Ultraviolet, Visible, And Near-infrared Research Articles

Large Interferometer For Exoplanets (LIFE)

Context. Following the recommendations to NASA (in the Astro2020 Decadal survey) and ESA (through the Voyage2050 process), the search for life on exoplanets will be a priority in the next decades. Two concepts for direct imaging space missions are being developed for this purpose: the Habitable Worlds Observatory (HWO) and the Large Interferometer for Exoplanets (LIFE). These two concepts operate in different spectral regimes: HWO is focused on reflected light spectra in the ultraviolet, visible, and near-infrared (UV/VIS/NIR), while LIFE will operate in the mid-infrared (MIR) to capture the thermal emission of temperate exoplanets. Aims. In this study, we aim to assess the potential of HWO and LIFE to characterize a cloud-free Earth twin orbiting a Sun-like star at a distance of 10 pc, both as separate missions and in synergy with each other. We aim to quantify the increase in information that can be gathered by joint atmospheric retrievals on a habitable planet. Methods. We performed Bayesian retrievals on simulated data obtained by an HWO-like mission and a LIFE-like one separately, then jointly. We considered the baseline spectral resolutions currently assumed for these concepts and used two increasingly complex noise simulations, obtained using state-of-the-art noise simulators. Results. An HWO-like concept would allow one to strongly constrain H2O, O2, and O3 in the atmosphere of a cloud-free Earth twin, while the atmospheric temperature profile is not well constrained (with an average uncertainty ≈100 K). LIFE-like observations would strongly constrain CO2, H2O, and O3 and provide stronger constraints on the thermal atmospheric structure and surface temperature (down to ≈10 K uncertainty). For all the investigated scenarios, both missions would provide an upper limit on CH4. A joint retrieval on HWO and LIFE data would accurately define the atmospheric thermal profile and planetary parameters. It would decisively constrain CO2, H2O, O2, and O3 and find weak constraints on CO and CH4. The significance of the detection is in all cases greater than or equal to the single-instrument retrievals. Conclusions. Both missions provide specific information that is relevant for the characterization of a terrestrial habitable exoplanet, but the scientific yield can be maximized by considering synergistic studies of UV/VIS/NIR+MIR observations. The use of HWO and LIFE together will provide stronger constraints on biosignatures and life indicators, with the potential to be transformative for the search for life in the Universe.

Deep-Ultraviolet Bialkali-Rare Earth Metal Anhydrous Sulfate Birefringent Crystal.

Birefringence is an important linear optical property of anisotropic crystals that plays a significant role in regulating light polarization. A new bialkali-rare earth metal sulfate, NaRbY2(SO4)4 compound, consisting of non-π-conjugated alkali metals and rare earth metal-centered dodecahedral YO8 has been synthesized. The structure analysis suggests that the three-dimensional (3D) structure of the compound is found to be attributable to the combination of dodecahedral YO8 and tetrahedral SO4 groups with Na+ and Rb+ located in the cavities. The ultraviolet, visible, and near-infrared (UV-vis-NIR) spectra reveal that the compound exhibits transparency at a wavelength of less than 200 nm. The observed birefringence of the compound is 0.045@550 nm, which is comparatively larger than that of most deep-ultraviolet (DUV) birefringent crystals. The birefringence mainly originated from the YO8 dodecahedron, which is suggested by first-principles calculations. This research work can provide a useful perspective to explore new DUV sulfates with excellent birefringence.

The influences of LaVO4:Eu3+,Cr3+ red phosphors on white light-emitting diode applications

<span>In this present paper, the </span><span lang="EN-ID">LaVO<sub>4</sub>:Eu<sup>3+</sup>,Cr<sup>3+</sup> (</span><span>LV:Eu,Cr) </span><span lang="EN-ID">red-orange phosphors</span><span>are introduced in WLED fabrication. The LV:Eu,Cr phosphor is synthesized with high-temperature solid-phase reaction</span><span lang="IN">.</span><span> The luminescence properties of the phosphor are monitored with ultraviolet-visible and near-infrared (UV-vis-NIR) measurements. The heat generating in the phosphor sample is also investigated with different power densities of the 980 nm laser. The phosphor exhibits absorption bands at 254 nm and 316 nm, suitable for UV light-emitting diodes (UV LED) applications. The Cr<sup>3+</sup> concentrations have noticeable effects on the luminescence of the phosphor. The increasing Cr<sup>3+ </sup>dosage initiates reduction in Eu<sup>3+</sup> emission intensity and luminescence lifetime average. The heat-activated amount in the phosphor is also significant with the higher concentration of Cr<sup>3+</sup> ions. When using the LV:Eu,Cr phosphor in white light-emitting model (WLED), the dominant red-orange emission centered at 595 nm is observed, in addition to the blue peak at 453 nm. The luminosity, color rendition, and color uniformity of the WLED light are also discussed. The findings indicate that the phosphor can be combined with other high-efficiency blue and green phosphors to obtain the improved color rendition and luminous performances and used in heat-creating optical applications.</span>

Sol-gel Spin Coated Hydrophilic Composite Titania-Silica Coatings on the Glass Substrates for Automotive Applications

The pollutants from the environment can also degrade the surface of the glass, which result in loss of transmittance of the glass surface. This necessitates the formation of a dedicated crew for the correct maintenance of glass furniture, notably in the Middle East. In this paper, we describe sol-gel spin coating of titania thin films on glass substrates, which may function as a hydrophilic coating by spreading water molecules across the substrate and removing pollutants and other dust particles, hence eliminating the need for maintenance and wipers. The fabricated coating was tested with X-ray diffractogram (XRD) and evidenced anatase nature of titania and amorphous nature of silica at Bragg angle 25° in the coating. Fourier transform infrared spectroscopy (FTIR) investigations endorsed Ti-O-Ti and Si-O-Si functional linkages at wavenumbers 551, and 957 cm-1 demonstrating the presence of titania and silica in the as-developed coating. Cross sectional field emission scanning electron microscopy (FESEM) investigation evidenced the formation of composite titania-silica film on the glass substrate with a thickness about 36 nm. The coating transmittance was studied by ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopy and found 95% transmittance in the visible region. Moreover, wetting study utilizing the sessile drop technique yielded a 74° contact angle when the water droplets were interacted.

A Review of Recent Advances for the Detection of Biological, Chemical, and Physical Hazards in Foodstuffs Using Spectral Imaging Techniques.

Traditional methods for detecting foodstuff hazards are time-consuming, inefficient, and destructive. Spectral imaging techniques have been proven to overcome these disadvantages in detecting foodstuff hazards. Compared with traditional methods, spectral imaging could also increase the throughput and frequency of detection. This study reviewed the techniques used to detect biological, chemical, and physical hazards in foodstuffs including ultraviolet, visible and near-infrared (UV-Vis-NIR) spectroscopy, terahertz (THz) spectroscopy, hyperspectral imaging, and Raman spectroscopy. The advantages and disadvantages of these techniques were discussed and compared. The latest studies regarding machine learning algorithms for detecting foodstuff hazards were also summarized. It can be found that spectral imaging techniques are useful in the detection of foodstuff hazards. Thus, this review provides updated information regarding the spectral imaging techniques that can be used by food industries and as a foundation for further studies.

Prediction of surface color of ‘crystal’ guava using UV-Vis-NIR spectroscopy and multivariate analysis

Ultraviolet, visible, and near infrared (UV-Vis-NIR) spectroscopy technique has been increasingly applied in sorting of agricultural products, especially fruits. This study aimed to evaluate the use of UV-Vis-NIR spectroscopy and multivariate analysis to predict the surface color (L*, a*, and b*) of ‘crystal’ guava. Wavelengths covering the UV-Vis (300-699 nm) and UV-Vis-NIR (300-1065 nm) area were investigated to obtain the best prediction accuracy. A total of 120 samples of guava fruits were harvested at the same maturity level, the samples were divided into 3 groups, which consisted of 40 samples per group. The first group was stored for 0 days. The second and third groups were stored for 4 and 8 days, respectively. Spectra data acquisition was performed at wavelengths of 300-1065 nm and interval of 3 nm. Multiplicative scatter correction (MSC) and standard normal variate (SNV) spectra correction methods were applied to improve prediction accuracy. Partial least squares regression (PLSR) was used as calibration method. Validation was done by the k fold cross validation. The best prediction of L* was obtained at UV-Vis-NIR wavelength with SNV correction method. The UV-Vis wavelength and SNV acquired the best prediction of a*. Original spectra and UV-Vis-NIR wavelengths resulted the best prediction of b*.

Non-Destructive Classification of Fruits Based on Vis-nir Spectroscopy and Principal Component Analysis

Fruits are one of the sources of nutrition needed for health. Fruit quality is generally assessed by physical and chemical properties. Measurement of fruit internal quality is usually done by destructive techniques. Ultraviolet, visible and near-infrared (UV-Vis-NIR) spec-troscopy is a non-destructive technique to measure fruit quality. This technique can rapidly measure the fruit quality, the measured fruit still remains intact, and can be marketed. Besides, UV-Vis-NIR spectrosco-py can also be used to classify fruits. The study aimed to classify var-ious types of fruits using UV-Vis-NIR spectroscopy with wavelengths of 300-1041 nm and Principal Component Analysis (PCA). First de-rivative savitzky-golay with 9 smoothing points (dg1) and multiplica-tive scatter correction (MSC) were applied to correct the spectra. The results showed that the use of uv-vis-nir spectroscopy and PCA com-bined with spectra pre-treatment of the MSC method were able to clas-sify various types of fruits with 100% success rate in all fruit samples including sapodilla, ridge gourd, mango, guava, apple and zucchini.

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance (EPR) or ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopies, we obtain useful information such as electron affinity, ionization potential, band-gap energies, the type of charge carriers, and degradation information that can be used to synthesize stable organic electronic devices. In this study, we present electrochemical and spectroelectrochemical methods to analyze the processes occurring in active layers of an organic device as well as the generated charge carriers.

Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds

Cyclic voltammetry (CV) is a technique used in the analysis of organic compounds. When this technique is combined with electron paramagnetic resonance (EPR) or ultraviolet-visible and near-infrared (UV-Vis-NIR) spectroscopies, we obtain useful information such as electron affinity, ionization potential, band-gap energies, the type of charge carriers, and degradation information that can be used to synthesize stable organic electronic devices. In this study, we present electrochemical and spectroelectrochemical methods to analyze the processes occurring in active layers of an organic device as well as the generated charge carriers.

Investigation of Luminescence Properties of Dy<sup>3+</sup> Doped Alkaline Earth Oxides Barium Phosphate Glasses

In this work, the optical and luminescence properties of Dy2O3 doped barium phosphate glass with different alkaline earth oxides (MgO, CaO and SrO) have been investigated. The glass samples were prepared by the melt-quenching technique at the melting temperature of 1200 °C. The absorption spectra of glasses were recorded in the ultraviolet, visible and near infrared (UV-Vis-NIR) region. The absorption bands centered at 385, 424, 452, 472, 754, 803, 901, 1093, 1273 and 1683 nm, respectively have been observed. The emission spectra of glass samples centered at 482, 574, 662 and 751 nm, respectively have been observed with 350 nm excitation wavelength. The result of radioluminescence spectra were slightly different with photoluminescence spectra. The coordinate of emitting color (x, y) for 350 excitation wavelength is 0.3781 and 0.4252, respectively which is located in white light region of CIE diagram.

Facile synthesis of P(EDOT/Ani) : PSS with enhanced heat shielding efficiency via two-stage shot growth.

Poly(3,4-ethylenedioxythiophene/aniline) : poly(styrene sulfonate), P(EDOT/Ani) : PSS, with enhanced absorption of near infrared light, was prepared by oxidative polymerization. We demonstrated that a two-stage shot growth process optimizes the absorption of the polymer in the near infrared region via a controlled monomer addition time. In other words, the optical properties of the polymer complex were improved by controlling the time intervals of aniline monomer addition. P(EDOT/Ani) : PSS was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The shielding efficiency of the P(EDOT/Ani) : PSS films was calculated by using data from ultraviolet, visible, and near infrared (UV-vis-NIR) spectroscopy. The introduction of polyaniline to PEDOT increased the absorption in the near infrared area. In comparison with PEDOT : PSS film, the total shielding efficiency of the P(EDOT/Ani) : PSS film increased to 65.8% from 54.6% at 60% transmittance. The maximum NIR shielding efficiency (SENIR) of the film is 92.7% and the transmittance is 46.5%. Also, large-scale P(EDOT/Ani) : PSS film was fabricated using roll-to-roll slot-die equipment and a heat shielding test of the film was conducted by measuring the temperature variation, in order to prove the enhanced heat shielding effect. P(EDOT/Ani) : PSS prepared by a two-stage shot growth system showed excellent potential as a heat shielding material.

UV-visible-NIR reflectance spectrophotometry in cultural heritage: Background paper.

Diffuse reflectance spectrophotometry in the ultraviolet, visible and near-infrared (UV-vis-NIR) range is becoming a widely-used tool for the non-invasive analysis of cultural heritage objects, especially in its variant with optical fibres, commonly dubbed FORS (Fibre Optic Reflectance Spectroscopy). It is especially useful to study objects such as medieval manuscripts for which sampling is prohibited by current conservation standards. This brief describes the most common types of application of FORS in the analysis of cultural heritage objects; it also illustrates the instrumentation used and the main advantages and limitations of the technique.

Location and Number of Sampling for Optical Reflectance Measurement of Chinese Cabbage and Kale Leaves

Non-destructive sensing of plant growth and components has been investigated recently, and sampling scheme affects accuracy and reliability of the approach. Objective of the paper was to determine location and number of sampling points for optical reflectance measurement of Chinese cabbage and kale plant leaves. Chinese cabbage and kale were grown in a plant factory, and 9 leaves for each cabbage and kale were sampled and optical reflectance spectra were measured with a UV/VIS/NIR (ultra-violet, visible, and near-infrared) spectrometer (Jaz instrumentation, Ocean Optics, FL, USA). Reflectance was measured in a range of 250~1,100 nm at 30 points (15 points on each vein and blade areas) over the entire leaf area. To determine optimum location and number of sampling, reflectance difference and cross correlation among the reflectance spectra were computed and compared. Reflectance difference was computed by subtracting averaged spectrum from each spectrum. Cross correlation method was used to calculate degree of similarity among spectra at different sampling locations. Four pre-processing methods were tried to reduce the spectral noise and to compare reflectance difference of cabbage and kale leaves. Reflectance of the blade part was greater and more reliable than that of the vein part for both of the cabbage and kale leaf samples. Reflectance measurement at 12 and 9 locations over the upper leaf part was considered as preferable for rapid and stable sensing of cabbage and kale leaves, respectively.

Comparison of Multivariate Calibrations for the Determination of Soluble Solids Content of Tea Beverage Using UV-VIS-NIR Spectroscopy

Ultra-violet, visible and near infrared (UV-VIS-NIR) spectroscopy combined with chemometrics was investigated for fast determination of soluble solids content (SSC) of tea beverage. In this study, a total of 120 tea samples with SSC range of 4.0-9.5 ºBrix were tested. Samples were randomly divided for calibration (n=90) and independent validation (n=30). Spectra were collected by a mobile fiber-type UV-VIS-NIR spectrophotometer in transmission mode with recorded wavelength range of 203.64-1128.05 nm. Various calibration approaches, i.e., principal components analysis (PCA), partial least squares (PLS) regression, least squares support vector machine (LSSVM) and back propagation artificial neural network (BPANN), were investigated. The combinations of PCA-BPANN, PCA-LSSVM, PLS-BPANN and PLS-LSSVM were also investigated to build calibration models. Validation results indicated that all these investigated models achieved high prediction accuracy. Especially, PLS-LSSVM achieved best performance with mean coefficient of determination (R2) of 0.99, root-mean-square error of prediction (RMSEP) of 0.12 and residual prediction deviation (RPD) of 15.16. This experiment suggests that it is feasible to measure SSC of tea beverage using UV-VIS-NIR spectroscopy coupled with appropriate multivariate calibration, which may allow using the proposed method for off-line and on-line quality supervision in the production of soft drink.

Green andradite stones: gemmological and mineralogical characterisation

A multi-methodological investigation of natural gem-quality andradite crystals occurring in serpentinites (Val Malenco, Italy; Nizhniy Tagil, Russia; Kerman, Iran, and Kaghan, Pakistan), or in skarn rocks (Erongo, Namibia, and Antetezambato, Madagascar) has been performed by means of gemmological standard testing, electron-microprobe chemical analyses in wavelength-dispersive mode (EMPA-WDS), ultraviolet, visible and near-infrared (UV-Vis-NIR) and mid-infrared (MID-IR) spectroscopy, and single-crystal X-ray diffraction, in order to describe the gemmological properties and the crystal chemistry of these marketable green stones. The EMPA-WDS data show that these green garnets are almost pure andradite [Adr (Ca3Fe2Si3O12)>96.1 mol%]. The Cr-content ranges, as Cr2O3, from <0.01 up to ~1.0 wt%. This chromophore element, if present, influences the garnet’s colour, which is mainly due to Fe3+. The Cr-content does not affect the unit-cell constant, at least within the range found here. The refined electron content at the Fe-site suggests that chromium occupies the octahedral site along with iron, as found in previous investigations. The MID-IR spectra show the presence of hydroxyl groups. The refined site occupancy factors of the Si-site, modelled with the scattering curve of silicon alone, range between 99.2(4) and 99.9(2), which barely suggests potential hydrogarnet substitution [ i.e. , (SiO4)4− ↔(O4H4)4−].

The spectral responses of Ceratophyllum demersum at varying depths in an experimental tank

This study was designed to investigate the spectral responses of Ceratophyllum demersum, a common submerged aquatic vegetation (SAV), with varying depth in columns of both clear and algae-laden water. The experiments were undertaken in a tank 20 500 l in volume, 360 cm in diameter and with a total depth of 150 cm. The first experiment was executed under a clear-water condition and the second was completed with an addition of algal solution to the tank. Spectral data were acquired using an ASD FieldSpec ultraviolet/visible and near-infrared (UV/VNIR) spectroradiometer with wavelengths ranging from 348-1074 nm. Results indicate that reflectance between 700-900 nm decreased as the depth of the macrophyte increased for both clear and algal-laden waters due simply to the absorption of light by the increasing volume of water. The 'green peak' of algal chlorophyll, on the other hand, increased as the depth to the macrophyte increased. The '700 peak' shifted towards shorter wavelengths as the macrophyte's depth increased. Spectral reflectance curves for depths of 100 cm and 110 cm tended to merge together. But the SAV could still be detected at wavelengths of 538 nm and 706 nm.

NIST High Accuracy Reference Reflectometer-Spectrophotometer.

A new reflectometer-spectrophotometer has been designed and constructed using state-of-the-art technology to enhance optical properties of materials measurements over the ultraviolet, visible, and near-infrared (UV-Vis-NIR) wavelength range (200 nm to 2500 nm). The instrument, Spectral Tri-function Automated Reference Reflectometer (STARR), is capable of measuring specular and diffuse reflectance, bidirectional reflectance distribution function (BRDF) of diffuse samples, and both diffuse and non-diffuse transmittance. Samples up to 30 cm by 30 cm can be measured. The instrument and its characterization are described.