Visible Reflectance Spectroscopy Research Articles

XPS valence band observable light-responsive system for photocatalytic acid Red114 dye decomposition using a ZnO–Cu2O heterojunction

ZnO–Cu2O composites were made as photocatalysts in a range of different amounts using an easy, cheap, and environment-friendly coprecipitation method due to their superior visible light activity to remove pollutants from the surrounding atmosphere. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) have demonstrated that ZnO–Cu2O catalysts are made of highly pure hexagonal ZnO and cubic Cu2O. X-ray photoelectron spectroscopy has confirmed that there is a substantial interaction between the two phases of the resultant catalyst. The optical characterizations of the synthesized ZnO–Cu2O composite were done via UV–vis reflectance spectroscopy. Due to the doping on ZnO, the absorption range of the ZnO–Cu2O catalyst is shifted from the ultraviolet to the visible region due to diffuse reflection. The degradation efficiency is affected by the Ratio of ZnO: Cu2O and ZnO–Cu2O composite with a proportion of 90:10 exhibited the most prominent photocatalytic activity on Acid Red 114, with a pseudo-first-order rate constant of 0.05032 min−1 that was 6 and 11 times greater than those of ZnO and Cu2O, respectively. The maximum degradation efficiency is 97 %. The enhanced photocatalytic activity of the composite is caused by the synergistic interaction of ZnO and Cu2O, which improves visible light absorption by lowering band gap energy and decreasing the rate at which the electron-hole pairs recombine. The scavenging experiment confirmed that hydroxyl radical was the dominant species for the photodegradation of Acid Red 114. Notably, the recycling test demonstrated the ZnO–Cu2O photocatalyst was highly stable and recyclable. These results suggest that the ZnO–Cu2O mix might be able to clean up environmental pollutants when it meets visible light.

Not all apparently gynandromorphic butterflies are gynandrous: The case of Polyommatus icarus and its relatives (Lepidoptera: Lycaenidae)

Beside the more than two thousand normal specimens of Polyommatus icarus (Rottemburg, 1775) yielded by rearing experiments, there was one perfectly bilateral dichromatic individual first considered to be gynandrous. On the basis of analysing genitalia traits, wing surface covering scale micromorphology, and the spectral characteristics of the blue colour generated by the cover scales, the gender of the specimen has been identified as female. This exemplar was investigated in comparison with gynandrous specimens from the collections of the Hungarian Natural History Museum exhibiting various degrees of intermixing of blue and brown coloration. Focus stacking microscopy for detailed scale morphology and UV–visible reflectance spectroscopy was used for the characterization of the optical properties. Inspecting literature references and the Lycaenidae collection of the museum, further examples have been found for female bilateral dichromatism in the closely related polyommatine lycaenid species Lysandra bellargus (Rottemburg, 1775) and Lysandra coridon (Poda, 1761) what suggests that polyommatine female dichromaticity may be displayed by the manner of bilaterality and mosaicism, phenomena hitherto solely connected to gynandromorphy.

Analysis of four heavy metal concentrations in sediments from the Jiaozhou Bay, China by visible and near infrared spectroscopy (225–975 nm)

As an important component ofbiogeochemical cyclein coastal ecosystems, sediments are the sink of heavy metals. Therefore, distribution and dynamics of heavy metals in sediments could assess ecological quality and predict ecological risks. In the new era, rapid and green technology are highly needed, especially that could determine multi-parameters simultaneously. Here, we explored a new method to rapidly determine concentrations of heavy metals in sediments by visible and near infrared reflectance spectroscopy (VIRS).We sampled sediments in the Jiaozhou Bay, China, collected their reflectance spectra, and measured concentrations of four heavy metals (As, Cr, Cu, and Zn). Heavy metal models were established and evaluated using substances highly correlated with heavy metals. This study provides an effective reference for rapid analysis of As, Cr, Cu, and Zn simultaneously in sediments, at least in the Jiaozhou Bay, and for ecological environment protection and resource development of the Jiaozhou Bay.

Preparation of high color fastness structural colored cotton fabric via SiO2@PDA photonic crystal

Structural color is an important way to achieve the ecological coloring of textiles. SiO2 microspheres with sizes in the range of 200–337 nm were synthesized by the Stober method and then covered with highly light-absorbing melanin PDA to form SiO2@PDA photonic crystals. The SiO2@PDA photonic crystals were assembled onto the surface of white cotton fabrics by gravity deposition to achieve structural color. The addition of polyvinylpyrrolidone (PVP) enhances interfacial bonding by forming multiple hydrogen bonds between its lactam group and the phenolic hydroxyl group of PDA, resulting in a structured color cotton fabric with high color fastness. Scanning electron microscopy (SEM) was used to study the structure and morphology of SiO2@PDA microspheres. The chemical compositions of PDA and PVP were surveyed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The surface structural color of cotton fabrics was investigated by UV–Vis reflectance spectroscopy.

Photocatalysis and irradiative TL defect center analysis studies of Cu2+ ionic ZnO nano lattice

The objective of the study is to create a series of ZnO nano powders doped with CuO using sol–gel technology in order to look into their photocatalytic activity for the photodegradation and cleaning process. XRD, BET surface area, surface morphology, chemical analysis, and FT-IR measurements have all been used to look at the nano powders' structure from this point of view. The results suggest that the materials were made at the nanoscale level, and their hexagonal shape makes them good as catalytic nano resources. Photoluminescence and UV–visible diffusion reflection spectroscopy were also used to test the nano powders. The results show that the nano powders that were made are visually active. To find out how photocatalytic the nanoparticles are, they were used to break down CR (10 ppm) and MV (10 ppm) dyes when exposed to light. The nano powder with 1.0 mol% of CuO doped ZnO nanoparticles had the highest photocatalytic efficiency (86 %). It had a band gap energy of 3.15 eV and reacted with both dyes for 90 min. Researchers looked at radical scavengers and the effect of catalyst dose on how well they broke down substances. The reaction that broke down had pseudo-first-order kinetics, and the rate of the reaction was four times faster when 1.0 mol% Cu was added to the ZnO catalyst. The degradation efficiency only dropped by 1 % after three rounds of the process. Because of this, the 1.0 mol% Cu-ZnO was used as a photocatalyst that broke down textile dyes well and had a lot of promise to be used again. The samples were also checked for thermoluminescence while they were exposed to 25 kGy of gamma radiation. Samples were tested for their trap depth characteristics, indicating the test samples' potential for TL activity.

Correlation of Visible Reflectance Spectrometry and Portable Raman Data for Red Pigment Identification

The accurate identification of pigments is of principal relevance in the field of cultural heritage conservation and restoration practices. In this preliminary study, a first attempt to set up a procedure for accurate red pigment identification, based on the assessment of the correlations existing between visible reflectance spectrometry (vis-RS) and Raman data, is presented. The proposed approach involved the realization of a library consisting of data acquired on a set of 35 pure red historical pigments supplied by ©Kremer Pigmente. In particular, vis-RS data, collected through a Konica Minolta CM-2600d spectrophotometer, were registered, together with the position of the Extrema Points (E.P.s) encompassing both the maximum and minimum points of the first derivative of the % spectral reflectance factor (SRF%) curves. Portable Raman spectroscopy measurements were collected by a B&W Tek Inc. portable Raman spectrometer equipped with a 785 nm laser. For each tested pigment, the positions and relative intensities of the characteristic Raman peaks were considered. The library was then tested for the characterization of the red/reddish painted areas of the medieval wall painting located within The Norman Castle of Aci Castello (Catania, Italy), and was shown to be essential for the unambiguous identification of the pigment used. It is worth noting that this study represents the first novel attempt to establish a reliable and efficient methodology for pigment identification, offering promising prospects in reducing uncertainties and ambiguities arising from the application of a single stand-alone approach.

Designed Mesoporous Architecture by 10–100 nm TiO2 as Electron Transport Materials in Carbon-Based Multiporous-Layered-Electrode Perovskite Solar Cells

Fully printable carbon-based multiporous-layered-electrode perovskite solar cells (MPLE-PSCs) are easy to fabricate and have excellent durability. In this study, the porosity of the mesoporous TiO2 layer as the electron transport layer in MPLE-PSCs was controlled by varying the particle diameter of TiO2 nanoparticles from 14 nm to 98 nm. Furthermore, the results of absorbed photon-to-current conversion efficiency, visible light reflectance spectroscopy, pore-size distribution, X-ray diffraction, field emission scanning electron microscopy, and photovoltaic parameters of MPLE-PSCs are discussed. Although the porous TiO2 layer with smaller nanoparticles showed higher photoabsorption, it was found that the more voids of perovskite crystals created in the TiO2 porous layer, the smaller the particle size (<18 nm). The porous TiO2 layers with particles over 26 nm are well filled with perovskite crystals, resulting in a higher photovoltaic capacity with TiO2 particles over 26 nm. As a result, the short-circuit current density (JSC) showed a maximum value using 43 nm TiO2 particles, with an average power conversion efficiency (PCE) of 10.56 ± 1.42%. Moreover, the PCE showed a maximum value of 12.20% by using 26 nm TiO2 nanoparticles.

3d-marigold-like barium-modified zinc oxide for antibacterial and anticancer studies

A chemical process involving multiple steps is often accounts for the loss of yield and longer reaction time. Herein, we explored a one-pot precipitation method to overcome these issues to produce barium-doped zinc oxide (BaZnO) with a 3 d-marigold like structure (MGS). The virgin ZnO was also prepared to compare its physicochemical and biological properties. The structural integrity of the prepared materials was determined using analytical tools such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet–visible reflectance spectroscopy, Fourier transform infrared spectroscopy), and photoluminescence spectroscopy. As a proof-of-concept, these materials have been utilized in biomedical applications. The BaZnO MGS exhibited the highest antibacterial activity compared with the ZnO NF. The anticancer activities of ZnO NF and BaZnO MGS were evaluated in human breast cancer cells (MCF-7). Among them, BaZnO MGS NPs demonstrated the most significant anticancer properties, with the lowest IC50 value exhibits of 21.2 μg/mL compared to ZnO NF. These findings suggest that the BaZnO MGS is a promising candidate for biomedical applications, potentially enhancing human life through its antibacterial and anticancer properties.

An investigation of the photostability of 19th century artists’ cochineal lake pigments using MFT and conventional accelerated ageing tests

ABSTRACT Red lake pigments are known for their high light-sensitivity generally when exposed to museum environments. In the cultural heritage field, the colour loss experienced by organic pigments is of special concern as the appearance of objects may be significantly altered after uncontrolled exposure to light. The present work focuses on the use of microfading testing (MFT) to study the light sensitivity of 19th century cochineal paints. MFT is a technique that combines visible reflectance spectroscopy with accelerated light ageing testing and was developed to perform in situ investigations of the light-sensitivity of cultural heritage materials in a relatively short amount of time. Reconstructions of these pigments following the manufacturing processes used by 19th century Winsor & Newton workers, as well as historic samples of cochineal pigments, were prepared using gum arabic and poly(vinylacetate). Purple cochineal paints showed a moderate sensitivity to light, while Carmine, Crimson and Scarlet paints were classified as high-sensitive materials. Overall, the carmine references turned out to be the most lightfast when mixed with gum-arabic while the scarlet pigment with poly(vinyl acetate) showed a slightly smaller colour change when compared with the almost complete loss of colour of the other poly(vinyl acetate) paints. Finally, advantages and drawbacks of the MFT method are addressed.

Assembling ZnMnFe2O4@Ag-AgVO3 nanostructure heterojunctions for photocatalytically degrading RhB and Pseudomonas aeruginosa bacteria under visible irradiation

Improving the separation of photocarriers is a vital approach to create highly effective heterojunction photocatalysts for the photodegradation of environmental pollutants. In this work, coprecipitation and hydrothermal methods were employed to develop a new heterojunction of Zn0.5Mn0.5Fe2O4@Ag-AgVO3 magnetic nanocomposite as photocatalysts for the photodegradation of Rhodamine B (RhB) and bacterial inactivation of Pseudomonas aeruginosa (P. aeruginosa) when exposed to illumination of visible light. FESEM, EDX, UV–vis reflectance spectroscopy (DRS), N2 adsorption/desorption, TEM, PL, Brunauer-Emmett-Teller (BET) surface area, Vibrating Sample Magnetometer (VSM), and XRD techniques were used to investigate the structural and optical properties of synthesized materials. The Zn0.5Mn0.5Fe2O4@Ag-AgVO3 photocatalyst demonstrated noticeably higher photocatalytic activity for RhB degradation when compared to the pure constituents AgVO3, Ag-AgVO3, and Zn0.5Mn0.5Fe2O4 samples. The results revealed that when RhB was used at a concentration of 20 ppm, the Zn0.5Mn0.5Fe2O4@Ag-AgVO3 possessed a high degradation rate (93.43 % within 180 min), and this was sufficient to get the highest total organic carbons (TOC) removal (90 %). Besides, Zn0.5Mn0.5Fe2O4@Ag-AgVO3 possesses complete inactivation efficiency (log(CFU) decreased from 6.5 to 0.00001) toward P. aeruginosa in 120 min of visible illumination. The photodegradation mechanism was explained by the surface plasmonic resonance Z-type heterostructure, and tested by trapping experiments. It can beinferredthat the Zn0.5Mn0.5Fe2O4@Ag-AgVO3 photocatalyst was very stable and efficient in removing different organic pollutants and pathogenic bacteria from wastewater.

Efficient sunlight-assisted degradation of organic dyes using V2O3/g-C3N4 nanocomposite catalyst

This study reports the synthesis of vanadium oxide (V2O3) and graphitic carbon nitride (g-C3N4) nanocomposite for simple sunlight-assisted degradation of Methylene Blue(MB) and Rhodamine B (RhB) dyes. Herein, the V2O3 and g-C3N4 are synthesized via hydrothermal and thermal decomposition techniques, respectively. X-ray diffraction (XRD) analysis confirms the formation of the rhombohedral and hexagonal structures of V2O3 and g-C3N4 in the nanocomposite, respectively, while scanning electron microscopy (SEM) reveals the sheet-like morphology of g-C3N4 and V2O3 nanoparticles. The optical band gap of the nanocomposite is estimated as 1.89 eV using a Tauc's plot generated from UV–Vis reflectance spectroscopy. The as-synthesized nanocomposite exhibits an excellent dye degradation efficacy displaying a 100 % degradation of RhB and 90 % degradation of MB dyes within 1 h of exposure to daylight. This performance is attributed to the synergistic effect of the V2O3/g-C3N4 nanocomposite wherein the composite benefits from the large surface area and high visible light adsorption of g-C3N4, combined with the active catalytic sites of the rhombohedral V2O3 structure, resulting in its high efficiency for photocatalytic dye degradation. Scavenger studies confirm the hydroxyl (.OH) radicals and oxygen (O2−.) radicals as the primary reactive species in the degradation process MB. Furthermore, the catalyst exhibited remarkable stability over three cycles of photocatalysis thus confirming its utility for real-time environmental remediation applications.

Precision Nitrogen Fertilization for Opium Poppy Using Combined Proximal and Remote Sensor Data Fusion

Proper management of within-field variability is crucial for maximizing crop yield, production outcomes and resource use efficiency and reducing environmental impacts. This study evaluated the agroeconomic and environmental feasibilities of site-specific nitrogen fertilization (SNF) in opium poppy (Papaver somniferum L.). On-line visible and near-infrared reflectance spectroscopy was used to estimate soil pH, organic carbon (OC), soil organic matter (SOM), P, K, Mg, Ca, Na, moisture content (MC), Ca:Mg and K:Mg for one field in Spain. Normalized difference vegetation indexes of the previous crop were retrieved from Sentine-2 images. Rasterization of soil and crop data layers created a spatially homogenous dataset followed by delineation of a management zone (MZ) map using a k-means cluster analysis. MZ clusters were ranked relying on the within-cluster soil fertility attributes. A strip experiment was conducted by creating parallel stripes distributed over the MZ map, over which two SNF treatments (i.e., SNF-Kings approach [KA] and SNF-Robin Hood approach [RHA]) were compared against the uniform rate N (URN) control treatment. In SNF-KA, the highest and lowest N dose was applied in the most and least fertile MZ, respectively, whereas the opposite approach was adopted in the SNF-RHA treatment. Yield and cost–benefit analyses provided both SNF treatments to produce more yield (KA = 2.72 and RHA = 2.74 t ha−1) than the URN (2.64 t ha−1) treatment, leading to increasing gross margins by EUR 91 ha−1 (SNF–KA) and EUR 88.5 ha−1 (SNF–RHA). While SNF-KA reduced N input by 66.54 kg N ha−1, SNF–RHA applied more N by 17.90 kg N ha−1 than URN. Additionally, SNF–RHA attempted to equalize yield responses to N across MZ classes, with a small increase in N input. This study, therefore, suggests adopting SNF–RHA for increasing yield and gross margin and accurate distribution of N according to per MZ N response. Future studies, however, should address the limitations of the current study by delineating MZ maps with the incorporation of additional soil information (e.g., mineral N and clay) for optimizing N doses as well as evaluating agroeconomic performance across multiple sites and years using a full-budget analysis.

Visible and near infrared spectroscopy for predicting soil nitrogen mineralization rate: Effect of incubation period and ancillary soil properties

Soil nitrogen mineralization rate (SNMR) influences crop N uptake and nitrate leaching leading to environmental pollution. This study aims at (i) examining whether visible and near-infrared reflectance spectroscopy (vis-NIRS) can predict SNMR and (ii) investigating if incubation periods and ancillary soil attributes can improve the prediction accuracy. Total 133 soil samples collected from seven fields were incubated under aerobic conditions for 60 days with seven batches of sub-samples. Mineral N was measured at regular time intervals and soil samples were scanned using a vis-NIRS sensor (Tec5 Technology, Germany) parallelly. SNMR was determined by fitting a zero-order kinetic to the net mineralized N as a function of the incubation time. Soil total nitrogen (TN), total carbon (TC) and electrical conductivity (EC) were determined once. Partial least squares regression (PLSR) models were calibrated individually for each field both for vis-NIR spectra and its combinations with TN, TC and EC. Six out of seven batches of sub-samples were used for calibrating PLSR when remaining one batch was used for model validation, and it rotated across all seven batches. Vis-NIRS alone predicted SNMR with moderate accuracy in five of seven fields (coefficient of determination, 0.53 ≤ R2 ≥ 0.66, ratio of prediction to deviation, 1.51 ≤ RPD ≥ 1.76), while models were poor in two fields (R2 = 0.23–0.26, RPD = 1.18 – 1.20). Inclusion of soil TC, TN and/or EC was expected to improve accuracy, but improvements varied across fields (R2 = 0.23–0.79, RPD = 1.18 – 2.26). Similarly, the incubation period increased vis-NIRS prediction accuracy, but frequently occurred among 2nd to 6th batches (R2 = 0.35–0.82, RPD = 1.28 – 2.44). Even incorporating secondary properties and increasing incubation duration hardly improved predictions, improvement can be compromised since it is not significant mostly and often underperformed or remained unchanged. Considering the time and effort required to incubate and analyze soil properties, this study suggests using a vis-NIRS sensor to estimate SNMR in fresh soil conditions i.e., without incubation and incorporation of secondary properties.

Sono-photo electrocatalytic reduction of CO2 to C2+ products using a p-n heterojunction Co2SnO4/CuO supported on a three-dimensional copper foam

This work demonstrates simultaneously employing light and ultrasonic irradiation to improve the electrocatalytic reduction of CO2 on Co2SnO4/CuO/Cu foam. We have synthesized n-type Co2SnO4 nanoparticles on p-type substrate CuO/Cu foam via hydrothermal method then investigated electrocatalytic, sono-electrocatalytic, photo-electrocatalytic and sono-photo electrocatalytic responses of Co2SnO4/CuO/Cu foam in the CO2-saturated electrolyte. The UV–visible differential reflectance spectroscopy (DRS) experiment displayed that Co2SnO4/CuO/Cu foam harvests more visible light energy than CuO/Cu foam. In cyclic voltammetry (CV) investigations, the electrocatalytic response of the Co2SnO4/CuO/Cu foam occurred at a higher positive potential (ΔE = 0.46 V) than the CuO/Cu foam, andsolo application of ultrasound and light irradiation resulted in 1.3- and 1.4-fold increases in cathodic current density, respectively, while synchronized ultrasound and light irradiation resulted in a 1.8-fold increase during the electrocatalytic CO2 reaction on the Co2SnO4/CuO/Cu foam. Based on the electrochemical impedance spectroscopy (EIS) tests, the formation of p-n heterojunction on Cu foam decreased charge transfer resistance from 198.8 Ω to 48.79 Ω, and under sono-photo irradiation, charge transfer irradiation resistance on Co2SnO4/CuO/Cu foam receded to 32.96 Ω. The chronoamperometry technique followed by gas chromatography-mass spectrometry revealed acetaldehyde and propylene glycol as CO2 conversion products with a 66 % coulombic efficiency.

Structural transition and magnetization reversal in rare earth doped R0.5Sr0.5Fe0.5Cr0.5O3 (R[dbnd]La, Nd and Sm) perovskite oxides containing mixed valent cations at B site: Magnetic, optical and transport properties

In the current paper, the effect of lanthanide metal cation substitution on structural, magnetic, optical and transport properties of R0.5Sr0.5Fe0.5Cr0.5O3 (RLa, Nd and Sm) perovskite oxides have been investigated. Structural investigations reveal that there is a phase transition from cubic to orthorhombic symmetry with the doping of heavier rare earth ion. The findings of XPS studies point to the existence of mixed valence states of Cr and Fe ions. The change in magnetization in response to an external magnetic field reveals that the phases have a mostly antiferromagnetic character with some trace amounts of ferromagnetic components. In temperature dependent magnetization studies, magnetic reversal has been observed in Nd doped sample, while La and Sm doped samples only show positive magnetization. The band gap energies of the synthesized materials determined from the UV–vis reflectance spectroscopy lie in the range of 1.60–1.78 eV indicating the semi-conducting nature of the samples. The temperature-dependent resistivity measurements show semi-conducting behaviour of the samples with decreasing temperature which finally become insulating at low temperature. It has been shown that the VRH model provides the best fit for the resistivity data when compared to the other transport mechanism models that were used to describe the electrical conduction process of synthesized phases.

Compositional Influence of Synthesized Magnetic Nanoparticles on Epoxy Composites: Dielectric, Magnetic, and Optical Characteristics

Epoxy nano-magnetic composites exhibit remarkable and promising properties by synergistically combining the properties of epoxy resin and magnetic nanofillers. The current study deals with the synthesis of Fe3O4, NiFe2O4, and CoFe2O4 nanoparticles and their respective nanoparticles-doped epoxy composites, as well as the structural, optical, and dielectric characterization of the resultant nano-composites. To investigate the surface morphology of the synthesized nanoparticles, field emission electron microscopy (FESEM) analysis was employed. By measuring electron diffraction spectroscopy (EDS), the presence of various chemicals was verified. X-ray diffraction (XRD) was used to determine the structural details of the synthesized nanoparticles and nanoparticles-doped epoxy composites. The structural chemistry and surface functionality of the nano-epoxy composites were investigated using Fourier transform infrared spectroscopy (FTIR). The magnetic properties of the synthesized nanoparticles and nanoparticles loaded epoxy composites were also studied using a vibrating sample magnetometer (VSM). UV–visible reflection spectroscopy was also carried out to find the optical properties of the synthesized nanoparticles, neat (undoped) epoxy, and nanoparticles-doped epoxy composites. Dielectric spectroscopy measurements of nanoparticles-doped epoxy composites were performed using an Agilent E4980A precision LCR (Inductance Capacitance Resistance) meter with an Agilent 16451B-test fixture LCR and vector network analyzer (VNA) in the frequency span of 10 kHz to 2 MHz and 200 MHz to 20 GHz, respectively. The influence of the synthesized nanoparticles on the neat (undoped) epoxy composites and the results in view of future applications are fully discussed.

Feasibility of using Vis-NIR spectroscopy and PXRF spectrometry to estimate regional soil cadmium concentration

Conventionally, soil cadmium (Cd) measurements in the laboratory are expensive and time-consuming, involving complex processes of sample preparation and chemical analysis. This study aimed to identify the feasibility of using sensor data of visible near-infrared reflectance (Vis-NIR) spectroscopy and portable X-ray fluorescence spectrometry (PXRF) to estimate regional soil Cd concentration in a time- and cost-saving manner. The sensor data of Vis-NIR and PXRF, and Cd concentrations of 128 surface soils from Yunnan Province, China, were measured. Outer-product analysis (OPA) was used for synthesizing the sensor data and Granger-Ramanathan averaging (GRA) was applied to fuse the model results. Artificial neural network (ANN) models were built using Vis-NIR data, PXRF data, and OPA data, respectively. Results showed that: (1) ANN model based on PXRF data performed better than that based on Vis-NIR data for soil Cd estimation; (2) Fusion methods of both OPA and GRA had higher predictive power (R2) = 0.89, ratios of performance to interquartile range (RPIQ) = 4.14, and lower root mean squared error (RMSE) = 0.06, in ANN model based on OPA fusion; R2 = 0.88, RMSE = 0.06, and RPIQ = 3.53 in GRA model) than those based on either Vis-NIR data or PXRF data. In conclusion, there exists a great potential for the combination of OPA fusion and ANN to estimate soil Cd concentration rapidly and accurately.

Morphological and semiconductive properties of the anodic oxide layers made on Fe3Al alloy by anodizing in tartaric-sulfuric acid mixture

It has recently been found that the anodizing of FeAl alloys allows the formation of iron-aluminum oxide layers with interesting semiconducting properties. However, the lack of systematic research on different anodizing regimes is hampering their full exploitation in numerous photoelectrochemical-related applications. This study address, for the first time, the systematic effect of the electrolyte composition on the formation of self-ordered oxide films by anodizing on cast Fe3Al alloy. The Fe3Al alloy was anodized in 3 electrolytes with different water-ethylene glycol (EG) ratios (pure water, 25 vol.%-EG, and 50 vol.%-EG solutions) at a constant tartaric-sulfuric acids concentration, different voltages (10–20 V) and treatment times (2–60 min). After anodizing, all anodic oxide layers were annealed at 900 °C to form semiconductive iron-aluminum crystalline phases. Conventional techniques were used to systematically ascertain the morphological (SEM/EDS, XRD, eddy-current measurements) and semiconductive (UV–VIS reflectance spectroscopy) properties of these oxide layers. The results confirmed the formation of homogeneous and self-ordered anodic oxide layers at 10 and 15 V, regardless of the electrolyte composition. Namely, anodic films formed in electrolytes containing EG showed lower pore sizes, growth rates, and film thicknesses than those anodic films formed in the aqueous-based electrolyte. The annealing post-treatment results in different Fe-Al oxides (FexOy, FeAl2O4, etc.) with superior band gap values than those for non-annealed films.

Effect of water intercalation into tungsten trioxide structure (WO3·xH2O) (x = 0,1,2): Correlation between structure and photocatalytic performances

Tungsten oxide (WO3) is a potential photoanode material for water oxidation, however, its employment is still restricted by its limited light absorption (Eg ∼ 2.75 eV). A particular interest was devoted to tuning its electronic structure and optical bandgap in order to enhance its photocatalytic performance in hydrogen production as well as in advanced oxidation process. One of the promising alternatives for the enhancement of these photocatalytic performances, is the introduction of guest molecules into the tungsten oxide structure. In this paper, the photocatalytic performances of tungsten trioxide were highly improved by the intercalation of water into its structure. The intercalated compounds of chemical formula WO3·xH2O were prepared and characterized by TGA-DSC, PXRD, FT-IR, Raman spectroscopy, SEM-EDS and XPS. The structures of intercalated materials were refined using Rietveld method and the electronic proprieties including bandgap energy, CB and VB edges were estimated using UV–visible reflectance spectroscopy. The obtained results show that the intercalation of water molecules into tungsten oxide structure reduces the gap energy of the WO3 (2.4 eV) to 2.16 eV for WO3∙H2O and to 2.31 eV for WO3∙2H2O. The photocatalytic efficiency of the obtained materials was studied through oxygen evolution reaction tests in the presence of an electron acceptor (Ag+) and the oxidative photodegradation of the orange G dye pollutant. We found that intercalated samples exhibit the highest efficiencies compared with anhydrous samples. These findings are correlated with the increase in the average W-O-W tilt angle in WO3∙2H2O and WO3∙H2O compared to that of WO3. This improvement in the tilt angle induces the shrinkage of the energy bandgap and increases the photocatalytic performance. Furthermore, the stability of the investigated materials was studied as a function of pH, the results reveal that the intercalation of water molecules is beneficial for the chemical stability of the hydrated tungsten oxides. These findings shed light on new alternatives for band-gap engineering and improvement of materials stability through intercalation with water molecules.

Enhanced photocatalytic activity in RhB dye degradation by Mn and B co-doped mixed phase TiO2 photocatalyst under visible light irradiation

Here, we report synthesis of undoped, manganese (Mn) doped, boron (B) doped and Mn-B co-doped TiO2 nanoparticles (NPs) by a cost-effective sol-gel method. The structural properties, phase, micro-morphology and particle size of the synthesized nanoparticles have been characterized by X-ray diffraction, Raman spectroscopy, Transmission Electron Microscopy (TEM) and Dynamic Light Scattering (DLS) techniques. These studies revealed that undoped and mono (Mn/B) doped TiO2 NPs exhibit only anatase phase, whereas (Mn and B) co-doped TiO2 NPs exhibit anatase and rutile mixed phase structure. Furthermore, co-doping reduces the particle size, agglomeration in aqueous medium and the sample possesses crystal defects. UV–Visible diffusive reflectance spectroscopy (DRS) revealed that the co-doped sample demonstrates extended optical response in the visible wavelength range of the solar spectrum and is red shifted when compared to undoped and mono doped TiO2 NPs. The obtained optical band gap (2.11 eV) and the Urbach energy (1.12 eV) for the Mn and B co-doped TiO2 NPs suggest the formation of mid-gap energy states, which might make this NPs a suitable candidate for photocatalysis in the visible light spectrum. We investigated the photocatalytic degradation of rhodamine B (RhB) dye by the synthesized NPs under visible light irradiation. Our studies revealed that co-doped TiO2 photocatalyst can degrade 99% of RhB dye within 90 min of visible light irradiation and can retain 95% degradation efficiency up to the third consecutive cycles. Finally, we provide a plausible explanation for such enhanced visible light assisted photocatalytic performance.