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Gallium oxide (Ga2O3) can be crystallized in several polymorphs exhibiting different physical properties. In this work, polymorphic structures consisting of the cubic defective spinel (γ) film on the top of the monoclinic (β) substrate are fabricated by disorder‐induced ordering, known to be a practical way to stack these polymorphs together. Such bilayer structures are annealed to investigate optical properties and phase transformations. Specifically, photoluminescence and diffuse reflectance spectroscopy are combined with transmission electron microscopy, Rutherford backscattering/channeling spectrometry and X‐ray diffraction to monitor the evolutions. As a result, a two‐stage annealing kinetics is observed in γ/β Ga2O3 bilayers associated with the epitaxial γ‐to‐β regrowth at the interface at temperatures below 700 °C and a non‐planar γ‐to‐β phase transformation starting at higher temperatures. Thus, the present data enhance understanding of the polymorphism in Ga2O3, interconnecting the phase transformation kinetics with the evolution of the optical properties. [ABSTRACT FROM AUTHOR]

This study examines parametric modeling and deposition control of diffuse reflectance for NIR-SWIR absorbing dyes on substrates, which is based on diffuse-reflectance theory and decomposition of the reflectance function by linear combinations of segmented reflectance contributions. The segmented reflectance contributions are distributed upon substrate surfaces according to different topologies. Parametric modeling of diffuse reflectance provides an approach for the control of a wide range of signature features associated with NIR-SWIR absorbing dyes on substrates. The dependence on the surface topology of diffuse-reflectance spectra for NIR-SWIR absorbing dyes on substrates is examined by case studies concerning composite-material layers on fabric substrates. Understanding the topological dependence of diffuse reflectance can assist in determining optimal composite-material configurations for specific reflectance specifications. [ABSTRACT FROM AUTHOR]

Developing a simple model of diffuse reflectance of multi-layered media has been accomplished based on a diffusion approximation in order to investigate the influence of thickness on measured spectra. The optical properties of both layers were selected to correspond human brain white and grey matter in which the reduced albedo of the upper layer (grey matter) turned out to be varied from 0.8 to 0.991 and from 0.933 to 0.976 for the lower layer (white matter). The refractive index of these two layers was the same and equaled to 1.4, and the anisotropy factor approximated to 0.9. Then, the thickness of the top layer varied from 0 to 10 cm (infinity). Reflectance was estimated theoretically based on the Monte Carlo algorithm and fitted to the developed model. Finally, an accurate model has been suggested and the applicability was investigated in which the relative error did not exceed 10%, which is more likely to use that model to predict thickness of the top layer based on the diffuse reflectance measurement. [ABSTRACT FROM AUTHOR]

The composite MoO 3 / Me MoO 4 (Me = Cu, Ni, Co, Fe, and Mn) ceramics were obtained by standard high-temperature sintering. Their structure was tested using XRD, SEM, EDS, and XPS. The occurrence of two phases was determined. The main MoO 3 phase exhibited an orthorhombic Pnma space group related to the ceramic grain of micrometre size. The second phase was induced by doping with the Me atom. It showed various monoclinic structures and a smaller grain size. The XPS test confirmed the coexistence of the phases, which was reflected in several lines in the patterns. The valence band of the undoped MoO 3 was located ∼3.3 eV below the Fermi level. An additional subband attributed to the Me 3d state was detected within the energy gap. The MoO 3 / Me MoO 4 composites showed a valence band shifted toward the Fermi level and overlapped with the subband, originating from hybridized Mo 4d – Me 3d states. Magnetic susceptibility showed an antiferromagnetic state below ∼20 K for the Ni- and Fe-doped composites. The estimated magnetic moment magnitudes indicated the contribution from Me 2+ and Me 3+ ions that marked the occurrence of oxygen vacancies. Diffuse reflectance spectra exhibited anomalies in the Vis (∼500–650 nm) and the NIR (∼700–850 nm) ranges and tails in the ∼900–1000 nm range. The estimated magnitudes of energy gaps were attributed to defect-induced states. They corresponded to deduced oxygen vacancies (2.05–2.38 eV) and states or subbands induced by the introduced Me atoms (1.34–1.89 eV). Electric dc resistivity temperature dependence showed thermally activated dependence. The estimated activation energy varied from 0.27 eV to 0.58 eV, depending on the doping of the Me atom. The electric features were consistent with the electronic structure determined using XRD and XPS tests. [ABSTRACT FROM AUTHOR]

In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination of ammonium and hydrogen sulfur in saliva using two colorimetric chemosensors. The ammonia reacts with 1,2-Naftoquinone 4 sulphonic acid (NQS) entrapped in polydimethylsiloxane (PDMS) and the hydrogen sulfide with AgNPs retained in a nylon membrane. The color changed from orange to brown in the case of ammonia chemosensors and from yellow to brown in the H2S. The experimental conditions to be tested have been established. Both analytes have been determined from their gaseous form; these are ammonia from ammonium and hydrogen sulfur from hydrogen sulfur. Good figures of merit have been obtained by using both measuring strategies (reflectance diffuse and digitalized images). The acquired results show that both sensors can be used and provide good selectivity and sensitivity for the determination of these biomarkers in saliva. Both measurement strategies have provided satisfactory results for the real saliva samples (n = 15). Recoveries on spiked samples were between 70% and 100%. This methodology can lead to possible in situ diagnosis and monitoring of certain diseases and pathologies related with NH4+ and/or H2S, in a fast, simple, cheap and non-invasive way. [ABSTRACT FROM AUTHOR]

Green-emitting BaSrGd4O8: Er3+ nanophosphor is effectively synthesized using the solution combustion route. For crystallographic and morphological attributes, the samples have been characterized by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The atomic parameters are refined with the aid of Rietveld refinement realization, and the orthorhombic phase with space group Pnma (62) is confirmed. EDS analysis reveals the chemical composition while SEM and TEM techniques confirm the irregular shapes. On near-UV excitation, the luminescence spectrum presents a fair green emission at 18,083 cm−1 wavenumbers consistent with the electronic transition 4S3/2 → 4I15/2. Diffuse reflectance spectroscopy is used to examine the bandgap energy. Radiative lifetime, quantum efficiency, and rates of radiation-less electronic transitions are also examined. The CIE (Commission International de l'Eclairage) coordinates and hence the CCT (color coordinate temperature) values of the chromaticity plot are thus finalizing their potential contention in SSL (solid-state lighting) and other advanced optoelectronic applications. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) thin film is widely used as the bottom electrode in substrate‐configured thin film solar cells due to its high conductivity and reflectivity. Mo grown onto microtextured substrates increases the diffuse reflection of incident photons via scattering/multiple reflections on the corner/edges, in addition to the contribution from increased surface area. Herein, bilayer Mo is grown using direct current magnetron sputtering onto plain and textured substrates. To texture the glass substrate surface, a periodic array of cross‐linked photoresist structures (SU‐8 2000.5 & SU‐8 2005) is introduced via UV‐lithography process. Characterizations are done using X‐ray diffractometer, optical microscope, scanning electron microscope, and optical profilometer. Angle‐dependent specular reflectance, diffuse reflectance, and electrical measurements done on Mo grown on plain and textured substrates lead to a comprehensive understanding of the advantages of growing Mo films on textured substrates. The electrical resistivity of Mo grown on plain and textured substrates is of the same order, measuring 3.09 × 10−5 Ω cm, 3.25 × 10−5 Ω cm, and 3.87 × 10−5 Ω cm, respectively. A high‐diffuse reflectance of 62.7% is obtained for SU‐8 2005 textured Mo films. Investigations using COMSOL simulations support the optical reflectance analysis. [ABSTRACT FROM AUTHOR]

Optical phantoms are important tools in biomedical imaging for calibration and validation of photonic instrumentation medicine, especially with readily available and relatively inexpensive materials to characterize the scattering property. In this work, using laser collimated transmission and diffuse reflectance, the optical properties of pasteurized milk-based phantoms are characterized and compared with the optical properties of intralipid-based phantoms to construct phantoms comparable to intralipid-based phantoms at 405 nm. To that end, three different types of pasteurized milk corresponding to three different manufacturers and intralipid 20% samples with varying concentrations were prepared and their optical properties were determined. The results show that the optical properties of intralipid-based phantoms and pasteurized milk-based phantoms are roughly comparable. The stability of pasteurized milk samples was also studied, and it showed that emulsions exhibit varying levels of stability up to three hours. Despite the short time stability of the constructed milk-based phantoms, the results demonstrate the potential of using readily available simple laser-based transmission and reflection measurements to prepare milk-based optical phantoms for rapid calibration and testing of optical measuring devices particularly for biphotonic applications. [ABSTRACT FROM AUTHOR]

Abstract In this research, the effect of grey mold inoculation and subsequent postharvest treatment with limonene‐liposomes and oxygen absorbers is observed on the storage characteristics of strawberries. The survival analysis of the end of sensory shelf‐life indicated that inoculated strawberries were 9.96 times more likely to be rejected compared to uninoculated strawberries. The inoculation also resulted in lower firmness, higher rate of weight loss, higher CO2 respiration rates, and higher total polyphenol contents. Among the inoculated strawberries, limonene‐liposome treated strawberries had a longer average shelf‐life by 1.5 days compared to control inoculated strawberries. Similarly, oxygen absorber treated strawberries had lower respiration rates and lower rate of weight loss. The sequential addition of variables in the multiple linear models fitting days till rejection (DTR) show that up to 52% of the variation in DTR can be explained from days of storage, state of inoculation, firmness, respiration rate and total anthocyanin content. The models built from storage characteristics other than state of inoculation can explain up to 26% of variation in DTR. The partial least square regression (PLSR) models for the prediction of DTR built from two different types of spectral data, UV‐VIS and NIR, yielded evaluation R2 up to 0.778 and 0.765 respectively.

A simple exponential model of diffuse reflectance for a two-layered medium was developed theoretically based on Monte Carlo simulation. Absorption and reduced scattering coefficients of these two layers were chosen to be different in which scattering property was dominant and the reduced albedo of the upper layer ranged from 0.8 to 0.99 and from 0.93 to 0.98 for the lower layer. Furthermore, the refractive index and anisotropy factor of these two layers were assumed to be equal 1.4 and 0.9 respectively. On the other hand, a finite element method was used to solve a diffusion approximation via COMSOL Multiphysics environment to compare the developed model with a diffusion approximation. The presented model has shown a low relative error, which did not exceed 20%. That was lower than the diffusion approximation results and it was in accordance with another complicated model developed by another research group. Consequently, the robustness of the presented model makes it more likely to predict a reflectance and reproduce the model to estimate a top layer thickness in real-time.

There is an urgent need for a mass population screening tool for diabetes. Skin tissue contains a large number of endogenous fluorophores and physiological parameter markers related to diabetes. We built an excitation‐emission spectrum measurement system with the excited light sources of 365, 395, 415, 430, and 455 nm to extract skin characteristics. The modeling experiment was carried out to design and verify the accuracy of the recovery of tissue intrinsic discrete three‐dimensional fluorescence spectrum. Blood oxygen modeling experiment results indicated the accuracy of the physiological parameter extraction algorithm based on the diffuse reflectance spectrum. A community population cohort study was carried out. The tissue‐reduced scattering coefficient and scattering power of the diabetes were significantly higher than normal control groups. The Gaussian multi‐peak fitting was performed on each excitation‐emission spectrum of the subject. A total of 63 fluorescence features containing information such as Gaussian spectral curve intensity, central wavelength position, and variance were obtained from each person. Logistic regression was used to construct the diabetes screening model. The results showed that the area under the receiver operating characteristic curve of the model for predicting diabetes was 0.816, indicating a high diagnostic value. As a rapid and non‐invasive detection method, it is expected to have high clinical value. [ABSTRACT FROM AUTHOR]

This study describes the estimation of dielectric response functions for NIR-SWIR absorbing dyes by inverse analysis of diffuse reflectance. The inverse analysis procedure is based on the Kramers–Kronig relations, the Kubelka–Munk model of diffuse reflectance, and the background subtraction of substrate spectra. The calculated response functions provide estimates of the dielectric response characteristics for NIR-SWIR absorbing dyes, as well as their sensitivity to material-background environments. This study demonstrates that Kramers–Kronig analysis can be adopted for calculating estimates of dielectric functions, given any reasonable estimate of absorbance. Specifically, that Kramers–Kronig analysis provides filtering of dielectric response structure with respect to spectrum artifacts due to inverse-analysis and spectroscopic-measurement procedures. This can significantly reduce the experimentation necessary to achieve desired dielectric response characteristics for NIR-SWIR dye and substrate combinations. Furthermore, these calculated response functions can support the construction of approximate effective medium models capable of estimating reflectance features for dyed fabrics. [ABSTRACT FROM AUTHOR]

Optical spectroscopy is studied to contribute to skin cancer diagnosis. Indeed, optical spectra are modified along cancer progression and provide complementary information (e.g., on metabolism and tissue structure) to clinical examination for surgical guidance [1,2]. The current original dataset is made of autofluorescence and diffuse reflectance spectra acquired in vivo on 131 patients’ skin with the SpectroLive device [3,4]. Spatially-resolved spectroscopy measurements were performed using a multi-fiber optic probe featuring 4 distances (0.4–1 mm) between excitation and collection optical fibers: spatial resolution allows spectra acquired at different distances to carry information from different depths in skin tissues. Five types of autofluorescence spectra were acquired using five different wavelength excitations (on the 365–415 nm spectral range) in order to collect information on several skin endogenous fluorophores (e.g., flavins, collagen). A sixth light source (white broadband) was used to acquire diffuse reflectance spectra carrying information about skin scattering properties and skin endogenous absorbers such as melanin and hemoglobin. Patients were proposed to be included into the clinical trial if they were suspected of suffering from actinic keratoses (precancerous skin lesions) or from basal or squamous cell carcinomas: in all cases, complete diagnostics is provided in the dataset. To increase the interest of the dataset and evaluate the dependence of optical spectra (intensity, shape) not only on pathological states but also on healthy skin features (civil age, skin age, gender, phototype, anatomical site), spectra were acquired for all 131 patients on two so-called “reference” skin sites known to rarely suffer from skin cancer: palm of the hand (featuring a thick skin type) and inner wrist (featuring thin skin). Spectra are available in .tab files: first column displays the spectral range on which intensity spectra were recorded (317–788 nm) and each following column provides an intensity spectrum acquired by each spectrometer for a given combination of light source excitation and distance. Each of the 131 folders corresponding to each of the 131 patients contains a .json file providing patients clinical features: gender, civil age, skin age, phototype score and class. All .tab files names include anatomical site and anatomopathological diagnostics of the skin site on which spectra were acquired: codes were defined to match a letter or an acronym to each diagnostic and anatomical site. To ensure quality control, a spectrum was acquired on the same calibration standard before starting spectra acquisition on each patient. It is therefore possible to follow the impact of the acquisition optical chain ageing during the 4.5 years that the patients were included. This dataset can be used by epidemiologists for the characterization of populations affected by skin cancers (gender ratio, mean age, anatomical sites typically affected, etc.); it may also be used by researchers in artificial intelligence to develop innovative methods to process such data and contribute to non-invasive diagnostics of skin cancers whose incidence is steadily increasing.

During the strategic military operations, the deployment of objects viz. tanks, rescue shelters, bunkers etc. need to masquerade from enemy sensors. The deployment of these objects with adaptive photochromic coatings with fast coloration & reversibility is highly effective way for their camouflaging. The present paper systematically reports the photochromic properties of W6+ transition metal doped TiO2 nanoparticles. Undoped as well as doped TiO2 nanoparticles have been synthesized by a one pot wet chemical method. The synthesized materials have been characterized by different techniques viz. XRD, AFM, Raman, SEM, EPR and UV–Vis spectroscopy. Photochromic behavior of functional material was studied by making its composite coatings in alkyd resin matrix. The effect of W6+ dopant ion concentration on photochromic properties has been explained. The coloration & reversibility characteristics of W6+: TiO2 is found superior as compared with V5+ & Mo6+ doped TiO2 nanomaterials, reported earlier.

In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination of ammonium and hydrogen sulfur in saliva using two colorimetric chemosensors. The ammonia reacts with 1,2-Naftoquinone 4 sulphonic acid (NQS) entrapped in polydimethylsiloxane (PDMS) and the hydrogen sulfide with AgNPs retained in a nylon membrane. The color changed from orange to brown in the case of ammonia chemosensors and from yellow to brown in the H2S. The experimental conditions to be tested have been established. Both analytes have been determined from their gaseous form; these are ammonia from ammonium and hydrogen sulfur from hydrogen sulfur. Good figures of merit have been obtained by using both measuring strategies (reflectance diffuse and digitalized images). The acquired results show that both sensors can be used and provide good selectivity and sensitivity for the determination of these biomarkers in saliva. Both measurement strategies have provided satisfactory results for the real saliva samples (n = 15). Recoveries on spiked samples were between 70% and 100%. This methodology can lead to possible in situ diagnosis and monitoring of certain diseases and pathologies related with NH4+ and/or H2S, in a fast, simple, cheap and non-invasive way.

Banana drying is an important process that used to extend the shelf life and increase the marketability of the dried banana. However, this process can lead to changes in weight loss, firmness, and color, which may influence consumer acceptance. As a result, it is crucial to monitor these changes to maintain the desired quality. Therefore, the aim of this study was to assess the quality of sliced bananas during the drying process by simultaneously monitoring their optical and physical properties using laser light backscatter imaging, near-infrared spectroscopy, and electrical impedance spectroscopy techniques. Banana sliced were prepared with 10 mm thickness and immersed into 4% ascorbic acid solution and water as treated and control samples dried at 50 °C for 6 h. The parameters measured were weight loss, color, firmness, NIR absorbance in the range from 740 to 1700 nm and electrical impedance in the frequency range from 30 kHz to 1 MHz. Absorption, reduced scattering and diffusion coefficients, penetration depth and full width at half maximum (FWHM) were computed on the LLBI signal at wavelengths of 532, 635, 780, 808, 850 and 1064 nm. The results showed that both the drying time and the ascorbic acid treatment and their interaction affected the measured values. The strong NIR absorption spectrum changes observed at wavelengths of 1064 and 1416 nm. The least squares partial regression model (PLSR) was performed with high accuracy for weight loss (%) and relaxation time (ms) at a coefficient of determination (R2) of 0.940 and 0.945 with a mean square error (RMSE) of 3.748 and 0.001, respectively. The electrical impedance spectral changes were found in the frequency range from 60 Hz to 1 MHz. The most sensitive laser wave lengths to evaluate optical properties were 532, 635, 780 and 1064 nm. Therefore, laser backscatter imaging together with NIR spectroscopy and impedance spectroscopy is a promising technique to assess the quality of sliced bananas during the drying process. [ABSTRACT FROM AUTHOR]

Purpose: To determine the degree of conversion (DC) and spectral diffuse reflectance of four different gingiva‐colored composites and to evaluate their color stability after various aging processes. Materials and Methods: The gingiva‐colored composites were assigned to four experimental groups (Anaxgum (AG), Crea.lign paste Gum (CB), Gradia Gum (GR), SR Nexco Gum (NC)). A total of 120 disc‐shaped specimens (10 × 2 mm) (n = 30/group) were polymerized in a Teflon mold. The nature of chemical bonding was studied by Fourier transform infrared spectroscopy (FTIR). Diffuse reflection spectra of the polymerized specimens were gathered using an ultraviolet‐visible‐near infrared (UV‐Vis‐NIR) spectrophotometer. Specimens subjected to aging methods were divided into three subgroups (n = 10): ultraviolet aging, hydrothermal aging, and autoclave aging. Color differences (ΔE*ab and ΔE00) were determined by colorimetry before and after aging. The statistical analysis was done using a two‐way ANOVA along with paired sample t‐test and Bonferroni's post hoc test. Results: Conversion degrees varied between 26.9% and 59.7% and all groups showed 3 or 4 maxima at different positions in the visible region of the spectrum. Both ΔE*ab and ΔE00 values were significantly different from the groups of different brands for all types of aging processes. Similarly, there were significantly different ΔE*ab and ΔE00 values according to the aging procedure for all groups of particular brands, except for ΔE00 of SR Nexco Gum (NC). Conclusions: The aging procedures resulted in significant color differences between similar shades of four commercial gingiva‐colored composites. The composite resins showed different degrees of conversion and diffuse reflectance spectra. The aging conditions tested affected the color stability. Patients with gingiva‐colored indirect restorations should be informed about time‐dependent discoloration. [ABSTRACT FROM AUTHOR]

Cultivating rice varieties with lower cellulose content in the bran layer has the potential to enhance both the nutritional value and texture of brown rice. This study aims to establish a rapid and accurate method to quantify cellulose content in the bran layer utilizing near-infrared spectroscopy (NIRS), thereby providing a technical foundation for the selection, screening, and breeding of rice germplasm cultivars characterized by a low cellulose content in the bran layer. To ensure the accuracy of the NIR spectroscopic analysis, the potassium dichromate oxidation (PDO) method was improved and then used as a reference method. Using 141 samples of rice bran layer (rice bran without germ), near-infrared diffuse reflectance (NIRdr) spectra, near-infrared diffuse transmittance (NIRdt) spectra, and fusion spectra of NIRdr and NIRdt were used to establish cellulose quantitative analysis models, followed by a comparative evaluation of these models' predictive performance. Results indicate that the optimized PDO method demonstrates superior precision compared to the original PDO method. Upon examining the established models, their predictive capabilities were ranked in the following order: the fusion model outperforms the NIRdt model, which in turn surpasses the NIRdr model. Of all the fusion models developed, the model exhibiting the highest predictive accuracy utilized fusion spectra (NIRdr-NIRdt (1st der)) derived from preprocessed (first derivative) diffuse reflectance and transmittance spectra. This model achieved an external predictive R2p of 0.903 and an RMSEP of 0.213%. Using this specific model, the rice mutant O2 was successfully identified, which displayed a cellulose content in the bran layer of 3.28%, representing a 0.86% decrease compared to the wild type (W7). The utilization of NIRS enables quantitative analysis of the cellulose content within the rice bran layer, thereby providing essential technical support for the selection of rice varieties characterized by lower cellulose content in the bran layer. [ABSTRACT FROM AUTHOR]

Organic UV filters have been known to generate harmful by-products and undergo photoreactive degradation, which ultimately poses a great threat to consumers using sunscreen products. Inorganic UV filters such as TiO2 and ZnO, although considered safer options, are not without threat considering their photocatalytic nature and ability to generate reactive oxygen species. A study was conducted to identify the influence of different metal ions on the photochemical properties of layered double hydroxides (LDH), Zinc-Titanium LDH (Zn-Ti LDH), Zinc-Aluminium LDH (Zn-Al LDH), and Magnesium- Aluminium LDH (Mg-Al LDH) and their prospects in photoprotection. The photocatalytic properties of the LDH were analyzed and compared to TiO2 and ZnO. The intermediate band gaps of Zn-Ti (3.72 eV) and Zn-Al LDH (3.3 eV) proved favorable and safer for the use of these LDH in cosmetic formulations as they offer lower photo-reactivity when compared to cosmetic grade ZnO and TiO2. The in vitro SPF values obtained for formulations containing 2 wt% Zn-Ti and 2 wt% Zn-Al LDH showed promise, with both samples claiming "broad spectrum" protection and valid claims of UVA protection. [ABSTRACT FROM AUTHOR]

Sedimentary arsenic (As) in the shallow aquifers of Bangladesh is enriched in finer-grained deposits that are rich in organic matter (OM), clays, and iron (Fe)-oxides. In Bangladesh, sediment color is a useful indicator of pore water As concentrations. The pore waters of orange sediments are usually associated with lower As concentrations (<50 µg/L) owing to abundant Fe-oxides which sorb As. Using this color signal as a guide, spectroscopic measurements alongside thermal treatment were extensively utilized for analyzing the properties of both Fe-oxides and clay minerals. This study uses Fourier transform infrared (FTIR) and diffuse reflectance (DR) measurements along with thermal treatment to evaluate the solid-phase associations of As from sediment collected along the Meghna River in Bangladesh. The samples analyzed in this study were chosen to represent the various lithologies present at the study site and included riverbank sands (1 m depth), silt (6 m depth), aquifer sand (23 m depth), and a clay aquitard (37 m depth). The concentrations of sedimentary As and Fe were measured by X-ray fluorescence, and the spectroscopic measurements were taken on the samples prior to the thermal treatment. For the thermal treatment, sediment samples were placed in a preheated furnace at 600 °C for 3 h. The thermal treatment caused a deepening of reddish-brown hues in all samples, and the greatest change in color was observed in the finer-grained samples. The FTIR spectral analysis revealed that the clay minerals were composed primarily of illite, smectite, and kaolinite. The DR results indicate that the majority of Fe in sands was present as goethite; however, in the clay and silt samples, Fe was incorporated into the structure of clay minerals as Fe(II). The amount of structural Fe(II) was strongly positively correlated with the sedimentary As concentrations, which were highest in the finer-grained samples. After thermal treatment, the concentrations of As in the finer-grained samples decreased by an average of 40%, whereas the change in the As concentrations of the sand samples was negligible. These findings indicate that significant proportions of solid-phase As may be retained by OM and Fe(II)-bearing clay minerals. [ABSTRACT FROM AUTHOR]

The samples ZnO:Mn were prepared using the conventional solid-state technique. To dope them with manganese, we used water solutions of MnSO4 and MnCl2. The properties inherent to both types of the obtained ceramics have been compared. It was found that the former demonstrated nonlinear current-voltage characteristics, whereas those of the latter were, in fact, linear. The analysis of EPR, diffuse reflectance and Raman spectra obtained for prepared ceramics allowed concluding that, in the samples doped with MnSO4, formation of Mn-related phase, namely, ZnMn2O4 spinel occurred at ZnO grain boundaries under sintering. It has been ascertained that a thin layer of this substance separates adjacent ZnO grains, which provides appearance of the back-to-back Schottky barriers at grain boundaries and “varistor behavior” of current-voltage characteristics. [ABSTRACT FROM AUTHOR]

This study presents the results of the classification of diffuse reflectance (DR) spectra and multiexcitation autofluorescence (AF) spectra that were collected in vivo from precancerous and benign skin lesions at three different source detector separation (SDS) values. Spectra processing pipeline consisted of dimensionality reduction, which was performed using principal component analysis (PCA), followed by classification step using such methods as support vector machine (SVM), multilayered perceptron (MLP), linear discriminant analysis (LDA), and random forest (RF). In order to increase the efficiency of lesion classification, several data fusion methods were applied to the classification results: majority voting, stacking, and manual optimization of weights. The results of the study showed that in most of cases the use of data fusion methods increased the average multiclass classification accuracy from 2% up to 4%. The highest accuracy of multiclass classification was obtained using the manual optimization of weights and reached 94.41%. [ABSTRACT FROM AUTHOR]

Background: Isoniazid is a leading tuberculosis treating medication. Global supply chains provide essential medicines such as isoniazid to resource-limited areas. Ensuring the safety and efficaciousness of these medicines is essential to public health programs. Handheld spectrometers are becoming increasingly approachable in cost and usability. As supply chains expand, quality compliance screening of essential medications is necessary in site-specific locations. Here, a brand-specific qualitative discrimination analysis of isoniazid is approached by collecting data from two handheld spectrometers in two countries with the intent to build a multi-location quality compliance screening method for a brand of isoniazid. Methods: Two handheld spectrometers (900–1700 nm) were used to collect spectra from five manufacturing sources (N = 482) in Durham, North Carolina, USA, and Centurion, South Africa. A qualitative brand differentiation method was established from both locations by applying a Mahalanobis distance thresholding method as a measure of assessing similarity. Results: Combining data from both locations resulted in a 100% classification accuracy, at both locations, for brand 'A' and resulted in the four other brands classifying as dissimilar. Bias was found between sensors in terms of resulting Mahalanobis distances, but the classification method proved to be robust enough to accommodate. Several spectral peaks found in isoniazid references appear within the 900–1700 nm range, as well as variation in the excipients per manufacturer. Conclusions: Results show promise for compliance screening isoniazid as well as other tablets in multiple geographic locations using handheld spectrometers. [ABSTRACT FROM AUTHOR]

Boron carbide powders were synthesized from elemental powders and studied using X‐ray diffraction (XRD) and UV–visible diffuse reflectance, Raman, and diffuse reflectance IR spectroscopies. Following reaction at 1400°C for 6 h, synthesized powders exhibited possible faulting as suggested by XRD patterns. B3C, B4.3C, and B5C powders contained graphitic carbon whereas the boron carbides with higher B/C ratios contained no residual carbon, suggesting that the carbon rich phase boundary is likely temperature dependent. Analysis by Raman and IR spectroscopy suggested that Raman spectra are influenced by excitation frequency due to resonance. We suggest that measurement of boron carbides with resonant Raman lifts the selection rules to allow measurement of Raman silent modes that are present in the IR spectra. Optical reflectance of the boron carbide powders revealed that the B/C ratio governed the indirect and direct optical band gaps of the faulted powders. B3C and B4.3C powders were light gray in spite of the presence of the carbon, whereas B5C, B6.5C, B10C, and B12C were gray, green, brown, and dark brown, respectively. Increasing carbon content increased the optical indirect band gap from 1.3 eV for B12C to 3.2 eV for B3C, causing the observed color changes. [ABSTRACT FROM AUTHOR]

A series of Ca9Gd(VO4)7: Dy3+ (x = 0.01–0.20) nanophosphor crystals emitting a cool white light were synthesized by solution combustion methodology. The X-ray diffraction patterns were analyzed and processed using Rietveld refinement. The fabricated nanophosphor was found to crystallize in a trigonal crystal lattice with space group R3c(161). The morphological behavior of the prepared nanophosphor was investigated using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The photoluminescence properties of the nanophosphor correspond to cool white emission upon near-ultraviolet (NUV) excitation at 327 nm due to 4F9/2 → 6H15/2 (bluish) and 4F9/2 → 6H13/2 (yellowish) radiative relaxations at 487 nm and 576 nm respectively. Also, there is a strong occurrence of double charge transfer from O2− ions to Dy3+ and V5+ ions with the latter being stronger due to the high positive charge of V5+ ions. Color coordinates (x = 0.2878, y = 0.3259) are consistent with white emission. Auzel's model was implemented to examine the non-radiative relaxation (113.5 ms−1), radiative lifetime (1.4856 ms), and quantum efficiency (83.13%) values. The crystalline and optical behavior of the synthesized cool white emitting nanophosphor facilitates its use in near-UV-based WLEDs and other advanced solid-state lighting. [ABSTRACT FROM AUTHOR]

The optical and electrical properties of sodium niobate crystals and ceramics doped with Mn atoms are studied. Na(Nb1−zMnz)O3 crystals exhibit actual z = 0–1.0 wt% Mn content. The Na(Nb1−zMnz)O3 ceramics contains Mn from the 0–5 wt% range. The (Na1−xBix)(Nb1−yMny)O3 ceramics is codoped with x = 0.015–0.50 and y = 0.01–0.33. Mn addition decreases the reflectance magnitude. Combined nonstoichiometry and local disorder in the crystal lattice, resulting from Mn doping and oxygen vacancies, induce contributions to the electronic structure. The visible and near‐infrared (Vis–NIR) diffuse reflectance, R(λ), spectra include a linear combination of contributions. The modified Kubelka–Munk function representation allows estimation of the optical energy gap, Egap. This estimation is qualitative because of the complex structure of the samples. Two optical gaps, showing dependence on Mn content, are discerned when Mn content <1 wt%. Egap,high changes toward the Shockley–Queisser limit, from 1.85 to 1.4 eV, when Mn content is low (z < 1 wt%). Simultaneous occurrence of Egap,low of 1.0–1.3 eV suggests tuning possibility. Egap of ≈1 eV dominates optical properties when Mn content is >1 wt%. The optical features are consistent with activation energy attributed to thermally generated electrical conductivity. [ABSTRACT FROM AUTHOR]

Precise knowledge about light propagation in biological tissues is necessary for accurate diagnostics and effective therapies utilizing optical technologies. In the current paper, the Monte Carlo simulation is applied to study light dispersion in normal and cancerous breast after irradiating to different laser beam shapes. Two distinct laser wavelengths (800–1100 nm) with planar and Gaussian shapes were employed. The spatially resolved steady-state diffuse reflectance of normal tissue and tumor was investigated using Monte Carlo simulation method via MCML and MCXLAB computations. The diffusion equation was solved to simulate the fluence rate at the tissue surface based on the optical parameter values (i.e., scattering and absorption coefficients). The results confirm differences in diffuse reflectance and optical fluence distribution between the normal and tumor tissues at each wavelength. Tissue optical parameters and the utilized laser beam shape control the distribution of the fluence rate within tissues. Therefore, offering visual representations of these distributions can provide a secure visual route for biological diagnostics. [ABSTRACT FROM AUTHOR]

To identify the malignancy in human breast, hand-held optical probes are simulated using the Monte Carlo method. These devices were used to scan different tissue equivalent numerical breast phantoms to detect the embedded cancerous tissues in them. The phantoms were simulated with glandular tissues embedded with ductal carcinoma of size 5 mm and 2 mm diameter at various depths. Two optical probes namely dual side detector (DSD) probe and a single side detector (SSD) probe are designed through which one million light photons of wavelengths 600 nm and 800 nm respectively were passed into the numerical phantoms. The photons that were backscattered from the phantoms were received by the detectors in both probes. They were measured as signals and both probes were able to detect the presence of the embedded cancerous tissues at different depths. The results indicate that the probes with a light source at 800 nm could detect deep-seated inhomogeneities. The absolute value of Peak Intensity (|PI|) and Full Width at Half Maximum (FWHM) would be indicative of their location and approximate size of the embedded tissues. The |PI| decreases with the size and depth of the embedded tissue, and the FWHM increases with depth. The results show that the designed probes are capable of detecting small variations in tissues.

This research reports a simple, innovative, and low-cost doping method of TiO2 nanoparticles presenting the effects of calcination and the weight ratio of TiO2:FeCl3 (1:0.33–1:4.5). The photocatalytic activity of the nanomaterials was investigated by decolorizing Rhodamine B (RhB) dye in an aqueous solution. The main results showed that there is anatase-to-rutile transformation after the calcination process. The Fe-doped process modified the TiO2 spectrum and showed a connection in the Ti–O–Fe vibration. The particle size is within the nanometer range, between 20–51 nm, except for calcined TiO2. The inclusion of Fe in TiO2 decreased the band gap energy from 3.16 (reference) up to 2.06 eV (1:3). Additionally, after the calcination, there was a decrease in this value from 3.03 eV (reference) up to 1.95 eV (1:1.6). The TiO2, with a ratio of (1:1.6), showed the highest activity in the photocatalytic degradation of RhB with an efficiency of 93.8% after 3 h of irradiation. [ABSTRACT FROM AUTHOR]

Hydrothermal and thermolysis techniques were used to create ZnWO 4 and 0.9ZnWO 4 -0.1MS (M = Cd, Zn, Pb) samples. The formed phases in each sample and their structure and microstructure were examined using Raman spectroscopy, Fourier-transform infrared spectroscopy and Rietveld refinement of Synchrotron x-ray diffraction data. The composition and morphology of the formed samples were investigated via scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS). The average crystallite size remains relatively constant regardless of the different metal chalcogenides. MS/ZnWO 4 samples have two distinct morphologies. The UV diffuse reflectance spectroscopy (UV-DRS) technique is used to investigate the linear and nonlinear optical parameters for different samples. Alloying ZnWO 4 with CdS or PbS affects the photo response region of the sample to include visible light. MS/ZnWO 4 (MS=CdS, ZnS, PbS) samples have optical band gap values of 2.56, 2.43, 2.99 and 3.1 eV, respectively. The CdS/ZnWO 4 and ZnS/ZnWO 4 samples exhibit the highest refractive index and optical dielectric constant values within the visible range. CdS or PbS/ZnWO 4 samples show the highest nonlinear optical parameters values within the visible range. The impact of MS samples on the photoluminescence emission of ZnWO 4 was explored. The CIE chromaticity diagram reveals that MS/ZnWO 4 (M = Zn and Pb) samples display a different degree of blue color while CdS/ZnWO 4 sample reveals green-yellow colors. • Raman spectra analysis confirmed the formation of CdS phase, nonexistence of the ZnS phase and could not detect PbS phase. • The values of n and k are influenced by the measured range of wavelengths and the type of alloying sample (MS) with ZnWO 4. • All samples exhibit a wide-ranging emission in the blue-green region. • The examined samples become more sensitive to daylight. [ABSTRACT FROM AUTHOR]

Cultivating rice varieties with lower cellulose content in the bran layer has the potential to enhance both the nutritional value and texture of brown rice. This study aims to establish a rapid and accurate method to quantify cellulose content in the bran layer utilizing near-infrared spectroscopy (NIRS), thereby providing a technical foundation for the selection, screening, and breeding of rice germplasm cultivars characterized by a low cellulose content in the bran layer. To ensure the accuracy of the NIR spectroscopic analysis, the potassium dichromate oxidation (PDO) method was improved and then used as a reference method. Using 141 samples of rice bran layer (rice bran without germ), near-infrared diffuse reflectance (NIRdr) spectra, near-infrared diffuse transmittance (NIRdt) spectra, and fusion spectra of NIRdr and NIRdt were used to establish cellulose quantitative analysis models, followed by a comparative evaluation of these models’ predictive performance. Results indicate that the optimized PDO method demonstrates superior precision compared to the original PDO method. Upon examining the established models, their predictive capabilities were ranked in the following order: the fusion model outperforms the NIRdt model, which in turn surpasses the NIRdr model. Of all the fusion models developed, the model exhibiting the highest predictive accuracy utilized fusion spectra (NIRdr-NIRdt (1st der)) derived from preprocessed (first derivative) diffuse reflectance and transmittance spectra. This model achieved an external predictive R2p of 0.903 and an RMSEP of 0.213%. Using this specific model, the rice mutant O2 was successfully identified, which displayed a cellulose content in the bran layer of 3.28%, representing a 0.86% decrease compared to the wild type (W7). The utilization of NIRS enables quantitative analysis of the cellulose content within the rice bran layer, thereby providing essential technical support for the selection of rice varieties characterized by lower cellulose content in the bran layer.

ZnFe2O4 (ZFO) NPs (nanoparticles), Co0.5Ni0.5Ga0.01Gd0.01Fe1.98O4 (CNGaGdFO) NPs and hard-soft spinel ferrite (H/S) (CNGaGdFO)x/(ZFO)y (x:y = 1:1, 1:2, 1:3, 2:1, 3:1 and 4:1) NCs (nanocomposites) were synthesized via a one-pot sol–gel auto combustion route. X-ray powder diffraction (XRD) analyses confirmed the purity of ZFO NPs, CNGaGdFO NPs and H/S (H/S) (CNGaGdFO)x/(ZFO)y (x:y = 1:1, 1:2, 1:3, 2:1, 3:1 and 4:1) (absence of any second phase). The crystallite size of NCs was between 39 and 52 nm. The cubic morphology was observed for ZFO NPs, CNGaGdFO NPs and all H/S NCs by the help of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. Energy dispersive X-Ray analysis (EDX) also confirmed the chemical formula of all the NC samples. Electrical and dielectric properties of ZFO NPs, CNGaGdFO NPs and H/S NCs were explored with an impedance analyzer with f ≤ 3.0 MHz, where f stands for frequency, and within the temperature range between 20 and 120 °C. Electric and dielectric parameters such as AC conductivity as well as DC conductivity, activation energy, dielectric constant, dielectric loss in addition to the dissipation parameter relevant to the electrical energy due to different physical processes were measured for each of the given compositional ratios. The AC conductivity was found to follow the frequency-dependent power law in general, being mainly reliant on the compositional ratios and the measured temperatures especially at lower frequencies. This study has shown that CoNiGaGdFeO-ZnFe2O4 H/S NCs carry out conduction mechanisms, which can be predominantly credited to grain–grain boundaries for various compositional ratios. The dielectric constant of (CNGaGdFO)x/(ZFO)y (x:y = 1:1, 1:2, 1:3, 2:1, 3:1 and 4:1) H/S NCs indicates common dielectric behaviours with frequency, largely dependent on compositional rates of the hard to soft spinel ferrites. It is observed that hard ferrite is dominant in the formation of the semicircles, and the diameter of the semicircles shows a drop as the temperature rises, suggesting a temperature-dependent relaxation mechanism. Consequently, the observed variation of the studied dielectric parameters with frequency can be explained by the conduction mechanism in most composition ratios of hard to soft spinel ferrites, which can be explained by a phenomenological method with Koop's model.

The use of the conventional Tauc’s method to determine optical bandgap energy from UV–vis spectroscopy data has been overemphasized for decades. However, a misuse of the Tauc’s formula in conjunction with the Kubelka-Munk function to determine the bandgap energy of semiconductors from diffuse reflectance data can lead to erroneous estimates. Particularly, large errors can be associated with computing values of the ordinate using the Tauc-Kubelka-Munk relationship for diffuse reflectance to produce Tauc’s plot. To address this apparent error, the present paper shows that the reflectance versus photon energy plot for bandgap estimation from UV–vis diffuse reflectance data can be employed to obtain reasonable bandgap values, suggesting that the conventional Tauc’s plot is not indispensable for accurate bandgap energy determination. The relatively simple method can be best choice when a researcher is unsure about the accurate computations from diffuse reflectance data which lead to proper Tauc’s plot. Interestingly, the rarely reported (if at all it can be found elsewhere) step-by-step approach to Tauc’s plot from diffuse reflectance data is described in this paper to serve as a simple guide for emerging material scientists. The UV–vis optical diffuse reflectance data for β-Ga2O3, ZnO and TiO2 semiconductor films are used for this study.

The optical properties of CsSnI3 perovskite thin films were investigated. The thin films were obtained from CsI and SnI2 precursors (special-purity grade, 99.999%, 5N), and also SnI2 (99%) by spin-coating from the corresponding solutions. The films were studied by X-ray powder diffraction analysis, scanning electron microscopy, and optical spectroscopy. It was shown that impurities in the initial components affect the optical properties of the obtained material: the absorption coefficient of the perovskite films synthesized from the special-purity grade SnI2 is higher than those of the films produced from 99% SnI2: 4 × 105 cm–1 and 6 × 105 cm–1, respectively. The optical band gap was estimated using the Tauc and Kubelka–Munk models. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temperature-dependent radiative properties of ceramic powders up to 1000 °C. • Diffuse reflectance measurements (1–20 µm) above temperature limit of background. • Sintered bauxite (ACCUCAST) evaluated for concentrated solar power applications. • ACCUCAST correlates most strongly to alumina and silica for wavelengths > 5 µm. • Thermal emittance of ACCUCAST larger than alumina and silica for T≥600 °C. Radiative properties are critical to quantify radiative energy fluxes between surfaces and in participating media. However, there is limited experimental data on temperature-dependent radiative properties of materials. This work focuses on experimentally measuring temperature-dependent diffuse reflectance in the near- and mid-infrared spectra (1–20 μm) for ceramic particles with applications as heat-transfer and thermal-storage media in concentrated solar power (CSP) plants. Specifically, a commercially available sintered bauxite proppant, ACCUCAST ID80, and its primary chemical constituents—alumina (Al 2 O 3) and silica (SiO 2)—are measured in powder form using a Fourier transform infrared spectrometer (FTIR) coupled with a specialized diffuse reflectance accessory and a heated stage. Room-temperature diffuse reflectance measurements show increased absorption in tests with greater mass fractions of the ceramic samples. There is a strong correlation in the measured reflectance spectra of ACCUCAST with alumina and silica in the spectral range 2000–500 cm−1 (5–20 μm). Whereas, for shorter wavelengths (< 5 μm), the absorptance for ACCUCAST is greater than the absorptance for alumina and silica, indicating contributions from other chemical species present in the composite material. For the first time, temperature-dependent diffuse reflectance measurements are reported for ACCUCAST up to 1000 °C. These results are compared against those of alumina and silica through the calculation of a thermal emittance. All three materials exhibit a calculated emittance of ∼0.9 at room temperature. However, this value decreases to ∼0.6 for ACCUCAST and drops to less than 0.4 for alumina and silica at 1000 °C. Thermal cycling in air at 1000 °C resulted in a visible color change from dark grey to light orange for ACCUCAST and a subsequent larger increase in reflectance for wavelengths less than 5 μm as compared to ACCUCAST thermally cycled at 1000 °C in vacuum. Alumina and silica spectra proved to be largely unaffected by thermal cycling under atmospheric conditions. Overall, this study establishes a powerful technique for the characterization of radiative properties of particulate materials as a function of temperature and presents a detailed case study of ACCUCAST, a candidate for next-generation particle-based CSP. [ABSTRACT FROM AUTHOR]

Zinc oxide is an environmentally friendly and readily synthesized semiconductor with many industrial applications. ZnO powders were prepared by alkali precipitation using different [Zn(acetate)2(amine)x] compounds to alter the particle size and aspect ratio. Slow precipitations from 95 °C solutions produced micron-scale particles with morphologies of hexagonal plates, rods, and needles, depending on the precursor used. Powders prepared at 65 °C with rapid precipitation yielded particles with minimal morphology differences, but particle size was dependent on the precursor used. The smallest particles were produced using precursors that yielded crystals with low aspect ratios during high-temperature synthesis. Particles produced during rapid synthesis had sizes ranging from 21–45 nm. The materials were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, BET, and diffuse reflectance. The materials prepared using precursors with less-volatile amines were found to retain more organic material than ZnO produced using precursors with more volatile amines. The amount of organic material associated with the nanoparticles influenced the photocatalytic activity of the ZnO, with powders containing less organic material producing faster rate constants for the decolorizing of malachite green solutions under ultraviolet illumination, independent of particle size. [Zn(acetate)2(hydrazine)2] produced ZnO with the fastest rate constant and was recycled five times for dye degradation studies that revealed minimal to no reduction in catalytic efficiency. [ABSTRACT FROM AUTHOR]

This work is an overview of silicon photomultipliers (SiPMs) with a view to defining their importance for bio-photonic and clinical applications. SiPMs are benchmarked against other common photodetectors, namely, PIN diodes and avalanche photodetectors (APDs) and are compared with respect to important circuit design parameters. It will be shown that careful selection of the design bias voltage, overvoltage, gain defining components and device integration to micro-optics can allow SiPM detectors to achieve considerable sensitivity for auto-fluorescence (AF) detection and a wide dynamic range at low optical powers (~1 pW to ~4 μW). The SiPM has a manageable bias voltage (~25 V to ~30 V DC) for systems integration, and with optimised sensitivity it will enhance bio-photonic research in the area of AF to detect intraoperatively, for example, brain tumour margins. [ABSTRACT FROM AUTHOR]

The surfaces of real objects can visually appear to be glossy, matte, or anywhere in between, but essentially, they display varying degrees of diffuse and specular reflectance. Diffuse and specular reflectance provides different clues for light estimation. However, few methods simultaneously consider the contributions of diffuse and specular reflectance for light estimation. To this end, we propose ReDDLE-Net, which performs Reflectance Decomposition for Directional Light Estimation. The primary idea is to take advantage of diffuse and specular clues and adaptively balance the contributions of estimated diffuse and specular components for light estimation. Our method achieves a superior performance advantage over state-of-the-art directional light estimation methods on the DiLiGenT benchmark. Meanwhile, the proposed ReDDLE-Net can be combined with existing calibrated photometric stereo methods to handle uncalibrated photometric stereo tasks and achieve state-of-the-art performance. [ABSTRACT FROM AUTHOR]

The accurate estimation of skin and skull optical properties over a wide wavelength range of laser radiation has great importance in optogenetics and other related applications. In the present work, using the Kubelka–Munk model, finite-element solution of the diffusion equation, inverse adding-doubling (IAD), and Monte-Carlo simulation, we estimated the refractive index, absorption and scattering coefficients, penetration depth, and the optical fluence distribution in rabbit head tissues ex vivo, after dividing the heads into three types of tissues with an average thickness of skin of 1.1 mm, skull of 1 mm, and brain of 3 mm. The total diffuse reflectance and transmittance were measured using a single integrating sphere optical setup for laser radiation of 532, 660, 785, and 980 nm. The calculated optical properties were then applied to the diffusion equation to compute the optical fluence rate distribution at the boundary of the samples using the finite element method. Monte-Carlo simulation was implemented for estimating the optical fluence distribution through a model containing the three tissue layers. The scattering coefficient decreased at longer wavelengths, leading to an increase in optical fluence inside the tissue samples, indicating a higher penetration depth, especially at 980 nm. In general, the obtained results show good agreement with relevant literature. [ABSTRACT FROM AUTHOR]

Butterfly wing scales feature complex nanostructures that influence wing coloration and various mechanical and optical properties. This configuration plays a key role in ecological interactions, flight conditions, and thermoregulation, facilitated by interactions with environmental electromagnetic energy. In tropical forests, butterflies occupy distinct vertical habitats, experiencing significant light and temperature variations. While wing nanostructures have been widely studied, their variation across different vertical flight preferences remains underexplored. This study investigates the wing nanostructures of 12 tropical butterfly species from the Nymphalidae family, focusing on their optical, morphological, and thermal properties across different forest strata. We analyzed the optical response through diffuse reflectance in the UV, Vis, and NIR ranges, correlating these findings with nanostructural configuration and thermal stability using thermogravimetric analysis (TGA). Our results reveal a significant correlation between flight stratification and wing optical responses, alongside distinct nanostructural features within each stratum. This study demonstrates the variability in butterfly wing nanostructures along the vertical stratification of the forest to cope with environmental conditions, raising new questions for future research on eco-evolutionary flight and thermal adaptations. Additionally, this underscores the importance of understanding how these structural adaptations influence butterfly interactions with their environment and their evolutionary success across different forest strata.

A smartphone-based spectrometer employing principle of diffuse reflection is reported for the surface analysis of solid samples. The instrument utilizes a thin-film grating to diffract incoming light, while a diffuse reflecting surface projects the image of this diffracted light onto the detector plane. The CMOS camera of smartphone camera directly captures the diffusely reflected photons within its limited field-of-view thus eliminating the need for collection, conditioning and converging optics. The optical setup of the instrument provides facility to calibrate the spectral response considering the nonlinear distribution of the wavelength across the diffraction direction. Additional correction in the detector response at different light intensity results a reduced spectral error with a maximum wavelength resolution of δλ=0.08 nm/pixel in the camera within the spectral range Δλ = (400 - 700) nm. As a proof of the concept, the instrument demonstrates successful detection of color pigments in food samples by absorption measurement of the samples at an average spectral error < 6 %. The distinct absorption peak associated with standard food colors are compared against the absorption profile of unknown food colors used in pastry cake. This field-functional smart analysis with internet connectivity opens opportunity of identifying food adulteration by using toxic chemical colors at the point-of-test and immediate reporting to others. The overall instrument is fabricated by utilizing low-cost and light weight plastic wood to make compact (110 mm × 105 mm × 125 mm), robust, inexpensive (∼$ 50) and suitable for field-portable (∼145 gm) hand-held operation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

One of the urgent tasks of modern medicine is to detect microcirculation disorder during surgery to avoid possible consequences like tissue hypoxia, ischemia, and necrosis. To address this issue, in this article, we propose a compact probe with sapphire tip and optical sensing based on the principle of spatially resolved diffuse reflectance analysis. It allows for intraoperative measurement of tissue effective attenuation coefficient and its alteration during the changes of tissue condition, caused by microcirculation disorder. The results of experimental studies using (1) a tissue-mimicking phantom based on lipid emulsion and hemoglobin and (2) a model of hindlimb ischemia performed in a rat demonstrated the ability to detect rapid changes of tissue attenuation confirming the feasibility of the probe to sense the stressful exposure. Due to a compact design of the probe, it could be useful for rather wide surgical operations and diagnostic purposes as an auxiliary instrument., (© 2024 Wiley‐VCH GmbH.)