Spectral Absorption Characteristics Research Articles

Optical and electrical properties and applications of two-dimensional carbon-based nanomaterials

As an emerging material, two-dimensional (2D) carbon-based nanomaterials have unique optical and electrical properties due to their unique atomic layer structure. On the one hand, due to their high transmittance, high carrier mobility, controllable Fermi level, and wide spectral light saturation absorption characteristics, they can be applied in new-generation solar cells, organic light-emitting diodes, touch screens, and fiber optic devices. On the other hand, due to their unique nanostructure, they have high specific surface area, low diffusion distance, high conductivity, and ion conductivity. They can serve as substrates and work together with other materials as electrode materials for future fuel cells and lithium-ion batteries and have significant advantages in fields such as sensors. This article mainly summarizes the impact of two-dimensional carbon-based nanomaterials represented by graphene, Mxene, and 2D covalent organic frameworks (COFs) on their optical and electrical properties, and summarizes the latest practical applications and research progress of these nanomaterials in the field of optics and electronics. In addition, a corresponding summary and outlook have been made on the problems that need to be solved in future applications of 2D carbon-based nanomaterials.

Ultrafast Self‐Powered Ti–Zn–N Photodetector‐Based Optocoupler for Power Electronics Applications

This study presents an early exploration into the application of a self‐powered photodetector based on titanium zinc nitride (TiZnN) films in power electronics, aiming to overcome inherent limitations of conventional optocouplers such as low switching speed and specific operating voltage requirements. The fabricated device demonstrates excellent performance metrics, including photosensitivity of 136, the responsivity of 3.22 mA W−1 at −8 V bias, and a peak detectivity of 1.76 × 108 Jones at 0 V bias. Remarkably, ultrafast rise (τs) and decay times (τd) of 0.11 and 0.10 ms, respectively, are achieved, alongside broad‐band spectral absorption characteristics. Experimental validation showcases the efficacy of the TiZnN‐based optocoupler in practical applications, notably in power electronics triggerable relay systems and AC–AC converters. Leveraging the self‐powering capability inherent to the TiZnN photodetector, this optocoupler eliminates external power source dependencies, thereby enhancing its versatility and applicability in diverse electronic systems. The rapid response time of the device and broad spectral absorption further underscore its suitability for high‐speed signal transmission across varied operating conditions. This research paves a path for developing stable, cost‐effective, and self‐powered ultrafast optocouplers, eliminating concerns about compromising electrical signal transit. These advancements hold significant implications for enhancing electronic system performance, reliability, and functionality in critical applications.

Variability in spectral absorption within cryptophyte phycobiliprotein types.

Cryptophytes are known to vary widely in coloration among species. These differences in color arise primarily from the presence of phycobiliprotein accessory pigments. There are nine defined cryptophyte phycobiliprotein (Cr-PBP) types, named for their wavelength of maximal absorbance. Because Cr-PBP type has traditionally been regarded as a categorical trait, there is a paucity of information about how spectral absorption characteristics of Cr-PBPs vary among species. We investigated variability in primary and secondary peak absorbance wavelengths and full width at half max (FWHM) values of spectra of Cr-PBPs extracted from 75 cryptophyte strains (55 species) grown under full spectrum irradiance. We show that there may be substantial differences in spectral shapes within Cr-PBP types, with Cr-Phycoerythrin (Cr-PE) 545 showing the greatest variability with two, possibly three, subtypes, while Cr-PE 566 spectra were the least variable, with only ±1 nm of variance around the mean absorbance maximum of 565 nm. We provide additional criteria for classification in cases where the wavelength of maximum absorbance alone is not definitive. Variations in spectral characteristics among strains containing the same presumed Cr-PBP type may indicate differing chromophore composition and/or the presence of more than one Cr-PBP in a single cryptophyte species.

Evaluation of the mechanism of Gong Ying San activity on dairy cows mastitis by network pharmacology and metabolomics analysis.

The goal of this investigation was to identify the main compounds and the pharmacological mechanism of the traditional Chinese medicine formulation, Gong Ying San (GYS), by infrared spectral absorption characteristics, metabolomics, network pharmacology, and molecular-docking analysis for mastitis. The antibacterial and antioxidant activities were determined in vitro. The chemical constituents of GYS were detected by ultra-high-performance liquid chromatography Q-extractive mass spectrometry (UHPLC-QE-MS). Related compounds were screened from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP, http://tcmspw.com/tcmsp.php) and the Encyclopedia of Traditional Chinese Medicine (ETCM, http://www.tcmip.cn/ETCM/index.php/Home/) databases; genes associated with mastitis were identified in DisGENT. A protein-protein interaction (PPI) network was generated using STRING. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment screening was conducted using the R module. Molecular-docking analyses were performed with the AutoDockTools V1.5.6. Fifty-four possible compounds in GYS with forty likely targets were found. The compound-target-network analysis showed that five of the ingredients, quercetin, luteolin, kaempferol, beta-sitosterol, and stigmasterol, had degree values >41.6, and the genes TNF, IL-6, IL-1β, ICAM1, CXCL8, CRP, IFNG, TP53, IL-2, and TGFB1 were core targets in the network. Enrichment analysis revealed that pathways associated with cancer, lipids, atherosclerosis, and PI3K-Akt signaling pathways may be critical in the pharmacology network. Molecular-docking data supported the hypothesis that quercetin and luteolin interacted well with TNF-α and IL-6. An integrative investigation based on a bioinformatics-network topology provided new insights into the synergistic, multicomponent mechanisms of GYS's anti-inflammatory, antibacterial, and antioxidant activities. It revealed novel possibilities for developing new combination medications for reducing mastitis and its complications.

Regulatory effect of bacterial melanin on the isoforms of new superoxide-producing associates from rat tissues in rotenone-induced Parkinson’s disease

According to recent research, selective neuronal vulnerability in Parkinson’s disease (PD) results from several phenotypic traits, including calcium-dependent, feed-forward control of mitochondrial respiration leading to elevated reactive oxygen species and cytosolic calcium concentration, an extensive axonal arbor, and a reactive neurotransmitter. Therefore, antioxidant therapy is a promising direction in the treatment of PD. In vitro studies have indicated the survival-promoting activity of bacterial melanin (BM) on midbrain dopaminergic neuron cultures. It has been established that BM has a number of protective and anti-inflammatory properties, so there is a high probability of a protective effect of BM in the early stages of PD. In this study, PD was induced through the unilateral intracerebral administration of rotenone followed by bacterial melanin. Tissues (brain, lungs, and small intestine) from the observed groups underwent isolation and purification to extract isoforms of new thermostable superoxide (О2−)-producing associates between NADPH-containing lipoprotein (NLP) and NADPH oxidase-Nox (NLP-Nox). The optical absorption spectral characteristics, specific amounts, stationary concentration of the produced О2−, and the content of NADPH in the observed associates were determined. The optical absorption spectra of the NLP-Nox isoforms in the visible and UV regions in the experimental groups did not differ from those of the control group. However, compared with the control group, the specific content of the total fractions of NLP-Nox isoforms associated with PD groups was higher, especially in the small intestine. These findings suggest that the described changes may represent a novel mechanism for rotenone-induced PD. Furthermore, bacterial melanin demonstrated antioxidant properties and regulated membrane formation in the brain, lung, and small intestine. This regulation occurred by inhibiting the release of new membrane-bound formations (NLP-Nox associates) from these membranes while simultaneously regulating the steady-state concentration of the formed О2−.

Concepts and principles for new rapid simple liquid chromatography method for quantification of antioxidants resveratrol, vitamin E, and coenzyme Q10 in capsules with high-performance liquid chromatography with a photo-diode array detector.

Principles and problems in the development of simultaneous liquid chromatography (LC) analytical methods for potent antioxidative molecules resveratrol, tocopherol, and coenzyme Q10 in capsules, have been investigated and systematically compared and summarized. For these purposes, experiments within the full polarity spectrum of LC techniques. were tested and recorded. The whole range of polarities included: Alkyl C18 bonded reversed phase, phenyl, cyanopropyl, diol, and the most polar base silica-filled column matrixes have been used. The summarized results concluded that all mentioned LC techniques could be used for the determination of the mentioned group of the three analytes with different run characteristics and efficiency. These successes could be achieved after careful analyses of molecular physicochemical data of analytes. They are especially organic solubilities. The ultraviolet spectral absorption characteristics of each analyte and the mobile phase constituents for appropriate separation were very important to be known. The ultimate targets were the development method with the isocratic mode of separation yielding symmetrical peak shapes for the best sensitivity and accuracy, with the shortest run time and best reproducibility. From an analytical point of view important for LC, the three analytes have quite distinct characteristics that contribute to successful method development. These features are their organic solvent and water solubility, molecular polarities, and ultraviolet-absorption characteristics, like spectra and absorptivities. All these mentioned parameters were taken into account for solving complications appearing in the development of rapid LC methods for the simultaneous determination of three antioxidant molecules.

Evaluation and design of photothermal conversion performance for multiple “complex-morphology” nanofluids via bidirectional deep neural network

The optical absorption and scattering of plasmonic nanoparticles are crucial for optimizing photothermal conversion efficiency, which holds great potential in various applications. Evaluating the photothermal conversion performance of nanofluids with known geometry is a computationally expensive task. The design of nanofluids that exhibit optimal photothermal conversion performance poses a complex inverse problem. The necessity to explore a wide parameter space, which encompasses various factors such as the shape, size, and material of nanoparticles, contributes to this challenge. In this study, we employ a combination of machine learning with high-throughput radiative transfer calculations to conduct a comprehensive analysis of the entire photothermal conversion process for various nanofluids. The modulation of resonance absorption peaks and spectral absorption can be achieved by adjusting the shape, material constituents, and geometric parameters of nanoparticles. Meanwhile, we establish a design space dataset that encompasses 14,060 groups of nanofluids. Based on the dataset, we demonstrate as a proof of concept bidirectional deep neural network model that enables an efficient and reliable solution to both the forward and inverse problems. The results show that the absorptivity of SiO2@Au nanofluids is significantly influenced by the volume fraction, particularly when it falls within the range of 1 × 10−5 to 1 × 10−4. However, the impact is significantly reduced within the range of 1 × 10−4 to 1 × 10−3. Furthermore, the SiO2@Au nanofluids exhibit enhanced full spectral absorption characteristics at the core-shell ratio of 0.1. Our proposed model achieves a forward prediction of the solar absorption spectra with 99% accuracy and an inverse design of the geometric parameter with 93% accuracy. In comparison to the experimental results, the relative errors for the predicted and design efficiency are 0.42% and 0.82%, respectively. The design geometry parameters including the effective radius and volume fraction exhibit relative errors of 3.88% and 1.6%, respectively. This work provides a widely applicable and computationally efficient method for the evaluation and design of nanofluids in photothermal conversion.

Estimation of the distribution patterns of heavy metal in soil from airborne hyperspectral imagery based on spectral absorption characteristics

Though soil is widely known as one of the most valuable resources for the world, its quality is going to be lower because of unsustainable economic development and social progress. Therefore, it is important for us to monitor and evaluate the quality of soil, especially its heavy metal contents which is too scarce to identify in soil spectra easily but poisonous enough to affect human health in a long run. Most of the existing estimation methods have based the characteristic bands on statistical analysis to a large extent, which is hard to accurately explain the retrieval mechanism. In this paper, the absorption characteristics of heavy metal are studied based on the soil spectra, and the distribution pattern is mapped in a large-scale continuous space, for environmental monitoring and further decision support. Taking Yitong County, China as the study area. After spectra continuum removal, the heavy metal contents were estimated by 11 features including the absorption depth, absorption area, and band ratio around 2200 nm, which showed the best performance. For arsenic (As), the best model yields Rp2 value of 0.8474, and the RMSEP value is 36.1542 (mg/kg). It is concluded that As is adsorbed by organic matter, clay minerals, and iron/manganese oxides in soil, and the adsorption of As by first two components is greater than that of the last. For airborne spectra after continuum removal, combining the spectral absorption characteristic parameters and the highly correlated bands is more accurate than using the spectral absorption characteristic parameters or bands alone. AdaBoost is presented for the heavy metal estimation, and the fitting ability of the method is found to be stronger than that of the traditional classical methods, with the Rp2 values of 0.6242 and the RMSEP value of 43.6481 (mg/kg). In summary, these results will provide a prospective basis for the rapid estimation of soil heavy metals, the risk assessment of soil heavy metals and soil environmental monitoring in a large scale.

Excited state dynamics of bay and peri benzothienyl perylene to understand the excimer formation and its dissociation

Many planar acenes such as pyrene, perylene etc. are known to form dimeric complex of their ground and excited state (excimer formation). Relaxation of excimer, carrier mobility & exciton diffusion in the solid state, and even singlet fission depends on the interaction between ground and excited state molecules in excimer. The role of excimer in triplet formation can be understood by: S0↑↓+S1↑↓⇄{S1S01↑↓↑↓}⇄{T1T11↑↑↓↓}⇄T1↑↑+T1↓↓. Intermediate excimer (T1T1)1 formation i.e., (SnS0)1 → (T1T1)1, and its decay to triplets have been studied by several groups, however, reports on the dissociation of excimer are very few. In this work, we aimed to study the dynamics of excimer formation and its further dissociation using perylene derivatives. We synthesized two positional isomers of benzothienyl substituted perylene i.e., peri-BT and bay-BT, and studied their photophysical properties in solution, nanoaggregates, and thermally evaporated thin films. Excited state dynamics in thin films suggest the dissociation of 1(excimer) to a monomeric singlet excited state in a microsecond timescale. Transient absorption spectral characteristics suggest the formation of a charge transfer state within picoseconds, followed by decay to a long-lived (few microseconds) excimer state. The formation of CT is promoted by strong intermolecular interaction in the thin film.

Extracting hydrothermally altered information using WorldView-3 data: a case study of Huitongshan, NW Gansu, China

Introduction: The Huitongshan skarn-type deposits, in which ore bodies primarily occur in the outer contact zone between K-feldspar granite and marble in the Beishan area, are evidently related to hydrothermal alteration of the surrounding rock. Key mineral alteration processes include serpentinization, epidotization, chloritization, carbonatization, jarosite, ferritization, and hematitization.Methods: WorldView-3 (WV-3), a satellite-recorded high-spatial resolution multispectral image, has been widely used in the exploration and prediction of different types of deposits around the world. In this study, WV-3 multispectral images were used to extract the spatial distribution data of the main altered minerals in the Huitongshan area. Dedicated radiometric calibration, atmospheric correction, and image fusion were used to pre-process the extracted spectral information related to hydrothermal alteration. In addition, directed principal component analysis (PCA) and a unique mineral index were designed based on the effective use of the WV-3 data band corresponding to the spectral absorption characteristics of altered minerals.Results: The findings of this study show that the PCA model and mineral index pro-posed herein are reliable both in theory and for practically obtaining extraction information. Additionally, the WV-3 data are well suited for identifying hydroxy-bearing alterations with rich short-wave infrared bands that distinguish Fe-OH–bearing alterations from Mg-OH–bearing alterations. The results obtained were applied to identify potential targets for skarn-type copper deposits and the implementation of prospecting practices.Discussion: This study provides a basis for the application of WV-3 data as an important and effective tool for alteration information extraction and determination of prospecting practice, thereby proving the validity of multispectral remote sensing images in mineral resource exploration.

Modelling the sound absorption of panels with tapered elliptic micro-perforations

A theoretical model is developed in the present study to predict the spectral characteristics of the sound absorption of solid panels with tapered elliptic micro-perforations backed by a rigid wall cavity. In the model, plane wave propagation is assumed along the length of the perforation in the presence of a viscous boundary layer at the internal wall of the perforation. End impedances are approximated using results in existing literature. Validation is done using impedance tube measurements. It is confirmed that the present tapered elliptic perforation model can give much better agreement with experimental results than the conventional cylindrical perforation model for all micro-perforation configurations tested. Results also suggest the importance of perforation density in controlling the variation of sound absorption of the panel absorbers upon changes in perforation configurations.

Rapid calculation of atmospheric molecular absorption characteristics in the terahertz band based on wideband K-distribution method

This paper focuses on rapidly calculating atmospheric molecular absorption properties in the 0.3–30 THz frequency range of terahertz waves. It conducts research related to spectral radiation models and fast computation model databases. Based on the latest version of the High-resolution transmission molecular absorption database-2020, in conjunction with the line-by-line (LBL) spectral radiative calculation method, the spectral absorption characteristics of nine atmospheric molecules (H2O, CO2, O3, NO, N2O, NO2, NH3, SO2, CH4) are analyzed. The relative contributions of the eight other gas molecules absorption abilities in the terahertz range are examined, with H2O molecule serving as the reference. Taking into account the non-gray absorption properties of atmospheric molecules and the need for fast computation, this study divides the frequency range of 0.3–30 THz into 24 calculation bands based on the spectral absorption distribution characteristics of atmospheric molecules. Utilizing LBL calculations with a resolution of 0.01 cm−1, a non-correlated wideband K-distribution model (WBK) is developed, which achieves nearly the same computational accuracy as LBL. Furthermore, the WBK radiation calculation model is validated under both uniform and non-uniform atmospheric conditions based on earth atmospheric environmental parameters. An exponential kernel fitting coefficient table for the rapid calculation of atmospheric molecular absorption coefficients is established based on the WBK radiation calculation model to improve computational efficiency further. This database enables fast calculation of 24 broadband absorption coefficients (corresponding to 7 Gaussian integration points) within 0–100 km altitude in earth atmosphere.

Clay minerals characterization of the Miduk ball mill output through spectral analysis

Porphyry copper deposits usually include typical alteration types, which are often composed of clay minerals. The mixing of clay minerals has a significant impact on their spectral absorption characteristics, and their identification and separation becomes complicated. One of the most accurate and widely used methods for identifying minerals is spectroscopy, which is a suitable alternative to traditional methods. Spectroscopy assists in identifying the mineral composition and classification. The aim of the following research is to quantitatively characterize clay minerals in mineral assemblage of ball mill output. Pure and composite samples were prepared through sampling from two alteration types and creating synthetic samples containing different percentages of clay minerals. Then they were subjected to spectral analysis in the range of 2500–350 nm and their output was subjected to necessary pre-processing. The results were used for classification by employing a hybrid algorithm. The analysis identified the following minerals in the Miduk deposit: hematite, carbonates, illite, biotite, kaolinite, chlorite and muscovite. Additionally, microscopic studies were conducted on the samples for further analysis. Finally, total and clay diffraction XRD analysis were used to validate the results.

Exploring high-resolution near-surface CO concentrations based on Himawari-8 top-of-atmosphere radiation data: Assessing the distribution of city-level CO hotspots in China

Carbon monoxide (CO) has notable effects on the atmospheric environment and human health. This study used Himawari-8 top-of-atmosphere radiation (TOAR) data, meteorological factors, and geographic information, combined with an interpretable deep forest (DF) model, to obtain high-spatiotemporal resolution near-surface CO concentrations (temporal resolution: 1 h; spatial resolution: 0.05°) in China from September 2015 to August 2021 and reveal the distribution and variation in city-level CO hotspots. Based on the feature importance method and the spectral absorption characteristics of pollutants, the optimal combination of Himawari-8 band for the TOAR-CO model was selected. The performance comparison of five machine learning models showed that the DF model was the most performant. The hourly average R2 value (using 10-fold cross-validation) of the TOAR-CO model ranged from 0.72 to 0.78 (10:00 to 15:00, Beijing time); the R2 values of daily, monthly, and annual averages were 0.79, 0.97 and 0.98, respectively. The feature importance of the model varied in the different seasons and regions, with TOAR and meteorological factors had significantly contributions to the model. During the study period, the CO concentration in most areas of China showed a decreasing trend, with an average decline rate of 7.2%·yr−1. Despite CO being a stable, long-lived gas, the TOAR-CO model still captured obvious intraday variation in CO, which reached a peak of 0.89 mg/m3 at 10:00 and dropped to 0.69 mg/m3 at 15:00. The spatiotemporal distribution of estimated CO was basically consistent with satellite and reanalysis data. The TOAR-CO model predictions reflected city-level CO pollution, and the distribution of CO hotspots was closely related to industrial structure and human activities. During the COVID-19 pandemic, CO concentration significantly dropped after the 4th week of control. The CO concentrations in the hotspot cities decreased more significantly, by over 50%. The research results provide some supports for the assessment of CO fine-scale pollution and related research.

A Novel Hybrid Retinal Blood Vessel Segmentation Algorithm for Enlarging the Measuring Range of Dual-Wavelength Retinal Oximetry

The non-invasive measurement of hemoglobin oxygen saturation (SO2) in retinal vessels is based on spectrophotometry and the absorption spectral characteristics of the tissue. The dual-wavelength retinal images are simultaneously captured via retinal oximetry. SO2 is calculated by processing a series of images and by calculating the optic density ratio of two images. However, existing SO2 research is focused on the thick vessels in the high-clarity region of retinal images. However, the thin vessels in the low-clarity region could provide significant information for the detection and diagnosis of neovascular diseases. To this end, we proposed a novel hybrid vessel segmentation algorithm. Firstly, a median filter was employed for image denoising. Secondly, high- and low-clarity region segmentation was carried out based on a clarity histogram. The vessels in the high-clarity areas were segmented after implementing a Gaussian filter, a matched filter, and morphological segmentation. Additionally, the vessels in the low-clarity areas were segmented using a guided filter, matched filtering, and dynamic threshold segmentation. Finally, the results were obtained through image merger and morphological operations. The experimental results and analysis show that the proposed method can effectively segment thick and thin vessels and can extend the measuring range of dual-wavelength retinal oximetry.

Electronic Excitation Characteristics and Spectral Behavior of Phosphate Anions.

Absorption spectra are fundamental bases for the qualitative and quantitative analysis of the target chemical, and the development of an analytical model can be improved by studying its characteristics and rules. In the present study, the electronic excitation characteristics of phosphate anions (H2PO4-, HPO42-, and PO43-) were analyzed based on the charge-transfer spectrum. In addition, the absorption spectra of phosphate anions at the energy level of PBE0/6-311+G (d,p) were recorded based on the time-dependent density functional theory (TD-DFT) method. Different (HPO42-)n·(H2O)10-n molecular clusters were theoretically constructed, and the combined TD-DFT method and independent gradient model revealed that red shift of the maximum absorption wavelength (λmax) with the increase of phosphate anion concentration (0-10 mM) may be caused by the decrease of hydrogen bond interaction. In addition, the prominent dispersion in the short-wave region mainly resulted in the red shift of λmax with the increase in optical path length (1-100 mm). Moreover, with the increase in spectral bandwidth (0.4-3.0 nm), λmax slightly blue-shifted because of the increase in energy through the slit, and repeatability of the corresponding absorbance measurement at λmax gradually improved. As the spectral bandwidth increased, light monochromaticity became poor, resulting in the decrease of the linearly fitted correlation coefficient of the concentration-absorbance curve. Finally, the multivariate analysis of variance results showed that the optical path length was the most significant factor that influenced the absorption spectral characteristics of phosphate anions. This study provides a basis for the qualitative and quantitative analysis of phosphate anions by using absorption spectra and also renders a theoretical reference for absorption spectroscopy of other chemicals.

Physiological response of red macroalgae <italic>Pyropia yezoensis</italic> (Bangiales, Rhodophyta) to light quality: a short-term adaptation

Light quality is a common environmental factor which influences the metabolism of biochemical substances in algae and leads to the response of algal growth and development. <i>Pyropia yezoensis</i> is a kind of economic macroalgae that naturally grows in the intertidal zone where the light environment changes dramatically. In the present study, <i>P. yezoensis</i> thalli were treated under white light (control) and monochromatic lights with primary colors (blue, green, and red) for 14 days to explore their physiological response to light quality. During the first 3 days of treatment, <i>P. yezoensis</i> grew faster under blue light than other light qualities. In the next 11 days, it showed better adaptation to green light, with higher growth rate and photosynthetic capacity (reflected by a higher rETRmax = 61.58 and Ek = 237.78). A higher non-photochemical quenching was observed in the treatment of red light than others for 14 days. Furthermore, the response of <i>P. yezoensis</i> to light quality also results in the difference of photosynthetic pigment contents. The monochromatic light could reduce the synthesis of all pigments, but the reduction degree was different, which may relate to the spectral absorption characteristics of pigments. It was speculated that <i>P. yezoensis</i> adapted to a specific or changing light environments by regulating the synthesis of pigments to achieve the best use of light energy in photosynthesis and premium growth and metabolism.

Spectral signatures for iron ore deposits in Tirthamalai area, Dharmapuri District, Tamil Nadu, India

The demand for iron ore has increased recently and employing geochemical and hyperspectral remote sensing techniques for discovering new ore and mineral resources have primarily been concentrated on the economic phases. The present study aimed to characterize the hyperspectral spectral signatures of iron ores of field samples to map the deposits that occurred in the Tirthamalai hill region, which lies in the parts of Harur Taluk, Dharmapuri district of Tamil Nadu state, India The measurement and study of spectral signatures of the different samples of the deposits showed strong spectral absorptions near 500 nm, 900 nm and 2400 nm wavelength regions and were confirmed with the Fourier Transform Infrared (FTIR) spectroscopy method. The spectral absorption characteristics of the samples were evaluated by the study of the physical, optical, and chemical characteristics of the samples. The study of hyperspectral and FTIR spectral signatures with petrographic and major chemical elements revealed the best absorption characteristics of the iron ore deposits of the study region and can be used elsewhere in the world. This report presents preliminary findings on the use of hyperspectral imaging to characterize iron ore. The mineralogical products produced from hyperspectral images may improve in situ grade control on an iron ore mine face. It will be extremely useful for businesses in measuring large numbers of commodities quickly and objectively.

NIR emissions from Nd3+-activated phosphate-based glass system for cost-effective, tunable, and miniaturised laser devices

This work represents a phosphate-based glass system of composition (40-x) P2O5 − 30 B2O3 − 30 ZnSO4 - x Nd2O3, ( × = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) to determine the optical absorption and emission spectral characteristics. Moreover, Judd-Ofelt (J-O) intensity and radiative parameters were computed. Samples were prepared using melt-quenching method and characterized using Archimedes measurement, Ultraviolet–Visible-Near Infrared Spectroscopy and Photoluminescence Spectroscopy. The density values of these samples were reduced as the Nd2O3 concentration increased. The absorption spectra revealed 11 peaks corresponded to Nd3+ transitions from the lowest electronic energy level (4I9/2) to various excited levels. The optical energy band gap was found to be reduced with Nd3+ doping. The refractive indices (n) increased as the Nd3+ increase. The improving tendency of n was clarified in terms of the enhancing trend of samples molar volume (obtained from density), indicating a structural-optical correlation in the proposed glass system. The obtained values of Urbach energy (Eu) have an increasing trend in the range of ∼ 0.318–0.711 eV. Tow significant NIR emission peaks were assigned to the 4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions of Nd3+. Values of J-O intensity parameters Ω2, Ω4 and Ω6 were found in the range of (1.63–2.25)× 10−19 cm2, (2.57–2.94)× 10−19 cm2 and (1.53–1.82)× 10−19 cm2, respectively. The obtained stimulated emission cross-section for the NIR transitions from Nd3+ ((23.83–26.64)× 10−20 cm2 for 4F5/2 → 4I9/2, and (10.93–17.91)× 10−20 cm2 for 4F3/2 → 4I9/2 obviously revealed the lasing effectiveness of the titled glass system.

Improving SPAD spectral estimation accuracy of rice leaves by considering the effect of leaf water content

AbstractThe spectral range <1,000 nm is commonly used for estimating the chlorophyll content of plants. However, the influence of the response band of leaf water content in the Short‐Wave InfraRed on the chlorophyll estimate model is uncertain. We measured the Visible‐Near InfraRed‐Short Wave InfraRed spectral reflectance and SPAD values of rice (Oryza sativa L.) leaves at different growth stages. The vegetation indices (VIs), red edge positions (REPs), and spectral characteristic parameters (SCPs) were calculated. The correlation between the above parameters and SPAD was analyzed. The effects of chlorophyll and water content on the spectral reflectance absorption characteristics of rice leaves were analyzed by the PROSPECT model. SPAD spectral estimation models were established with different inputs using the Random Forest (RF) regression algorithm. Our results are described as follows: (a) The spectral reflectance after continuum removal of rice leaves was highly correlated with SPAD in 600–690, 720–760, 1,400–1,490, and 1,900–1,980 nm. (b) Compared with VIs and REPs, the SCPs after continuum removal including the Depth (D1) and Area (A1, A2) parameters had the highest correlation with SPAD. (c) By taking into account the influence of leaf water content (LWC), the accuracy of SPAD estimation may be enhanced. The RF SPAD estimate model with SCPs of all absorption valley as inputs performed the best. The findings reveal on the mechanism of the influence of LWC on the accuracy of chlorophyll spectra estimation. It provides technical support for estimating SPAD in rice leaves with high accuracy and for developing chlorophyll tachistoscopes.