Diffuse Reflectance Spectroscopy Data Research Articles

Evaluating hyperpigmentation: is invasion of the skin necessary?

BackgroundThe combination of long wavelength ultraviolet A1 radiation (LWUVA1) and visible light (VL) has been shown to produce photodamage and the majority of organic sunscreens lack protection against this spectrum. Currently, established testing protocols for VL photoprotection are lacking.ObjectiveTo compare pigmentation assessment methods, including Investigator’s Global Assessment (IGA) scoring, Diffuse Reflectance Spectroscopy (DRS), and immunohistochemistry, to assess the utility of each in evaluating VL + LWUVA1 induced pigmentation.MethodsAnonymized IGA, DRS, and immunohistochemistry data for 37 subjects (Fitzpatrick skin phototypes IV-VI) was retrospectively analyzed for pigment evaluation. Pigmentation was induced on the subjects’ backs with VL + LWUVA1 (0%–0.5% UVA1) irradiation at a dose of 480 J/cm2. Comparisons were made for all three assessment techniques between non-irradiated skin and VL + LWUVA1 irradiated skin, as well as between pure VL (0% UVA1) and VL + LWUVA1 (0.5% UVA1) irradiated sites. All comparisons were made for data collected approximately 24 h after irradiation to evaluate persistent pigment darkening (PPD).ResultsAmong all 37 subjects, both IGA scores and DRS detected a statistically significant difference in PPD between irradiated and non-irradiated sites, as well as between VL + LWUVA1 and pure VL irradiated sites. However, MART-1/Melan-A did not indicate a statistically significant difference in PPD between irradiated and non-irradiated sites or between VL + LWUVA1 and pure VL irradiated sites.ConclusionSubjective and objective noninvasive assessments were more sensitive in detecting VL + LWUVA1 induced pigmentation and should be preferred over invasive methods. Researchers are advised to initiate assessments with IGA and subsequently incorporate DRS for more objective and comprehensive insights in pigment evaluation.

Margin assessment during breast conserving surgery using diffuse reflectance spectroscopy.

During breast-conserving surgeries, it is essential to evaluate the resection margins (edges of breast specimen) to determine whether the tumor has been removed completely. In current surgical practice, there are no methods available to aid in accurate real-time margin evaluation. In this study, we investigated the diagnostic accuracy of diffuse reflectance spectroscopy (DRS) combined with tissue classification models in discriminating tumorous tissue from healthy tissue up to 2mm in depth on the actual resection margin of in vivo breast tissue. We collected an extensive dataset of DRS measurements on ex vivo breast tissue and in vivo breast tissue, which we used to develop different classification models for tissue classification. Next, these models were used in vivo to evaluate the performance of DRS for tissue discrimination during breast conserving surgery. We investigated which training strategy yielded optimum results for the classification model with the highest performance. We achieved a Matthews correlation coefficient of 0.76, a sensitivity of 96.7% (95% CI 95.6% to 98.2%), a specificity of 90.6% (95% CI 86.3% to 97.9%) and an area under the curve of 0.98 by training the optimum model on a combination of ex vivo and in vivo DRS data. DRS allows real-time margin assessment with a high sensitivity and specificity during breast-conserving surgeries.

Synthesis and characterization of (Pb1−x Sr x )MnBO4: a structural and spectroscopic study

Abstract The presence of ns 2 stereo-chemical active lone electron pairs (LEPs) causes asymmetric atomic environments around a given p-block cation, leading to change the crystal chemistry of a respective system. Here we report a series of mullite-type compounds to understand at what extend Sr2+ replaces the stereochemical active Pb2+ cation in (Pb1−x Sr x )MnBO4. Each member of the solid solution has been synthesized by conventional solid-state method. The polycrystalline samples are characterized using X-ray powder diffraction followed by Rietveld refinement. Substitution of Pb2+ with Sr2+ leads to contraction of the a lattice parameter with slight elongation in the b and c direction. For a difference of 1 pm of the ionic radius between Sr2+ and Pb2+, the cell volume contracts about 4 % between the end members as the spatial requirement of the LEP activity in the MBO4 2− channels significantly decreases. Within the solid solution, two distinct Pb/Sr–O2 bond distances significantly differ, which gradually decreases with increasing strontium content leading to a more symmetric coordination around strontium. The calculated BVS of Pb2+/Sr2+ exhibits a linear correlation with the Wang–Liebau eccentricity parameter, indicating to an increased bonding ability cation. The vibrational properties are characterized by both Raman and FTIR spectroscopy, complementing the XPRD results. Electronic band gaps of selected (Pb1−x Sr x )MnBO4 samples were obtained from diffuse reflectance spectroscopy data. Additionally, the Sr containing samples show higher thermal stability than the Pb containing counterparts.

Spectral Analysis of Injectable Depot Medroxyprogesterone Acetate From the International Market With Diffuse Reflectance Spectrometers: Potential Public Health Implications With Benchtop and Handheld Spectrometers

Depot-medroxyprogesterone acetate (DMPA) is an essential medication used as a form of family planning by millions around the world. Diffuse reflectance spectroscopy (DRS) has a long history as a quality assurance measure for raw ingredient verification in pharmaceutical manufacturing. There are a multitude of DMPA manufacturers in the global marketplace. Prudent supply chain management requires identification of potential suppliers that can be contacted if a current supplier is unavailable. Here, DRS data were collected with benchtop (350–2500 nm) and handheld (900–1700 nm) spectrometers for 16 brands of DMPA. Spectra from sample vials ( N = 262) are compared through principal component analysis and Mahalanobis distances. The benchtop spectrometer proved to be an efficient gauge of the similarities and differences amongst DMPA brands, with subcontracted manufacturers resulting in very similar results to the primary manufacturers. The handheld spectrometer offers advantages in portability and cost and was shown to be an effective brand discrimination tool but was less reliable in the context of identifying potentially suitable supply chain substitution options of DMPA due to several key DMPA spectral features appearing just outside of the handheld spectrometer's range. Data collected from the benchtop spectrometer was used to identify several potential supply chain substitutions, dependent on various other subsequent due-diligence activities (i.e., product documentation reviews and manufacturing site audits). These potential substitutions can be shortlisted for further auditing review prior to being identified as a potential supply chain substitution.

Tuning electrochemical behavior and band gap energy of ammonium phosphomolybdate/polymer composite and facilitate reduction of Cr(VI) in contaminated water

Binary composites of ammonium phosphomolybdate (APM) with polyaniline and poly(N-methylaniline) namely APM/PAni and APM/PNMAni were synthesized respectively in situ by exploiting the oxidizing ability of APM. The composites were characterized using fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopy. Further, the electrochemical behavior of these composites was investigated using cyclic voltammetry. The redox peaks obtained for APM, APM/PAni and APM/PNMAni at 0.302, 0.228 and 0.298 V respectively could be attributed to MoV/MoVI electron process. The appreciable shift in the peak could be attributed to the electron donating behavior of methyl groups in APM/PNMAni. Additionally, the band gap energy was calculated using diffuse reflectance spectroscopy data. The optical band gap of the composites increased considerably as compared to APM. A higher band gap was observed for APM/PNMAni as compared to APM/PAni, indicating the influence of methyl substitution in tuning the band gap energy. In addition, the role of these composites and its constituents in the removal of hexavalent chromium ions from aqueous solution was also explored. The removal of Cr(VI) from aqueous solution was monitored using UV–Visible spectroscopy. While removal of Cr(VI) as high as 96.3 % could be achieved using polymers, composites exhibited the ability to reduce toxic Cr(VI) moieties to environmentally benign Cr(III) ions.

Designing a use-error robust machine learning model for quantitative analysis of diffuse reflectance spectra.

Machine learning (ML)-enabled diffuse reflectance spectroscopy (DRS) is increasingly used as an alternative to the computation-intensive inverse Monte Carlo (MCI) simulation to predict tissue's optical properties, including the absorption coefficient, and reduced scattering coefficient, . We aim to develop a use-error-robust ML algorithm for optical property prediction from DRS spectra. We developed a wavelength-independent regressor (WIR) to predict optical properties from DRS data. For validation, we generated 1520 simulated DRS spectra with the forward Monte Carlo model, where to , and to . We introduced common use-errors, such as wavelength miscalibrations and intensity fluctuations. Finally, we collected 882 experimental DRS images from 170 tissue-mimicking phantoms and compared performances of the WIR model, a dense neural network, and the MCI model. When compounding all use-errors on simulated data, the WIR model best balanced accuracy and speed, yielding errors of 1.75% for and 1.53% for , compared to the MCI's 50.9% for and 24.6% for . Regarding experimental data, WIR model had mean errors of 13.2% and 6.1% for and , respectively. The errors for MCI were about eight times higher. The WIR model presents reliable use-error-robust optical property predictions from DRS data.

Unravelling co-catalyst integration methods in Ti-based metal-organic gels for photocatalytic H2 production.

The synthesis, characterization and photocatalytic hydrogen evolution reaction (HER) performance of a series of metal-organic gels (MOGs) constructed from titanium(IV)-oxo clusters and dicarboxylato linkers (benzene-1,4-dicarboxylato and 2-aminobenzene-1,4-dicarboxylato) are described. All the MOGs exhibit a microstructure comprised of metal-organic nanoparticles intertwined into a highly meso-/macroporous structure, as demonstrated by cryogenic transmission electron microscopy and gas adsorption isotherms. Comprehensive chemical characterization enabled the estimation of the complex formula for these defective materials, which exhibit low crystallinity and linker vacancies. To gain deeper insights into the local structure, X-ray absorption fine structure (XAFS) spectroscopy experiments were performed and compared to that of the analogous crystalline metal-organic framework. Additionally, the ultraviolet-visible absorption properties and optical band gaps were determined from diffuse reflectance spectroscopy data. The MOGs were studied as light absorbers for the sacrificial photocatalytic HER under simulated solar light irradiation using a platinum co-catalyst by either (1) in situ photodeposition or (2) ex situ doping process, through a post-synthetic metalation of the MOG structure. The chemical analysis of the metalation, along with high-angle annular dark-field scanning transmission electron microscopy, revealed that although the in situ addition of the co-catalyst led to greater HER rates (227 vs. 110 μmolH2 gMOG-1 h-1 for in situ and ex situ, respectively), the ex situ modification provided a finer distribution of platinum nanoparticles along the porous microstructure and, as a result, it led to a more efficient utilization of the co-catalyst (45 vs. 110 mmolH2 gPt-1 h-1).

Multiwavelength Fluorescence and Diffuse Reflectance Spectroscopy for an In Situ Analysis of Kidney Stones

This study explores the use of diffuse reflectance spectroscopy (DRS) and multiwavelength fluorescence spectroscopy for real-time kidney stone identification during laser lithotripsy. Traditional methods are not suitable for in situ analysis, so the research focuses on optical techniques that can be integrated with lithotripsy fibers. Experiments were conducted ex vivo, using DRS and multiwavelength fluorescence spectroscopy (emission–excitation matrix (EEM)) to distinguish between 48 urinary stones of three types: urate, oxalate and hydroxyapatite, with infrared spectroscopy as a reference. A classification model was developed based on EEM and DRS data. Initial classification relying solely on EEM data achieved an f1-score of 87%, which increased to 92% when DRS data were included. The findings suggest that optical spectroscopy can effectively determine stone composition during laser lithotripsy, potentially enhancing surgical outcomes via the real-time automatic optimization of laser radiation parameters.

A study on the impact of [BO33−], [PO43−] and [SO42−] ions in normal cubic structures via structural and photoluminescence properties of Y2O3:Eu3+ phosphors

A series of Y2O3-AG: Eu3+ (where AG = Anionic Groups [PO43−, SO42− and BO33−]) nanophosphors were synthesized via a chemical combustion method and their structural and photoluminescence properties were investigated. The crystal structure and the surface morphology studies were analysed through the X-Ray powder diffraction (XRPD), Field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The XRD results showed that undoped Y2O3 phosphors crystalized in a cubic crystal structure, while the Y2O3-AG phosphors transformed from the pure Y2O3 cubic structures, except for SO42− based phosphor materials. The SEM micrographs showed that the particles were formed in the micrometer range with different sizes and shapes. The FTIR spectra revealed the presence of various structural groups in the Y2O3, Y2O3-AG: Eu3+ phosphors. Moreover, the optical diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) properties were investigated. Using the DRS data, the optical band gap energy values were obtained from the Kubelka-Munk function theory. Upon 395 nm excitation, the Y2O3-AG: Eu3+ phosphors emitted red light at 615 nm wavelength. Among all the samples, the Y2O3-BO3: Eu3+ produced the highest intensity of red-light emission. The International Commission on Illumination color coordinates indicated that these phosphors are potential candidates for producing enhanced red color components in white light-emitting diode (W-LEDs) applications.

Unveiling the effect of strain engineering on the electrochemical properties of hydrothermally grown nanostructured indium doped ZnSeO3 for photoanode applications

The crucial role of In as a dopant on the structural, optical, and thermogravimetric characteristics of the zinc selenite (ZnSeO3) nanopowders has been investigated in detail using X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Energy Dispersive Spectroscopy (EDS), Raman spectroscopy, diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and Thermogravimetric Analysis (TGA). The structural analysis indicates that all patterns are assigned to the ZnSeO3 orthorhombic structure. Also, XRD analysis shows that In3+ ions may have replaced Zn2+ ions, which causes lattice expansion. Both the Debye–Scherrer method, and the Williamson–Hall method have also been applied to study the influence of strain on the calculation of the crystallite size. The crystallite size was observed to increase with an increase in dopant concentration. The FE-SEM corroborated that the prepared samples are orthorhombic, with the EDS and mapping confirming the presence of In as a dopant. Raman spectroscopy results corroborated the XRD results indicating an expansion in the crystal structure of ZnSeO3 with the introduction of dopants. Based on DRS data, the introduction of In decreases the energy band gap of the synthesized ZnSeO3 nanopowder samples from 3.305 to 3.276. PL spectra confirm the presence of indium with the green emission band attributed to dopants dominating the emission. The TGA investigation shows an improvement in the mass loss with the introduction of dopants. EIS results indicated an improvement in the conductivity as the charge transfer resistance decreased from 525.04 to 21.95 kΩ for the undoped ZnSeO3 and 0.75% In–ZnSeO3 thin films showing improvement in charge mobility.

Tailoring robust luminescent-based BaSrY4O8: Eu3+ platform opens new avenues for screening diverge surface prompted cheiloscopy, WLED's, and dosimetric applications

The discovery, evaluation, and manipulation of material can open new avenues in different technological applications in a real-time practical implementation scenario is highly necessary. In this regard, the present work deals with the synthesis of a series amber-red color emitting BaSrY4O8:Eu3+(1–9 mol %) nanophosphors followed by a solution combustion route. X-ray diffraction studies of the prepared phosphors confirmed the orthorhombic phase with Pnma (62) space group. Scanning electron microscopy results revealed that the particles are dumbbells in shape with network-like structures. From diffuse reflectance spectroscopy data, the energy band gap was estimated and found to be ∼5.72–5.92 eV. The photoluminescence emission spectra of the prepared nanophosphors consist of intense and sharp peaks located at ∼ 578, 594, 612, 650, and 708 nm, which attributed to 5D0→7F0, 5D0→7F1,5D0→7F2,5D0→7F3 and 5D0→7F4 transitions of Eu3+ ions, respectively. The estimated Commission International de I'Eclairage color coordinates were found to be tuned from pink to amber-red region. Thermoluminescence glow curve of BaSrY4O8: Eu3+ (5 mol %) nanophosphor after irradiated with various γ –ray doses ranging from 1 to 8 KGy exhibits a broad band with maximum intensity at 340 °C. Thanks to intensive luminescence and nano-regime of the nanophosphor, which enable latent lip prints to visualize on various non-porous surfaces by revealing defined type I–V groove patterns without any background hindrance or color distraction under the excitation. The aforementioned results create new perspective avenues by demonstrating the versatility of the prepared nanophosphor as an excellent red component for white light-emitting diodes, dosimetry, and cheiloscopy applications.

Electronic structure characterization of TiO2-II with the α-PbO2 structure by electron-energy-loss-spectroscopy and comparison with anatase, brookite, and rutile

TiO2-II is a high pressure form of titania with a density about 2% larger than that of rutile. In contrast to the common polymorphs anatase, brookite and rutile its electronic structure and optical properties are poorly characterized. Here we report on a comparative electron-energy-loss-spectroscopy (EELS) study for which high resolution valence-loss and core-loss EELS data were acquired from nanocrystalline (<75 ​nm sized) titania particles with an energy resolution of about 0.2 ​eV. Electronic structure features revealed from titanium L3,2 and oxygen K electron energy loss near-edge structures show a strong similarity of TiO2-II with both rutile and brookite, which is attributed to similarities in the connectivity of octahedral TiO6 units with neighboring ones. From combined valence-loss EELS and UV-VIS diffuse reflectance spectroscopy data the band gap of TiO2-II was determined to be indirect and with a magnitude of ∼3.18 ​eV, which is very similar to anatase (indirect, ∼3.2 ​eV), and distinctly different from rutile (direct, ∼3.05 ​eV) and brookite (direct, ∼3.45 ​eV).

A Novel Shift in the Absorbance Maxima of Methyl Orange with Calcination Temperature of Green Tin Dioxide Nanoparticle-Induced Photocatalytic Activity

Background: The photocatalytic degradation of toxic organic compounds has received great attention for the past several years. Dyes, such as methyl orange (MO), are one of the major pollutants which create environmental hazards in the hydrosphere, living organisms and human beings. During photocatalytic degradation, NPs are activated in the presence of UV–Vis radiation which in turn creates a redox environment in the system and behaves as a sensitizer for light-induced redox mechanisms. Tin oxide (SnO2) is one of the prominent, but less investigated, nanomaterials compared to titanium oxide (TiO2) and Zinc oxide (ZnO) nanoparticles (NPs). Methods: Herein, Buxus wallichiana (B. wallichiana) leaf extract was utilized as a reducing and capping agent for the biosynthesis of SnO2 NPs. The effects of the calcination temperature on their photocatalytic, structure and surface properties were then examined. The degree of crystallinity and the crystallite size were determined through X-ray diffraction (XRD) analysis. The pore size and surface area were calculated by Burnett–Emmitt–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods based on nitrogen desorption data. Morphological changes were assessed by scanning electron microscopy (SEM). The optical behavior was analyzed through UV–Vis diffuse reflectance spectroscopy (DRS) data and the band gap subsequently calculated. The photocatalytic efficiency of SnO2 NPs was evaluated by double beam UV–Vis spectrophotometry under the influence of initial MO concentration, catalyst dose and pH of MO solution. The surface functional moieties were identified using Fourier transform infrared (FTIR) spectroscopy. All the calcined SnO2 NPs were used as photocatalysts for the mineralization of MO in aqueous media. Results: The degree of crystallinity and the crystallite size increased with the calcination temperature. The transmittance edge obtained for all the calcined SnO2 NPs shows a maximum absorbance in the visible range (λ-max = 464 nm). Moving toward higher wavelengths, a sudden intense red shift (from 464 nm to 500 nm), attributed to the incorporation of a hydroxyl radical at the ortho-position in the benzene ring associated with the dimethylamine group of MO, was observed in the absorbance of the samples calcined up to 300 °C. The percentage degradation of MO was found to decrease with increasing calcination temperatures. The optimal photocatalytic activity toward MO (15 ppm) in a solution of pH = 6 was obtained with 15 mg SnO2 NPs calcined at 100 °C. Conclusions: UV–Vis absorption spectroscopy demonstrates that the absorption spectra of MO are strongly modified by the calcination temperature. This work opens new avenues for the use of SnO2 NPs as photocatalysts against the degradation of industrial effluents enriched with different dyes.

Copper- and silver-containing heterometallic iodobismuthates(iii) with 4-(dimethylamino)-1-methylpyridinium cation: structures, thermal stability and optical properties

Reactions of BiI3, copper or silver iodide and 4-(dimethyl-amino)-1-methylpyridinium iodide [(Me-DMAP)I] result in formation of heterometallic complexes (MeDMAP)2{[Bi2Cu2I10]} and (MeDMAP)2{[Bi2Ag2I10]}. Their crystal structures, thermal stability and optical properties have been studied. Optical band gaps calculated from diffuse reflectance spectroscopy data are 1.81 and 2.06 eV for copper- and silver-containing complexes, respectively.

Dimensionality Reduction Statistical Models for Soil Attribute Prediction Based on Raw Spectral Data

To obtain a better performance when modeling soil spectral data for attribute prediction, researchers frequently resort to data pretreatment, aiming to reduce noise and highlight the spectral features. Even with the awareness of the existence of dimensionality reduction statistical approaches that can cope with data sparse dimensionality, few studies have explored its applicability in soil sensing. Therefore, this study’s objective was to assess the predictive performance of two dimensionality reduction statistical models that are not widespread in the proximal soil sensing community: principal components regression (PCR) and least absolute shrinkage and selection operator (lasso). Here, these two approaches were compared with multiple linear regressions (MLR). All of the modelling strategies were applied without employing pretreatment techniques for soil attribute determination using X-ray fluorescence spectroscopy (XRF) and visible and near-infrared diffuse reflectance spectroscopy (Vis-NIR) data. In addition, the achieved results were compared against the ones reported in the literature that applied pretreatment techniques. The study was carried out with 102 soil samples from two distinct fields. Predictive models were developed for nine chemical and physical soil attributes, using lasso, PCR and MLR. Both Vis-NIR and XRF raw spectral data presented a great performance for soil attribute prediction when modelled with PCR and the lasso method. In general, similar results were found comparing the root mean squared error (RMSE) and coefficient of determination (R2) from the literature that applied pretreatment techniques and this study. For example, considering base saturation (V%), for Vis-NIR combined with PCR, in this study, RMSE and R2 values of 10.60 and 0.79 were found compared with 10.38 and 0.80, respectively, in the literature. In addition, looking at potassium (K), XRF associated with lasso yielded an RMSE value of 0.60 and R2 of 0.92, and in the literature, RMSE and R2 of 0.53 and 0.95, respectively, were found. The major discrepancy was observed for phosphorus (P) and organic matter (OM) prediction applying PCR in the XRF data, which showed R2 of 0.33 (for P) and 0.52 (for OM) without using pretreatment techniques in this study, and R2 of 0.01 (for P) and 0.74 (for OM) when using preprocessing techniques in the literature. These results indicate that data pretreatment can be disposable for predicting some soil attributes when using Vis-NIR and XRF raw data modeled with dimensionality reduction statistical models. Despite this, there is no consensus on the best way to calibrate data, as this seems to be attribute and area specific.

Synthesis, crystal structure, and characterization of two bismuth phosphates Rb2CaBi2P4O15 and Rb3SrBiP4O14

Two new polyphosphates Rb2CaBi2P4O15 and Rb3SrBiP4O14 were synthesized through the conventional high-temperature solid-state reactions. Single crystal measurement indicates that Rb2CaBi2P4O15 crystallizes in the centrosymmetric space group P21/c and Rb3SrBiP4O14 crystallizes in the noncentrosymmetric space group P212121. Rb2CaBi2P4O15 consists of [CaO6], [BiO6], [BiO5], [P2O7] dimer and isolated [PO4] tetrahedron, while Rb3SrBiP4O14 consists of [BiO5], [SrO7] and [P2O7] dimer. They are both composed of [P2O7] dimer and the Bi–P2O7 ring. In addition, the synthesis, IR spectra, UV–vis–NIR diffuse reflectance spectroscopy data, thermal stability and theoretical calculation have been reported.

Synthesis, crystal structure and photocatalytic activity of new Dion-Jacobson type titanoniobates

New Dion-Jacobson type layered perovskite compounds A'Ln2Ti2NbO10 (A′ ​= ​Rb, H; Ln ​= ​Pr, Nd) were synthesized for the first time. The phase and chemical purity of the compounds were proved by X-ray diffraction (XRD) and EDX. Compounds RbPr2Ti2NbO10 and RbNd2Ti2NbO10 were synthesized using solid-state reactions, whereas HPr2Ti2NbO10·1.5H2O and HNd2Ti2NbO10·2H2O were obtained from Rb-containing phases by ion-exchange reactions. Crystal structures of RbPr2Ti2NbO10 (P4/mmm, a ​= ​0.38223 (1) nm, c ​= ​1.51485 (8) nm, Rwp ​= ​3.87%) and RbNd2Ti2NbO10 (P4/mmm, a ​= ​0.38153 (1) nm, c ​= ​1.51200 (6) nm, Rwp ​= ​3.62%) were refined using the Rietveld method. The distortions of polyhedrons in the structures were studied in detail. The thermal behavior of compounds was established using DTA. The ion-exchange products were found to be metastable hydrates. Optical band gap, valence band edge and conduction band edge potentials of obtained compounds were calculated from diffuse reflectance spectroscopy data. Photocatalytic experiment of methylene blue degradation under ultraviolet (UV) light was conducted with ground synthesized compounds. The particle size distributions were measured by laser diffraction before and after grinding. RbNd2Ti2NbO10 showed the highest photocatalytic activity, while HPr2Ti2NbO10·1.5H2O and HNd2Ti2NbO10·2H2O showed none.

Optimization of diffuse reflectance spectroscopy measurements for direct and rapid screening of pesticides: A case study of spinach

Although diffuse reflectance spectroscopy (DRS) measurements can be collected rapidly and simultaneously, the resulting datasets are imbalanced and redundant due to the highly correlated spectral features collected on relatively few samples. Consequently, modelling these datasets using machine learning (ML) techniques is challenging and necessitates longer training times and more computational resources. Furthermore, models developed with such data are frequently prone to overfitting, resulting in promising but often non-reproducible results. We demonstrate the advantage of using an eigenvector decomposition principal component analysis (PCA) in reducing the dimensionality and data mining of DRS measurements in the short near-infrared region (750–900 nm). A total of 547 DRS measurements consisting of 151 wavelengths were acquired from spinach samples sprayed with two different pesticides and control samples. The measurements were later preprocessed with a Savitzky-Golay filter and multiplicative scatter analysis. After performing PCA on the preprocessed data, two principal components (PCs) that explained 77% of the cumulative variance and maximized the interclass variation were extracted and used as inputs to three ML models namely; artificial neural networks, support vector machine and random forest, to classify the samples. Re-sampling was used to tune the models and avoid overfitting. The performance of the models was compared using raw DRS data, pre-processed (PP) DRS data, and PCs data. The results show that pesticide classification using PCs data requires the least amount of training time (average 2.4 s) for all the models, and achieves 100% classification accuracy. In addition, it was observed that spectral data pre-processing improves accuracy and training time when compared to using raw spectral data. These findings are particularly encouraging since they demonstrate the possibility of developing rapid and accurate classification models for screening pesticide residues in fresh produce based on DRS measurements with minimal computational resources.

A Z-scheme Cobalt(II) oxide-silver tungstate nano photocatalyst: Experimental design and mechanism study for the degradation of methylene blue

Ag2WO4 and CoO nanoparticles (NPs) and their binary coupled CoO-Ag2WO4 system (CS) were prepared and characterized via powder UV-Vis diffuse reflectance spectroscopy (DRS) and scanning electron microscopy equipped with an energy dispersed x-ray system (SEM-EDX). The band gap energies for CoO, Ag2WO4, and CoO/Ag2WO4 were obtained as 3.07, 3.11, and 2.67 eV by DRS data, while their pHpzc values were 7.9, 7.4, and 7.4. In the initial methylene blue (MB) removal steps, about 22, 23, and 35% MB molecules were removed by CoO, Ag2WO4, and CoO/Ag2WO4 photocatalysts. The CoO: Ag2WO4 mole ratio of 1:2 had the best photocatalytic efficiency. In the RSM study, the model goodness was confirmed by the model F-value of 491.13 > F0.05, 13, 12 = 2.4, and the lack-of-fit F value of 4.19 < F0.05, 10, 3 = 8.79. The optimal runs’ conditions were pH: 11, catalyst dosage: 0.3 g/L, irradiation time: 60 min, and CMB: 3 mg/L. A scavenging agent study confirmed all four reactive species have critical roles in the MB photodegradation, while the main critical effects belong to the photogenerated holes and superoxide radicals. Finally, the results confirmed that the photodegradation pathway follows the direct Z-scheme mechanism to degrade MB molecules because this pathway accumulates the photoinduced electrons in the CB-CoO and the holes in the VB- Ag2WO4 as the critical reducing and oxidizing centers, respectively.

Benchtop Electrochemical Growth and Controlled Alloying of Polycrystalline InxGa1–xAs Thin Films

Compared to Si, GaAs offers unique material advantages such as high carrier mobility and energy conversion efficiency, making GaAs a leading competitor to replace Si on several technological fronts related to optoelectronics and solar energy conversion. Alloying the GaAs lattice with elemental In allows the direct bandgap of the resulting ternary alloy to be tuned across the near-infrared (NIR) region of the electromagnetic spectrum from ∼0.9 to 3.5 μm. However, methods of fabricating high-quality crystalline GaAs are currently limited by their high cost and low throughput relative to Si growth methods, suggesting the need for alternative low-cost routes to GaAs growth and alloying. This research documents the first instance in the literature of the electrodeposition and controlled alloying of polycrystalline InxGa1–xAs films at ambient pressure and near-room temperature using the electrochemical liquid–liquid–solid (ec-LLS) process. X-ray diffraction and Raman spectroscopy support the polycrystalline growth of (111)-oriented InxGa1–xAs films. Consistent redshifts of the GaAs-like TO peaks were observed in the Raman data as the In composition of the liquid metal electrode was increased. Optical bandgaps, determined via diffuse reflectance measurements, displayed a consistent decrease with the increase in the In composition of InxGa1–xAs films. While Raman, diffuse reflectance, and energy-dispersive X-ray spectroscopy data support controlled alloying efforts, all techniques suggest an overall decrease of the In/Ga ratios present in deposited films relative to those of the liquid metal electrodes. These results lend support for the continued development of ec-LLS as a viable method of achieving crystalline growth and alloying of binary and ternary semiconductor material systems using a benchtop setup under ambient pressure and near-room temperature.