Total Reflection Method Research Articles

Supercritical CO2/Ionic Liquid Systems: What Can We Extract from Infrared and Raman Spectra?

Infrared (IR) spectroscopy has been successfully applied to study the solubility of supercritical (sc) CO2 in an ionic liquid (IL), the swelling of the IL under scCO2, the diffusion of CO2 in the IL, and the molecular interaction between the IL and scCO2 using a single defined experimental setup. The study has been performed using 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6] and scCO2 with a pressure of up to 150 bar at 313 K. The solubility of scCO2 in the IL was calculated via the intensity of the CO2 antisymmetric stretching mode, which was measured using the attenuated total reflection (ATR) method. This approach allowed to determine also the swelling of the IL under scCO2 using several IL bands. The knowledge gained about the solubility and swelling allowed the calculation of the molar fraction of CO2 in the IL and the attainment of similar data as previously determined by other methods. The kinetic measurement of the infrared spectra also offered the opportunity to observe the evolution of the concentration of CO2 in the IL and allowed an estimation of the diffusion coefficient of CO2 in IL under high pressure. Finally, information about the molecular interactions between the IL and scCO2 could also be gained in situ using both infrared and Raman spectroscopy.

SURFACE PHONON–POLARITON MODES OF WURTZITE STRUCTURE InN SEMI-INFINITE CRYSTAL

In this paper, theoretical study on the surface phonon–polariton (SPP) modes of wurtzite (α-) structure indium nitride ( InN ) semi-infinite crystal is presented. Based on an anisotropy model, the surface polariton (SP) dispersion curve of α- InN is simulated. The characteristics of this dispersion curve are discussed. The relevant experimental information by attenuated total reflection method is given. For comparison, the SP dispersion curve of cubic (β-) structure InN simulated based on isotropy model is also presented. Due to optical anisotropic, the SP dispersion curve of α- InN exhibits an extra branch as well as an extra SPP mode as compared to α- InN . In addition, the SPP mode of α- InN is found to be 4 cm-1 smaller than that of β- InN .

Infrared Surface Analysis Using a Newly Developed Thin-Sample Preparation System

We developed a new sampling system, the Nano Catcher, for measuring the surface chemical structure of polymers or industrial products and we evaluated the performance of the system. The system can directly pick up surface species whose depth is on the order of approximately 100 nm and can easily provide a sample for a Fourier transform infrared (FT-IR) system without the necessity of passing it over to a measurement plate. The FT-IR reflection data obtained from the Nano Catcher were compared with those obtained using the attenuated total reflection (ATR) method and sampling by hand. Chemical structural analysis of a depth region from a few tens of nanometers to a few hundred nanometers can be directly performed using this system. Such depths are beyond the scope of conventional X-ray photoelectron spectroscopy (XPS) and ATR methods. We can expect the use of the Nano Catcher system to lead to a great improvement in the detection of signals of surface species in these depth regions.

Detecting Drift and Classifying Concentration of Pesticide on the Basis of Infrared Spectral Feature Analysis

We describe spectral classification of pesticide residue. This classification is done by using the attenuated total reflection method (ATR) of Fourier transform infrared spectroscopy (FT-IR). Recently, there has been increased concern about food safety. Not only consumers but also farmers are concerned with levels of pesticide residue. Furthermore, the dispersion of the pesticide (drift) has become an urgent problem. We used ATR Infrared spectroscopy to detect drift and to classify its. Spectral features have been extracted by using soft independent modeling of class analogy (SIMCA) appropriate to the concentration. The spectra of the calibration set were classified into each class on the basis of the concentration, and SIMCA was used to make the classification models. The concentration of pesticide residues of unknown samples was classified by applying the spectra to the classification model.

Topological bumped surface induced by the lattice extension of the RuCr intermediate layer for granular-type perpendicular recording media

Surface roughness caused by the grain growth of the RuCr non-magnetic intermediate layer (NMIL) was evaluated using the X-ray total reflection method. In the case of Ru NMIL, the value of root mean square roughness of NMIL ( σ) increases from 0.59 to 1.45 nm with increase in Ar gas pressure and/or thickness of the Ru layer. Judging from the loop slope and normalized coercivity, the degree of magnetic isolation increases as σ increases, independent of the Cr content of a RuCr NMIL. Furthermore, it was found that σ of NMIL is strongly correlated with wettability to the seed layer material and is enhanced by the lattice extension of NMIL.

Resonant phase jump with enhanced electric field caused by surface phonon polariton in terahertz region

We investigated surface phonon polariton in cesium iodide with terahertz time-domain attenuated total reflection method in Otto configuration, which gives us both information on amplitude and phase of surface electromagnetic mode directly. Systematic experiments with precise control of the distance between a prism and an active material show that the abrupt change of pi-phase jump appears sensitively under polariton picture satisfied when the local electric field at the interface becomes a maximum. This demonstration will open the novel phase-detection terahertz sensor using the active medium causing the strong enhancement of terahertz electric field.

3118 全反射法による接触面の可視化とヒト手指の振動検出能の計測(S40-3 第14回卒業研究コンテスト(3),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

3118 全反射法による接触面の可視化とヒト手指の振動検出能の計測(S40-3 第14回卒業研究コンテスト(3),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

Interpretation of attenuated-total-reflection dips observed in surface plasmon resonance

We present an interpretation that differs from an accepted explanation for resonance excitation of surface plasmons (SPs) on a metal using an attenuated total reflection (ATR) method. The metal ATR phenomenon is well expressed in terms of wave optics and accompanies an enhanced evanescent field. The ATR curves and the electric field and absorption distributions in the film layer for the noble metals are simulated numerically using electromagnetic wave analysis. The calculation results provide interpretation that the ATR dips are caused by an absorption loss of the metals produced by enhanced electric fields rather than the energy loss of a transfer excitation to the SPs: the damping loss converted into the SPs or the damping absorption of the once-converted propagation SPs. The sharp ATR dips do not necessarily demonstrate the high-resonance excitations of the SPs, and the metal ATR phenomenon is not restricted to the SPR.

Surface Chain Orientation during Crystallization Induction Period of Poly(pentamethylene 2,6-naphthalate) Studied with Polarized FTIR-ATR

Thermoinduced surface orientation behaviors were studied in situ by Fourier transform infrared spectroscopic (FTIR) measurements along with attenuated total reflection (ATR) and transmission methods during the cold crystallization of melt-quenched amorphous poly(pentamethylene 2,6-naphthalate) (PPN) film. The chain in the crystalline phase formed during the cold crystallization process was found to orient parallel with the film surface with a naphthalene ring perpendicular to the film plane. By observing the isothermal crystallization process via polarizing optical microscopy and wide-angle X-ray diffraction methods, it was revealed that PPN shows very slow crystallization kinetics, even when crystallized at the temperature associated with the fastest crystallization rate. Furthermore, the crystallization induction period was longer than 150 min, during which time a significant amount of crystalline phase was not to be formed. The chain orientation at the surface during the crystallization induction period was again measured via polarized FTIR-ATR spectroscopy. It was found that the preferential surface orientation occurs during the early stage of the induction period, and no further orientation was observed during the subsequent crystallization process. Rapid local ordering that occurred during the crystallization induction period, especially at the surface, appears to be followed by gradual packing of the locally ordered chain to form the crystalline phase.

Electroosmotic flow-switchable poly(dimethylsiloxane) microfluidic channel modified with cysteine based on gold nanoparticles

An electroosmotic flow (EOF)-switchable poly(dimethylsiloxane) (PDMS) microfluidic channel modified with cysteine has been developed. The native PDMS channel was coated with poly(diallyldimethylammonium chloride) (PDDA), and then gold nanoparticles by layer-by-layer technique was assembled on PDDA to immobilize cysteine. The assembly was followed by infrared spectroscopy/attenuated total reflection method, contact angle, EOF measurements and electrophoretic separation methods. EOF of this channel can be reversibly switched by varying the pH of running buffer. At low pH, the surface of channels is positively charged, EOF is from cathode to anode. At high pH, the surface is negatively charged, EOF is from anode to cathode. At pH 5.0, near the isoelectric point of the chemisorbed cysteine, the surfaces of channels show neutral. When pH is above 6.0 or below 4.0, the magnitude of EOF varies in a narrow range. And the modified channel surface displayed high reproducibility and good stability, a good reversibility of cathodic–anodic EOF transition under the different pH conditions was observed. Separation of dopamine and epinephrine as well as arginine and histidine were performed on the modified chip.

Novel method for transmission infrared analysis of clay minerals using silicon wafer substrates

AbstractA novel method for the analysis of clay minerals using Fourier transform infrared spectroscopy is presented. Clay mineral suspensions are dried on a Si wafer substrate for transmission infrared (IR) analysis. Four natural Source Clays from the Source Clays Repository of The Clay Minerals Society, SWy-2, SAz-1, SHCa-1 and KGa-1b, as well as the synthetic hectorite, Laponite RD, were analyzed using the described method with signal to noise (s/n) ratios in excess of 100,000 for the strongly absorbing Si-O stretching frequency. Scanning electron microscopy (SEM) images show that the mineral films possess suitable uniformity and low surface roughness for transmission IR measurements that is confirmed by minimal deviations in the baseline of collected IR spectra. The IR spectra are generated and peak locations are compared to previously reported values, generated from KBr pellet and attenuated total reflectance methods.

Characterization of tubular zeolite NaA membranes prepared from clear solutions by FTIR-ATR, GIXRD and FIB-TEM-SEM

Zeolite NaA (LTA) membranes supported by a porous alumina tube were hydrothermally synthesized under four clear solution synthesis conditions which are composed of seeding and regrowth from the clear solution. The clear solution method produced various LTA membrane surface morphologies and pervaporation (PV) dehydration performances of ethanol/water mixture. The aim of this paper is to present a novel and comprehensive structural characterization study of the tubular LTA membranes prepared from clear solutions. The four tubular LTA membranes were characterized by Fourier transform infrared attenuated total reflectance method (FTIR-ATR), grazing incidence 2 θ scan X-ray diffraction analysis (GIXRD) and transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with a focused ion beam (FIB) cross-section specimen preparation technique. By combining the four LTA membranes and the three characterization methods, amorphous-like adhered materials on membrane surface, depth profile of preferred orientation and an intermediate layer including many voids between columnar LTA layer and alumina support were presented. Furthermore, those relations with the PV dehydration performance were discussed. The structural information presented here pointed out a diversity and complexity of the LTA membranes prepared from clear solution. The present characterization study provides a novel information to discuss a relationship between fine structure of the membrane and ethanol/water separation mechanism.

Optical and transmission electron microscopical study of the evolution of surface layer on recycled aluminium along the rolling mills

A deformed near-surface region, also referred as ‘surface layer’, is always present on rolled aluminium alloy sheets. This paper studies in detail the evolution of the surface layer along the production line on a ‘recycled’ commercial alloy (AA5050). A microscopic investigation of a step-by-step formation of the surface layer has been carried out in the roll-bite. The effect of thermo-mechanical processing on the microscopic and optical characteristics of the surface layer has been studied. The distribution of the alloying elements within the surface layer has been investigated along the production line. The importance of the Total Reflectance (TR) method has been demonstrated for accurate estimation of the average thickness of the surface layer. Based on these results, a correlation has been drawn between the microscopic characteristics of the surface layer and the TR profile which in turn shows that the TR can be used in lieu of TEM for estimation of the surface layer thickness at different production stages.

Refractive index measurement for biomaterial samples by total internal reflection

The refractive index of biological tissue is a fundamental parameter in applications of optical diagnosis and laser treatments. In the present work, the refractive indices and thermo-optic coefficients of some basic biomaterials, such as blood plasma, haemoglobin solution and lipid membrane, were studied by the method of total internal reflection at the wavelengths of 532 and 632.8 nm that are the most frequently used laser wavelengths in the biomedical field. The effects of the sample concentration and the temperature on refractive index were measured, and empirical relationships were summarized, accompanied by a theoretical explanation based on molecular polarization theory. The results provide some fundamental data for the refractive indices of these biomaterials under variant conditions, and also demonstrate that the total internal reflection method is a feasible and reliable way to measure the refractive indices of biological samples.

Structural Changes of Y2O3 and La2O3 Films by Heat Treatment

Structural changes of Y2O3 films and La2O3 films deposited on some oxidized silicon substrates were studied using X-ray photoelectron spectroscopy (XPS), Secondary ion mass spectrometry (SIMS), and Fourier transform infrared spectroscopy attenuated total reflection method (FT-IR ATR). Y2O3 and La2O3 films on chemical oxide and NH3 annealed oxy-nitride were prepared by the Low-pressure chemical vapor deposition (LPCVD) method using an lanthanide–dipivaloyl-methanate (Ln–DPM) complex. The Y2O3 film and the La2O3 film on the both kinds of substrate already contained a partly silicate structure at the interface side as a result of an interface reaction during the deposition process. During post deposition annealing, the whole film structure of the Y2O3 and the La2O3 on the chemical oxide changed to a silicate structure due to silicon diffusion with interface reaction. In the case of the Y2O3 film, this interface reaction can be suppressed using thermal oxy-nitride as the interfacial layer. In the case of the La2O3 film, the suppression effect using oxy-nitride was smaller than the case with the Y2O3 film. Also, it was found that there was a strong correlation between the structural change of the films and the change of flat-band-voltage of both Y2O3 and La2O3 MIS diodes during post-deposition-annealing.

Excitation of a surface plasmon with an elastomeric grating

We report on a new method to excite surface plasmon polaritons on a thin metal slab surface using an elastomeric grating which is fabricated by replica molding technique. The grating is placed on the metal surface which creates a periodic perturbation on the surface matching the momentum of the incident light to that of the surface plasmon. The conformal contact between the metal surface and the elastomeric grating changes the dielectric medium periodically and allows the observation of an effective surface plasmon polariton at the metal-air and metal-polymer interfaces of the grating. To clarify the nature of the observed plasmon, comparison of the elastomeric grating with elastomeric slabs was performed with the attenuated total reflection method.

Enhancement of the biofilm formation on polymeric supports by surface conditioning

The aim of this study is to determine the influence of the surface properties on the microbial adhesion to different substratum. Six polymer supports have been selected. Further, the possibility to improve the biofilm growth on the carriers using a conditioning film of PMMA/PAC was proposed. The role of the hydrophobic/hydrophilic interactions between bacterial and support surfaces was determined using contact angle measurements. Scanning electron microscopy was used to compare biofilm morphology on different supports. Mid-infrared microspectroscopy has allowed analyzing in situ the attached biomolecules at various periods of the biofilm development. The infrared attenuated total reflectance method was found to be convenient for surface analysis. Epifluorescence microscopy after DAPI labeling was used to reveal the biofilm structure and the cell density. Indigenous microorganisms from an industrial wastewater-recycling unit were used. The monitoring of the biofilm formation showed the advantages of the coated materials, which allowed faster colonization and higher cell densities. Optimal colonization was observed when the difference between the surface free energies of the support and the bacteria was maximized. Tests on the biodegradation of wastewater exhibiting high COD concentrations attest the biofilm potential in fast COD decay.

Evaluation of Fine Structure of Tubular Zeolite NaA Membrane by FTIR-ATR and FIB-TEM

A zeolite NaA (LTA) membrane supported by an alumina porous support tube for pervaporation (PV) dehydration of ethanol was characterized by transmission electron microscopy (TEM) using a focused ion beam (FIB) thin-layer specimen preparation technique and by Fourier transform infrared attenuated total reflectance method (FTIR-ATR) using a diamond prism as the waveguide. FIB-TEM clearly presented cross-section images up to about 15 microm depth from the membrane surface. FTIR-ATR monitored the Si-O asymmetric stretching vibration spectrum. The Si-O spectrum was compared with the TEM image and their relationships were discussed. By combining the two methods, we could study the thickness of surface LTA crystals, the grain boundary, the LTA/alumina interface structure and the crystallinity and density of materials inside of the alumina porous support. Consequently, fine structure changes of the LTA membrane corresponding to the hydrothermal synthesis condition could be sensitively detected.

HLB number of Vitamins C, E, coenzyme Q 10 derivatives and their transportation efficiency into skin

We have been proposing a new delivery system of medicines and supplements. Derivatives of vitamin C, E and coenzyme Q 10 were examined regarding the relationship between the hydrophile-lipophile balance (HLB) number and the transdermal transportation efficiency into the skin. Non-invasive vibrational spectroscopies, infrared attenuated total reflection (IR-ATR) and near-infrared diffusive reflection (NIR-DR) methods were used in order to evaluate transported materials in the skin. Vitamin C derivatives of sodium l-ascorbyl-2-phosphate (hereafter abbreviated as APS) and sodium l-ascorbyl-2-phosphate-6-palmitate (APPS) were examined. APPS contains both a hydrophilic group and a hydrophobic group, since APS has been modified to APPS by deriving palmitic acid ester in the 6-OH position. APPS has the value of HLB around 9.0, while APS has that of 20. The iontophoretic efficiency of APPS is higher than APS. Vitamin E derivatives of DL-α-tocopheryl N, N-dimethylglycinate (TDMG) and α-tocopheryl acetate (TA) were examined regarding the transdermal transportation effect. Those HLB numbers are 2.3 and 0, respectively. TA is hydrophobic, while TDMG has a hydrophilic terminal group of dimethylglycine HCl materials. Coenzyme Q 10 (CoQ 10) is hydrophobic and a portion of benzoquinone is also hydrophobic, thus, HLB = 0. CoQ 10 has been modified to a reduced form of CoQ 10 (CoH 2Q 10) by NaBH 4. CoH 2Q 10 has a hydroquinone structure of hydrophilic property and HLB = 3.9. Supersonic perforation transported a greater amount of CoH 2Q 10 into the skin than CoQ 10. The balance of the hydrophilic group and the hydrophobic group in the transported material is an important factor for the effective transportation into the skin.

FTIR-ATR Study of the Surface of a Tubular Zeolite NaA Membrane Ultrasonically Reacted with Water and Acetic Acid

For the dehydration process of biomass alcohol using a zeolite NaA (LTA) membrane supported by an alumina porous support tube, it is very important to understand damage of the surface crystal, which may be caused by acetic acid. Therefore, the surface structure and the chemical composition of the LTA membrane that reacted with water or acetic acid (pH 3-4) were investigated by the Fourier Transform Infrared Attenuated Total Reflectance method (FTIR-ATR), with a diamond prism as the waveguide, scanning electron microscope and an energy-dispersive X-ray analysis. For leaching experiments using water and acetic acid, ultrasonication was applied to promote the leaching rate and to surely prepare damaged membranes as a model experiment. The Si-O asymmetric stretching vibration spectra of the original LTA membranes showed a bimodal peak. LTA membranes after water leaching also showed the same peak. However, for the LTA membrane reacted with acetic acid of pH 3, damage of the surface LTA crystal and the loss of sodium by dissolution were clearly observed. Also, its Si-O spectral shape was broad, which suggests amorphous-like substances secondarily formed on the membrane surface. Sodium acetate was not detected for all LTA membranes reacted with acetic acid. To evaluate surface-damaged and sodium-loss membranes, FTIR-ATR can sensitively detect a Si-O spectral change corresponding to the surface structure and the chemical composition of the LTA membrane.