NIR Spectrometer Research Articles

Growth, structural, thermal, dielectric and nonlinear optical properties of potassium hexachloro cadmate (IV) a novel single crystal

The Potassium hexachloro cadmate (IV) (PHC) single crystal was grown from the aqueous of the solution by a controlled evaporation method. Single crystal XRD solved the structure. FTIR is used to identify the functional groups of grown crystal. The UV–Vis–NIR spectrometer was used to find out the UV cut off region and to calculate the optical band gap of the Potassium hexachloro cadmate (IV) single crystal. The EDAX spectrum has been used to identify the compounds present in title compound. The TG-DTA profile shows the thermal stability of the grown crystal of Potassium hexachloro cadmate (IV). The Vicker's hardness measurement was used to calculate the material hardness of the title compound. The dielectric loss and constant varied with frequencies and activation energy is also calculated. The solid state parameters like plasma energy, Penn gap, Fermi energy, electronic polarizability using Penn analysis and Clausius-Mossotti equation were also calculated for the title compound. The Z-scan technique is used to calculate the third order nonlinear susceptibility of a real and imaginary part.

Transfer of calibration model between near-infrared spectrometers for hematocrit measurement of grazing cattle

A major concern for the practical use of NIR spectroscopy is calibration transfer. In this study, different ways of calibration transfer were tried and compared to seek the optimal solution for our developed portable NIR spectrometers, which are designed for rapid diagnosis of bovine anemia due to parasites and are believed to be promising to replace the current time-consuming centrifugation way of measuring Hematocrit value (%) for final diagnosis. Our results show the importance of a robust model during the process of calibration transfer. It is risky to transfer a model which is not robust enough by using standardization algorithm.

Comparison the optical properties for Bi2O3 and NiO ultrathin films deposited on different substrates by DC sputtering technique for transparent electronics

Bismuth and Nickel transparent oxides thin films were grown on glass and flexible polyethylene terephalate (PET) substrates by DC sputtering technique at room temperature 300 K. The structures of Bi2O3 and NiO films were analyzed by X-ray diffraction (XRD) analyses and scanning electron microscopy (SEM). A profilometry is used to measure the thicknesses of the ultrathin films. These values were established by a spectro-ellipsometry technique with a new amorphous dispersion model in the range of 200 nm–2200 nm with one nm increment. In addition, the optical constants of these films were investigated using a double beam UV–Vis–NIR spectrometer and a spectro-ellipsometry and compared using the same wavelength range. They present an excellent agreement. According to the optical transmittance spectra of the films a high average transmittance in the visible region of each sample deposited onto different substrates is measured. Moreover, the absorption coefficients and the optical energy gaps for four types of optical transitions (allowed direct, forbidden direct, allowed indirect, forbidden indirect) of the films were determined and compared with the two different techniques. Finally, the nature of the structure and morphology of Bi2O3 and NiO ultrathin films has been analyzed and compared.

Water Structure in Proteins in Solid State Studied by Near Infrared Spectroscopy

Water adsorption in proteins is the crucial process of protein folding and structure stabilizing. Adsorption of water on proteins can be evaluated by near-infrared spectroscopy, a useful technique for observing combination frequency of a water molecule. In this work, albumin, lysozyme, and silk, were used as models for α-helix and β-pleated sheet proteins. Their NIR spectra during water adsorption process were measured by using an NIR spectrometer equipped with a transflectance accessory. Moreover, the quantitative adsorption of water was determined by gravimetric technique. The results indicate that, there are five different NIR absorptions arise from the OH combination frequencies of water adsorbed by albumin in the 5300-5100 cm-1 region. But there are only four absorptions for lysozyme and silk. The OH combination frequencies arising from water molecules in albumin indicate that it acquires free water molecules (5280 cm-1) and adsorbed water molecules through carbonyl-water interactions (5248 and 5160 cm-1) and amino-water interactions (5200 and 5120 cm-1). Interestingly, there is no indication for the presence of free water molecules in lysozyme and silk. Furthermore, the gravimetric results indicate that the rate of water adsorbed follows the order RW.Alb<RW.Lys<RW.Sil and total mass of water adsorbed per gram solid follows the order WAlb<WLys=WSil.

Studies on Dilute Magnetic Semiconducting Co-Doped CdS Thin Films Prepared by Chemical Bath Deposition method

The Co-doped CdS polycrystalline thin films were deposited onto the glass substrates by chemical bath deposition method. All the deposited films were characterized for structural, surface morphology, elemental, optical and magnetic properties using X-ray diffractometer, scanning electron microscopy (SEM), energy dispersive X-ray, UV–Vis. NIR spectrometer and Vibrating sample magnetometer before and after doping. The thin films exhibit hexagonal wurtizite structure with (0 0 2) preferential orientation and the calculated crystallite size is 29 and 18 nm for pristine and Co-doped CdS films respectively. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of Cd, S and Co peaks along with O 1s peak. The studies revealed that the surface Cd atoms of films are found to be bound either to S atoms or O atoms. SEM images showed grainy surface for pristine which gets modified under Co doping. Energy dispersive analysis using X-rays confirmed the presence of Cd, S and Co in the films. From optical transmittance spectra, the bandgap was estimated and found to be varying from 2.4 to 2.27 eV with the increase of Co concentrations. The room-temperature ferromagnetic behavior was exhibited by Co-doped CdS films.

Judd–Ofelt analysis of spectroscopic properties of Sm3+ doped P2O5–SrO glasses

The glass composition P2O5 60%, SrO 40% (mol%) was prepared then doped with Sm3+ with different mol% (3.2, 6.4, 9.6 and 15%). UV–VIS–NIR spectrometer was used to carry out the absorption spectra of the studied glass samples. The most nominal transitions were assigned among a large number of transitions. Then the radiative properties of the Sm3+ ions were calculated using J–O analysis. The results show a large value of Ω2 than the values Ω4 and Ω6. Another parameter such as the oscillator strength, radiative life time, the transition probabilities, the spectroscopic quality and factors branching ratio of several excited states of the Sm3+ ions was calculated. The laser transition level from 6F9/2→6H5/2, the gain cross-section has been predicted. The emission profile of Sm3+ ions in the present glass shows that the peak of the gain coefficient is shifted toward shorter wavelength as the increase of the inversion. The Optical properties introduce this doped Sm3+ glass as a promising candidate for optical applications.

Calibration transfer between different analytical methods

The procedure for transfer of calibration models between different analytical methods is suggested. It is based on the direct standardization (DS) algorithm earlier suggested for data conversion between physically different instruments of the same type. As a result, multivariate regression models obtained e.g. for NIR spectroscopic measurements in one wavelength range can be successfully applied for predictions from the data obtained with another NIR spectrometer in another wavelength range. The performance of the suggested method was tested with two simulated and two real datasets. In the latter case calibration models constructed for energy-dispersive X-ray fluorescence, UV–Vis spectrometry and NIR spectrometry were addressed. The observed performance of the method implies that it can have a broad range of possible applications in analytical chemistry; some of them are suggested in the paper.

Deposition rate dependant formation and properties of Sn2S3 and SnS thin films by co-evaporation

We report the effect of deposition rate on the formation and properties of tin sulfide (Sn2S3 and SnS) thin films prepared by co-evaporation technique. The structural, morphological and optical properties of these films have been investigated as the function of deposition rate. X-ray photoelectron spectroscopy analysis confirmed the transformation of Sn2S3 phase to SnS phase with the increase in deposition rate of tin. The structural analysis by XRD and Raman showed the formation of Sn2S3 and SnS phases. The variation in surface morphology and roughness of the as- deposited films have been examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). UV–Vis–NIR spectrometer was employed to record the transmission spectra of the samples in the wavelength range of 200–3000 nm. Film thickness (d), optical band gap (Eg), refractive index (n) and extinction coefficient (k) of the deposited thin films are estimated from the optical data. Photo conductivity of the as-deposited films has been studied using two probe method. Hall effect measurements show an n-type to p-type conversion in electrical conductivity with increase in deposition rate.

In-situ and real-time monitoring of enzymatic process of wheat gluten by miniature fiber NIR spectrometer

The degree of hydrolysis (DH), peptide content and angiotensin I-converting enzyme (ACE) inhibitory activity of hydrolysates are the three most important indexes for process control in proteins enzymatic hydrolysis and ACE inhibitory peptides preparation. In this study, a miniature fiber optical spectrometer in conjunction with multivariate analysis for in-situ and real-time monitoring of the parameters (DH, peptide content and ACE inhibitory activity) in wheat gluten (WG) hydrolysis process. Synergy interval partial least square (Si-PLS) algorithm was performed to variables selection and the regression model was calibrated. The performance of a model was evaluated by the correlation coefficient (Rp) and the root mean square error (RMSEP) in the prediction set. The results showed that Rp=0.9270, RMSEP=1.73% for DH; Rp=0.9673, RMSEP=0.79mg/ml for peptide content; Rp=0.9507, RMSEP=5.12% for ACE inhibitory. This work demonstrated that miniature fiber optical spectrometer combined Si-PLS model can be used as an alternative method for in-situ and real-time monitoring the enzymatic process of WG.

Synthesis and characterization of Cu2Sn1−xGexS3

Cu2SnS3 (CTS) is a promising compound for use as an absorber layer in thin‐film solar cells because it is made up of low‐cost and abundant elements. However, the band gap energy of 0.94 eV for monoclinic Cu2SnS3 is less than the optimal value for absorber layers in single‐junction solar cells. On the other hand, the band gap energy of Cu2GeS3 (CGS) is approximately 1.5–1.6 eV. Therefore, in this study, we carried out the synthesis of Cu2Sn1−xGexS3, which is a solid solution of Cu2SnS3 and Cu2GeS3. The structure of the prepared samples was investigated using X‐ray diffraction and Raman analyses. Diffuse reflectance spectra were obtained using a UV–Vis–NIR spectrometer and used to estimate the band gap energy. In X‐ray diffraction patterns from the synthesized compounds, the diffraction peaks were found to shift to higher 2θ values with increasing x, indicating a decrease in the lattice constants. In addition, the estimated band gap energy increased from 0.86 to 1.53 eV with increasing x. Cu2Sn1 − xGexS3 is, therefore, a potential candidate for use as the absorber layer in thin film solar cells because its band gap energy can be adjusted simply by varying its composition.

Effect of rapid thermal annealing on optical properties of zinc sulphide thin films

Zinc sulphide (ZnS) thin films were prepared on clean surface glass substrates by thermal evaporation under pressure of 10−5 Torr. Thickness of thin films was uniform 55 nm measured by ellipsometry. These films were also kept into a quartz glass tube for rapid thermal annealing at 30 and 60 s by using a 500 W halogen lamp for crystalline the structure. The cubic structure of the films was verified by X-ray diffraction and the intensity of predominant peak increases with annealing time. The optical absorption study was carried out by UV–ViS–NIR spectrometer in the range of 200–800 nm. The optical band gap changes from 3.48 to 3.08 eV, with rapid thermal annealing. Thermo electric power studies confirm the n-type nature of ZnS thin films and thermoelectric power increases with increase in temperature. This study is important because ZnS is potentially important material for antireflection coating and window layer material in hetero-junction solar cells.

Evaluation of intra-ring wood density profiles using NIRS: comparison with the X-ray method

Pith-to-bark wood density profiling is interesting in forestry science. By comparing it with the X-ray method, this study proved that a fiber optic NIR spectrometer with a high-precision displacement system could accurately measure intra-ring wood density with a spatial resolution of 0.5 mm. Most near-infrared spectroscopy (NIRS) studies for wood density determination use samples that have been pulverized beforehand. Attenuation of ionizing radiation is still the standard method to determine wood density with high spatial resolution. However, there is evidence that NIRS could be an accurate and affordable method for determining intra-ring density in solid wood strips. In this study, we research whether the results published for intra-ring density predictions in wood can be improved when calibrated with X-ray microdensitometry. The measurements were made using a fiber optic probe with a separation between measurement points of 0.508 mm in a range between 1200 and 2200 nm. A total of 4520 density points were used to create partial least squares regression (PLSR). X-ray densitometry data were used as reference values. Twenty PLSR calibrations were randomly executed on 31 samples collected from 28 Pinus radiata D. Don trees. Upon selecting 20 latent variables, the R 2 value was 0.873 for the training group and 0.895 for the validation group, while RMSEP values are 43.1 × 10−3 and 47.1 × 10−3 g cm−3 for the training and validation groups, respectively. The range error ratio (RER) was 13.7. The RER was high and almost in the range suggested for quantification purposes. Results are superior to wood density studies in the literature which do not employ spatial resolution and to those found in studies using hyperspectral imaging.

Rapid discrimination and determination of antibiotics drugs in plastic syringes using near infrared spectroscopy with chemometric analysis: Application to amoxicillin and penicillin

The aim of this study was to investigate near infrared spectroscopy (NIRS) combined to chemometric analysis to discriminate and quantify three antibiotics by direct measurement in plastic syringes.Solutions of benzylpenicillin (PENI), amoxicillin (AMOX) and amoxicillin/clavulanic acid (AMOX/CLAV) were analyzed at therapeutic concentrations in glass vials and plastic syringes with NIR spectrometer by direct measurement. Chemometric analysis using partial least squares regression and discriminative analysis was conducted to develop qualitative and quantitative calibration models. Discrimination of the three antibiotics was optimal for concentrated solutions with 100% of accuracy. For quantitative analysis, the three antibiotics furnished a linear response (R²>0.9994) for concentrations ranging from 0.05 to 0.2 g/mL for AMOX, 0.1 to 1.0 MUI/mL for PENI and 0.005 to 0.05 g/mL for AMOX/CLAV with excellent repeatability (maximum 1.3%) and intermediate precision (maximum of 3.2%). Based on proposed models, 94.4% of analyzed AMOX syringes, 80.0% of AMOX/CLAV syringes and 85.7% of PENI syringes were compliant with a relative error including the limit of ± 15%.NIRS as rapid, non-invasive and non-destructive analytical method represents a potentially powerful tool to further develop for securing the drug administration circuit of healthcare institutions to ensure that patients receive the correct product at the right dose.

Avaliação de espectrômetro NIR portátil e PLS-DA para a discriminação de seis espécies similares de madeira amazônicas

Supervising wood exploitation can be very challenging due to the existence of many similar species and the reduced number of wood identification experts to meet the demand. There is evidence that valuable endangered wood species are being smuggled disguised as other species. Near infrared spectroscopy (NIRS) and chemometrics has been successfully used to discriminate between Amazonian wood species using high resolution instruments. In this study, a handheld spectrometer was evaluated for the discrimination of six visually similar tropical wood species using PLS-DA. Woods of mahogany (Swietenia macrophylla) and cedar (Cedrela odorata), both high value tropical timber species included in Appendixes II and III of the CITES, respectively; crabwood (Carapa guianensis); cedrinho (Erisma uncinatum); curupixa (Micropholis melinoniana); and jatoba (Hymenea coubaril). The data for model development and validation take into account both laboratory and field measurements. Outlier exclusion was performed based on Hotelling T2, residuals Q and errors in the estimated class values. The efficiency rates were higher than 90% for all species, showing that the handheld NIR combined with PLS-DA succeeded in discriminate between these species. These results stimulate the application of handheld NIR spectrometers in the supervision of wood exploitation, which can contribute to the species preservation.

Enhancing the electron transfer and band potential tuning with long-term stability of ZnO based dye-sensitized solar cells by gallium and tellurium as dual-doping

A series of ZnO nanoparticles with Ga and Te dual-doping were successfully synthesized by using a facile sol–gel route, and their performance as the photoanode material in DSSCs was employed for the first time. The effects of simultaneously Ga–Te dopants into ZnO host (GaxTe1-xZnO where the values of x ranging from 0 to 1mol % with increments of 0.25mol %) on the structural, optical, morphological, and compositional properties of the resulting samples were characterized via XRD, Raman, UV–vis–NIR spectrometer, PL, BET, AFM, FE–SEM, EDX, and XPS measurements. The incorporation of Ga–Te enlarges the surface area of the photoanodes, leading to higher dye-loading capability. Moreover, the PL intensity of pure ZnO drastically decreases by Ga–Te dopants, which demonstrates the reduction of oxygen vacancies, indicating the slow recombination of photoinduced charge carriers. Owing to the doping effect of Ga–Te, the energy conversion efficiencies of the DSSCs based on these photoanodes lie in the range of 4.79–7.08%, which is higher than that of pure ZnO (3.53%). This improvement of efficiency can be mainly ascribed to the combined effects of faster electron transport rate, retarded charge recombination, enhanced dye adsorption capability, longer electron lifetime as well as shifted negatively of conduction band edge in dual-doped ZnO films. Furthermore, it is noteworthy that after 1200h, the degraded Ga0.25Te0.75ZnO device still shows 86% of their initial efficiency. This study provides a strategy for constructing self-powered systems using a device such as GaxTe1-xZnO based DSSC described here for the first time.

Comparing the analytical performances of Micro-NIR and FT-NIR spectrometers in the evaluation of acerola fruit quality, using PLS and SVM regression algorithms

The main goal of this study was to investigate the analytical performances of a state-of-the-art device, one of the smallest dispersion NIR spectrometers on the market (MicroNIR 1700), making a critical comparison with a benchtop FT-NIR spectrometer in the evaluation of the prediction accuracy. In particular, the aim of this study was to estimate in a non-destructive manner, titratable acidity and ascorbic acid content in acerola fruit during ripening, in a view of direct applicability in field of this new miniaturised handheld device. Acerola (Malpighia emarginata DC.) is a super-fruit characterised by a considerable amount of ascorbic acid, ranging from 1.0% to 4.5%. However, during ripening, acerola colour changes and the fruit may lose as much as half of its ascorbic acid content. Because the variability of chemical parameters followed a non-strictly linear profile, two different regression algorithms were compared: PLS and SVM. Regression models obtained with Micro-NIR spectra give better results using SVM algorithm, for both ascorbic acid and titratable acidity estimation. FT-NIR data give comparable results using both SVM and PLS algorithms, with lower errors for SVM regression. The prediction ability of the two instruments was statistically compared using the Passing-Bablok regression algorithm; the outcomes are critically discussed together with the regression models, showing the suitability of the portable Micro-NIR for in field monitoring of chemical parameters of interest in acerola fruits.

Feasibility of filter‐based NIR spectroscopy for the routine measurement of olive oil fruit ripening indices

The aim of this work was to apply and validate a NIR spectrometer based on a discrete filter system for the rapid measurement of the moisture, oil, sugar, and phenolic compounds contents of olive oil fruits. The batches of olive oil fruits were collected during seven crop seasons from several farms located in Tuscany and then they were crushed into olive paste. The water content was measured gravimetrically, oil content was measured using the Soxhlet method, sugar content was measured enzymatically and phenolic compound content was measured by HPLC. NIR spectra were recorded from 1400 to 2400 nm at 19 selected wavelengths. Calibration and validation models were processed using PLS regression. In PLS models built for moisture, oil, and sugar contents, the r2 in calibration ranged between 0.90 and 0.93 with low standard error of calibration (SEC) values (i.e. 2.5, 3.6 and 4.0, respectively). For these parameters the standard error of prediction (SEP) and the standard error of laboratory (SEL) values proved to be comparable (i.e. 2.4 vs. 3.2, 6.0 vs. 4.4, and 6.7 vs. 4.7, respectively). Instead, the calibration and validation results concerning the phenolic compounds were not satisfactory, probably because the necessary wavelengths in the section of absorbance from 1100 to 1400 nm were not covered.Practical applications: NIR spectrometers based on discrete filter systems may be interesting since they are cost‐saving compared to the more sophisticated FT‐NIR and NIR‐AOTF instruments (i.e. the cost is approximately half). Our study also showed that with this instrument it was possible to build some effective models for predicting moisture, oil, and sugar contents in olive paste. The results obtained for moisture and oil contents are comparable with those obtained with other spectrometers, and a predictive model was obtained for sugar content for the first time. Instead the tool did not prove suitable for obtaining predictive models for total phenolic compounds or oleuropein contents. The additional use of a filter‐based NIR spectrometer is therefore to be suggested to rapidly monitor olive fruit ripening on the basis of moisture, oil, and sugar contents.The used filter‐based NIR spectrometer, relevant spectra, and calibration‐validation results.

Potential of Near-infrared Spectroscopy to Detect Defects on the Surface of Solid Wood Boards

Defects on the surface of solid wood boards directly affect their mechanical properties and product grades. This study investigated the use of near-infrared spectroscopy (NIRS) to detect and classify defects on the surface of solid wood boards. Pinus koraiensis was selected as the raw material. The experiments focused on the ability to use the model to sort defects on the surface of wood into four types, namely live knots, dead knots, cracks, and defect-free. The test data consisted of 360 NIR absorption spectra of the defect samples using a portable NIR spectrometer, with the wavelength range of 900 to 1900 nm. Three pre-processing methods were used to compare the effects of noise elimination in the original absorption spectra. The NIR discrimination models were developed based on partial least squares and discriminant analysis (PLS-DA), least squares support vector machine (LS-SVM), and back-propagation neural network (BPNN) from 900 to approximately 1900 nm. The results demonstrated that the BPNN model exhibited the highest classification accuracy of 97.92% for the model calibration and 97.50% for the prediction set. These results suggest that there is potential for the NIR method to detect defects and differentiate between types of defects on the surface of solid wood boards.

New post-harvest aproach for high quality fresh ‘Medjhool’ date

In Israel, ‘Medjhool’ has become the major date fruit variety. In a certain ripeness stage they become super succulent, juicy, tasty (“Super Fresh” ‘Medjhool’) and have a high market value compared to regular ‘Medjhool’ dates. At this particular stage, the dates are very difficult to handle (picking up, removing etc.). Harvesting of ‘Medjhool’ dates after having matured but before ripening (Khalal ‘Medjhool’) followed by suitable postharvest treatment to enforce ripening, might provide farmers a method to produce a high quality product. At this pre-ripe stage, dates' total soluble solid (TSS) content varies considerably. The objectives of this study were to find an appropriate post-harvest treatment to produce “Super Fresh” ‘Medjhool’ dates from the Khalal fruits and to develop a method for online sorting of Khalal ‘Medjhool’ dates according to their TSS content using a mini NIR spectrometer. A cells' conveyor, an automatic sorting apparatus and a NIR (850–1880nm) scanning device were designed and constructed, simulating a real sorting operation. Spectral models for TSS prediction were developed, based on Partial Least Squares regression. The root mean square prediction error of TSS was in the range of 0.9–1.6% in the different prediction models. This study establishes the basis for sorting dates for consequent postharvest treatment, using NIR spectroscopy, in the production process of “Super Fresh” ‘Medjhool’ dates.

Multiple receivers in a high-resolution near-infrared heterodyne spectrometer.

The paper describes a modification of a high-resolution heterodyne NIR spectrometer described by Rodin, et al. in Opt. Express22, 13825 (2014), wherein the noise amplitude of the heterodyne signal squared was proportional to the power of the incoherent radiation source (the sun). The addition of a second receiver collecting radiation from the sun into a second single-mode fiber created up to a factor of two increase in detected source power spectrum. The ability to add uncorrelated heterodyne IF signals as Gaussian noise (variance) provides the means by which multiple heterodyne receivers of signal from an incoherent source can increase the detected source power by the same multiple, thus avoiding the limit imposed by the antenna theorem for a single receiver (A. E. Siegman, Appl. Opt.5, 1588 (1966)).