Visible Near-infrared Spectrophotometer Research Articles

Sustainable reutilization of ion-adsorbed rare earth tailings: Preparation of low-cost functionalized pigments

In order to alleviate the ecological pressure caused by rare earth tailings, this study focuses on the application of ion-adsorbed rare earth tailings in the preparation of functional pigments. By using mechanical grinding and high-temperature calcination, 33 new functionalized red pigments were successfully prepared by doping iron and lanthanum elements. X-ray diffraction (XRD), scanning electron microscopy (SEM), CIE 1976 color space system, and ultraviolet–visible–near-infrared spectrophotometer were used for characterization. The synthesized pigment exhibits a rich color range from light yellow to reddish brown. Compared with commercially available iron red pigments, it exhibits significantly enhanced near-infrared reflectance, excellent acid and alkali resistance, and strong thermal stability up to 900 °C. It is worth noting that pigment P-1-2-1 achieved the best red value (L* = 43.73, a* = +24.07, b* = +15.65) with a maximum near-infrared reflectance of 91 %. Therefore, the utilization of rare earth tailings as raw materials for the preparation of functional pigments has significant effects. This study provides valuable insights for the development of eco-friendly pigments, which not only helps alleviate the urban heat island effect but also promotes the sustainable utilization of rare earth tailing resources, contributing to the achievement of carbon neutrality goals.

A Wavelength Selection Model Based on Successive Projections Algorithm for pH Detection of Water by VIS-NIR Spectroscopy

A novel pH detection method using VIS-NIR (visible near infrared) spectroscopy for water is introduced in this paper. In order to improve prediction accuracy and calculation speed of pH detection using VIS-NIR spectroscopy, a wavelength selection model of SPA-MLR (successive projections algorithm and multiple linear regression) is proposed. Two experiments (pH measurement experiment by VIS-NIR spectrophotometer and pH measurement experiment by VIS-NIR grating spectrograph) are employed to evaluate the performance of SPA-MLR. At meanwhile, PLS (partial least squares), GA-PLS (genetic algorithm and partial least squares) are introduced to compare with SPA-MLR. The results indicate that, the prediction accuracy and calculation speed of SPA-MLR are all better than that of PLS and GA-PLS. Under the pH measurement experiment using VIS-NIR spectrophotometer, only one wavelength is selected from 351 original wavelengths for calibration, the RMSEP (root mean square errors of prediction) is 0.35, and the model training speed is 2.36s. Under the pH measurement experiment using VIS-NIR grating spectrograph, 3 wavelengths are selected from 2860 original wavelengths for calibration, the RMSEP is 0.50, and the model training speed is 56.45s. For the two experiments, the selected wavelength variables by SPA are distributed mainly in the band of 870 nm to 990 nm.

Electroless deposited black nickel-phosphorous solar absorber coatings on carbon steel: Effect of plating bath pH

One of the challenges of solar energy collection is energy conversion efficiency, particularly the absorbent surface capability to convert solar energy to thermal energy. In this work, nickel-phosphorous (Ni-P) coating was deposited onto a carbon steel substrates using the electroless plating process containing nickel sulfate as the nickel source and sodium hypophosphite as the reducing agent. This study focuses on the study of plating bath pH effect on the light absorption properties of the black surface after blackening process and at the same time maintain the characteristic of protective coating to protect the substrate from corrosion. The electroless nickel plating was conducted at various plating bath pH (4.5, 5.0, and 6.0) for 3 h at a constant bath temperature and composition. Electroless black Ni-P surfaces were obtained through an etching process of Ni-P coating with 9 mol/L nitric acid solution. The surface morphology of Ni-P coating and black Ni-P coating were observed using scanning electron microscopy (SEM). The chemical composition of Ni-P coating deposited at various pH was measured using energy dispersive X-ray (EDX) equipped on the SEM. The SEM results show that black Ni-P coating for pH 4.5 sample has the highest porosity which is 47.1% of the surface area with highest phosphorus content shown by EDX analysis. The cross-sectional analysis showed that the depth of the etching effect occurred only up to the 33% of the coating thickness. The remaining 67% of coating thickness still uniformly attached on the substrate without the presence of any defects or flacking after the etching process. The visible near-infrared spectrophotometer, (VIS-Nir) showed that the black Ni-P coating of pH 4.5 sample had the highest absorption capability which is 92% of light absorption due to its high surface roughness.

Structure and optical properties of CrOxNy films with composition modulation

ABSTRACTThe composition and structure properties of the CrOxNy films deposited by RF reactive magnetron sputtering were investigated and correlated with their optical properties. Two kinds of targets Cr2O3 and CrN compounds with variation of N2 and O2 gas flow were used to prepare two series of samples. The phase structure, chemical composition and optical properties of CrOxNy films were characterised by X-ray diffraction, X-ray photoelectron spectroscopy and ultraviolet–visible near-infrared spectrophotometer, respectively. The films mainly consist of Cr2N and CrO3 phases. The Cr/ON ratio derived by XPS varies with the variation of nitrogen with Cr2O3 target. But only lower nitrogen content is detected with variation of oxygen using CrN target. The CrOxNy films with higher nitrogen content possess high absorbance around at 35% in the visible light range no matter the target.

Improving anti-infrared radiation and heat insulation by potassium hexatitanate whisker-doped Al 2 O 3 –SiO 2 composite xerogel

Taking potassium hexatitanate whisker (PTW) modified by silane coupling agent KH550, aluminium nitrate inorganic salt and tetraethyl orthosilicate and deionized water, respectively, as infrared sunscreen, aluminium source and raw materials forming the network structure of a composite xerogel, a series of structurally intact PTW-doped Al2O3–SiO2 composite xerogel thermal-insulating materials were prepared by the sol–gel method and dried under atmospheric pressure. The infrared spectral characteristics, infrared radiation transmittance, microstructures, morphology and thermal conductivity of different composite materials prepared have been determined by a Fourier transform infrared spectrometer, UV–visible–near-infrared spectrophotometer, X-ray diffractometer, scanning electron microscope and thermal conductivity tester. The results exhibit that when the Al to Si molar ratio is 1 : 9, the composite material with 5 wt% modified PTW shows the best infrared radiation blocking performance and the lowest thermal conductivity (0.0604 W m−1 K−1).

Transparent heat insulation coatings with high selective shielding ability designed with novel superstructures of copper sulfide nanoplates

In the present work, novel CuS superstructures composed of intersectional CuS nanoplates (CuS i-nanoplates) and snowflake-like CuS nanoplates (CuS s-nanoplates) were successfully synthesized at a low temperature (80 °C) by a simple chemical precipitation method. It has been found that the as-synthesized CuS superstructures were formed by the growth of CuS i-nanoplates along the direction perpendicular to the basal nanoplate with a thickness of 29.64 ± 3.16 nm and CuS s-nanoplates were prepared with the snowflake-like morphology with a thickness of 16.82 ± 3.62 nm. Subsequently, a new transparent heat insulation coating with CuS superstructures composed of CuS i-nanoplates as NIR shielding agent (coded as H–X coating) was prepared by mixing with acrylic-amino-alkyd baking varnish and coating to ordinary glass substrates. Simultaneously, another transparent heat insulation coating with s-nanoplates (coded as S–X coating) was also synthesized. Optical properties of those coatings were studied as a function of the CuS content by using ultraviolet–visible–near-infrared spectrophotometer. And the H–X coatings were shown to have a higher selective shielding ability for solar light than S–X coatings since the shielding ability of S–X coatings in the region of 1180–2500 nm rapidly weakened with increasing wavelength. The comparative study on the properties of nanomaterials with different morphologies in this paper may provide some new guidance for material design to improve its performance. Moreover, the CuS superstructure-based transparent heat insulation coatings with excellent NIR shielding property have a potential application in energy-saving windows for architectures and vehicles.

Tellurite suboxide based near-infrared reflector and filter

TeO1.4/SiO2 one-dimensional photonic crystals (1D PCs) were prepared using radio frequency (RF) magnetron sputtering to fabricate a reflector and a filter with photonic band gaps (PBGs) in the near infrared (NIR) region. Stoichiometry and phase state of the TeOx thin film were characterized via X-ray photoelectron spectroscopy (XPS) and X-Ray Diffraction (XRD), respectively. The microstructural and optical characteristics of the 1D PCs were evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM) and ultraviolet visible near-infrared spectrophotometer (UV-VIS-NIR). The experimental reflectance spectra were consistent with the theoretical results simulated using the transfer matrix method (TMM). For the reflector, a PBG of 1273–1676 nm (Δλ = 403 nm) was achieved in the NIR region. For the filter, the introduction of a defect layer in the 1D PC led to a resonant peak at the central wavelength of 1461 nm within the PBG of 1250–1733 nm (Δλ = 483 nm). The effects of the structural parameters, including the incident angle, the state of polarization and the thickness of the defect layer, were also theoretically analyzed.

Bio-inspired self-assembly of waxberry-like core-shell SiO2@TiO2 nanoparticles towards antiglare coatings.

Waxberry-like core–shell SiO2@TiO2 nanoparticles were prepared by liquid-phase deposition (LPD) method. The dip-coating self-assembly of waxberry-like core–shell SiO2@TiO2 nanoparticles has been used to fabricate coatings with excellent antiglare properties in the large angle and wide wavelength range. The field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements showed that the surface of SiO2 nanoparticles were coated by titania as a shell with controllable and uniform thickness. The ultraviolet visible near-infrared spectrophotometer (UV-Vis-NIR) results indicate that the maximum transmittance of the antiglare coating is up to 95.80% in the visible band, whereas that of the pure glass substrate is only 92.10%. The scattering and haze of the films have been measured to show that such specifically structured coatings exhibited good antiglare properties in the large angle and wide wavelength range.

Visible light-induced super-hydrophilic anatase porous thin film with easy-to-clean and antifogging properties

Atmospheric dust on the surface of modern building glass requires frequent cleaning to keep high diaphaneity and esthetics. Visible light-induced super-hydrophilic anatase porous thin films with easy-to-clean and antifogging properties were controllably synthesized through the neutralization of ammonia and nitric acid-driven phase separation by sol–gel spin coating method. Surface microstructure, root-mean-squared roughness, crystalline structure, surface chemical composition, transmittance, hydrophilic, antifogging, and easy-to-clean properties of the films were characterized by super depth of field microscopy, atomic-force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet–visible–near-infrared spectrophotometer and automatic contact angle measuring device, respectively. With NH3·H2O concentration increasing from 0.7 to 1.1 vol.%, the average pore size of anatase porous thin films increases from 1.05 to 2.36 μm and the water contact angles decrease from 5.2° to 1.7° under 100-lux visible light irradiation (400–800 nm). Besides, the larger NH3·H2O concentration, the larger root-mean-squared roughness roughness, ranging from 5.67 to 88.00 nm. Moreover, X-ray photoelectron spectroscopy results demonstrate that there are Ti–O bonds and Si–O bonds on the samples surface, indicating that porous area bottom is Si–O bonds by soda-lime glass. These films exhibit excellent visible light-induced super-hydrophilic, antifogging and easy-to-clean properties, which make them suitable to be used in modern buildings and automotive glass.

Surface modification nanoporous titanium oxide films using continuous wave CO2 laser

This study investigated the characteristics of titanium dioxide (TiO2) films modified through laser annealing by using a CO2 laser source (CSS 500 AIR, Spectral Inc., Italy) with a wavelength of 10,600 nm and a continuous wave mode. Commercial TiO2 thin films with a thickness of 100 nm were prepared through radio-frequency magnetron sputtering on soda-lime glass substrates. The optical properties (optical absorption and transmittance spectra), surface morphology, and surface chemical composition characteristics of the TiO2 films depended on the laser irradiation conditions. The characteristics of the films were systematically analyzed using a ultraviolet–visible near-infrared spectrophotometer, an X-ray photoelectron spectroscope, and a field emission scanning electron microscope. The experimental results demonstrated that the experimental transmittance spectra exhibited slight changes caused by laser annealing and a maximum transmittance in the visible region of approximately 91.4 %. The absorbance of all annealed TiO2 films exceeded that of as-deposited films. Moreover, the absorption band edge moved toward the long-wavelength side (red shift) as the annealing speed decreased because the heat applied during annealing caused the TiO2 film grains to grow. Diffusion and mobility between the films and glass substrates during laser annealing segregated elemental Ag.

Al 2 O 3 and Sn/Al 2 O 3 nanowires: fabrication and characterisation

Self-ordered anodised aluminium oxide membranes can be used as a base for the growth of different nanoarrays. In this reported work, an efficient and effective method is implemented to fabricate highly ordered alumina nanowires (ANWs) covered with a uniform shell of 12 ± 2 nm Sn nanoparticles (Sn/ANWs). A two-step anodisation process followed by a selective etching process was used to prepare highly ordered ANWs with diameters smaller than 36 nm. The thermal evaporation technique was used to ensure the deposition of a Sn nanoshell on the fabricated nanowires. The fabricated nanostructures were characterised by energy-dispersive X-ray spectroscopy, X-ray diffraction, field emission-scanning electron microscopy and an ultraviolet–visible–near-infrared spectrophotometer. Analysis of the scanning electron microscopy images showed that the etching rate is 0.73 nm/min and ANWs are obtained after etching the membrane for 110 min. The measured reflection spectra revealed that Sn/ANWs exhibit a redshift of the UV absorption band relative to the ANWs and a reflectance of nearly 100% in the near-infrared region. For optical comparison, glass slides were coated with Sn under the same conditions for 90 and 120 s. The reflection spectrum of the 120 s Sn-coated glass slide shows three modes at 210, 296 and 700 nm because of the excitation and interference of plasmonic waves.

Synthesis of SnO2@SnS2 core–shell nanorods by double crucible method and their photocatalysis

SnO2@SnS2 core–shell structural nanorods were prepared by the solid phase double crucible method. The structure, morphology and optical properties of the as-prepared samples were characterized by X-ray diffraction, transmission electron microscope and ultraviolet–visible–near-infrared spectrophotometer. The results indicated that the mixture of hexagonal phases SnS2 and tetragonal phase SnO2 was formed at 400 and 500 °C and the molar ratio of SnO2 to thioacetamide was 1:3. SnS2 was uniformly coated on the surface of SnO2 nanorods, and SnO2@SnS2 core–shell nanorods with the shell thickness of about 3–5 nm were obtained. Furthermore, their photocatalytic properties were tested for the degrading of methyl orange in water under visible light (λ > 420 nm) irradiation. Compared with pure SnS2 nanomaterials, the core–shell nanorods demonstrated more superior photocatalytic activity. These meaningful results had laid certain foundation for further research on metal oxide@metal sulfide core–shell structure nanomaterials.

Preparation of single-layer antireflective SiO2 coating with broadband transmittance using PEG-modified sol–gel method

Adding polyethylene glycol (PEG) with different molecular weights, a usual acid-catalyzed sol–gel was modified to prepare single-layer antireflective SiO2 coatings with high and broadband transmittance and relatively better hardness. The test results of atomic force microscope and field emission scanning electron microscope show that the addition of PEG significantly affects the porosity and surface morphology of the coating layer. Due to the addition of PEG, the surface of the coatings presents groove-like and their porosity is increased, both of which contribute to the increase in transmittance. In the case of same PEG mass, PEG4000 modified coating has higher porosity and higher transmittance than PEG1000 modified one. In the present paper, the reflectance of samples for both sides was tested by ultraviolet–visible–near-infrared spectrophotometer (LAMBDA 950). The best coating’s reflectance can be decreased below 5 % from 460 to 1,740 nm. The transmittance peak value of the substrate is 90.6 % and its average value is 90.0 %, while the peak value of the best coating can reach up to 99.4 % and its average value is 95.5 % which increased by 5.5 % from wavelength of 325 to 1,000 nm. Hardness measurements show that the coatings have relatively better hardness.

Photocatalytic Activity of TiO<SUB>2</SUB> Nanotubes Doped with Ag Nanoparticles

TiO2 nanotubes formed on the surface of commercially pure titanium were prepared by anodizing processing and were then heat-treated. The silver doping was processed with different molar concentration of AgNO3 aqueous solution. The silver-doped TiO2 nanotubes were characterized using field emission scanning electron microscopy, ultraviolet visible near-infrared spectrophotometer and ampere-volts (I-V) curve system. The 20-100 nm Ag nanoparticles were well doped atop, inside, and between the nanotubes. The I-V curve of the TiO2 nanotubes increased with heat treatment temperature. The silver-doped TiO2 nanotubes with anatase plus rutile phases had better photocatalytic activity.

Structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique

In this work, we report the structural, morphological, and optical properties of TiO2 thin films synthesized by the electro phoretic deposition technique. The TiO2 film was formed on a doped fluorine tin oxide (SnO2:F, i.e., FTO) layer and used as a photo electrode in a dye solar cell (DSC). Using spectroscopic ellipsometry measurements in the 200 to 800 nm wavelengths domain, we obtain a thickness of the TiO2 film in the range of 70 to 80 nm. Characterizations by X-ray diffraction and atomic force microscopy (AFM) show a polycrystalline film. In addition, AFM investigation shows no cracks in the formed layer. Using an ultraviolet–visible near-infrared spectrophotometer, we found that the transmittance of the TiO2 film in the visible domain reaches 75%. From the measured current–voltage or I-V characteristic under AM1.5 illumination of the formed DSC, we obtain an open circuit voltage Voc = 628 mV and a short circuit current Isc = 22.6 μA, where the surface of the formed cell is 3.14 cm2.

Using the near-infrared system to sort various beef middle and end muscle cuts into tenderness categories

The objectives of this study were to determine the effectiveness of a visible-near-infrared (VIS-NIR) system to predict the ultimate tenderness rating of various beef muscles and conclude if a relationship exists between predicted LM shear force and tenderness of other subprimal cuts. Carcasses (n = 768) were scanned with the VIS-NIR system in 2 commercial beef-processing facilities. Carcasses were categorized based on their predicted 14-d LM slice shear force value. After carcass scanning, 100 carcasses were randomly selected based on their tenderness classification, and subprimals (ribeye rolls, clods, knuckles, top sirloins, inside rounds, and eye of rounds) were removed, vacuum-packaged, and transported to the Oklahoma State University Food and Agricultural Products Research Center, where 2.54-cm steaks (n = 6) were fabricated and stored in refrigerated conditions (1 degrees C +/- 1) and aged for 14 d. The center steak from right-side subprimals was designated for slice shear force (LM) or Warner-Bratzler shear force (all other subprimals) analysis. The remaining steaks were categorized based on predicted tenderness taken at 2 d postmortem with the VIS-NIR spectrophotometer and used in a consumer taste study. The test population of carcasses (n = 100) scanned in-plant predicted 27 carcasses as tender, 45 carcasses as intermediate, and 28 carcasses as tough. The VIS-NIR system correctly classified 26 of the 28 (92.9% accuracy) tough carcasses. Overall consumer satisfaction was greatest (P < 0.05) for steaks classified as tender and was intermediate compared with the steaks classified as tough. It was concluded that in-plant VIS-NIR scanning can properly identify and sort carcasses into tenderness groups, which may lead to the development of certified not-tough programs.

Potential of visible and near-infrared spectroscopy to derive colour groups utilising the Munsell soil colour charts

A study was undertaken to investigate the potential of visible (VIS) and near-infrared (NIR) spectroscopy to derive soil colour groups as a new methodology that might assist in soil type classification. A fibre-optic VIS–NIR spectrophotometer (306.5 – 1710.9 nm) was used to measure the light properties in reflectance mode of 342 dry soil samples collected from fields in Belgium and Northern France. The colour of soil samples was measured with the Munsell soil colour charts, dividing soil samples into two groups of 236 and 106 samples belonging to Hue 2.5Y and Hue 10YR, respectively. Factorial Discriminant Analysis (FDA) was performed separately on each Hue data using the first five Principal Components (PCs) of a Principal Component Analysis (PCA) carried out on colour groups defined a priori. Considering the 2.5Y Hue group, soil samples were classified successfully into four colour groups with a correct classification (CC) of 87.3% and 81.8% for the calibration and validation spectra, respectively. Lower accuracy was observed for the 10YR Hue group for classification into three groups, since 79.6% and 75.0% of samples were correctly classified for calibration and validation sample sets, respectively. Establishing four colour groups by combining both Hue groups decreased the classification accuracy considerably. In order to improve the classification accuracy, the first 5 PCs and first 2 PCs of PCA performed on soil spectra and on the total carbon (Tot-C), extractable phosphorous (Ext-P) and texture index (Ti), respectively, were pooled (concatenated) into a signal matrix and analysed newly by the FDA. This led to improvement of the classification results of four Hue 2.5Y groups (CC of 82.1% and 89.1%) and three Hue 10YR groups (CC of 84.1% and 82.4%). However, best concatenation results of four groups for the combination of both Hue groups were obtained when only Tot-C and Ext-P were considered without Ti, obtaining a CC of 84.2% of the validation data sets. This suggests that the VIS-NIR spectroscopy combined with chemometric tools has the potential of identifying different soil colour groups for a large geographical area.

Optimisation of soil VIS–NIR sensor-based variable rate application system of soil phosphorus

Uniform phosphorous fertilisation has economical, ecological and agronomical shortcomings. This study was undertaken to optimise the variable rate (VR) elemental P application using a previously developed on-the-go visible (VIS) and near infrared (NIR) soil sensor. This VIS–NIR sensor consists of a chisel unit, to which the optical unit to detect soil extractable phosphorous (P-ext) was attached. A mobile, fibre-type VIS–NIR spectrophotometer (Zeiss Corona 45 visnir, Germany ) with a measurement range between 305 and 1711 nm was used to measure soil spectra in reflectance mode. On-the-go measurement of soil spectra was carried out in two fields (A and B) situated near Leuven in Belgium. From the spectra, P-ext was calculated in soil and subsequently the required elemental P was determined. Different averaging windows (AW) of the predicted P-ext from successive spectra (2–22) and five recommendation classification intervals (RCI) of elemental P of 20, 10, 5, 2 and 1 kg ha −1 were assigned and tested. The VR of elemental P was compared with uniform rate (UR) application. Results showed that among the five RCIs, the minimum elemental P application rate was for interval of 5 kg ha −1, with small differences of among the different RCIs. In the fields under study, the amount of elemental P fertiliser according to the VR approach was higher than the UR application with an extra elemental P of 4 and 2.38 kg ha −1 for fields A and B, respectively. However, this higher elemental P fertiliser recommendation of VR is only valid when an equal number of samples (1200 in field A and 660 in field B) is considered for both VR and UR methods. Larger amounts of elemental P fertiliser were needed for plots and/or fields having higher variation in measured P-ext. The results also showed that in both fields the application rate decreased with larger AWs. Averaging of less than five P-ext successive values was not a proper choice with any RCIs due to the large deviation between the target and classified elemental P into the different RCIs. The combination of RCI 5 and AW between 10 and 15 is recommended to provide a good matching between uniform and applied elemental P at low cost.

Design and testing of a new high-accuracy ultraviolet–visible–near-infrared spectrophotometer

A new high-accuracy spectrophotometer has been developed at the National Research Council of Canada to measure regular transmittance factors over the spectral range from 200 to 2500 nm. The most significant feature of this automated single-beam instrument is a highly collimated normal-incidence beam geometry, which eliminates the need for polarization corrections or for an averaging sphere for the calibration of regular-transmittance reference materials. The instrument also possesses a large uniformmeasurement beam that minimizes errors caused by sample nonuniformity. We describe the instrument's design and the testing, optimization, and verification procedures that have been carried out for measurements in the visible and near-infrared regions. Systematic errors that have been determined and corrected for include wavelength shifts, stray light, system drift, and nonlinearity. In the visible and near-infrared regions, the overall photometric accuracy is estimated to be 2.5 and 4.0 parts in 10(4), respectively. The wavelength scale is accurate to within +/-0.1 nm with a reproducibility of +/-0.03 nm over its entire design range from 200 to 2500 nm.