Transmission Spectrophotometry Research Articles

Fat Content and Energy Calculation in Pasteurized Human Milk: Comparison Between Infrared Analysis and Creamatocrit Method.

Aims: This study aimed to analyze and compare the quantity of energy and fat using the infrared analysis and creamatocrit method in pasteurized human milk (HM) samples. Methods: This cross-sectional study analyzed 1,858 pasteurized human samples from 317 mothers at a single center. Infrared transmission spectrophotometry (Miris, Human Milk Analyser [HMA], Uppsala, Sweden) and the creamatocrit method were used to evaluate the quantity of energy and fat in pasteurized HM samples. Results: The average age of donor mothers was 29.7 ± 5.1 years, and the median duration of lactation was 22 days (interquartile range [IQ]: 7.7-59.2). Full-term births were observed in 196 (95.1%) of the women. The values of energy (difference: +8.96 kcal/dL, 95% CI: 8.52-9.44 kcal/dL; p < 0.001) and fat (difference: +0.40 g/dL, 95% CI: 0.35-0.45 g/dL; p < 0.001) in HM samples obtained by Miris were higher than those by the creamatocrit method. The energy calculated and the fat measured by Miris in the HM samples correlated moderately and directly with the obtained by creamatocrit (fat, r = 0.585; p < 0.001 and energy, r = 0.591; p < 0.01). The linear regression, adjusted for maternal age and lactation time, showed that the energy values calculated by creamatocrit were directly associated with those of Miris (energy kcal/dL = 38.43 + [0.516 × kcal/dL of creamatocrit]). Conclusion: The energy and fat quantity of pasteurized HM samples obtained by the creamatocrit and infrared methods were significantly correlated. However, the values calculated by the creamatocrit method were significantly lower than those by the infrared analyzer.

Anion Doping of Tungsten Oxide with Nitrogen: Reactive Magnetron Synthesis, Crystal Structure, Valence Composition, and Optical Properties

Anion doping of tungsten trioxide by nitrogen is used to obtain electrochrome cathode materials, the spectral transmittance of which can be controlled by the doping level. A series of samples was synthesized by reactive magnetron sputtering of a metal tungsten target in a mixture of argon, nitrogen, and oxygen gases, the flow rate of the latter was varied at a constant pressure of the gas mixture. Warm-colored tungsten oxynitride films were prepared at higher doping levels with their morphology and elemental composition characterized using scanning electron microscopy, crystal structure described using X-ray diffraction and the valence state of constituents revealed with X-ray photoelectron spectroscopy techniques. Optical properties were measured by making use of transmission spectrophotometry and spectroscopic ellipsometry. These extensive experimental studies revealed an increase in absorption towards shorter wavelengths below the wavelength of 0.5 µm with an increase in the doping level. At the same time, it was found that with an increase in the doping level, partial reduction of the tungsten occurs, and the fraction of non-stoichiometric oxygen steadily increases to half of the total oxygen content. It is a common belief that the imperfection of the doped material facilitates the intercalation of the material by electrolyte ions.

Ordinary and Extraordinary Complex Refractive Indices Extraction of a Mylar Film by Transmission Spectrophotometry.

A new spectrophotometric technique for the determination of both ordinary and extraordinary complex refractive indices (CRIs) of a stretched polyethylene terephthalate (Mylar) film is proposed. The sample was placed between two identical polarizers, and the transmission spectra of two different configurations (incident polarization parallel and perpendicular to the Mylar film optical axis) were recorded. Ordinary and extraordinary complex refractive indices are then extracted by fitting the experimental spectra with a theoretical model that we had elaborated in advance. A new formula for transmittance dispersion, based on the Fresnel’s coefficients formalism and using the Cauchy model, was derived to describe n and κ wavelength dependence. The suggested theoretical model succeeded in reproducing the Mylar transmission spectra across the entire visible spectral range (400, 750 nm) for both configurations, and the retrieved dispersion curves of the refractive indices, extinction coefficients, and the birefringence are comparable to results found in the literature. The proposed method is fast, straightforward, easy to set up, and cost-effective. It proved to be an excellent alternative to more conventional methods such as spectroscopic ellipsometry.

High Refractive Index Silica-Titania Films Fabricated via the Sol-Gel Method and Dip-Coating Technique-Physical and Chemical Characterization.

Crack-free binary SiOx:TiOy composite films with the refractive index of ~1.94 at wavelength 632.8 nm were fabricated on soda-lime glass substrates, using the sol–gel method and dip-coating technique. With the use of transmission spectrophotometry and Tauc method, the energy of the optical band gap of 3.6 eV and 4.0 eV were determined for indirect and direct optical allowed transitions, respectively. Using the reflectance spectrophotometry method, optical homogeneity of SiOx:TiOy composite films was confirmed. The complex refractive index determined by spectroscopic ellipsometry confirmed good transmission properties of the developed SiOx:TiOy films in the Vis-NIR spectral range. The surface morphology of the SiOx:TiOy films by atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods demonstrated their high smoothness, with the root mean square roughness at the level of ~0.15 nm. Fourier-transform infrared (FTIR) spectroscopy and Raman spectroscopy were used to investigate the chemical properties of the SiOx:TiOy material. The developed binary composite films SiOx:TiOy demonstrate good waveguide properties, for which optical losses of 1.1 dB/cm and 2.7 dB/cm were determined, for fundamental TM0 and TE0 modes, respectively.

E‐Beam Evaporation of Silicon: Native Oxidation and Quasicontinuous Tailoring of Optical Properties

An experimental study of native oxidation of silicon during electron beam evaporation is carried out. A set of SiOx thin films is prepared at varying e‐beam current (50–300 mA) without inflow of oxygen gas from external supply. The O:Si stoichiometry ratio of grown SiOx films, as estimated through X‐ray photoelectron spectroscopy (XPS) measurement, is found to be mainly governed by the deposition rate. Optical analysis using transmission spectrophotometry and spectroscopic ellipsometry measurements reveal gradual variation of refractive index (1.58–4.09@650 nm) and bandgap (3.65–1.90 eV) of grown films with the increase in e‐beam current. Such high contrast changes in Si‐based optical materials just by variations of e‐beam current are not reported previously. Deposition rate‐dependent oxidation and optical constants are confirmed by investigating two separate films at lower substrate heights. Finally, utilizing the quasicontinuous variation of optical constants of SiOx films, antireflection (AR) coating is designed and experimentally demonstrated on Si wafer and achieved reflectance loss of ≈2.7% in wavelength range of 400–900 nm. The native oxidation under varying e‐beam current is envisaged to be an effective and a facile method for preparing quasicontinuously tunable silicon‐based optical materials.

Effect of grape seed extract on skin fibroblasts exposed to UVA light and its photostability in sunscreen formulation.

Grape seed extract (GSE) is rich in polyphenolic compounds, particularly (+)-catechin (C) and (-)-epicatechin (EC). Strong antioxidant activity of these compounds makes GSE to be value-added to the cosmetics with anti-aging properties. However, a lack of stability in different environmental conditions makes GSE challenging for the development of photostable cosmetic sunscreen products. To evaluate photoprotective effects of GSE on human dermal fibroblasts irradiated with UVA light and assess photostability of catechins in cream formulations containing GSE alone or in combination with octyl methoxycinnamate (OMC). MTT assay was used to assess protective effects of GSE on fibroblasts irradiated with UVA light. A photostability of C and EC in GSE and in cream formulation containing GSE was investigated using high-performance liquid chromatography and confirmed by reflection and transmission spectrophotometry using Transpore™ tapes and polymethacrylate (PMMA) plates as substrates. High UVA doses damaged fibroblast structure and inhibited their growth. However, GSE increased cell viability and effectively protected them from UVA damage. Photostability of C and EC was achieved by combination of GSE and OMC that also improved absorption capacity of UV filter and increased overall efficacy of formulation. PMMA plates showed better applicability for in vitro photostability testing of sunscreen formulations. However, despite the instability of Transpore® tape under heat from UV exposure, it can still be economically a substrate of alternative choice for screening. GSE can be used as an effective and sustainable natural resource for prevention of UV-induced skin damage providing long-term protection against premature skin aging.

Preparation of amphiphilic Janus SiO2 particles and its application on polyacrylate emulsion

Amphiphilic Janus SiO2 particles were prepared at the liquid-liquid interface by atom transfer radical polymerization (ATRP). The structure of the particles was characterized by contact angle, fluorescent labeling and dynamic light scattering (DLS). The emulsifying ability of the particle was characterized by fluorescent labeling and emulsifying experiment. The results shown that amphiphilic Janus SiO2 particles had good emulsifying ability and the critical micelle concentration was 0.079 mg/mL. The amphiphilic Janus SiO2 particles were used as surfactants to stabilize acrylate monomers, and polyacrylate emulsion was obtained through free radical polymerization. The solid content, conversion rate, infrared spectrum and DLS were characterized. The surface morphology of latex film was characterized by AFM and SEM. The properties of emulsion film were characterized by the video optical contact angle, water absorption and light transmission spectrophotometry. The results shown that the amphiphilic Janus SiO2 particles had good dispersibility and introduction of inorganic particles improved the light transmission, water resistance and mechanical properties of the polyacrylate emulsion film.

The Optical Constants of Solution‐Processed Semiconductors—New Challenges with Perovskites and Non‐Fullerene Acceptors

AbstractAccurate determination of the optical constants of thin film solids has been an ongoing endeavor in optoelectronics and related fields for decades. These constants, namely the refractive index and extinction (or attenuation) coefficient, are the fundamental material properties that dictate electromagnetic field propagation in any medium. They form the inputs to well‐established models that allow for design and optimization of multilayer stack structures such as thin film solar cells, light‐emitting diodes, and photodetectors. These determinations are particularly challenging for materials that are scattering and highly absorbing. In this work, a new and resource‐efficient approach for optical constant determination based upon transmission spectrophotometry in combination with an iterative, reverse transfer matrix model and the Kramers–Kronig relation is reported. The approach is validated using more conventional ellipsometry for a number of functionally important semiconductors, including the recently emergent organic non‐fullerene electron acceptors (NFAs) and perovskites for which the optical constants in the UV–vis–near IR region are provided. Notably, the NFAs are found to present anomalously high refractive indices and extinction coefficients that are predicted to have a profound influence on the cavity electro‐optics of the new record efficiency organic solar cells of which they are key components.

Demonstration of tunable Ag morphology from nanocolumns to discrete nanoislands using novel angle constrained glancing angle EB evaporation technique

In glancing angle electron beam evaporation technique, the deposition geometry has been engineered in a novel manner in this work to produce extensive tunablity of Ag morphology. A physical plate (collimator) parallel to the substrate has been suitably placed in order to constrain the angle of incoming deposition vapor flux. The distance between substrate and this collimator as well as the distance between substrate to crucible orifice has been optimized for maximum variation in Ag morphology which resulted in the discussed tunability. SEM images acquired across the sample surface on the best optimized sample show variation of Ag morphology from nearly continuous film to Ag nanocolumns (dia-135 nm) and then to Ag nanoislands of varying size (26–83 nm) with the variation in height from substrate bottom edge. Surface plasmon resonance (SPR) peak of this Ag nanostructure has been found to shift to longer wavelength and to broaden with the increase of thickness across the substrate surface. The estimated band gap values of the Ag nanostructure are non-zero which reveals its dielectric like dispersion behavior. Thickness and optical constants at various locations on the best optimized sample have been estimated through spectroscopic ellipsometry measurements and the obtained results have been validated with measured transmission spectrophotometry spectra. Three different ellipsometry models have been tried to fit the ellipsometry data of such grown ultrathin film consisting of Ag nanoislands/nanocolumns. An effective media consisting of the mixture of bulk Ag, dielectric media represented by Lorentz oscillator and air was found to be the best to describe the disperision behavior of the deposited Ag film. The dielectric like dispersion behavior of Ag ultrathin film has been ascribed to localized surface Plasmon resonance (LSPR) effect of Ag nanoislands in optical wavelength region. Due to the gradual variation of thickness and optical constants across the film, the optimized film exhibits variation in average optical transmittance (600–1000 nm) from 1.1% to 91% across 40 mm distance which demonstrates its potential for application as variable optical transmission attenuator. Finally, this novel deposition flux constrainment technique has been regarded as an effective method for fabrication of tunable Ag nano-morphologies for optical and surface plasmonic applications.

Quantitative analysis of cefazolin sodium in lyophilized powder by infrared spectrophotometry: Green, low cost, fast and effective.

Cefazolin sodium is a broad-spectrum antibiotic used in the treatment of infectious diseases in humans and in the surgical prophylaxis. Thus, since a considerable number of people have access to this drug, it is of great interest of quality control. The aim of this study was development and validation of a green method by Fourier-Transform Infrared (FT-IR) transmission spectrophotometry for the quantification of cefazolin sodium in lyophilized powder. This technique is widely used in the pharmaceutical industry due to its ease of execution, low cost, safety and high precision and accuracy. It has been employed in the quality control routine of numerous pharmaceuticals in order to identify them and quantify their active principles. The proposed method was completely validated according ICH guidelines, showing selectivity, accuracy, precision, robustness and linearity. It was linear over the concentration range of 0.4-1.7 mg with correlation coefficient 0.999, limits of detection and quantification of 0.017 mg and 0.052 mg, respectively, precise, accurate and robust when changes in the time, pressure and mark of potassium bromide were carried out during the preparation of the pellets. The proposed method was successfully applied to the qualitative and quantitative quality control of cefazolin sodium in lyophilized powder. In addition, the method is considered green, clean and sustainable since it uses only a single reagent; it is a fast, low-cost and environmentally friendly method.

Colorimetric Analysis of Hibiscus Beverages and their Potential Antioxidant Properties.

In food industry, roselle beverages and their subproducts could be functional ingredients since they are an excellent source of bioactive compounds with improved performance due to their important anthocyanins content. The aim of this study was to analyze anthocyanin content and antioxidant properties of aqueous infusions elaborated with color contrasting Hibiscus materials and design a mathematical model in order to predict color-composition relationship. Color measurements of beverages from roselle (Negra, Sudan and Rosa) were made by transmission spectrophotometry, anthocyanins quantification was determined by HPLC, and antioxidant potential was evaluated by in vitro methods (ABTS and FRAP assays). Beverages prepared with particle size minor of 250μm presented until 4- and 2- times more anthocyanins content and antioxidant capacity respectively, in comparison to beverages prepared with powders with particle size major of 750μm. Positive correlations among pigments composition and color parameters were found (p < 0.05), showing that anthocyanins content, antioxidant capacity, C*ab and hab values increased in relation with the smallest particle size of flours. Also, mathematical models were stablished to predict anthocyanin content (r ≥ 0.97) and antioxidant capacity (r ≥ 0.89) from color data; we propose equations for quick estimation of the antioxidant capacity in the Hibiscus beverages with high anthocyanin content. The obtained models could be an important tool to be used in food industry for pigment characterization or functional compounds with potential health benefits.

Effect of oxygen partial pressure in deposition ambient on the properties of RF magnetron sputter deposited Gd2O3 thin films.

Gadolinium oxide is an excellent optical material that offers high transmission in a wide wavelength range of 200-1600nm and exhibits a high bulk refractive index of ∼1.80 at 550nm. In the present study, a set of Gd2O3 thin films has been deposited on fused silica substrates by RF sputtering of a Gd2O3 target under various O2 to Ar flow ratios. The samples have been characterized by grazing incidence x-ray diffraction (GIXRD) to study the long range structural behavior, by GIXR to study density and surface roughness of the films, by atomic force microscopy measurements to study morphological properties, by Rutherford backscattering measurements for compositional studies, and by transmission spectrophotometry and spectroscopic ellipsometry techniques to study their optical properties. It has been observed that the films deposited with 10% oxygen partial pressure have low density, high surface roughness, and high void content, which results in a low value of refractive index of this film, and film quality improves as oxygen partial pressure is further increased. Extended x-ray absorption fine structure measurement with synchrotron radiation has also been employed to extract local structural information around Gd sites, which has in turn been used to explain some of the observed macroscopic properties of the films.

Measuring absorption coefficient of scattering liquids using a tube inside an integrating sphere.

A method for measuring the absorption coefficient μa of absorbing and scattering liquid samples is presented. The sample is injected into a small transparent tube mounted through an integrating sphere. Two models for determining the absorption coefficient using the relative optical output signal are described and validated using aqueous ink absorbers of 0.5 vol.% (0.3 mm-1<μa<1.55 mm-1) and 1.0 vol.% (1.0 mm-1<μa<4.0 mm-1) concentrations with 1 vol.% (μs'≈1.4 mm-1) and 10 vol.% (μs'≈14 mm-1) Intralipid dilutions. The low concentrations give μa and μs values, which are comparable with those of biological tissues. One model assumes a uniform light distribution within the sample, which is valid for low absorption. Another model considers light attenuation that obeys Lambert-Beer's law, which may be used for relatively high absorption. Measurements with low and high scattering samples are done for the wavelength range of 400-900 nm. Measured spectra of purely absorbing samples are within 15% agreement with measurements using standard transmission spectrophotometry. For 0.5 vol.% ink absorbers and at wavelengths below 700 nm, measured μa values are higher for samples with low scattering and lower for those with high scattering. At wavelengths above 700 nm, measured μa values do not vary significantly with amount of scattering. For 1.0 vol.% ink absorbers, measured spectra do not change with low scattering. These results indicate that the method can be used for measuring absorption spectra of scattering liquid samples with optical properties similar to biological absorbers, particularly at wavelengths above 700 nm, which is difficult to accomplish with standard transmission spectrophotometry.

Effect of oxygen partial pressure on properties of asymmetric bipolar pulse dc magnetron sputtered TiO_2 thin films

A set of titanium dioxide thin films have been deposited on fused silica substrates by the novel asymmetric bipolar pulsed dc reactive sputtering technique using different oxygen partial pressures in the sputtering ambient in the range of 0%–21%. For investigating long-range structural properties of the samples, grazing incidence x-ray diffraction (GIXRD) measurements and for probing local structure surrounding Ti sites, extended x-ray absorption fine structure (EXAFS) measurements have been carried out. Optical properties of the films have been investigated by transmission spectrophotometry in UV–visible–near IR range and it has been observed that as oxygen partial pressure in the sputtering ambient is increased, refractive index of the films varies in a nonlinear fashion. Microscopically, it has been found that this nonlinear variation can be explained by the local structure tool EXAFS, while GIXRD which works on average long-range order fails to explain this. Such a variation of optical properties with increase in oxygen partial pressure during deposition of the films is attributed to the competition between the two processes, viz., improvement in the stoichiometry of the films and reduction in the mobility of the adatoms on the surface of the growing films.

English

In this paper the preparation of chitosan nanoparticles was carried out using methacrylic acid (MAA) and studied by both ultraviolet (UV)- visible transmission spectrophotometry and transmission electron microscopy (TEM). Nanoparticles with sizes as small as 17 to 25 nm were achieved. The obtained nanoparticles had a homogeneous morphology showing a quite uniform particles size distribution with a spherical shape. The solution was pH-sensitive, due to swelling and aggregation of the nanoparticles. The use of slow release fertilizer has become a new trend to save fertilizer consumption and to reduce environmental pollution. In this work, chitosan (CS) nanoparticles were obtained for the loading of NPK fertilizers. The stability of the CS-PMAA colloidal suspension was higher with the addition of nitrogen and potassium than with the addition of phosphorus, due to the higher anion charge from the calcium phosphate than the anion charges from the potassium chloride and urea. The mean diameter increase of the CS-PMAA nanoparticles in suspension with the addition of different compounds was P > K > N which indicates that the elements are being aggregated and loaded on the surface of the chitosan nanoparticles. Key words: Nanoparticles formation, chitosan, fertilizers, nanosolution.

A search for methane in the atmosphere of GJ 1214b via GTC narrow-band transmission spectrophotometry★

We present narrow-band photometric measurements of the exoplanet GJ 1214b using the 10.4 m Gran Telescopio Canarias (GTC) and the OSIRIS instrument. Using tuneable filters we observed a total of five transits, three of which were observed at two wavelengths nearly simultaneously, producing a total of eight individual light curves, six of these probed the possible existence of a methane absorption feature in the 8770 - 8850 {\AA} region at high resolution. We detect no increase in the planet-to-star radius ratio across the methane feature with a change in radius ratio of $\Delta$R = -0.0007 $\pm$ 0.0017 corresponding to a scale height (H) change of -0.5 $\pm$ 1.2 H across the methane feature, assuming a hydrogen dominated atmosphere. We find a variety of water and cloudy atmospheric models fit the data well, but find that cloud-free models provide poor fits. These observations support a flat transmission spectrum resulting from the presence of a high-altitude haze or a water-rich atmosphere, in agreement with previous studies. In this study the observations are predominantly limited by the photometric quality and the limited number of data points (resulting from a long observing cadence), which make the determination of the systematic noise challenging. With tuneable filters capable of high resolution measurements (R ~ 600 - 750) of narrow absorption features, the interpretation of our results are also limited by the absence of high resolution methane models below 1 $\mu$m.

Optical transmission photometry of the highly inflated exoplanet WASP-17b★

We present ground-based high-precision observations of the transit of WASP-17b using the multiband photometer ULTRACAM on ESO's New Technology Telescope (NTT) in the context of performing transmission spectrophotometry of this highly inflated exoplanet. Our choice of filters (SDSS u′, g′ and r′ bands) is designed to probe for the presence of opacity sources in the upper atmosphere. We find evidence for a wavelength dependence in the planet radius in the form of enhanced absorption in the SDSS r′ band, consistent with a previously detected broad sodium feature. We present a new independent measurement of the planetary radius at Rpl = 1.97 ± 0.06RJ, which confirms this planet as the most inflated exoplanet known to date. Our measurements are most consistent with an atmospheric profile devoid of enhanced TiO opacity, previously predicted to be present for this planet.

Effect of substrate bias and oxygen partial pressure on properties of RF magnetron sputtered HfO2 thin films

Among all dielectric materials, hafnium oxide qualifies to be one of the most significant candidates as high index optical coating material due to its excellent chemical and thermal stability with SiO2, the low refractive index material, apart from its excellent laser radiation resistance. In this article, microstructural, physical, and optical properties of two sets of hafnium oxide thin films deposited by radio frequency (RF) magnetron reactive sputtering under a mixed ambient of argon and oxygen have been investigated: one set at various oxygen partial pressure and with substrate biasing by 50 W pulse direct current (DC) and another set at similar gaseous ambient as above but without any substrate bias. Structure of all the HfO2 thin films have been found to be monoclinic through grazing incidence x-ray diffraction measurements. Mass density of the samples has been estimated by grazing incidence x-ray reflectivity measurements and compared with the atom density of the samples estimated through Rutherford back scattering study. The evolutions of optical properties of the films with respect to the variation of oxygen partial pressure and substrate biasing have been investigated by transmission spectrophotometry and spectroscopic ellipsometry. It has been observed that RF sputtering with pulse DC substrate bias and with 15–30% oxygen partial pressure in the ambient helps in achieving better quality HfO2 films with low void fraction and high refractive index.

Growth and quality of gallium selenide (GaSe) crystals

High quality nonlinear infrared crystal material GaSe was grown using a seed aided Bridgman–Stockbarger method having a size of 24–26mm in diameter and 55–70mm in length. The crystals were characterized using X-ray diffraction, electron energy scattering, transmission spectrophotometry and infrared microscopy. The transmission spectrum showed that the infrared transmission is about 67% in an 8mm thick sample cleaved along (001) face, and mean absorption 0.01–0.08cm−1 in the range 0.9–15μm. It may be suitable for the fabrication of infrared nonlinear optical devices, photoelectric analyzers of polarized light and so on. Crystals grown by this method with the described procedures may also be useful for other similar layered compounds.

Synthesis and optical properties of poly(N-isopropylacrylamide) nanogel containing silver nanoparticles

Composite nanoparticles representing silver nanoparticle-containing polymer gels have been synthesized. The synthesis comprises two main stages. Initially, monodisperse hydrogel particles with a controlled diameter of approximately 500 nm are obtained by N-isopropylacrylamide polymerization. Then, silver ions are reduced on the surface of the polymer network. Variations in the concentration ratio between reductants and silver nitrate make it possible to produce silver nanoparticles with sizes in a range of 10–30 nm and different packing densities on the gel particle surface. The resultant nanocomposites have been studied by transmission electron microscopy, spectrophotometry, and dynamic light scattering. Depending on the size and packing density of the silver nanoparticles on the polymer particle surface, the plasmon resonance of the nanocomposites varies in a range of 420–750 nm, which determines variations in the color of the colloid from yellow, orange, and red to blue and blue-green. After the inclusion of silver nanoparticles, nanogels of poly(N-isopropylacrylamide) retain their capability for thermosensitive phase transition with a lower critical mixing temperature of 31°C.