Total Reflection Method Research Articles

SPECTRA OF ATTENUATED TOTAL REFLECTION OF NITRIDED SiO2/Si STRUCTURES

We studied the behavior of nitrogen in silicon dioxide films on single-crystal silicon substrates by the attenuated total reflection (ATR) method and time-of-flight secondary ion mass spectrometry. Nitrogen was introduced into a dielectric formed by pyrogenic oxidation at a temperature of 850 ºС in an atmosphere of wet oxygen by implantation of N+ ions with an energy of 40 keV at doses of 2.5‧1014 and 1.0‧1015 cm–2,
 followed by rapid thermal annealing at a temperature of 1000 or 1050 ºС with a duration of 15 s in air. Nitridization of some of the samples was carried out during thermal annealing in a nitrogen atmosphere with the addition of a small amount of oxygen at a temperature of 1200 ºС for 120 minutes. It is established that during heat treatments, the majority of nitrogen atoms diffuse to the SiО2/Si interface and accumulate in the near-boundary region of the oxide. The ATR spectra show an absorption band with maxima at ~2320 and 2360 cm–1, which is probably due to vibrations of double cumulative bonds of the O=Si=N− type. The formation of these bonds is due to the interaction of nitrogen with dangling bonds at the silicon-dielectric interface, as a result of which uncompensated or strained bonds are replaced by more stable ones. The resulting stronger chemical bonds prevent charge accumulation on the surface of the SiО2/Si interface.

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Application of the total internal reflection method for the study of liquid-phase medium based on botulinum toxin

Application of the total internal reflection method for the study of liquid-phase medium based on botulinum toxin

Evaluation of Changes in Polymer Material Properties Due to Aging in Different Environments.

With the increase in awareness of the importance of engagement in physical activities, high requirements have been placed on polymers intended for use in sports. A number of authors investigated the influence of aging factors on the performance of the polymer. Still, there is a lack of aging protocols that would be product-centered, especially when high performance is imperative. This paper presents a new approach to polymer aging and examines the change of the identified set of properties due to aging under different conditions, and the duration of each (topography, thickness, moisture management, elongation, and bursting force). The results of the testing revealed the increase in thickness due to exposure, especially to the sun-exposed materials. The ability of materials to elongate until the moment of rupture decreases due to exposure to the sun (strong relationship to the time of exposure; R2 reaches 0.99) and the bursting force (up to 6.8%). Furthermore, results indicate the significantly impaired capacity of the polymer material to absorb moisture. The results of measurements indicated (derived) by spectroscopic studies, based on the ATR-FTIR (attenuated total reflectance) method, showed that there was no detectable influence of aging in the sun or shade on the chemical structure of polyester samples.

Research on the Quality of Asphalt Pavement Construction Based on Nondestructive Testing Technology

In order to better evaluate the construction quality of asphalt pavement, nondestructive testing techniques are used to inspect newly paved asphalt mixture pavement. The proposed system for the evaluation of asphalt pavement construction quality uses three-dimensional ground-penetrating radar (GPR) and a non-nuclear density gauge. The GPR and the non-nuclear density gauge test results were used to establish a dielectric constant–porosity model by fitting. This approach can more accurately determine the dielectric constant selection scheme of the GPR based on the average value of every 10 dielectric constant data points in the length direction of the radar antenna and every three data channels in the width direction. The GPR collected the dielectric constants of the road surface based on the total reflection method and used the average value of the local dielectric constant to evaluate the construction quality of the road. The non-nuclear density gauge used the local porosity to assess the construction quality of the road. It is recommended that the two testing schemes described above be used to evaluate the quality of asphalt pavement construction. They can provide theoretical guidance for future applications in practical processes.

Numerical approach to design the graphene-based multilayered surface plasmon resonance biosensor for the rapid detection of the novel coronavirus

In this article, a graphene-based multilayered surface plasmon resonance (SPR) biosensor of (BK7/WS2/Au/BaTiO3/Graphene) is proposed for the rapid detection of the novel coronavirus (COVID-19). The proposed SPR biosensor is designed based on the angular interrogation attenuated total reflection (ATR) method for rapid detection of the COVID-19 virus. The sensor’s surface plasmon polaritons (SPPs) and the sensing region refractive index (RI) are changed, owing to the interaction of various concentrated ligand-analytes. The specific ligand is mechanized with the proposed sensor surface and the target analyte that has flowed onto the sensing surface. The proposed sensor is capable of detecting the COVID-19 virus rapidly in two different ligand-analytes environments, such as: (i) the virus spike receptor-binding domain (RBD) as an analyte and monoclonal antibodies (mAbs) as a probe ligand, and (ii) the monoclonal antibodies (IgG or IgM) as an analyte and the virus spike RBD as a probe ligand. Due to the binding of the target ligand-analytes, the concentration level of the sensing region is incremented. As the increment in the concentration level, the RI of the sensing medium increases, therefore the change in RI causes the shift in the SPR angle resulting in the output reflectance intensity. The performance of the multilayered SPR sensor is analyzed numerically using the finite element method (FEM) method. Numerically, the proposed sensor provides the maximum angular shift sensitivity at 230.77 deg/refractive index unit (RIU), detection accuracy (DA) at 0.161 deg−1, and the figure of merits (FOM) is at 37.22 RIU−1. In addition, with each additional graphene layer number (L), the proposed sensor exhibits the angular shift sensitivity increment (1 + 0.7L) times. The novelty of the proposed multilayer (BK7/WS2/Au/BaTiO3/Graphene) sensor is highly angular sensitivity, and capable of detecting the COVID-19 virus rapidly without a false-positive report.

Identification Methods for Pseudo-crystalline Polymorphs of Thiamine Chloride Hydrochloride, Which Transform Easily Depending on the Handling Environment

Three forms of pseudo-crystalline polymorph of thiamine chloride hydrochloride are dependent on hydration states. We investigated how the measurement environment affects the transition of the pseudo-crystalline polymorph, and aimed to establish a reliable method of identifying the forms clearly by IR spectrophotometry. We prepared three pseudo-crystalline forms and compared their IR spectra. In the IR spectra obtained by the potassium chloride (KCl) disk method, Form II was identified based on its characteristic absorption, but Forms I and III could not be distinguished clearly. Form I transformed to Form III after mixing with undried KCl powder, and Form III transformed to Form I by simply being left in the laboratory environment. These results suggested that the reversible transformation between Forms I and III occurred depending on the hydration status during the process of measurement, as measured by the shift in the absorption wavenumber of the primary alcohol stretching vibration. In addition, Forms I and III could not be distinguished clearly by the X-ray powder diffraction and their crystalline forms were similar plate crystals. However, in the IR spectra by the attenuated total reflection (ATR) method, the three forms could be identified based on each characteristic absorption. In summary, the ATR method does not require pretreatment for sample analysis, can be performed quickly, and is thus suitable to identify crystalline polymorph forms such as pseudo-crystalline polymorphs of thiamine chloride hydrochloride, which transform easily depending on the hydration status in a measurement environment.

Combination of Digital Image Processing and Statistical Data Segmentation to Enhance SPR and SPRi Sensor Responses

The work reports the combination of basic digital image processing (DIP) techniques and statistical segmentation strategy (SDS) to improve surface plasmon resonance curve (SPRc) and SPR imaging (SPRi) sensors' performance. The SPR image is used for sensing and monitoring biological events in the so-called SPR imaging process. In the traditional SPR process based on the attenuated total reflection (ATR) method, the image is used to create the SPR curve, and the curve features tracking is employed on sensing applications. The SPR curve features are enhanced after the pixels of the SPR image have been processed with low-complexity filters in the spatial domain (brightness, contrast, threshold, and morphological). The bootstrap was used as a statistical processing approach, selecting lines and columns from the image that was less affected by imperfections and noises in the image detector, and consequently reducing the SPR sensor instrumentation disturbances. Experimental tests with reversible binding water-mixture were performed, and both image and statistical processing were reported. The combination of DIP and SDS approaches improves the extraction of the curve features, increasing the performance in terms of resonance position sensitivity to 81%.

Study of silicon-to-silicon carbide transformation stages in the process of atomic substitution by the methods of total external X-ray reflection and X-ray diffractometry

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion. Keywords: total external reflection, X-ray reflectometry, silicon carbide, plasmons.

Study of silicon-to-silicon carbide transformation stages in the process of atomic substitution by the methods of total external X-ray reflection and X-ray diffractometry

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion. Keywords: total external reflection, X-ray reflectometry, silicon carbide, plasmons.

Surface Plasmon Photodetectors Based on Noble Metals

In this work, high sensitivity noble metals used in the Kretschmann configuration based photodetectors applied to detect the presence of biological and chemical species in solutions are investigated. The angle of incidence and film thickness dependencies of the surface plasmon polariton resonance (SPPR) of gold, silver and copper by the attenuated total reflection (ATR) method are studied to monitor and evaluate the SPR reflectance angle and reflectivity change. The analysis of the electric field of the surface plasmon wave which appears at the interface between the metallic layer and the air is carried out by the finite element method (FEM). The simulation is performed using COMSOL Multiphysics software which supports FEM. The aim of the present study is to find the most suitable noble metal and its optimum thickness to improve the performance of the SPR photodetector. Keywords: Attenuated total reflection method, FEM based COMSOL multiphysics software, Kretschmann configuration, noble metals, reflectivity.

Исследование этапов превращения кремния в карбид кремния в процессе атомного замещения методами полного внешнего отражения рентгеновских лучей и рентгеновской дифрактомерии

X-ray diffraction and total external reflection of X-rays (X-ray reflectometry) methods were used to study the successive stages of synthesis of epitaxial SiC films on Si (100) X-ray diffraction and total external X-ray reflection (XRD) methods were used to study successive stages of synthesis of epitaxial SiC films on Si (100) surfaces, (110) and (111) surfaces by the atom substitution method. The data on the transformation evolution of (100) surfaces were studied, (110) and (111) Si, into SiC surfaces. A comparative analysis of the X-ray structural quality of the SiC layers grown on Si by the atom substitution method with the quality of SiC layers grown by Advanced Epi by the standard CVD method. A modified technique for the total outer X-ray reflection method, based on measurements of the intensity of the reflected X-rays using a special parabolic mirror. It is shown that the method of total external reflection method makes it possible to obtain important information about the degree of surface roughness of SiC layers, the evolution of their crystal structure and plasmon energy in the process of Si to SiC conversion.

Attenuated total reflection FTIR dataset for identification of type 2 diabetes using saliva

Diabetes is one of the top 5 non-communicable diseases that occur worldwide according to the World Health Organization. Despite not being a fatal disease, a late diagnosis as well as poor control can cause a fatal outcome, because of that, several studies have been carried out with the aim of proposing additional techniques to the gold standard to assist in the diagnosis and control of this disease in a non-invasive way. Considering the above, and in order to provide a solid starting point for future researches, we share a primary research dataset with 1040 saliva samples obtained by Fourier Transform Infrared Spectroscopy considering the Attenuated Total Reflectance method. Database include: gender, age, individuals (patients) with/without diabetes, the glucose value, and the result to the A1C test for the diabetic population. We believe that sharing dataset as is could increase experimentation, research, and analysis of spectra through different strategies broaden its range of applicability by chemists, doctors, physicists, computer scientists, among others, to identify the effects that the virus causes in the body and to propose possible clinical treatments as well as to develop devices that allow us to assist in the characterization of possible carriers.

Quantitative analysis of formaldehyde solution based on terahertz attenuated total reflection and chemometric methods

In order to explore the possibility of using terahertz attenuated total reflection (THz-ATR) technology combined with chemometric methods to quantitatively analyze different concentrations of formaldehyde solutions, the THz-ATR was applied to measure the formaldehyde solution with a concentration of 0% to 10%, and the absorption coefficient and refractive index of the samples in the frequency range of 0.2 to 1.2 THz were calculated. Partial least squares (PLS) and back propagation (BP) neural network (BPNN) algorithms are used to establish the mathematical model to predict the relation between the absorption coefficient and the concentration as well as the refractive index and the concentration. Correlation coefficient R and the root-mean-square error RMSE obtained from the PLS prediction model based on the refractive index are 98.99% and 0.4604, respectively, and those based on the absorption coefficient are 99.05% and 0.4464, respectively. Meanwhile, the correlation coefficient R and root-mean-square error RMSE obtained from the BPNN prediction model based on the refractive index are 99.80% and 0.2407, while those based on the absorption coefficient are 99.93% and 0.1182, respectively.

Study of Deuterium Isotope Separation By Anion Exchange Membranes Water Electrolysis

1. IntroductionHydrogen energy is one of solutions for decarbonized society. Water electrolysis is promising as hydrogen production. Currently, water electrolysis with a solid polymer electrolyte membrane has been developed. The electrolysis using a cation-exchange membrane (PEM) has been widely used, while one using an anion-exchange membrane (AEM) is studied as a next-generation method with nonprecious catalysts.Hydrogen isotope separation is applied as a new application of water electrolysis. The nuclear fusion reactor ITER, which uses deuterium and tritium as fuel, will be operated around 2035 when the isotope separation/enrichment technology will be required.We have studied deuterium (D) separation by both PEM- and AEM-type. The separation ability of PEM electrolysis remarkably depended on the ratio of water supplied to the current density (stoichiometric ratio: λ) [1]. Interestingly, AEM one was better than PEM [2]. In this study, AEM electrolysis was investigated at various λ in order to improve the separation performance.2. ExperimentalThe electrolyte was 0.1 M KOH with 10 at% D. The D concentration was adjusted by D2O. The electrolyte was supplied from the lower part of only the anode side. The ready-made AEM (A201, Tokuyama) was employed as electrolyte. Pt catalyst was used as the anode catalyst and CuCoOx was used as the cathode one. The electrolysis was conducted at constant current densities or water feed at room temperature. The hydrogen gas was analyzed by a quadrupole mass spectrometer to determine the mass number (m = 2 (H2), 3 (HD), 4 (D2)), while the solution discharged from the anode was investigated by FTIR using the attenuated total reflection (ATR) method with a diamond prism.3. Results and discussionFigure 1 shows the D content in hydrogen gas evolving from the cathode. In the figure, αgas indicates the separation factor, which is the ratio of protium (H) atomic concentration of the gas to the supplied water. The value of αgas decreased with decreasing λ. The present result suggests H dilution in the gas as well as PEM-type. It should be noted that AEM one could be electrolyzed and keep draining the electrolyte from the anode even at λ ≤ 4, while PEM-type discharged the almost all volume of the electrolyte from the cathode side [1]. This might be explained by the mass transportation by the diffusion and electroosmosis whose flows direction depend on the membrane type.In our presentation, the other results such as D concentration in electrolyte and pH variation depending on λ will be introduced. We will discuss the D separation mechanism by AEM electrolysis from the viewpoints of the water distribution and the mass transportation in the membrane.References K. Harada et al., Int. J. Hydrog. Energy, 45 (2020) 31389-31395..H. Matsushima et al., Int. J. Electrochemical Society, 166 (10) F566-F568 (2019) Figure 1

Nanoscale Imaging of RNA-Protein Interactions with a Photoactivatable Trimolecular Fluorescence Complementation System.

Imaging RNA-protein interaction in the cellular space with single molecule sensitivity is attractive for studying gene expression and regulation, but remains a challenge. In this study, we reported a photoactivatable trimolecular fluorescence complementation (TriFC) system based on fluorescent protein, mIrisFP, to identify and visualize RNA-protein interactions in living mammalian cells. We also combined this TriFC system with photoactivated localization microscopy (PALM), named the TriFC-PALM technique, which allowed us to image the RNA-protein interactions with single molecule sensitivity. Using this TriFC-PALM technique, we identified the actin-bundling protein, FSCN1, specifically interacting with the HOX Transcript Antisense RNA (HOTAIR). The TriFC-PALM imaging acquired a higher resolution compared with the traditional method of total internal reflection (TIRF) imaging. The TriFC-PALM thus provides a useful tool for imaging and identifying the RNA-protein interactions inside cells at the nanometer scale.

Estimation of Rabbit Pancreas Dispersion Between 400 and 1000 nm

Current biophotonics methods cover the entire optical spectrum from the deep ultraviolet to the terahertz. To optimize such methods for diagnostic and therapeutic applications, the need to obtain the wideband dispersion of tissues is high. The pancreas is a very important organ in the human body, since it produces insulin and its malfunction may induce diabetes. A reduced number of biophotonics publications regarding the pancreas is available, meaning that studies to determine its optical properties and their variation during optical clearing treatments are necessary. Considering this fact, we used the total internal reflection method to measure the refractive index of the rabbit pancreas for wavelengths between 400 and 850 nm. The experimental results allowed to calculate the pancreas dispersion with the Cauchy, Conrady and Cornu equations. It was observed that all those equations provided good data fitting in the spectral range of the measurements, but differences were observed outside these limits. Considering the wavelength of 633 nm, the mean value from the three dispersions was 1.3521, while the one published for porcine pancreas is 1.3517. The dispersion calculated with the Conrady equation does not present a fast decreasing behavior for shorter wavelengths as the ones calculated with the Cauchy and Cornu equations, but comparing these curves with a dispersion for a tissue-like material, all seem to have good agreement.

FTIR Measurement of the Hydrogenated Si(100) Surface: The Structure-Vibrational Interpretation by Means of Periodic DFT Calculation

The periodic density functional theory (periodic DFT) method was employed for the interpretation of infrared radiation spectra (IR spectra) measured for the hydrogen-covered H/Si(100) surface after the standard step of native oxide removal by brief etching in 40% NH4F. The IR employed the attenuated total reflectance (ATR) method. The periodic DFT calculations of IR spectra focused on reconstructions of H/Si(100) that involved combinations of surface-terminating Si–H groups including the double-occupied dimer (DOD), dihydride (DH), and trihydride (TH). The IR spectra calculated with periodic DFT for H/Si(100) surfaces were compared with the IR spectra calculated by means of DFT in Si–H clusters. The periodic DFT provided considerably better and more reliable theoretical description of the IR spectra by keeping the periodicity of the silicon material that guaranteed proper spatial distribution of the Si–H species within H/Si(100). The calculated IR spectrum for H/Si(100) that involved a combination of two DOD and three DH groups (7 × 1 reconstruction) was in good agreement with the measured IR spectrum. Moreover, a combination of the calculated IR spectra for DH in 1 × 1 reconstruction and the spectra for adjacent DH and DOD in 3 × 1 reconstruction (no long-range ordering) also agreed with the experiment. The periodic DFT further indicated that the IR peaks measured above 2120 cm–1 can originate in mutual steric interactions of adjacent DH species within H/Si(100). Accordingly, we hypothesize that the H/Si(100) surface prepared by the standard treatment likely involves combinations of DOD and DH but not TH.

Photo-electrochemistry of metallic titanium/mixed phase titanium oxide

In this study, the effect of potassium hydroxide concentration in anodization bath, anodization time, and calcination temperature on the photo-electrochemical behavior of metallic titanium/mixed phase titanium oxide is investigated. Further, the phase structure of a titanium oxide photocatalyst prepared on a titanium electrode through a high-voltage anodization method is examined. The study exploits photo-electrochemical, Fourier transform infrared spectroscopy attenuated total reflectance (FTIR–ATR), X-ray diffraction, and Raman spectroscopic methods to obtain better insights into the mechanism of mixed-phase titanium oxide formation. In this regard, the photo-electrochemical properties of the photocatalysts prepared in single excitation energy, violet light (410 nm), were investigated. The anodization time and the potassium hydroxide concentration in the anodization bath have significant effects on the photo-electrochemical properties of the photocatalysts. The experiments show that the effect of potassium hydroxide concentration is a function of the anodization potential applied, demonstrating different patterns as the anodization potential changes. Furthermore, FTIR-ATR, X-ray diffraction, and Raman spectroscopic studies reveal that the extended anodization times decrease the population of OH-containing groups, leading to lower photo-electrochemical performance. On the other hand, the formation of anatase phases becomes more favorable only in the extended anodization times before application of the calcination process. Additionally, the calcination temperature has a significant impact on the anatase to rutile ratio. Finally, increasing potassium hydroxide concentration leads to the formation of an amorphous titanium oxide layer. It can be concluded that the obtained information might have a significant impact on the preparation of titanium oxide and other metal oxide photocatalysts through the high voltage anodization process.

Discrimination of cellulose fabrics using infrared spectroscopy and newly developed discriminant analysis

Identifying cellulose fibers in fabric products is necessary for quality control and appropriate distribution but can be difficult because of their similarities. A novel technique to identify cellulose fabrics has been developed that uses infrared spectroscopy with the attenuated total reflection (ATR) method, evaluated with an improved Fisher’s discriminant analysis including regularization coefficients and orthogonal decompositions. Sequential discrimination of six different types of cellulose fibers —cotton, ramie, and linen, which are natural fibers, and rayon, cupra, and lyocell, which are regenerated fibers— was achieved using the new technique.