Total Reflection Mode Research Articles

Revealing Catalytically Relevant Surface Species by Kinetic Isotope Effect Spectroscopy: H-Bonding to Ester Carbonyl of trans-Ethyl Pyruvate Controls Enantioselectivity on a Cinchona-Modified Pt Catalyst.

Monitoring active surface species on an operating technical catalyst is a challenging task due to the presence of multiple different adsorption sites and the abundance of bulk species. In this work, kinetic isotope effect (KIE) spectroscopy is introduced to capture the signals of catalytically relevant hydrogenation species from the IR spectroscopic detection in attenuated total reflection mode. The catalytic interface formed between a cinchona-modified Pt/Al2O3 catalyst and the solvent toluene is sensitively probed directly at the rate limiting step(s) during the asymmetric hydrogenation of ethyl pyruvate by measuring the effects of substituting H2 by D2 kinetically and spectroscopically in the same operando experiment. The application of KIE spectroscopy provides unprecedented molecular level insight into the structure of the diastereomeric intermediate surface complex and the phenomenon rate enhancement, which revolutionizes our understanding of chirally modified metal catalysts.

Comparing the analytical performance of near and mid infrared spectrometers for evaluating pomegranate juice quality

Near infrared (NIR) and mid infrared (MIR) spectral acquisition modes were compared for predicting organoleptic and phytochemical quality attributes of pomegranate juice. Three Fourier transform infrared (FT-IR) spectrometers namely, a FT-NIR spectrometer, FT-MIR spectrometer in attenuated total reflection mode and FT-MIR spectrometer in transmission mode were used. Calibration models were constructed by subjecting the spectral data to partial least squares regression analysis. The models were assessed based on their overall performance (lower root mean square error of prediction, the number of latent variables and residual predictive deviation). The predictive abilities of the instruments for juice quality attributes were statistically compared using Bland and Altman, and Passing-Bablok. The outcomes are critically discussed, which showed the suitability of the FT-MIR spectrometer in transmission mode for predicting selected quality attributes of pomegranate juice.

Advantages of infrared transflection micro spectroscopy and paraffin-embedded sample preparation for biological studies

Fourier-Transform Infrared micro-spectroscopy is an excellent method for biological analyses. In this paper, series metal coating films on ITO glass were prepared by the electrochemical method and the different thicknesses of paraffin embedding rat's brain tissue on the substrates were studied by IR micro-spetroscopy in attenuated total reflection (ATR) mode and transflection mode respectively. The Co-Ni-Cu alloy coating film with low cost is good reflection substrates for the IR analysis. The infrared microscopic transflection mode needs not to touch the sample at all and can get the IR spectra with higher signal to noise ratios. The Paraffin-embedding method allows tissues to be stored for a long time for re-analysis to ensure the traceability of the sample. Also it isolates the sample from the metal and avoids the interaction of biological tissue with the metals. The best thickness of the tissues is 4 μm.

Characterization and Comparison of the Solid State Inclusion Compounds of alfa-, beta-Cyclodextrins and its 2-Hydroxypropyl Derivatives with Uracil and 5-fluorouracil

The objective of the present work was to obtain and evaluate the solid inclusion complexes of a-, b-cyclodextrins and hydroxypropyl-a-, hydroxypropyl-b-cyclodextrins derivatives with uracil (U) and anti-cancer agent 5-fluorouracil (5FU). The thermogravimetry (TG), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR) and scanning electron microscopy (SEM) were used to characterize these inclusion compounds. New information on the physicochemical behavior of these solid state complexes synthesized by melting in solution was obtained. Corelating the experimental data we found that the complexation occurs for each host:guest system thus, the preparation method exhibited a real efficiency to interaction achievements. The inclusion capability and the thermal stability of the studied complexes were due to both the flexibility and the size of the cyclodextrin ring as well the stereoelectronic effect of the U or 5FU molecule. We appreciated that the complexes between U or 5FU with 2-hydroxypropyl derivatives of a- and b- CD have the largest content of guest and are the most stable. The obtained results could be useful in formulation of the pharmaceutical products and also in drug delivery.

FTIR as an easy and fast analytical approach to follow up microbial growth during fungal pretreatment of poplar wood with Phanerochaete chrysosporium

Since the determination of the fermentation kinetics is one of the main challenges in solid state fermentation, the quantitative measurement of biomass growth during microbial pretreatment by FTIR spectroscopy in Attenuated Total Reflectance mode was evaluated.Peaks at wave numbers of 1651 cm−1 and 1593 cm−1 showed to be affected during pretreatment of poplar wood particles by Phanerochaete chrysosporium MUCL 19343. Samples with different microbial biomass fractions were obtained from two different experiments, i.e., shake flask and fixed-bed reactor experiments. The glucosamine concentration was compared to the normalized absorbance ratio of the 1651 cm−1 to 1593 cm−1 peak, measured by FTIR-ATR, and resulted in a linear relationship. The application of a normalized absorbance ratio in function of time provided a graph that was similar to the microbial growth curve.Application of FTIR in ATR mode to follow-up kinetics during solid state fermentation seems to be a fast and easy alternative to laborious measurement techniques, such as glucosamine determination.

Spectral characteristics of a photonic bandgap fiber

With the help of numerical simulation, we study the propagation of light in an all-glass photonic crystal fiber. A comparison of the spectral characteristics of a fiber with the idealized hexagonal structure and a fiber with transverse profile deformations is conducted. The calculations use methods based on a spatial Fourier transform. It is shown that total internal reflection modes and the fundamental mode of the photonic bandgap can be excited simultaneously. Structural deformation of a photonic crystal fiber results in the shifting and narrowing of the photonic bandgap. Excitation of the total internal reflection modes leads to increased absorption on the boundaries of the spectral band of the fiber.

Optical properties of phenylene–thiophene-based polyazomethine thin films

Thin films of new aromatic polyazomethines, containing thiophene rings in their polymer chain structures, were obtained by the chemical vapor deposition method, via a polycondensation process from thiophene-2,5-dicarbaldehyde and one of four different aromatic diamines, as initial monomers. Spectroscopic ellipsometry, attenuated total reflectance mode of Fourier transform infrared spectroscopy, atomic force microscopy, and wide-angle X-ray diffraction techniques have been used to characterize these films. However, the optical transmission and reflectivity measurements, within the wide spectral UV-Vis-NIR range (0.5–6.2 eV), were the basic method of presented investigations. On the basis of optical measurements, the absorption coefficient spectra of these thin films were obtained and the absorption edge parameters, that is, the energy gap ( EG) and Urbach energy ( EU), were calculated in a way typical for amorphous semiconductors. These parameters allowed one to evaluate the length of conjugation and the extension of localized, defect states inside the energy gap, respectively, and to discuss the electronic transitions, being dependent on the chemical structure and conformation of polymer chains. Optical properties of these new phenylene–thiophene-based polyazomethine films were compared with their entirely phenylene counterparts. In general, the energy gaps of investigated films were clearly smaller (about 0.2 eV) than those of their phenylene counterparts, confirming that the presence of thiophene rings in polyazomethine structures improves conjugation.

Current trends and opportunities for the applications of in situ vibrational spectroscopy to investigate the supercritical fluid processing of polymers

High-pressure and supercritical CO2 (scCO2) have the potential to be employed as alternatives to organic solvents for processing polymeric materials. High-pressure and scCO2 offer advantages for polymer processing that include, inter alia, plasticisation, phase separation in blends, crystal modification, and swelling of polymers. These effects can be useful for selectively treating polymeric samples for a range of applications. This opinion paper will discuss the importance of Fourier transform infrared (FTIR) spectroscopy, in attenutated total reflection (ATR) mode, to aid the understanding of polymeric processing based on their unique molecular vibrations. This information is integral for developing more efficient processing pathways which will mean that the full potential of high-pressure and scCO2 processing can be realised. The current state-of-the-art will be reported that will include an overview of key recent advances utilising FTIR spectroscopy. Challenges and future areas of research will be outlined where new and exciting opportunities using this “green” processing technology will be predicted.

A New Chemometric Approach for Automatic Identification of Microplastics from Environmental Compartments Based on FT-IR Spectroscopy.

One key step studying interactions of microplastics with our ecological system is to identify plastics within environmental samples. Aging processes and surface contamination especially with biofilms impede this characterization. A complex and time-consuming cleaning procedure is a common solution for this problem. However, it implies an artificial change of sample composition with a risk of losing important information or even damaging microplastic particles. In the present work, we introduce a new chemometric approach to identify heavily weathered and contaminated microplastics without any cleaning. The main idea of this concept is based on an automated curve fitting of most relevant vibrational bands to calculate a highly characteristic fingerprint that contains all vibrational band area ratios. This new data set will be used to estimate the similarity of samples and reference standards for identification. A total of 300 individual naturally weathered plastic particles were measured with Fourier transformation infrared spectroscopy in attenuated total reflection mode (FT-IR ATR) and identified successfully with the new method. To that end, all samples were compared with a selection of common reference plastics and bio polymers. As it turns out, the accuracy of identification rises significantly from 76% by means of conventional library searching algorithms to 96% by identifying microplastics with our new method. Therefore, the new approach can be a useful tool to compare and describe similarities of FT-IR spectra of microplastics, which may improve further research studies on this topic.

IR‐ and NEXAFS‐spectroscopic characterization of plasma‐nitrogenated polyolefin surfaces

Modification of polyethylene and polypropylene surfaces by atmospheric‐pressure plasmas using mixtures of nitrogen and hydrogen was studied using Fourier‐transform infrared spectroscopy in the attenuated total reflection mode (FTIR‐ATR) and by near‐edge x‐ray absorption fine structure spectroscopy (NEXAFS) in order to shed some light on the chemical nature of nitrogen‐containing functional groups on the polymer surface. Using FTIR‐ATR spectroscopy combined with hydrogen‐deuterium isotope exchange of active hydrogen atoms, it was shown that the direct treatment of PE foils by dielectric barrier discharges (DBDs) in N2/H2 mixtures and a subsequent exposure of the samples to the ambient air results in the formation of –NH2 moieties of primary amides on the polymer surface. Corresponding in situ experiments with streaming N2/H2 DBD post‐discharges virtually free of H2O and O2, on the other hand, showing the absence of –NH2, proving that no primary amines or amides are formed by this treatment although substantial amounts of nitrogen are incorporated. Moreover, directly N2/H2‐plasma‐treated polymer surfaces, similar to afterglow‐treated low‐density polyethylene (LDPE), show amphiphilic character as to be seen by chemical derivatization with nucleophilic reagents 4‐(trifluoromethyl)phenylhydrazine and 4‐(trifluoromethyl)benzyl­amine, in addition to electrophilic aromatic aldehydes normally used to derivatize such surfaces. The presence of imines or other functional groups with CN moieties which may be invoked to explain the dual (amphiphilic) reactivity is proven by NEXAFS studies on ultrathin plasma‐treated PE films, confirming significant amounts of nitrogen in CN bonds and carbon in CC bonds.

Difference of Near-Interface SiO2 Structures between O2-Oxidation and H2O-Oxidation of 4H-SiC (0001) and Its Impact on MOS Interface Characteristics

For 4H-SiC MOSFETs, the control of MOS interface properties have been one of the most challenging issues to meet the requirements of low on-resistivity and high-reliability. The dominant factors which deteriorate the channel characteristics have not yet been clarified well. In this study the effects of the oxidant species, i.e. O2 or H2O on 4H-SiC MOS interface properties were investigated from the viewpoints of SiO2 microscopic structures, to discuss the possible physical origins of the significantly different MOS electrical properties between O2- and H2O-oxidized interfaces.4°-off 4H-SiC (0001) Si-face wafers covered with 5μm-thick epitaxitial layers were thermally-oxidized at different temperatures in dry-O2 or in wet ambient prepared by flowing O2, N2, and their mixed gas through deionized water kept at different temperatures to control the humidity. After determining oxide thicknesses accurately by x-ray reflectivity or Si2p XPS, infrared absorption spectroscopy with attenuated total reflection mode (ATR-FTIR) of grown oxide film was investigated. The films were etched-back repeatedly in a diluted HF solution to investigate the thickness dependence of the spectrum. The structural difference of the oxides especially in the region within a few nanometers from the interface (near-interface region) was investigated by ATR-FITR. Since the peak frequency of Si-O-Si asymmetric vibration mode sensitively reflects the strain in SiO2 (structural strains or non-stoichiometry of the film) [1], the formation of strained structure in near interface region is indicated by a significant shift of the peak frequency when the film thickness was reduced below ~2 nm by chemical etching [2]. For the cases of dry oxidation, we also found that such strain in near-interface region was not affected at all by simply changing the oxidation temperatures [2]. Thus we can conclude that employing H2O as the oxidant is crucial for the relaxation of near-interface SiO2 microscopic structure. It was also found that the peak width was also smaller for H2O-oxidation than O2-oxidation, which indicates a formation of near-interface oxide with more uniformity in microscopic structure. It is a reasonable assumption that the relaxation of locally-strained structures would be beneficial to reduce the density of carrier-trapping sites in oxide. The superior channel performances with wet-oxidation, reported frequently for 4H-SiC (000-1) C-face [3] will be also attributable to the effects of H2O to modify the strained structure of near-interface SiO2.Next we fabricated lateral n-MOSFETs on p-type 4H-SiC (0001) with dry oxidation at 1300ºC followed by post-oxidation annealing in H2O/O2 mixed ambient at as low temperature as 800ºC. Even though the low temperature annealing in wet ambient results in additional oxide growth with a small thickness around only 1 nm or less, we successfully observed a significant enhancement of the channel mobility. This result is suggesting the modification of near-interface structure is achievable by an additional oxidation of only a few monolayers of SiC surface, which is expected to reduce the near-interface trap density.Acknowledgements: This work is partially supported by CSTI, Cross-ministerial Strategic Innovation Promotion Program, “Next-generation power electronics” (funding agency: NEDO), and by JSPS KAKENHI.

Surface enhanced infrared absorption spectroscopy for graphene functionalization on copper

The monolayer form of CVD graphene is imposing crucial challenges in characterization of the targeted covalent functionalization due to the low amount of grafting moieties on the surface, which in turn hampers drawing conclusions about reactivity-properties relationships. Due to the growing interest in chemically modified graphene new, reliable and non-destructive methods for its characterization are critically required. Herein we demonstrate the use of surface-enhanced infrared absorption spectroscopy for detection of characteristic vibration modes of species being grafted to the material either via radical (Meerwein arylation) or nucleophilic substitution pathway on copper foil. The phenomenon is allowed by the appropriate metal surface morphology and no signal could have been obtained neither on Si/SiO2 substrate, nor on bare copper. The surface of copper foil exhibit partial corrosion during the reaction which leads to the creation of active substrate for SEIRA. The measurements were performed using reflection-absorption and attenuated total reflection modes with almost identical results, thus making this analytical approach feasible, practical, non-destructive and easy to use for routine characterization of graphene functionalization.

Poly(vinyl alcohol) and poly(vinyl amine) blend membranes for isopropanol dehydration

ABSTRACTBlended membranes of hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(vinyl amine) (PVAm) were prepared and crosslinked with glutaraldehyde. The prepared membranes were characterized using infrared (attenuated total reflection mode) spectroscopy, differential scanning calorimetry, X‐ray diffractometry, and scanning electron microscopy measurements. Pervaporation performances of the membranes were evaluated for the separation of water‐isopropanol (IPA) mixtures. As the PVAm content increased from PVAm0 to PVAm1.5, the flux through a 70 μm film increased from 0.023 to 0.10 kg/m2 h at an IPA/water feed ratio of 85/15 at 30 °C. The driving force for permeation of water increased due to the temperature but it has no effect on IPA permeation. Activation energies for the permeation of IPA and water were calculated to be 17.11 and 12.46 kJ/mol, respectively. Controlling the thickness of the blend membrane could improve the permeation flux with only a marginal reduction in the separation factor. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45572.

Preparation and properties of solid polymer electrolyte based on imidazolium-based ionic liquids for structural capacitors

We prepared solid polymer electrolytes (SPEs) composed of poly(ethylene glycol) monomethyl ether acrylate (1A9OMe) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][OTF]) and 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfonyl) imide ([EMIm][TFSI]) as the ionic liquid. The SPEs formed by appropriately adding ionic liquids in the 1A9OMe prior to thermal cure. The ratio of 1A9OMe and ionic liquid was 1:9, 3:7, and 5:5, respectively. The characterization of solid polymer electrolytes were investigated using Fourier transform infrared spectroscopy in the attenuated total reflectance mode (FTIR-ATR), Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and glavanostatic charge-discharge test. The highest ionic conductivity of SPEs was found to be 4.90×10−4 S/cm in a 1A9OMe/[EMIm][OTF] of 3:7. As IL contents were increased, the specific capacitance of supercapacitor was increased. The specific capacitance of supercapacitor for ionic liquid with large ion size was lower than that for ionic liquid with smaller ion size.

Characterization of sodium tripolyphosphate and sodium citrate dehydrate residues on surfaces

Sodium tripolyphosphate (STPP) and sodium citrate dihydrate (sodium citrate) are the most widely used components in detergent formulations. Here, we characterized these two components on glass surfaces to assess their possible exposures from white spots on dishwasher-washed dishes. Ultraviolet/visible near infrared spectroscopy (UV/Vis-NIR), Fourier transform infrared spectroscopy (FTIR) in the attenuated total reflectance mode (ATR-FTIR), Raman spectroscopy and laser ablation-inductively coupled plasma mass spectroscopy (LA-ICP-MS) were utilized to design calibration models for a range of STPP and sodium citrate concentrations 1–8% w/w) precipitated on glass surfaces. STPP and sodium citrate residues on the dishwasher-washed dishes were also determined quantitatively using ATR-FTIR by utilizing these calibration models. In addition, cytotoxicity assays were performed to elucidate the influence of STPP and sodium citrate on human embryonic kidney cell survival. Cell viability results showed a decreasing trend in the number of cells cultured with increasing concentrations and exposure time of STPP and sodium citrate in the medium. Cell survival was minimum on day four when cells were exposed to 84mg/kg of body/day of STPP and sodium citrate separately. This is the first report about detection and quantification of STTP and sodium citrate and assessment of cytotoxicity. Results of this study provide opportunities for the quantification of detergent residues on dishes and assessment of their possible toxicity on live cells.

2DCOS and PCMW2D analysis of FT-IR/ATR spectra measured at variable temperatures on-line to a polyurethane polymerization

In the present communication the potential of 2DCOS analysis and the spin-off technique perturbation-correlation moving window 2D (PCMW2D) analysis is illustrated with reference to spectroscopic changes observed in a data set recorded by in-line fiber-coupled FT-IR spectroscopy in the attenuated total reflection (ATR) mode during a polyurethane solution polymerization at different temperatures. In view of the chemical functionalities involved, hydrogen bonding plays an important role in this polymerization reaction. Based on the 2DCOS and PCMW2D analysis, the sequence of hydrogen bonding changes accompanying the progress of polymerization and precipitation of solid polymer can be determined. Complementary to the kinetic data derived from the original variable-temperature spectra in a previous publication the results provide a more detailed picture of the investigated solution polymerization.

UV-Surface Treatment of Fungal Resistant Polyether Polyurethane Film-Induced Growth of Entomopathogenic Fungi.

Synthetic polymers are the cause of some major environmental impacts due to their low degradation rates. Polyurethanes (PU) are widely used synthetic polymers, and their growing use in industry has produced an increase in plastic waste. A commercial polyether-based thermoplastic PU with hydrolytic stability and fungus resistance was only attacked by an entomopathogenic fungus, Metarhiziumanisopliae, when the films were pre-treated with Ultraviolet (UV) irradiation in the presence of reactive atmospheres. Water contact angle, Fourier transform infrared spectroscopy in attenuated total reflection mode (FTIR-ATR), scanning electron microscopy (SEM), and profilometer measurements were mainly used for analysis. Permanent hydrophilic PU films were produced by the UV-assisted treatments. Pristine polyether PU films incubated for 10, 30, and 60 days did not show any indication of fungal growth. On the contrary, when using oxygen in the UV pre-treatment a layer of fungi spores covered the sample, indicating a great adherence of the microorganisms to the polymer. However, if acrylic acid vapors were used during the UV pre-treatment, a visible attack by the entomopathogenic fungi was observed. SEM and FTIR-ATR data showed clear evidence of fungal development: growth and ramifications of hyphae on the polymer surface with the increase in UV pre-treatment time and fungus incubation time. The results indicated that the simple UV surface activation process has proven to be a promising alternative for polyether PU waste management.

Oxidation‐grafting surface modification of waste silicone rubber composite insulator powder: Characterizations and properties of EPDM/modified waste powder composites

ABSTRACTIn order to broaden the applications of waste silicone rubber composite insulator powder (WSP), modified waste powder (WSP‐KH570) was prepared by a two‐step treatment process involving improved surface oxidation approach by using acidic H2O2 solution and subsequently grafting of KH570. Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR‐ATR) analysis revealed the presence of KH570 on the powder surface. The result was confirmed by thermogravimetric analysis (TGA). Blends of ethylene propylene diene monomer (EPDM) with WSP‐KH570 were prepared. The effects of WSP‐KH570 on mechanical properties and thermal properties of the blends were investigated. The WSP‐KH570 showed an observed improvement in tensile strength and elongation at break of EPDM/WSP‐KH570 blends compared with corresponding compositions of EPDM/WSP blends. The TGA cure showed that EPDM filled with WSP‐KH570 had higher thermal stability at 210–380 °C than EPDM/WSP. Dynamic mechanical analysis indicated EPDM and WSP‐KH570 were better miscible with the blend ratio (90/10). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45438.

Submicron surface roughening of aliphatic polyamide 6,6 fabric through low temperature plasma and its effect on interfacial bonding in rubber composite

The present study aims to produce submicron surface roughening of aliphatic polyamide 6,6 (nylon 6,6) fabric using dielectric barrier discharge-based atmospheric low temperature plasma for improving the adhesion bonding with rubber. The plasma treatment was done in the time ranging from 15 s to 300 s. Formation of surface roughness on the fabric due to plasma treatment and the associated chemical changes were studied through high-resolution scanning electron microscope, geometrical surface roughness by Kawabata evaluation system surface tester, contact angle measurements and Fourier transform infrared in Attenuated total reflectance mode. Scanning electron microscope micrographs revealed the presence of submicron roughness on the nylon 6,6 fibre surface with pores of around 100 nm (0.1 µm) for the optimum treatment time of 180 s above which the pore merging effect dominated resulting in the net low surface roughness. Geometrical roughness (SMD) results were also well in agreement with the scanning electron microscope results for the roughening and the optimum effect of the plasma treatment. The control and plasma treated nylon 6,6 samples were used as reinforcements for rubber composite. The peel strength of the rubber composite, which is a measure of interfacial bonding, increased to 150% as the maximum for the optimum plasma treatment time of 180 s. Intense rubber deposits over the 180 s plasma treated samples were observed while only a few deposits of rubber were observed on the control fabric when their interfaces were examined through scanning electron microscope after peeling test.

Characterization of the Migration of Bisphenol A and F Diglycidyl Ethers from Epoxy-coated Containers to Food Simulants

ABSTRACTThis study evaluated the migration of bisphenol A diglycidyl ether (BADGE) and its chlorinated and hydrolyzed derivatives and bisphenol F diglycidyl ether (BFDGE) from the inner surface coatings of food containers into three food simulants including 3% (w/v) aqueous acetic acid, 10% (v/v) aqueous ethanol, and sunflower oil. After a storage period of 429 days from 155 to 584 days, BFDGE, a prohibited chemical by the European legislation, was not detected in any samples by high-performance liquid chromatography with fluorescence detection. However, BADGE, BADGE.H2O, BADGE.HCl.H2O, and BADGE.2H2O were found at levels below the European Union limits. Conducted analyses using Fourier transform infrared spectroscopy in attenuated total reflectance mode showed that epoxy–phenolic lacquers may be used as food container coatings. Additional work using atomic force microscopy did not reveal the signs of degradation of the inner coatings in contact with the simulants.