR reflectance for sparsely surface-distributed particles of the explosive RDX. Diffuse IR spectra are modeled using a formulation that considers spectral features due to target-material reflectance, i.e., RDX, substrate reflectance and resonance scattering resulting from finite sizes of surface-distributed particles. The results of this study demonstrate an approach for parametric modeling of diffuse IR reflectance for sparsely surface-distributed particles. The mathematical formulation of this approach is that of a phenomenological scattering-matrix representation.

Threat chemicals such as explosives may persist on surfaces, enabling them to be detected by non-contact or standoff optical methods such as diffuse IR reflectance. However, due to particle size effects and optical coupling to the substrate, their IR spectral signatures will differ from laboratory reference measurements of bulk materials. This study presents an inverse analysis of diffuse IR reflectance from sparsely surface-distributed particles of the explosive PETN. A methodology using spectrum templets is applied for inverse analysis of measured spectra. The methodology is based on a generalization of extended multiplicative signal correction (EMSC). The results of this study demonstrate application of the inverse analysis methodology for extraction of spectral features for surface-distributed particles of specified dielectric response.

Even though recent advances in medical devices have significantly improved clinical interventions, more accurate differentiation of biological tissues is still required to improve clinical decision-making. Tissue identification can be performed by using molecular-sensitive techniques such as diffuse reflectance spectroscopy (DRS), which is allows label-free, non-invasive, real-time and in situ interrogation of biological tissues. In this study, we used broadband DRS to extract biomolecule concentrations of gastrointestinal tissues and evaluated its potential for tissue identification and cancer detection. Diffuse reflectance spectra were analysed in an extended wavelength range between 350 nm and 1900 nm. This range covers the third optical window, which may allow better tissue identification for laparoscopy and gastrointestinal robotic surgery. Chromophore concentrations were obtained by using an inverse Monte Carlo Lookup table model to fit the reflectance spectrum.

The oxygenation state of the blood is a key determinate of physiological state of patient. Several techniques are available for determining the average oxygenation state of the blood in a tissue. However, these techniques cannot resolve relative local volume fractions of reduced/- oxyhemoglobin concentration within the bulk of a highly scattering tissue. Prompt detection of these parameters are important for the clinical diagnosis and effective treatment planning in ICU patients. Therefore, aim of this study is to detect local volume fractions of reduced/- oxyhemoglobin concentrations. The diffuse reflectance spectroscopy can non-invasively measure the various pathophysiological functions by measuring the absorption from blood. Thus, in this study relative local volume fractions of reduced hemoglobin and oxyhemoglobin concentration are measured from the capillary beds close to the upper layer of the lips through the diffuse reflectance spectra.

The aim of the study was to compare the metabolic activity of brain cortex after the acute hypoxia caused by the impairment of breathing or blood circulation. Male Wistar rats were randomized in two groups: impaired breathing and blood circulation failure groups. Fluorescence under 365 and 450 nm excitation and diffuse reflectance intensity at 550–820 nm range were estimated. We found that after long-term hypoxic conditions, notable metabolic changes occur. We suppose that oxygen deficiency causes an activation of the GABA shunt mechanism. In cases of blood circulation failure, fluorescence intensity changes faster than in cases of breathing impairment.

This paper presents the results of the experiments which were performed using the optical biopsy system specially developed for in vivo tissue classification during the percutaneous needle biopsy (PNB) of the liver. The proposed system includes an optical probe of small diameter acceptable for use in the PNB of the liver. The results of the feasibility studies and actual tests on laboratory mice with inoculated hepatocellular carcinoma and in clinical conditions on patients with liver tumors are presented and discussed. Monte Carlo simulations were carried out to assess the diagnostic volume and to trace the sensing depth. Fluorescence and diffuse reflectance spectroscopy measurements were used to monitor metabolic and morphological changes in tissues. The tissue oxygen saturation was evaluated using a recently developed approach to neural network fitting of diffuse reflectance spectra. The Support Vector Machine Classification was applied to identify intact liver and tumor tissues. Analysis of the obtained results shows the high sensitivity and specificity of the proposed multimodal method. This approach allows to obtain information before the tissue sample is taken, which makes it possible to significantly reduce the number of false-negative biopsies.

In this study, [{Rh2(O2CCF3)4}{Pt2(piam)2(NH2CH3)4}2](CF3SO3)4·2H2O (2f, piam = pivalamidate), which is a one-dimensional (1D) hexanuclear complex aligned as Pt–Pt–Rh–Rh–Pt–Pt, was successfully synthesized and characterized. When [Pt2(piam)2(NH3)4]2+ was mixed with [Rh2(O2CCF3)4], infinite 1D [{Rh2(O2CCF3)4}{Pt2(piam)2(NH3)4}2]n(CF3CO2)4n·2nEtOH·2nH2O (1f) chains, aligned as –{Pt–Pt–Rh–Rh–Pt–Pt}n–, were obtained, where the end platinum atoms were separated from neighboring end platinum atoms by a distance of 3.0791(15) A. The diffuse reflectance spectra revealed two absorptions at 2.67 and 2.23 eV in 1f, which are attributed to transitions between σ-type orbitals, and a single absorption at 2.77 eV in 2f chains. These results prove that 1f forms a band structure due to metal–metal bonds formed along the 1D heterometallic chain.

Partial least squares models were built for the direct determination of cocaine in seized impregnated smuggled materials. Measurements are based on the attenuated total reflectance middle infrared spectra (ATR-MIR) and diffuse reflectance spectra in the near range (DR-NIR) obtained directly from the surface of the impregnated materials. The aforementioned procedures offer fast, cheap and environmentally friendly green alternatives to the reference method based on the extraction of the drug and its quantification by gas chromatography. Additionally it has been verified that results found are statistically comparable with those obtained by the reference method with root mean square errors of prediction (RMSEP) of 0.60% w/w and 0.88% w/w for MIR and NIR methods, and ratio of performance to deviation (RPD) values of 13.20 and 7.54, respectively. Examples of application for the quantification of cocaine in impregnated clothes, pulp paper and foam have been also provided.

The paper focuses on the first attempt at investigating the effect of high-temperature modification with SiO2 nanoparticles on the diffuse reflectance spectra within 0.2–2.2 μm and on the particle-size distribution of barium sulphate powders. It has been found that there exists the correlation between changes in diffuse reflectance spectra and particle size distribution during heating and modifying BaSO4 micropowders with SiO2 nanoparticles. By high-temperature heating (800 °C) of BaSO4 micropowder and by deposition of SiO2 nanoparticles (C = 1 wt%), one can increase the reflectance capacity of BaSO4 powder. Additionally, it is shown that SiO2 nanoparticles deposited onto the surface block the formation of BaSO4 micropowder granules.

This paper presents the synthesis and characterization of novel Eu2+, Ce3+, and Dy3+ doped BaMg2Al6Si9O30 nanophosphors by combustion method at 550 °C. Eu2+ and Ce3+ ions show the broadband emission assigned due to the 5d–4f transition. Whereas, Dy3+ activated BaMg2Al6Si9O30 nanophosphor shows the characteristic emission bands due to f–f transition respectively. From the observed excitation and emission bands of donor and acceptor, we have studied the critical distance of energy transfer (ET) in Ce3+/Dy3+ ions. Further, the phosphor was well characterized by XRD, SEM, TEM for the confirmation of phase purity, surface morphology and crystallite size respectively. The band gap of the material is measured from the diffuse reflectance spectra. From emission characteristics, it is seen that the prepared nanophosphor may be a promising candidate for solid-state lighting.

Total polyphenols (TP), caffeine, and free amino acids (FAA) constitute tea taste. The feasibility of developing a cross-category model for predicting TP, caffeine and FAA contents in Chinese black, dark, oolong, and green teas, was investigated. Diffuse reflectance spectra (4000–10,000 cm−1) of tea were collected using Fourier transform near-infrared (NIR) spectroscopy, and a hybrid method was applied to enhance characteristic signals. Random frog and competitive adaptive reweighted sampling (CARS) were used to select key variables for partial least squares (PLS) calculation. For calibration, the best predictive performance was achieved by the CARS-PLS models. The coefficients of determination and root mean squared errors in the prediction set were 0.994 and 0.595 for TP, 0.986 and 0.070 for caffeine, and 0.993 and 0.063 for FAA, respectively. The results highlight the potential of NIR coupled with chemometrics for the simultaneous testing of TP, caffeine and FAA contents in Chinese tea from different categories.

Two noncentrosymmetric polyphosphates, namely LiCsP2O6 and LiRbP2O6 have been synthesized from the high temperature solution. The structural analysis suggests that both of them crystallize in orthorhombic space group Fdd2 (No.43), with lattice parameters: a = 18.517(4) A, b = 19.037(4) A, c = 13.011(3) A, and Z = 32 for LiRbP2O6, while a = 19.009(13) A, b = 19.402(13) A, c = 13.180(9) A, and Z = 32 for LiCsP2O6. In the structure, the PO4 polyhedra are connected through corner-sharing to form 1D infinite (PO3) ∞ chains stretching along the c axis, which are further linked by the LiO4 polyhedra to construct a 3D framework with two types of tunnels. And the Rb/Cs atoms are filled in or around the periphery of the tunnels to keep the charge equilibrium. The IR spectra verify their structural validity. In addition, other characterizations including the UV−vis−NIR diffuse reflectance spectra, as well as first-principles theoretical studies have been performed on the two compounds.

A single-composition LiSrPO4:Eu2+,Y3+ phosphor was synthesized via a high-temperature solid-state method. LiSrPO4:Eu2+ without Y3+ show a narrow emission band with a full-width half maximum of about 50 nm. When Y3+ substitutes for Sr2+ partly, emission spectra have been broadened and red-shifted obviously. Through studying their excitation spectra, diffuse reflectance spectra and fluorescent lifetimes, multiple Eu2+ luminescent centers are confirmed to be reason for the changes. Besides, energy transfers from high-energy centers to low-energy centers in multiple luminescence centers systems are demonstrated, which also can trigger the red shifts of emission spectra in some scale.

This work presents the use of near-infrared (NIR) spectroscopy as a fast and eco-friendly alternative to the conventional methods currently used for the quality control of cocoa beans. A key feature of this study was that the multivariate calibration models were built from the spectra of 81 samples of commercial cocoa beans from different producing regions and sampled over the period of 1 year. This aspect is crucial to demonstrate the feasibility of NIR for predicting chemical parameters of cocoa beans, since it provides a realistic variability in the calibration models. PLS regression models were constructed from the near-infrared diffuse reflectance spectra, allowing the prediction of moisture, pH, acidity, fat, shell content, protein, total phenolic compounds, caffeine, and theobromine through direct analysis of samples milled and sieved without any additional preparation. All of these parameters were predicted with adequate coefficient of determination values (R2), which ranged from 0.67 to 0.89 and relative errors smaller than 10.2%, which is quite suitable when compared to the coefficients of variation of the reference methods. Thus, the results demonstrated that the use of NIR combined with chemometrics is effective and recommended for the quality control of commercial cocoa beans.

Four hybrid 3,3'-(alkane-1,n-di-yl)-bis(1-methyl- 1H- imidazole-3-ium) halobismuthates were prepared by a facile solution route and characterized by diffuse reflectance spectra and photoluminescence measurements. Crystal structure of 3,3'-(buthane-1,4-di-yl)-bis(1-methyl- 1H- imidazole-3-ium) bromobismuthate (1) contains zero-dimensional Bi 2 Br 10 anions. Crystal structure of 3,3'-(pentane-1,5-di-yl)-bis(1-methyl- 1H- imidazole-3-ium) iodobismuthate (4) contains zero-dimensional Bi 2 I 9 anions.

The potential of near infrared (NIR) spectroscopy combined with chemometrics methods was studied to rapidly detect intramuscular fat (IMF) content in pork. Near infrared diffuse reflectance spectra were recorded both with an FT-NIR and a USB4000 spectrometer. The data analysis was compared on different sample preparation, spectral range and spectra pretreatment. According to calibration statistics, best calibration for IMF showed R2cal of 0.94, R2val of 0.92, RMSEC of 0.233, RMSEP of 0.462 and RPD of 2.29. The prediction of IMF content for minced samples was more accurate than that for intact samples. The spectra obtained using FT-NIR contained much information correlating to the IMF content than the Vis-NIR spectra of USB4000. The results showed that NIR spectroscopy technique can be used to determine the IMF content in pork as a rapid, convenient, and feasible analysis tool.

Incorporation of guest materials into semiconducting single crystalline hosts leads to the formation of semiconducting single-crystal composites. However, limited efforts have been made to comprehensively investigate the property of these potential functionalized single-crystal composites. Herein, PbI2/gel single-crystal composites have been successfully prepared. Diffuse reflectance spectra show a clear increase in the band gap of PbI2 after gel incorporation. The band gap is further increased through expanding the area of host/guest interfaces or enhancing the interatomic forces at the interfaces. The interatomic forces (electrostatic interaction) at the host/guest interfaces are attributed to this band gap shift. As such, this study provides a novel and facile way for band gap engineering by gel incorporation.

Using hydrothermal reactions, three series of rare-earth borate-sulfates, namely, RE(SO4)[B(OH)4](H2O) (RE = La (1), Sm (2), Eu (3)), RE(SO4)[B(OH)4](H2O)2 (RE = Pr (4), Nd (5), Sm (6), Eu (7), Gd (8)), and RE(SO4)[B(OH)4](H2O)·H2O (RE = Tb (9), Dy (10), Ho (11), Er (12), Tm (13), Yb (14), Lu (15), Y (16)), have been synthesized, which represent the first rare-earth borate-sulfate mixed-anion compounds. All these compounds possess the same fundamental building anionic units of SO4 and B(OH)4 tetrahedra; however, they exhibit three different types of two-dimensional (2D) layered structures composed of 1D RE–B–O and RE–S–O chains. The rare-earth borate chains are similar in all compounds, while the rare-earth sulfate chains differ in each type of compound due to the various coordination modes of sulfate groups. On the basis of the measured UV–vis diffuse reflectance spectra, the optical band gaps of compounds 2, 3, 6, and 7 are estimated to be 4.66, 4.53, 4.62, and 4.50 eV, respectively. Luminescence studie...

Two new Co(II)-based coordination polymers, [Co(HL)(H2O)2] (1) and [Co(HL)(bpy)]·H2O (2) (H3L = 5-((4-carboxyphenoxy)methyl)benzene-1,3-dioic acid, bpy = 4,4′-bipyridine), have been synthesized under hydrothermal conditions. The two compounds have been characterized by single crystal and powder X-ray diffraction analyses, infrared analyses, elemental analyses and thermogravimetric analyses. Compound 1 shows a 3D 2-fold interpenetrating hms framework, whereas compound 2 reveals a typical 3D pcu net. The UV–vis diffuse reflectance spectra of compounds 1 and 2 have been investigated. Moreover, the magnetic susceptibilities of compounds 1 and 2 have been studied.

A new mixed-anion diphosphate, Li1.52Na4.48Cd8(PO4)2(P2O7)4, was synthesized by standard high-temperature solid state technique for the first time. It crystallizes in triclinic space group P-1, with unit cell parameters a = 6.7330(3) A, b = 9.5603 (4) A, c = 11.3838 (5) A, α = 98.5630(10) °, β = 92.3460(10) °, γ = 90.4500(10) °. The crystal structure contains four types of dimensions, that is zero-dimensional (0D) Cd4O16 groups, one-dimensional (1D) [M2P5O20]∞ (M = Li/Na, Na) chains, two-dimensional (2D) Na/CdO6 layers and the complex three-dimensional (3D) framework. After careful structural analysis, it is found that the number of cations has an effect on the degree of polymerization of the [PO4] groups. Thermal behaviors indicate that the title compound melts congruently and infrared (IR) spectrum shows the existences of PO4 and P2O7 groups. The ultraviolet-visible light-near infrared (UV/Vis/NIR) diffuse reflectance spectra are also performed on this compound.

Spectral (in the wavelength range of 1 – 25 μm) and total emissivity of reaction bonded silicon nitride were determined together with their temperature dependence in the range between room temperature and 1573 K. The influence of ytterbium oxide and nickel impurities on the optical properties of the material was investigated. Emissivity was determined from the total reflectance spectra at room temperature, the diffuse reflectance spectra at temperatures up to 1173 K, and by monochromatic radiation pyrometry, and measurement results were compared.

Three new borates [Cu(1,3-dap) 2 (H 2 O) 2 ][Cu(1,3-dap) 2 (B(OH) 3 ) 2 ][B 4 O 5 (OH) 4 ] 2 ( 1, 1,3-dap = 1,3-diaminopropane), [Cu(py) 4 (H 2 O)][B 5 O 6 (OH) 4 ] 2 ·3py·H 2 O ( 2 , py = pyridine) and (HDMF) 2 [NH(CH 3 ) 3 ] 4 [NH 2 (CH 3 ) 2 ] 2 Mg 2 [B 17 O 26 (OH) 4 ][B 17 O 27 (OH) 4 ]·NH 3 ( 3 , DMF = N , N -dimethylformamide) have been synthesized under mild solvothermal conditions and characterized by elemental analysis, IR spectra, diffuse reflectance spectra, thermogravimetric analysis, single-crystal X-ray diffraction and powder X-ray diffraction. 1 and 2 exhibit 3-D supramolecular hydrogen-bonded architectures constructed from isolated oxoboron clusters [B 4 O 5 (OH) 4 ] 2 − and [B 5 O 6 (OH) 4 ] − , respectively. The structure of 3 features two different 1-D chains built by unprecedented [B 17 O 26 (OH) 4 ] 5 − and [B 17 O 27 (OH) 4 ] 7 − clusters, respectively. And the adjacent chains are alternatively linked by H-bonding to form a 3-D supramolecular framework.

To automate and improve the quality of postharvest potato grading, simultaneous discrimination of various external defects is important; surface optical characteristics may hold the key to this. In this research diffuse reflectance in the UV–vis-NIR region of various potato surface defects were measured in order to characterize the optical properties of undamaged skin and various surface defects or characteristics, i.e. mechanical damage, greening, common scab, and soil deposits on the skin. Genetic algorithm-PLS were used as a variable selection method to identify the most sensitive wavelength set to classify each defect category. The selected wavelengths consist of subsets in the visible and near-infrared range i.e. 577–580; 688–690; 696; 916–918; 1132; and 1651–1654 nm. The most accurate classification results were obtained using a Subspace Discriminant classification model with the accuracy of 99% for calibration and 97.6% for validation. The observed differences in diffuse reflectance spectra were then considered in terms of biophysical parameters. This information can now be used to develop a more advanced system for defect discrimination.