Infrared Transmission Spectroscopy Research Articles

“White” Photoluminescence of Carbon Nаnoclusters Dispersed in Fumed Silica

Fumed silica with specific area of 295 m2/g was carbonized by successive procedures of chemical modification by phenyltrimethoxysilane followed by annealing in inert atmosphere up to 650 oC. Strong ultraviolet and visible photoluminescence was observed in the samples after chemical modification and thermal annealing. Emission, excitation, kinetics and photo-induced bleaching effects were investigated by steady state and time-resolved photoluminescence spectroscopy. Interatomic bonds were studied by infrared transmission spectroscopy. It has been shown that ultraviolet photoluminescence in chemically modified fumed silica is associated with phenyl groups while near ultraviolet and visible emission in annealed samples originates from inorganic pyrolytical carbon precipitates dispersed in silica host matrix. Two types of emission bands were identified depending on the annealing temperature: one is in the near UV and another is in the visible range. The relative contribution of these bands depends on samples preparation. All the obtained results have been compared with those observed in fumed silica carbonized using other carbon precursors and treatment procedures. It has been found that these two bands can be observed irrespective to the carbonization procedure. Based on the emission/excitation analysis of these two bands, as well as on correlations with the synthesis conditions, a structural-energy concept of light-emitting centers has been proposed. According to this model, the light-emitting centers are associated with sub-nanometer carbon clusters that can be bonded or adsorbed on the silica surface. It is assumed that the energy of emission photons is determined by the presence or absence of a chemical bond between the emitting clusters and silica surface. A detailed (S)TEM-EELS study has been performed to check these points. By doing so, we have confirmed the presence of 2-6 nm carbon nanoclusters, which are not evenly distributed at the surface of the silica nanoparticles. These carbon nanoclusters are mostly amorphous although they possess some degree of graphitization and local order; the fraction of sp2 carbon in these nanoclusters has been estimated to be close to 80 %. Spectral distribution of light emission in visible range of black body at 6000 K (corresponding to natural day-lighting) and PL of the samples annealed at 600 oC (excitation 355 nm) is almost identical. Spectral properties of the emission (in terms of RGB concept - correlated color temperature) can be easily tuned by variation of synthesis procedure. Such light emission properties of environment friendly single component phosphor make them very attractive for artificial white light sources like white LEDs with near-UV excitation or compact fluorescent lamps.

Design of non-invasive glucose meter using near-infrared technique

Diabetics need to keep track of their blood glucose level and measure it regularly to determine their insulin dose intake and to ensure that glucose level is always within the normal range. In this article, a system that enables the measurement of blood glucose level non-invasively is designed. This article uses a near infra-red (NIR) transmittance spectroscopy, without drawing blood, puncturing the skin, or causing pain. It involves a light source and light detector circuits positioned on a certain region of the body. The attenuated received infra-red signal by the detector is a measure of the blood glucose level of that region. Data are collected from the receiving circuit and sent to a microcontroller using CoolTerm application, then exporting it to Excel Sheet, in which mean values and graphs are obtained. The performance of the circuit with and without Filtering is examined. A downward pattern was noticed, as the glucose concentration in the solution increased, the voltage output decreased, meaning that a less intensity light was detected by the receiving circuit. An improvement in the accuracy of measurements by 17% was achieved, when a notch filter is implemented to cut the voltage components corresponding to the power line noisy signals.

Distribution of Te Inclusions in CdMnTe Crystal Grown by Traveling Heater Method

This study investigated Te inclusions in CdMnTe crystals grown by the traveling heater method (THM). Three CdMnTe ingots were grown under different growth temperatures of 850°C, 900°C, and 950°C by the THM method. In the CdMnTe ingots, the concentration of Te inclusion was lower in the middle-to-deposit part, and the size of Te inclusions kept growing till the last-to-deposit part. The concentrations of Te inclusions along the CdMnTe ingots were in the range of 104–106 cm−3, with the size in the range of 3–16 μm. CdMnTe crystals grown under 900°C had the lowest density and size of Te inclusion, due to the smooth and near-planar growth interface as revealed by infrared (IR) transmission microscopy. The relationship between the origin of Te inclusions and growth interface was analyzed during the THM growth of CdMnTe. IR transmission spectrometry was used to characterize Te inclusions in CdMnTe crystals. Current–voltage (I–V) and energy response measurements were carried out to reveal the resistivity (ρ) and energy resolution of CdMnTe detectors. The effects of Te inclusions on the optical and electrical properties of CdMnTe crystals for nuclear detector applications are discussed.

Nondestructive Measurement of Hemoglobin in Blood Bags Based on Multi-Pathlength VIS-NIR Spectroscopy

Hemoglobin concentration is an indicator for assessing blood product quality. To measure hemoglobin concentration in blood products without damaging blood bags, we proposed a method based on visible-near infrared transmission spectroscopy. Complex optical properties of blood bag walls result in measurement irregularities. Analyses showed that the slope of the light intensity-pathlength curve was more robust to the influence of the blood bag wall. In this study, the transmission spectra of red blood cell suspensions at multiple optical pathlengths were obtained, and the slopes of logarithmic light intensity-pathlength curves were calculated through curve fitting. A nondestructive measurement of hemoglobin content was achieved by using a regression model correlating slope spectra and hemoglobin concentration. Sixty samples with hemoglobin concentrations ranging from 72 to 161 g/L were prepared. Among them, 40 samples were used as a calibration set, and the remaining 20 samples were used as a prediction set. The determination coefficient of the prediction set was 0.97, with a mean square error of 2.78 g/L. This result demonstrates that a non-destructive measurement of hemoglobin levels in blood bags can be achieved by multiple-pathlength transmission spectroscopy.

Synthesis of Nickel Nanoparticles by the Reduction of Its Salts Using the Modified Polyol Method in the Presence of Sodium Polyacrylates with Various Molecular Weights

Nickel nanoparticles were synthesized by the reduction of its salts by hydrazine hydrate in a polyol medium in the presence of sodium polyacrylates with molecular weights of 1200, 5100, and 8000. The nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, IR spectroscopy, and thermogravimetric analysis. The effect of the synthesis conditions, such as temperature, molecular weight of sodium polyacrylate, and polyol and precursor types, on the reduction products were studied. It was shown that the average particle sizes, their aggregation and polydispersity degrees increase as the polymer molecular weight increases.

Application of transmission infrared spectroscopy and partial least squares regression to predict immunoglobulin G concentration in dairy and beef cow colostrum.

The objective of this study was to explore the potential of transmission infrared (TIR) spectroscopy in combination with partial least squares regression (PLSR) for quantification of dairy and beef cow colostral immunoglobulin G (IgG) concentration and assessment of colostrum quality. A total of 430 colostrum samples were collected from dairy (n = 235) and beef (n = 195) cows and tested by a radial immunodiffusion (RID) assay and TIR spectroscopy. Colostral IgG concentrations obtained by the RID assay were linked to the preprocessed spectra and divided into combined and prediction data sets. Three PLSR calibration models were built: one for the dairy cow colostrum only, the second for beef cow colostrum only, and the third for the merged dairy and beef cow colostrum. The predictive performance of each model was evaluated separately using the independent prediction data set. The Pearson correlation coefficients between IgG concentrations as determined by the TIR-based assay and the RID assay were 0.84 for dairy cow colostrum, 0.88 for beef cow colostrum, and 0.92 for the merged set of dairy and beef cow colostrum. The average of the differences between colostral IgG concentrations obtained by the RID- and TIR-based assays were -3.5, 2.7, and 1.4 g/L for dairy, beef, and merged colostrum samples, respectively. Further, the average relative error of the colostral IgG predicted by the TIR spectroscopy from the RID assay was 5% for dairy cow, 1.2% for beef cow, and 0.8% for the merged data set. The average intra-assay CV% of the IgG concentration predicted by the TIR-based method were 3.2%, 2.5%, and 6.9% for dairy cow, beef cow, and merged data set, respectively.The utility of TIR method for assessment of colostrum quality was evaluated using the entire data set and showed that TIR spectroscopy accurately identified the quality status of 91% of dairy cow colostrum, 95% of beef cow colostrum, and 89% and 93% of the merged dairy and beef cow colostrum samples, respectively. The results showed that TIR spectroscopy demonstrates potential as a simple, rapid, and cost-efficient method for use as an estimate of IgG concentration in dairy and beef cow colostrum samples and assessment of colostrum quality. The results also showed that merging the dairy and beef cow colostrum sample data sets improved the predictive ability of the TIR spectroscopy.

The profile of the bending mode band in solid CO2

Context. Solid carbon dioxide (CO2 ) is one of the most abundant species detected in icy grain mantles in dense molecular clouds. Its identification is based on the comparison between astronomical and laboratory spectra. In the past 30 yr the profile of solid CO2 infrared absorption bands has been extensively studied experimentally, however, the debate on the structure (amorphous versus crystalline) of CO2 samples obtained in laboratory by the thin-film technique is still open.Aims. The aim of this work is to investigate if the presence of the double peak feature in the profile of the CO2 bending mode band is related to the crystalline or amorphous structure of the sample.Methods. We performed new laboratory experiments depositing CO2 under ultra high vacuum (UHV) conditions at 17 K. We investigated, using infrared transmission spectroscopy, the influence of various experimental parameters on the profile of the CO2 bands, namely deposition rate, sample thickness, annealing, and presence of H2 O, CH3 OH or CO co-deposited with CO2 . Results. We found that, within experimental uncertainties, under UHV conditions the profile of the CO2 bands in pure solid samples does not depend on the deposition rate or the sample thickness in the ranges investigated. In all cases the bending mode band profile shows a double peak (at 660 and 655 cm-1 ). The spectra also show the Fermi resonance features that cannot be active in crystalline samples. On the other hand, when a small fraction of H2 O or CH3 OH is co-deposited with CO2 the double peak is not observed while it is observed when a CO2 :CO mixture is considered. Furthermore, we measured the density of solid CO2 and the refractive index (at 543.5 nm) at 17 K and at 70 K: ρ (17 K)= 1.17 g cm-3 , ρ (70K)= 1.49 g cm-3 , n (17K)= 1.285, and n (70K)= 1.372. Conclusions. Our experimental results indicate that the presence of the double peak in the profile of the bending mode band is not an indication of a crystalline structure of the sample and they do not exclude the presence of amorphous solid CO2 in space.

IR spectroscopy analysis of pancreatic lipase-related protein 2 interaction with phospholipids: 2. Discriminative recognition of various micellar systems and characterization of PLRP2-DPPC-bile salt complexes

The interaction of pancreatic lipase-related protein 2 (PLRP2) with various micelles containing phospholipids was investigated using pHstat enzyme activity measurements, differential light scattering, size exclusion chromatography (SEC) and transmission IR spectroscopy. Various micelles of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and lysophosphatidylcholine were prepared with either bile salts (sodium taurodeoxycholate or glycodeoxycholate) or Triton X-100, which are substrate-dispersing agents commonly used for measuring phospholipase activities. PLRP2 displayed a high activity on all phospholipid-bile salt micelles, but was totally inactive on phospholipid-Triton X-100 micelles. These findings clearly differentiate PLRP2 from secreted pancreatic phospholipase A2 which is highly active on both types of micelles. Using an inactive variant of PLRP2, SEC experiments allowed identifying two populations of PLRP2-DPPC-bile salt complexes corresponding to a high molecular weight 1:1 PLRP2-micelle association and to a low molecular weight association of PLRP2 with few monomers of DPPC/bile salts. IR spectroscopy analysis showed how DPPC-bile salt micelles differ from DPPC-Triton X-100 micelles by a higher fluidity of acyl chains and higher hydration/H-bonding of the interfacial carbonyl region. The presence of bile salts allowed observing changes in the IR spectrum of DPPC upon addition of PLRP2 (higher rigidity of acyl chains, dehydration of the interfacial carbonyl region), while no change was observed with Triton X-100. The differences between these surfactants and their impact on substrate recognition by PLRP2 are discussed, as well as the mechanism by which high and low molecular weight PLRP2-DPPC-bile salt complexes may be involved in the overall process of DPPC hydrolysis.

Surfactant dependence on physicochemical properties of magnetite nanoparticles

In presented paper magnetite nanoparticles (MNP), with various types of surface stabilizers has been fabricated. Nanostructures were obtained by thermal decomposition of Fe(acac)3 precursor in organic solutions. Five types of long-chain carboxylic acids and four types of amines were used for stabilization of nanoparticles. It was also tested, how surfactant concentration influences on the nanoparticles morphology and its properties. Obtained nanoparticles were examined by X-ray diffraction, Transmission Electron Microscopy and Infrared spectroscopy. Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy and Vibrating Sample Magnetometry. Magnetization and Mössbauer measurements show how stabilizer layer influence the magnetic state of particles. It has been analyzed the importance of the CC chain length, its spatial configuration or compound properties on magnetic state of the particles for few examples. From tested agents as a best, giving most even in shape and well distributed nanoparticles, hexylamine was selected.

Technical note: Feasibility of near infrared transmittance spectroscopy to predict cheese ripeness

The aim of the study was to evaluate the feasibility of near infrared (NIR) transmittance spectroscopy to predict cheese ripeness using the ratio of water-soluble nitrogen (WSN) to total nitrogen (TN) as an index of cheese maturity (WSN/TN). Fifty-two Protected Designation of Origin cow milk cheeses of 5 varieties (Asiago, Grana Padano, Montasio, Parmigiano Reggiano, and Piave) and different ripening times were available for laboratory and chemometric analyses. Reference measures of WSN and TN were matched with cheese spectral information obtained from ground samples by a NIR instrument that operated in transmittance mode for wavelengths from 850 to 1,050 nm. Prediction equations for WSN and TN were developed using (1) cross-validation on the whole data set and (2) external validation on a subset of the entire data. The WSN/TN was calculated as ratio of predicted WSN to predicted TN in cross-validation. The coefficients of determination for WSN and TN were >0.85 both in cross- and external validation. The high accuracy of the prediction equations for WSN and TN could facilitate implementation of NIR transmittance spectroscopy in the dairy industry to objectively, rapidly, and accurately monitor the ripeness of cheese through WSN/TN.

The Electric Field Standing Wave Effect in Infrared Transmission Spectroscopy.

When band ratios in infrared absorbance spectra of films are compared (which had been converted from transmittance spectra), it can be noted that even after background correction and removal of interference fringes these band ratios change with the thickness of the films. The main goal of this work is to show that this effect is a consequence of an electric field standing wave based on the coherent superposition of light waves in the film. We further investigate how transmittance and reflectance, as well as absorbance and the (from absorbance) regained index of absorption, depend on the thickness of the film and how these parameters influence the positions of bands. We compare the results with those for the incoherent case and the case where a single pass of light through the film without reflection loss is assumed.

Studies on removal of phenol sulfonic acid-syntan in aqueous medium using ozonation

ABSTRACTThe removal of phenol sulfonic acid-syntan (PSAS) in terms of chemical oxygen demand (COD) was studied at different pH, ozone and initial PSAS concentrations and the optimum condition was found to be pH 7, ozone concentration of 5.2 × 10−3 mmol/L and initial PSAS concentration of 500 mg/L. The increase in BOD5/COD ratio confirmed the bio-treatability of ozonated PSAS effluent. The excitation–emission matrix intensity and Fourier transmission infra-red spectroscopy confirmed the generation of intermediate by-product during degradation of PSAS. The ozonation of PSAS was found to obey fast regime pseudo-first-order reaction with a rate constant of 3.7 × 10–9 mol−1 s−1. The mean oxidation state of carbon value between +2 and +3 confirmed that the ozonation of PSAS resulted in partial mineralization.

Composite Fibers Based on Cellulose and Tetraetoxysilane: Preparation, Structure and Properties

A method for producing cellulose-based composite fibers with the addition of tetraethoxysilane (TEOS) with a high degree of dispersion of the additive in the cellulose matrix through a “solid phase” dissolution step of the cellulose in N-methylmorpholine-N-oxide (NMMO) is proposed. Investigation of the phase state and morphological features of mixtures of cellulose solutions with TEOS additives in NMMO has shown that in the entire range of concentrations studied, the solutions are biphasic emulsions, and their dispersity and the shape of dispersed phase droplets depend on the prehistory of solution preparation. It is established that the rheological behavior of cellulose solutions with TEOS additives varies depending on the amount of the additive. A theory about a mechanism for changing the rheological behavior of cellulose solutions with TEOS is formulated. X-ray diffraction analysis, scanning and transmission microscopy and IR spectroscopy were used to characterize the structure and morphology of composite fibers. The mechanical properties of composite cellulose fibers with TEOS are investigated.

Fibrillar assembly of bacterial cellulose in the presence of wood-based hemicelluloses

Composite materials mimicking the plant cell wall structure were made by culturing cellulose-producing bacteria together with secondary-wall hemicelluloses from wood. The effects of spruce galactoglucomannan (GGM) and beech xylan on the nanoscale morphology of bacterial cellulose were studied in the original, hydrated state with small-angle X-ray scattering (SAXS). The SAXS intensities were fitted with a model covering multiple levels of the hierarchical structure. Additional information on the structure of dried samples was obtained using scanning and transmission electron microscopy and infra-red spectroscopy. Both hemicelluloses induced a partial conversion of the cellulose crystal structure from Iα to Iβ and a reduction of the cross-sectional dimensions of the cellulose microfibrils, thereby affecting also their packing into bundles. The differences were more pronounced in samples with xylan instead of GGM, and they became more significant with higher hemicellulose concentrations.

Prediction of minerals, fatty acid composition and cholesterol content of commercial cheeses by near infrared transmittance spectroscopy

Prediction models for the mineral, fatty acid (FA) and cholesterol contents of commercial European cheeses using near infrared transmittance spectroscopy were developed. Cheese samples (n = 145) were from different dairy species and ripening time. Sample spectra were matched with mineral, FA and cholesterol reference data to develop prediction models. Modified partial least squares regressions were validated through cross-validation procedure on the complete dataset (n = 145) and through external validation after dividing the data into calibration (74%) and external validation (26%) sets. Satisfactory models were developed for Ca, P, S, Mg and Zn, and for FA groups (saturated, unsaturated, monounsaturated and polyunsaturated FAs), major FAs (myristic, palmitic and oleic acids) and some minor FAs, whereas cholesterol content could not be predicted with adequate accuracy. Results of the present study are a precursor to at-line utilisation of prediction models for the most abundant cheese minerals and FAs at an industry level.

Phytochemical profile, antimicrobial potential and GC-MS analysis of wild variety of Olea Europaea (Olive) cultivated in Pakistan

Olive plant produces a variety of bioactive molecules and thus has important medicinal value in folk medicine. In this study, different leaf and fruit extracts of Pakistani wild variety of Olea europaea was tested for their phytochemical content, antimicrobial activity and mass spectrometric analysis. Olive leaves and fruit samples were extracted with five different solvents to obtain the crude extract and screened for various kinds of phytochemicals. Phytochemicals were further confirmed through Fourier Transmission Infra-red Spectroscopy (FTIR).The plant extract showed significant antimicrobial activity against all the strains tested. Methanol, ethanol and ethyl acetate extracts were found more effective against most of the pathogenic bacteria with high zone of inhibition. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed that olive fruits have Oleic acid, Palmitic acid, Linoleic acid, Octadecadienoic acid, Stearic acid, Palmitoleic acid and Tridecanoic acid as oil contents. In this work, the antimicrobial potential and phytochemical contents were explored which may further pave the way for the bio-industrial applications. Keywords: Olea europaea; Phytochemical content; Antimicrobial activity; GC-MS analysis http://dx.doi.org/10.19045/bspab.2017.60032

Unsaturated-compound hydrogenation nanocatalysts based on palladium and platinum particles immobilized in pores of mesoporous aromatic frameworks

Heterogeneous catalysts for the hydrogenation of unsaturated hydrocarbons have been synthesized on the basis of palladium and platinum nanoparticles immobilized in pores of mesoporous aromatic frameworks, which represent a new class of carbon supports with a diamond-like ordered structure. The resulting materials have been characterized by transmission electron microscopy, IR spectroscopy, and NMR spectroscopy. It has been shown that the catalyst activity in the hydrogenation reaction depends on the substrate molecule size and adsorbability on the surface of nanoparticles. Catalytic activity has been studied in the hydrogenation of a number of unsaturated compounds at temperatures of 60 and 80°C and pressures of 1.0 and 3.0 MPa.

Noninvasive and Label-Free Sensing of Endotoxin Contamination in Ophthalmic Viscosurgical Devices Using a Fiber-Optic Fourier-Transform Infrared Spectroscopy Based Method

Ophthalmic viscosurgical devices (OVDs) are essential medical tools for ophthalmic surgeons to use routinely in cataract surgery. OVD endotoxin contamination has been implicated in toxic anterior segment syndrome, a severe inflammatory condition after surgery. Current standard methods for endotoxin detection in medical devices rely on dwindling Horseshoe Crab resources for Limulus amoebocyte lysate assay or rabbit intracameral and intravitreal assays. Endotoxin recovery from OVDs poses particular challenge due to the nature and composition of the device. In the present proof-of-concept study, we demonstrate real-time detection capability of endotoxin by employing a noncontact and label-free fiber-optic Fourier transform infrared transmission spectroscopy based sensing method in the midinfrared spectral range of 1.6–12 μm. We performed testing on OVD samples spiked with a series of different concentrations of endotoxin. The study suggested that endotoxin contamination in OVD might be associated with fingerprint spectral peak shift in the wavenumber ranges of $\text{2925}- \text{2890}\,\text{cm}^{- 1}$ and $\text{1125}-\text{1100}\,\text{cm}^{- 1}$ , and the distance of shifting is dependent upon endotoxin concentration in OVD. FO-FTIR integrated with multivariate approaches such as hierarchical clustering and principal component analysis provides significant differentiation of OVD, endotoxin, and contaminated OVD at different concentrations.

Positioning in spectral measurement dominates estimation performance of internal rot in onion bulbs

The feasibility of visible and near infrared (VIS/NIR) transmittance spectroscopy for nondestructive discrimination of healthy and diseased onion bulbs was examined. Rottenness occurring in inner scales that were hard to diagnose by the five human senses was targeted. First, VIS/NIR spectra were acquired for six bulb positions. Subsequently, the degree of rot was measured by visual inspection of vertically cut surface based on our proposed criteria and by weighing of sectioned rotted parts. Our evaluation criteria functioned as an alternative mode of the weighing method. The basal plate of onion bulb had remarkable scattering properties. Therefore, spectral features differed not only by the rot levels but also by positioning the bulb against the sensor setup. The partial least squares regression model developed from the longitudinal position, for which the basal plate did not overlap against the system optical axis, showed the best performance and classified rotted bulbs above level 1 with 98.4% accuracy. Absorbance below 736nm was the informative region for bulb rottenness detection.

Quantitative analysis of electronic absorption of phosphorus donors in diamond

In this work, phosphorus donors in diamond have been investigated by means of Fourier Transform Infra-Red (FTIR) transmission spectroscopy on a series of fully-characterized homoepitaxial layers. Low-temperature FTIR absorption spectra have been obtained for concentrations of donors in the range ND=3.7×1016–3.5×1018cm−3 and compensating acceptor impurities in the range NA=2.3×1016–3.0×1018cm−3. The absorption spectra is shown to exhibit two peaks at 4220cm−1 and 4540cm−1 corresponding to electronic transitions from the ground state to the 2p0 and 2p± excited states, respectively, of phosphorus donors in the neutral state of charge. The intensity of the most intense peak at 4540cm−1 is found proportional to ND-NA over two decades. The absorption cross-section of the corresponding transition is deduced providing a calibration law for the determination of ND-NA in phosphorus-doped diamond. Furthermore, the linewidth of the peak exhibits a linear variation with the compensating acceptor concentration, interpreted as the effect of the distribution of ionized impurities. The use of the non-destructive and contact-less FTIR optical method is finally discussed to determine the compensation ratio in phosphorus-doped diamond.