Reflectance Spectroscopy Research Articles

μ-FTIR Reflectance Spectroscopy Coupled with Multivariate Analysis: A Rapid and Robust Method for Identifying the Extent of Photodegradation on Microplastics.

Understanding the origins of microplastics (MPs) and evaluating the consequences of plastic pollution require precise chemical information. Moreover, MPs undergo chemical changes due to photoaging, which are worth investigating since they can influence the effects of MPs on living beings and the environment. Micro-Fourier-transform infrared (μ-FTIR) spectroscopy is a key technique for screening MPs, combining optical imaging with chemical information from IR spectra. While reflectance μ-FTIR spectroscopy's sensitivity to particle thickness and photodegradation complicates automated spectral matching, it can provide valuable information if coupled with multivariate analysis of the data. This study developed a robust method for identifying MPs, even when they are modified by photodegradation. Various acquisition methods (ATR-IR and μ-transflectance-IR), data pretreatments, and data set analysis procedures were examined, and critical aspects were addressed. The proposed method, using μ-TR-IR and principal component analysis (PCA), proved effective for classifying MPs and analyzing their degradation, offering increased sensitivity and a faster workflow compared with manual spectral comparison. μ-TR-IR showed earlier changes in relevant bands, indicating higher sensitivity to degradation than ATR-IR spectroscopy. Despite the notorious issue of spectral artifacts, our results suggest that valuable information can be collected without using sophisticated preprocessing techniques. On the contrary, the presence of the artifacts allows extracting some information on the particles' thickness. Finally, PCA results were successfully validated for the polymer classification reliability by a test set and compared with the carboxyl index (CI) method to validate the ability to assess degradation. While CI is the most diffused parameter to assess polymer degradation, PCA, which considers the entire spectrum and does not rely on manual integration of single peaks, is inherently more robust than CI and can take into account multiple degradation mechanisms.

Effect of Fe doping on structural, optical and magnetic properties of CdS quantum dots

Abstract Pure CdS nanoparticles and Fe-doped CdS quantum dots (Cd₁₋ₓFeₓS, where x = 0.0, 0.03, 0.06, 0.09, and 0.12) were successfully synthesized using the co-precipitation method. X-ray diffraction (XRD) analysis confirmed the cubic phase structure of CdS without additional peaks, indicating the effective incorporation of Fe ions into the CdS lattice. The crystallite size exhibited a gradual increase with increasing Fe content. High-resolution transmission electron microscopy (HR-TEM) revealed a well-defined spherical morphology for pure CdS, while Fe doping induced notable agglomeration in the quantum dots. X-ray photoelectron spectroscopy (XPS) confirmed the formation of the CdFeS composition and provided insights into the valence states of Cd, Fe, and S. UV-Vis diffuse reflectance spectroscopy (DRS) demonstrated a decrease in the optical band gap from 2.29 eV to 2.18 eV with Fe doping, indicating a modification of the electronic structure. Magnetization studies revealed a transition from diamagnetic behavior in pure CdS to ferromagnetic behavior in Fe-doped samples. Additionally, Fe doping significantly influenced the magnetic parameters, including saturation magnetization, remanence, and coercivity. These results highlight the structural, optical, and magnetic properties of CdS can be tuned through Fe doping, making these materials promising candidates for optoelectronic and spintronic applications.
Keywords: CdS quantum dots, XRD, XPS, optical energy gap, ferromagnetism.

The Associations Between Physical Activity and Skin Carotenoid Levels in a Small Sample of Preschoolers: A Pilot Study.

Recent literature proposed an association between physical activity (PA) and carotenoid status due to their overlapping role in mediating oxidative stress. However, this relationship has yet to be explored in young children. This study examined the relationship between objectively measured PA (ActiGraph triaxial accelerometry) and skin carotenoid levels (pressure-mediated reflection spectroscopy) in a sample of 3- to 5-years-old. Fourteen children (44 ± 7 months old, 71% male) from a single child care center were included in this cross-sectional analysis. Linear regression modeling indicated more time spent in PA was associated with higher skin carotenoid scores (β = 3.448, p = 0.032). These findings from our pilot study indicate a potential cross-sectional link between physical activity and carotenoid status in young children.

Discriminating the adulteration of varieties and misrepresentation of vintages of Pu’er tea based on Fourier transform near infrared diffuse reflectance spectroscopy

In the Pu’er tea market, the ubiquity of blending different varieties and the fraudulent representation of vintage years present a persistent challenge. Traditional sensory evaluation and experience are often inadequate for discerning the true variety and vintage of tea, highlighting the need for more sophisticated analytical methods to ensure authenticity and quality. Fourier transform near infrared diffuse reflectance spectroscopy combined with radial basis function neural network (RBFNN) was applied for determination of the varieties and vintages of Pu’er tea. For vintage identification, the accuracy, precision, recall, and F1-score of the RBFNN model for the prediction set were 99.2%, 98.2%, 98.0%, and 98.0%, respectively. For identification of varieties adulteration, the corresponding parameters were 98.9%, 97.2%, 96.7%, and 96.6%, respectively. These results illustrated the feasibility to identify the adulteration of varieties and misrepresentation of vintages of Pu’er tea with near infrared spectra and RBFNN model, proving an efficient alternative for Pu’er tea quality inspection, and offering a robust method for combating the pervasive issues within the market.

Ti3AlC2 MAX/MXene for Hydrogen Generation via Photocatalytic Hydride Hydrolysis

Reducing dehydrogenation temperature while preserving high hydrogen generation capacity obstructs the hydrolysis of sodium borohydrides (NaBH4). The two-dimensional (2D) MAX phase of titanium aluminum carbide (Ti3AlC2) and MXene (Ti3C2Tx) multilayers was investigated for hydrogen generation via NaBH4 hydrolysis with and without light. The material was characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). The activity of Ti3AlC2 was significantly enhanced by the integration of UV light radiation during hydrolysis. Ti3AlC2/Ti3C2Tx improved the dehydrogenation rates of NaBH4 at ambient conditions and maintained high hydrogen generation rates (HGRs) over time compared to a conventional method. It exhibited a HGR of 200–300 mL·min−1·g−1. Photo-assisted hydrolysis over the catalyst can be maintained for several times at ambient temperature. The catalyst demonstrated effective performance even after five cycles of usage.

Microstructural, magnetic, dielectric, and optical studies of La‐doped Sr2Fe0.5Hf1.5O6 double perovskite oxides

AbstractHerein, we report on the structural, magnetic, dielectric, and optical properties of La‐doped Sr2‐xLaxFe0.5Hf1.5O6 (SLFHO, 0.0 ≤ x ≤ 2.0) double perovskite oxides synthesized by solid‐state reaction method. X‐ray powder diffraction data and their Rietveld refinement reveal that the SLFHO powders crystallize in an orthorhombic structure with the Pnma space group. The SLFHO powders exhibit spherical morphology with an average particle size of 160 nm, as shown from SEM images. Their molar ratios of the Sr:La:Fe:Hf elements were determined as 1.77:0.50:0.50:1.95 by energy dispersive X‐ray spectroscopy data, approaching their nominal stoichiometry. X‐ray photoelectron spectra verified that Sr2+, La3+, Fe3+, and Hf4+ (Hfx+) ions existed in the SLFHO powders, and oxygen existed in species lattice oxygen and adsorbed oxygen, respectively. The SLFHO powders exhibit ferromagnetic behavior at 2 and 300 K, respectively, and at 2 K the saturated magnetization was 5.66 emu/g (or 0.60 μB/f.u.). Magnetic transition temperature, TC was determined to be 867 K. Dielectric measurements demonstrated a strong frequency‐dependent dielectric behavior observed in the SLFHO ceramics and a relaxor‐like dielectric behavior appearing in the temperature range of 200–600 K. Such relaxor‐like dielectric behavior is ascribed to the dielectric response of the singly‐ionized oxygen vacancies ( an activation energy of 0.54 eV. Room temperature optical properties of the SLFHO powders examined by using UV–vis diffuse reflectance spectroscopy exhibit high optical absorption in this wavelength region, and a wide indirect optical bandgap (Eg = 3.39 eV) was estimated using the Tauc's relation from the diffuse reflectance spectra. The SLFHO double perovskite oxides display high‐temperature ferrimagnetism, relaxor‐like dielectric behavior, and wide optical bandgap, making them potential to be employed in the fields of high‐temperature spintronics and magnetic semiconductor devices.

Identifying the color and absorption band properties of Fe oxides in Danxia red beds by the visible diffuse reflectance spectrum

This study investigates the Danxia Basin, the place where Danxia landforms were first named, by employing diffuse reflectance spectroscopy to analyze samples from various hue sequences of red beds. The colors of the Danxia red beds were precisely and quantitatively analyzed using the CIE color space and the Munsell color system. The raw spectra of the samples were then transformed using the second derivative of the Kubelka–Munk function and continuum removal techniques to perform spectral analysis, aiming to elucidate the absorption characteristics of Fe oxides and their influence on the coloration of the Danxia red beds. The results show that the Munsell hues of the Danxia red beds span from 6.5R to 9YR, while powdered samples exhibit a slight yellow shift, ranging from 2.5YR to 0.1Y, with increased chroma and significantly higher lightness. Fe oxides display three main absorption bands in the visible spectrum: (4E; 4A1) ← 6A1, 4T2 ← 6A1, and 2(4T1) ← 2(6A1) (EPT). Among these, the EPT band plays a pivotal role in determining the color. Since the Fe oxides in the Danxia red beds are predominantly composed of hematite with minor goethite, the EPT (Hem) absorption band is the most prominent, occurring between 526 and 544 nm. While the CIE color space offers superior precision for color measurement and analysis, the Munsell system provides ease of description. Therefore, a combination of both systems is recommended for practical applications.

Online analysis of Amazon's soils through reflectance spectroscopy and cloud computing can support policies and the sustainable development.

Analyzing soil in large and remote areas such as the Amazon River Basin (ARB) is unviable when it is entirely performed by wet labs using traditional methods due to the scarcity of labs and the significant workforce requirements, increasing costs, time, and waste. Remote sensing, combined with cloud computing, enhances soil analysis by modeling soil from spectral data and overcoming the limitations of traditional methods. We verified the potential of soil spectroscopy in conjunction with cloud-based computing to predict soil organic carbon (SOC) and particle size (sand, silt, and clay) content from the Amazon region. To this end, we request physicochemical attribute values determined by wet laboratory analyses of 211 soil samples from the ARB. These samples were submitted to spectroscopy Vis-NIR-SWIR in the laboratory. Two approaches modeled the soil attributes: M-I) cloud-computing-based using the Brazilian Soil Spectral Service (BraSpecS) platform, and M-II) computing-based in an offline environment using R programming language. Both methods used the Cubist machine learning algorithm for modeling. The coefficient of determination (R2), mean absolute error (MAE) and root mean squared error (RMSE) served as criteria for performance assessment. The soil attributes prediction was highly consistent, considering the measured and predicted by both approaches M-I and M-II. The M-II outperformed the M-I in predicting both particle size and SOC. For clay content, the offline model achieved an R2 of 0.85, with an MAE of 86.16gkg⁻1 and RMSE of 111.73gkg⁻1, while the online model had an R2 of 0.70, MAE of 111.73gkg⁻1, and RMSE of 144.19gkg⁻1. For SOC, the offline model also showed better performance, with an R2 of 0.81, MAE of 3.42gkg⁻1, and RMSE of 4.57gkg⁻1, compared to an R2 of 0.72, MAE of 3.66gkg⁻1, and RMSE of 5.53gkg⁻1 for the M-I. Both modeling methods demonstrated the power of reflectance spectroscopy and cloud computing to survey soils in remote and large areas such as ARB. The synergetic use of these techniques can support policies and sustainable development.

Effects of adding copper to bismuth titanate for photocatalytic hydrogen production

Effects of adding copper to bismuth titanate for photocatalytic hydrogen production

Evaluation of a hybrid near infrared reflectance spectroscopy approach to calculate nutrient digestibility of rabbit feeds

Evaluation of a hybrid near infrared reflectance spectroscopy approach to calculate nutrient digestibility of rabbit feeds

Photocatalytic performance of binary and ternary composites based on TiO2 modified with tin and/or carbon in the hydrogen production reaction

Titanium dioxide modified with tin and/or carbon was synthesized by sol-gel method and characterized by X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller and Barret–Joiner–Halenda methods, Fourier transform infrared and UV-vis diffuse reflection spectroscopies. Modification of TiO2 with tin led to the formation of three-phase samples consisting of anatase (TiO2), rutile (TiO2), and SnO2 with a rutile-type crystal lattice. Simultaneous modification of TiO2 with carbon and tin favored the formation of two-phase samples with anatase and rutile structures. Modification of TiO2 with tin and/or carbon led to increased specific surface area and reduced band gap. The photocatalysts have shown good performance for the photocatalytic production of hydrogen under the irradiation with ultraviolet light using ethanol as the sacrificial agent. The results showed that the TiO2 modified with tin exhibited twice an increase in photocatalytic activity over the pristine TiO2. Among the three-phase samples, the most active one contained 2.29% at. Sn, while among the two-phase samples, the sample 1SnO2/C/TiO2 with atomic percentage of modifier 6.59 (C) and 2.06 (Sn) showed the better activity. The improvement in photocatalytic performance is attributed to the increase in specific surface area, the reduction in the band gap and the presence of heterojunctions between the different phases.

Refining thyroid function evaluation: a comparative study of preprocessing methods in diffuse reflectance spectroscopy

Thyroid dysfunction, comprising conditions such as hyperthyroidism and hypothyroidism, represents a substantial global health challenge, necessitating timely and precise diagnosis for effective therapeutic intervention and patient welfare. Conventional diagnostic modalities often involve invasive procedures, that could cause discomfort and inconvenience for individuals. The non-invasive techniques like diffuse reflectance spectroscopy (DRS) can offer a promising alternative. This study underscores the critical role of preprocessing methods in enhancing the accuracy of thyroid hormone functionality through a non-invasive approach. In the proposed study the spectral data acquired from the DRS setup are subjected to different preprocessing techniques to improve the efficacy of the prediction model. Thirty individuals with thyroid dysfunction were included in the study, and preprocessing methods such as baseline correction, multiplicative scatter correction (MSC), and standard normal variate (SNV), were systematically evaluated. The study highlights that SNV preprocessing outperformed other methods with a root mean square error (RMSE) of 0.005 and an R² of 0.99. In contrast, MSC resulted in an RMSE of 0.87 and an R² of 0.86, while baseline correction showed a RMSE of 0.84 and an unusual R² of 1.09, indicating potential issues. SNV proved to be the most effective technique.

Insights into the expeditious photocatalytic performance of greenly fabricated CeVO4 nanoparticles using Polyalthia longifolia leaf extract

Insights into the expeditious photocatalytic performance of greenly fabricated CeVO4 nanoparticles using Polyalthia longifolia leaf extract

Bismuth Vanadate Microspheres: Utilizing Temperature-driven Phase Transition for Improved Sunlight-Driven Photocatalysis and Antibacterial Efficacy

In this work, bismuth vanadate (BiVO4) microspheres are synthesized using a simple, cost effective, co-precipitation technique. This study investigates how the annealing temperature influences the photocatalytic and antimicrobial properties of nanoparticles made of BiVO4. Examining the phase structure, chemical compounds state, composition of chemicals, shape, as well as optical characteristics of the prepared materials, by using X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Raman analysis, UV-Vis diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy studies. Based on XRD analysis data, BiVO4 exhibits a phase change of the tetragonal structure to monoclinic at 500 °C (BiVO4@500 °C). It is interesting to note that under sunlight irradiation, BiVO4 nanoparticles annealed at 500 °C show excellent photocatalytic behavior in opposition to the dye methylene blue (k = 0.0151 min-1). According to investigations on the development of antibacterial activity through the utilization of BiVO4@500 °C sample by well diffusion method appears to be an effective growth inhibitor of both gram-positive and gram-negative bacteria, such as Bacillus subtilis (B. subtilis), Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), Proteus vulgaris (P. vulgaris)), respectively.

Assessing plastic ingestion in the White stork (Ciconia ciconia) through regurgitated pellets.

Pollution is one of the main factors that threaten biodiversity nowadays. Plastic waste is a global problem which impacts not only on the marine environment but also on the terrestrial one. Great amounts of this kind of refuse are compiled in landfills, where lots of avian species feed. In contrast to seabirds research, there are limited studies that have considered how plastic is being ingested by land birds even when they are being affected both physically and at an endocrine level. We tried to assess the number of plastics and microplastics ingested by individuals of a White stork (Ciconia ciconia) colony in central Spain by collecting regurgitated pellets. The chemical composition of the elements was determined, as well as the relation between the amount of ingested plastic by individuals and their use of a landfill. Our results show that 3.44% of the pellet was formed by plastic (n = 50). Polyethylene, polystyrene, polypropylene and PET were the most abundant polymers, all of them being potentially problematic to the organism according to the literature. Each polymer was identified by Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR). We observed that the total amount of ingested plastics was stable along the use of the landfill, meaning White storks obtained plastic not only from anthropogenic sources but also from natural areas, indicating its high rate of pollution. Our study remarks the importance of addressing plastic ingestion in White storks as well as other terrestrial species, not only to understand the possible damage to the population but also to the whole ecosystem.

Characterisation and visible light induced antibacterial activity of Cu-doped zinc oxide nanoparticles

ABSTRACT Zinc oxide particles doped with copper were produced using a cost-effective sol-gel approach at a temperature of 80°C. The process involved combining Zn(NO3)2, Cu(NO3)2, and citrate precursors. A variety of analytical techniques, including scanning electron microscopy, Energy-dispersive X-ray spectroscopy (EDX), diffuse reflectance spectroscopy (UV-Vis DRS), and energy dispersive X-ray diffraction spectroscopy (XRD), were employed to study the physical and chemical characteristics of the nanoparticles. The addition of copper resulted in a significant decrease in the size of wurtzite ZnO nanoparticles, reducing from 180 nm for undoped ZnO to 133 and 40 nm for 10% Cu-doped and 25% Cu-doped ZnO, respectively. The absorption spectra displayed a gradual shift towards the visible range as the concentration of copper in the ZnO particles increased. The calculated band gaps for the various samples were determined to be 3.1 eV for undoped ZnO, 2.3 eV and for 10% Cu-doped ZnO, and 1.8 eV for 25% Cu-doped ZnO. The antibacterial efficacy of Cu-doped ZnO was observed to be significantly greater than that of the undoped sample. Additionally, it demonstrated antibacterial activity under visible light conditions, which suggests the successful synthesis of zinc oxide particles that are induced by visible light.

Enhanced photocatalytic degradation of Rhodamine B using polyaniline-coated XTiO3(X = Co, Ni) nanocomposites

In this study, novel polyaniline-coated perovskite nanocomposites (PANI@CoTiO3 and PANI@NiTiO3) were synthesized using an in situ oxidative polymerization method and evaluated for the photocatalytic degradation of Rhodamine B (RhB) a persistent organic pollutant. The nanocomposites displayed significantly enhanced photocatalytic efficiency compared to pure perovskites. The 1%wt PANI@NiTiO3 achieved an impressive 94% degradation of RhB under visible light after 180 min, while 1wt.% PANI@CoTiO3 reached 87% degradation under UV light in the same duration. X-ray diffraction (XRD) confirmed that the crystalline structures of CoTiO3 and NiTiO3 remained intact post-polymerization. At the same time, Fourier transform infrared spectroscopy (FTIR) verified the successful deposition of PANI through characteristic functional group vibrations. Diffuse reflectance spectroscopy (DRS) revealed reduced band gaps of 2.63 eV for 1wt.% PANI@NiTiO3 and 2.46 eV for 1wt.% PANI@CoTiO3, enhancing light absorption across UV and visible ranges. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis demonstrated the uniform distribution of PANI, ensuring consistent surface activity and efficient charge transfer. The photocatalytic test confirmed a pseudo-first-order degradation mechanism. The study elucidates the degradation mechanism through intermediate identification via HPLC-MS analysis, highlighting N-de-ethylation, aromatic ring cleavage and eventual mineralization into CO2 and H2O as critical pathways. Furthermore, the 1wt.%PANI@NiTiO3 nanocomposite demonstrated excellent stability and recyclability, maintaining its degradation efficiency over four consecutive cycles with minimal change. These findings highlight the potential of PANI@XTiO3 nanocomposites for sustainable and efficient wastewater treatment, addressing diverse environmental challenges by tailoring photocatalysts to specific light sources.

Doppler-free selective reflection spectroscopy of electric-quadrupole transitions

Doppler-free selective reflection spectroscopy of electric-quadrupole transitions

Empowering wastewater treatment with step scheme heterojunction ternary nanocomposites for photocatalytic degradation of nitrophenol

The ongoing challenge of water pollution necessitates innovative approaches to remove organic contaminants from wastewater. In this work, new two-dimensional S-scheme heterojunction photocatalysts Bi2O3/CdS and MoS2/Bi2O3/CdS that are intended for the effective photocatalytic destruction of 4-nitrophenol, a dangerous organic pollutant, are synthesized and characterized. Utilizing a solvothermal method, successfully generated these ternary nanocomposites, which were characterized through various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), high resolution transmission electronmicroscopy (HRTEM), Brunauer-Emmett-Telle (BET) and diffuse reflectance spectroscopy (DRS). Our results demonstrated that the Bi2O3/CdS heterojunction achieved an 86% degradation rate of 4-nitrophenol, while the MoS2/Bi2O3/CdS composite exhibited exceptional photocatalytic performance, achieving nearly complete degradation (99%) within 120 min under visible light irradiation. Most importantly the improved photocatalytic activity of MoS2/Bi2O3/CdS heterojunction originated from the release of internal electric field in S-scheme heterojunction. This enhanced activity is attributable to the synergistic effects of the heterojunctions that facilitate more effective charge separation and generation with more OP and RP confirmed the composite synthesis using S-scheme. The S-scheme is further confirmed by XPS, DRS, XPS-VB and photocurrent response. These findings highlight the promising application of these advanced photocatalysts in real-world wastewater treatment processes, offering a sustainable solution to combat water pollution.

Light Absorbing Particles Deposited to Snow Cover Across the Upper Colorado River Basin, Colorado, 2013–2016: Interannual Variations From Multiple Natural and Anthropogenic Sources

AbstractAtmospheric particulate matter (PM) as light‐absorbing particles (LAPs) deposited to snow cover can result in early onset and rapid snow melting, challenging management of downstream water resources. We identified LAPs in 38 snow samples (water years 2013–2016) from the mountainous Upper Colorado River basin by comparing among laboratory‐measured spectral reflectance, chemical, physical, and magnetic properties. Dust sample reflectance, averaged over the wavelength range of 0.35–2.50 μm, varied by a factor of 1.9 (range, 0.2300–0.4444) and was suppressed mainly by three components: (a) carbonaceous matter measured as total organic carbon (1.6–22.5 wt. %) including inferred black carbon, natural organic matter, and carbon‐based synthetic, black road‐tire‐wear particles, (b) dark rock and mineral particles, indicated by amounts of magnetite (0.11–0.37 wt. %) as their proxy, and (c) ferric oxide minerals identified by reflectance spectroscopy and magnetic properties. Fundamental compositional differences were associated with different iron oxide groups defined by dominant hematite, goethite, or magnetite. These differences in iron oxide mineralogy are attributed to temporally varying source‐area contributions implying strong interannual changes in regional source behavior, dust‐storm frequency, and (or) transport tracks. Observations of dust‐storm activity in the western U.S. and particle‐size averages for all samples (median, 25 μm) indicated that regional dust from deserts dominated mineral‐dust masses. Fugitive contaminants, nevertheless, contributed important amounts of LAPs from many types of anthropogenic sources.