Multiple Internal Reflectance Research Articles

Chemical, Structural and Elemental Characterization of Biosorbents Using FE-SEM, SEM-EDX, XRD/XRPD and ATR-FTIR Techniques

The chemical, structural, and elemental composition of any adsorbents plays undoubtedly crucial role and has paramount significance in adsorption process. The present study of chemical, structural, and elemental characterization of powdered Pinus densiflora pine cones, lignite and coconut shell-based activated carbon fiber (ACF), and powdered oyster shell prior employed for anionic surfactant sodium dodecyl sulfate (SDS) adsorption was undertaken using field emission scanning electron microscope (FE-SEM), scanning electron microscope coupled with energy dispersive x-ray (SEM-EDX), X-ray diffraction/X-ray powder diffraction (XRD/XRPD), and multiple internal reflectance (MIR) or attenuated transform reflectance – fourier transform infrared spectroscopy (ATR-FTIR) techniques. The FESEM imaging observed at three different magnifications depicted the change in surface texture of aforementioned biosorbents before and after SDS adsorption. SEM-EDX analysis indicated alteration in the concentration and distribution of different compositional elements. The XRD analysis suggested the amorphous character in lignite and coconut shell-based ACF and powdered Pinus densiflora cones, whilst indicating the sample of powdered oyster shell to be crystalline in nature and entirely composed of CaCO3 with the very trivial amount of impurities. Further, infrared (IR) spectroscopy demonstrated variation in IR spectra of the samples prior to and after surfactant adsorption and also further suggested occurrence of complexing or (complexation) process between ionizable functional groups and DS― or Na+ ions of SDS. In addition, iodine number of the lignite and coconut shell-based ACF, powdered Pinus densiflora cones, and powdered oyster shell were found to be 285.86 mg/g, 25.01 mg/g, and 28.48 mg/g, respectively.

Effect of a CPP-ACP agent on the demineralization and remineralization of dentine in vitro

Objectives The aim of this study was to determine in vitro the effect of a commercial paste based on CPP-ACP complex on the demineralization of sound human dentine and on remineralization potential of artificial caries-like lesions formed on dentine surfaces. Methods Forty dentine specimens were prepared with hard tissue microtome. The specimens were divided in four groups the A, B, C and D ( n = 10). The specimen surfaces were subjected to surface analysis by Fourier transformance micro multiple internal reflectance infrared spectroscopy (micro MIR-FTIR). Tooth mousse was applied on surface specimens of A group, while no agent were applied on the specimens of B group. Afterwards, groups A, B, C and D were immersed in demineralization solution for 7 days. Afterwards, the surfaces were subjected to micro MIR-FTIR analysis and the mineral to matrix ratio was used to assess the extent of dentin demineralization (DM). Tooth mousse was applied on specimens of group C, while no agent was applied on specimens of group D. The groups C and D immersed in artificial saliva for 7 days and were subjected to analysis by micro MIR-FTIR and the mineral to matrix ratio was used to assess the extent of dentin remineralization (RM). Results Group A showed significant lower %DM in comparison to group B. Group C resulted in a significant higher %RM compared to group D. Conclusions The presence of agent CPP-ACP on dentine surfaces provoked lower demineralization and higher remineralization in comparison with the dentine surfaces without agent.

Maleic Anhydride Grafting on EPDM: Qualitative and Quantitative Determination

Several attempts have been made to compatibilize immiscible blends by introducing suitably-chosen polymer additives. This work studies the EPDM elastomer, chemically modified with maleic anhydride (MA), through reaction in solution of EPDM and MA, using dibenzoyl peroxide as an initiator. The best conditions for obtaining the maximum grafting were studied at different times and percentage weights of maleic anhydride. The evaluation of MA grafting onto EPDM was determined with multiple internal reflectance infrared spectroscopy as discussed in detail.

Multitechnique characterization of articular surfaces of retrieved ultrahigh molecular weight polyethylene acetabular sockets.

The articular surfaces of 10 retrieved ultrahigh molecular weight polyethylene acetabular sockets were studied by optical microscopy, X-ray fluorescence spectrometry, multiple internal reflectance FTIR spectroscopy, scanning electron microscopy, and wavelength dispersive X-ray microanalysis. The results revealed characteristic wear patterns including polishing, scratching, pitting, cratering, folding, shredding, burnishing, cracking, embedding of particles, and development of acquired biofilms with various degrees of mineralization. The biofilms formed were mainly of proteinaceous origin, and mineralized regions were composed of calcium phosphates with carbonate impurities. The crystallinity of the polyethylene at the articular surfaces was enhanced compared to the bulk, which was possibly due to the cold work produced in vivo. The mineralized regions were classified into two groups based on the grey levels of the backscattered images obtained. The high-contrast regions that were mainly composed of Ca and P with traces of Al and Si were associated with bone fragments; the low-contrast regions composed of K, Na, Ca, Mg, Si, Al, Fe, Cl, and P were associated with acquired biofilm calcification, which implies the active engagement of biofilms in the long term performance of acetabular sockets in vivo.

Multitechnique characterization of articular surfaces of retrieved ultrahigh molecular weight polyethylene acetabular sockets

The articular surfaces of 10 retrieved ultrahigh molecular weight polyethylene acetabular sockets were studied by optical microscopy, X-ray fluorescence spectrometry, multiple internal reflectance FTIR spectroscopy, scanning electron microscopy, and wavelength dispersive X-ray microanalysis. The results revealed characteristic wear patterns including polishing, scratching, pitting, cratering, folding, shredding, burnishing, cracking, embedding of particles, and development of acquired biofilms with various degrees of mineralization. The biofilms formed were mainly of proteinaceous origin, and mineralized regions were composed of calcium phosphates with carbonate impurities. The crystallinity of the polyethylene at the articular surfaces was enhanced compared to the bulk, which was possibly due to the cold work produced in vivo. The mineralized regions were classified into two groups based on the grey levels of the backscattered images obtained. The high-contrast regions that were mainly composed of Ca and P with traces of Al and Si were associated with bone fragments; the low-contrast regions composed of K, Na, Ca, Mg, Si, Al, Fe, Cl, and P were associated with acquired biofilm calcification, which implies the active engagement of biofilms in the long term performance of acetabular sockets in vivo. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 48: 365–373, 1999

The use of in situ Fourier-transform infrared spectroscopy for the study of surface phenomena on electrodes in selected lithium battery electrolyte solutions

This paper presents some examples of surface studies of noble metals and Li electrodes in Li battery electrolyte solutions using in situ FT-IR spectroscopic techniques. These examples include the study of a mixture of solvents, the role of the reduction of salt in the build-up of surface films on the electrodes and the impact of contaminants such as traces of oxgen and water. The techniques included multiple and single internal reflectance modes and external reflectance (SNIFTIRS-type) mode. The following conclusions were drawn from this study: (i) salts containing the -SO 2CF 3 group are much more reactive on Li than LiAsF 6. Their reduction dominates the surface chemistry developed on Li in ethereal solutions; (ii) water reduction on Li in wet 1,3-dioxolane solution may not form stable LiOH films due to the further reaction of the hydroxy group with the solvent; (iii) in spite of its low solubility, oxygen dissolved in propylene carbonate and tetrahydrofuran solutions has some impact on the surface chemistry developed on Li in these solutions (probably due to Li 2O formation).

Effect of topical fluoride agents on the morphologic characteristics and composition of resin composite restorative materials

Statement of problem. The high reactivity of fluoride agents used in topical fluoride treatments have raised important questions on their potential adverse effects on restorative materials. Purpose. The purpose of this study was to evaluate the effect of topical fluoride agents used for office or home treatments on the surface morphologic characteristics and composition of composite restoratives. Material and methods. The fluorides used were Act, Phosflur, Gel II, Prevident, Stop, Butler APF, Nupro, and Omni Gel & Rinse. The composites tested were Brilliant DI, Heliomolar Ro, Herculite XRV, and P-50. The pH of the fluorides was measured as received and after dilution with water at a 1:3 volume ratio. The composites were subjected to the fluoride treatments until the total number of applications simulated the equivalent of 4 years under treatment. The changes induced on the surface morphologic features and composition of the restoratives were assessed by multiple internal reflectance Fourier transform infrared spectroscopy, scanning electron microscopy, and x-ray microanalysis. Results. All fluorides showed an acidic pH that was not significantly changed after dilution, except Stop, which exhibited a significant pH reduction. All fluorides increased the amount of loosely bound water in the composite matrix. Butler APF gel was the most aggressive for Brilliant DI and Herculite XRV, leading to excessive surface degradation, porosity, destruction of the filler-matrix interface, filler dissolution, and debonding. A reduction in the extent of remaining C = C bonds was observed in Herculite XRV after Butler APF treatment; Phosflur, Gel II, and Prevident had a milder effect. Treatment of Brilliant Dl and Herculite XRV with Omni Gel & Rinse resulted in the formation of a stable precipitation layer rich in barium, phosphorus, tin, oxygen, and fluoride. P-50 was severely affected at the resin-matrix interface after Stop treatment, whereas Omni Gel & Rinse induced fewer surface changes. Heliomolar Ro was the least affected restorative regardless of the type of fluoride used. (J Prosthet Dent 1997;77:405-13.)

Nanoscale Lithography of Silicon Dioxide Using Electron Beam Patterned Carboxylic Acids as Localized Etch Initiators

We report on the use of self‐assembled monolayers of long chain carboxylic acids as initiators in the high temperature (120°C) HF vapor etching of silicon dioxide thin films and on their use in a unique nanolithographic process we have named chemically enhanced vapor etching. Spectroscopic ellipsometry, Rutherford backscatter spectroscopy, Raman spectroscopy, and multiple internal reflectance infrared characterizations of monolayers of n‐octadecyltrichlorosilane and/or myristic and 10‐undecenoic carboxylic acids on silicon dioxide are reported. IR data support acid adsorption on the surface via hydroxyl coordination, Raman data provide evidence for the cross‐linking of the hydrocarbon backbone upon exposure to the electron beam. Comparative etch behavior of various samples with differing monolayers on the oxide surface provide strong support for the carboxylic acid moiety as the primary reaction initiator for silicon dioxide etching at the temperature employed in these systems. Monolayers of 10‐undecenoic acid on silicon dioxide have been patterned using electron beams and subsequent etch processing of the samples has yielded oxide test patterns with linewidths as narrow as 0.1 μm. These systems thus hold promise as novel patterning tools for nanolithography.

Characterization of thin amorphous silicon films with multiple internal reflectance spectroscopy

Infrared multiple internal reflection (MIR) spectroscopy has been applied here to the characterization (ex situ) of thin amorphous silicon layers on crystalline silicon substrates. The specimens are tightly clamped against a Ge prism with 45° bevel angle for the entrance and exit sides, allowing for up to 25 multiple internal reflections. This greatly enhances the thin-film absorption, and the stretching bands of SiHn bonds in amorphous Si are detected in a range of film thickness from 3 to 600 nm. Very thin films (with thickness less than 50 nm) exhibit a different hydrogen bonding compared to the thin ones, due to hydrogenated sublayers that are not visible in IR spectra for larger film thickness. Sublayers are found both at the film/substrate interface and at the film free surface. Another transitional layer, with increased concentration of SiH2 groups and considerably less than 30 nm, is found at the film/substrate interface. MIR is also applied to study the step-by-step etching in CF4/O2 of a 70-nm-thick amorphous silicon layer. This experiment is able to define the location of the sublayers.

The decomposition of straw in soil: use of Multiple Internal Reflectance Infrared Spectroscopy

SUMMARYChanges in the surface layers of wheat and barley straw internodes incubated in soil at 15°C for up to 448 d were analysed using multiple internal reflectance (MIR) infrared spectroscopy. Results were compared with chemical analyses of total C and N and polysaccharides in straw and soil‐straw mixtures. Detectable spectroscopic changes occurred only at the inner surface of the straw. There was progressive enhancement of lignin absorption bands relative to those of polysaccharide and enhanced acetyl absorption. There was a greater association of clay mineral matter with the inner surfaces of the wheat straw than with those of the barley.Using the absorbance ratio of carbohydrate to lignin and assuming a negligible change in lignin content, it was estimated that for wheat straw about 75% of the carbohydrate in the surface layers was lost within the first 14 d of incubation. The barley straw showed no loss until 28 d, and 75% loss only after 112 d.In the early phases, the pattern of decomposition of straw carbohydrate in soil as revealed by MIR resembled that in sheep's rumen, but the rate of decomposition was much slower.Changes in the carbohydrate content of the soil‐straw mixtures measured chemically paralleled those observed spectroscopically, but only gross chemical changes were observable.MIR infrared spectroscopy was shown to provide a sensitive measure of the early stages of plant tissue decomposition.

Estimation of the 1,8-cineole yield ofEucalyptus camaldulensis Dehnh. Leaves by multiple internal reflectance infrared spectroscopy

Peaks characteristic of 1,8-cineole consistently appeared in spectra obtained by multiple internal reflectance spectroscopy (MIR) from the surfaces of 1,8-cineole-rich Eucalyptus camaldulensis Dehnh. leaves. The absorbances derived from the peaks at wave numbers of 1050 and 1078 cm−1 were well correlated (r2 = 0.87 and 0.91 respectively) with the 1,8-cineole yield of leaves from trees in the field known to have high, medium and low yields of this compound. Absorbances at these wave numbers were not recorded in spectra from a contrasting cineole-poor chemotype of high sesquiterpene content. The wave pattern of this chemotype was readily distinguishable from the pattern of the regular, 1,8-cineole-rich phenotype. Multiple internal reflectance spectroscopy may be useful for field-testing eucalypts for their potential 1,8-cineole production.

Solid-state interaction of magnesium oxide and ibuprofen to form a salt.

During formulation development work involving ibuprofen, a solid-state interaction between MgO and ibuprofen was observed. In this study the interaction of MgO and ibuprofen was investigated for 1:1 and 2:1 M mixtures of ibuprofen and MgO, which had been stored at 55 degrees C, using the differential scanning calorimetric (DSC), thermogravic analysis (TGA), and multiple internal reflectance infrared (MIR) techniques. Evidence for the reaction was the disappearance of the melting endotherm at 79 degrees C and appearance of a new endotherm at 161 degrees C after less than 1 day of storage at 55 degrees C and, also, the change in the physical appearance of the mixtures. Comparison of the DSC, TGA, and MIR data for the reacted ibuprofen and MgO mixtures and synthetic Mg(ibuprofen)2 indicated that MgO and ibuprofen react to form the Mg salt of ibuprofen. The interaction of ibuprofen and MgO was also studied at 30 and 40 degrees C, using 1:1 M mixtures. At 30 degrees C no significant interaction was observed for up to 80 days; however, at 40 degrees C a reaction was evident on day 1. NaHCO3, K2CO3 1.5H2O, CaO, and Mg(OH)2 also showed solid-state reactions with ibuprofen. MgCl2 and Al(OH)3 did not show this reaction.

Rumen digestion of untreated and alkali‐treated cereal straws: A study by multiple internal reflectance infrared spectroscopy

AbstractMultiple internal reflectance (MIR) infrared spectroscopy of wheat and barley straw shows fundamental chemical differences between their inner and outer surface layers (1‐3 μm thick). Inner layers were dominated by polysaccharide in which cellulose and hemicellulose characteristics could be identified. Weak absorption arising from small amounts of lignin and acetyl groups was also detectable. In contrast, the outer layers were silicified (SiO2), more highly lignified, and contained ester groups which originate predominantly in cutin and long‐chain waxes in the outermost cuticular layer.MIR spectra of rumen‐incubated straw clearly indicate that little or no degradation occurred at the outer surface but that appreciable polysaccharide had been solubilised from the inner surface after 120 h of digestion. This was concluded from the detection of much higher levels of lignin at the inner surface, suggesting that the concentration of this component may be a limiting factor in the progress of the degradation. Absorption due to acetyl groups was also enhanced in spectra of the digested inner surface, suggesting that these groups also may be indirectly implicated in control of digestion.From changes in MIR spectra it was concluded that alkali pretreatment of straw scarcely alters the chemistry of the inner surfaces but significantly modifies that of the outer layers as a result of hydrolysis of cutin and acetyl ester groups and dissolution of a large proportion of the silica phase. These chemical changes result in surface disruption, probably providing additional routes by which enzymic attack can proceed beyond the point at which digestion of untreated straw ceases. An as yet unidentified organic component presumably of microbial origin accumulated preferentially on the outer straw surfaces during rumen digestion. It is not yet known whether this component exerts any influence on digestibility.

X-ray photoelectron and infrared spectroscopy of microwave plasma etched polyimide surfaces

I n situ x-ray photoelectron spectroscopy (XPS) and thermal desorption measurements indicate that etching of polyimide (PI) in a microwave oxygen plasma results in increased carbonyl (C–O) bonds on the etched surfaces, which can be removed by heating. Addition of CF4 to oxygen plasma enhances the etch rate, but also gives rise to fluorine coverages which appear to scale with the atomic F concentration in the gas mixture. XPS study of selected fluorinated model compounds shows that changes in the C 1s spectra of PI surfaces, etched in plasmas with different CF4 concentrations can be interpreted either as formation of Teflon-like passivation layers or as simply fluorinated benzenes. Exposure to x-ray irradiation at a constant flux or isothermal heating in vacuum caused the fluorine coverage to desorb in two stages, suggestive of two different fluorine-containing desorbing species. Experimental evidence obtained by multiple internal reflectance and transmission Fourier transform infrared spectroscopy indicates that for up to 50% CF4 additions, etching is accompanied by an increasing degree of fluorination of aromatic carbon. This is in contrast to the general belief that formation of a Teflon-like layer is responsible for inhibition of etch rate at higher CF4 concentrations in the gas mixture. A self-consistent model is proposed to explain these observations.

Mechanism of microwave plasma etching of polyimides in O 2 and CF 4 gas mixtures

A mechanistic study of microwave plasma etching of polyimides in oxygen plus CF 4 gas mixtures was carried out with several mutually complementary surface-sensitive characterization techniques. In-situ X-ray photoelectron spectroscopy was used to characterize the polyimide surfaces before and after etching while multiple internal reflectance and Fourier transform IR spectroscopy was employed to obtain additional information on molecular structure and chemical bonds on these surfaces. In addition, steady-state and temperature-programmed mass-spectrometric measurements were made to identify the etching products, their precursor states and desorbing species. When the experimental evidence obtained by these techniques is pieced together a coherent picture of the etching process emerges. Attachment of atomic oxygen produced in the plasma to selected carbon sites on the PI surface causes aromatic ring opening, forming precursors to volatile etching products. Addition of CF 4 to oxygen plasma in small amounts increases the efficiency of oxygen production and concomitant flourination of aromatic carbon provides excess energy for ring opening and promotes imide and ether bond cleavage. At higher CF 4 concentrations flourination exhausts the reaction sites for oxygen, thus inhibiting the etch rate. Thermal desorption studies indicate that the fluorine coverage desorbs in the first stage as fluorine molecules.

Electric-field effects on the infra-red absorption of H in a SiO2 film

A simple model of a localized, anharmonic oscillator is developed to simulate the dynamics of hydrogen in amorphous SiO2. The absorption coefficient in the presence of a strong electric field is evaluated in order to make a comparison with experimental multiple internal reflectance infra-red spectrum.

Amino acids from cellulose reacted in radio-frequency plasmas containing hydrogen and nitrogen

In a radio-frequency plasma of hydrogen and nitrogen, cellulose placed between the electrodes served as the source of carbon in the synthesis of a water-soluble film which was deposited downstream from the electrodes. The nitrogenous material was analysed by multiple internal reflectance infrared spectroscopy, electron emission spectroscopy and ultraviolet spectroscopy. Analysis showed that the material was almost entirely composed of amino acids. Seventeen different acids were detected with glycine, alanine, serine, and aspartic and glutamic acids predominant.

Multiple internal reflectance infrared spectra of variably hydrated hemoglobin and myoglobin films: effects of globin hydration on ligand conformer dynamics and reactivity at the heme.

Multiple internal reflectance infrared (IR) spectra are reported for variably hydrated films (1.2-0.1 g of H2O/g of protein) of the carbon monoxy and oxy forms of human Hb and sperm whale Mb. The spectra show that even the limited removal of liquid and icelike hydration constraints at the globin surface is sufficient to cause a dramatic, but completely reversible, shift toward a normally minute population of sterically unhindered, linear-perpendicular, Fe-CO conformer modes (nu CO = 1968-1967 cm-1), and the destabilization of distally hindered, tilted (or bent), Fe-CO modes (nu CO = 1951, 1944-1933 cm-1). Corroborative evidence from IR band broadening trends [delta delta nu 1/2 (1968, 1967 cm-1) approximately 2-4 cm-1], corresponding changes in the visible, and H-D exchange kinetics confirm that the shift toward 1968-1967 cm-1 results in a more open distal heme pocket configuration and that it is also accompanied by a buildup of deoxy-like steric hindrance proximal to the heme. Denaturation effects are eliminated as a potential cause of the shifts, as are specific protein-protein, ion-protein, intersubunit, and MIR crystal-film surface interactions. The hydration effect exhibits globin-dependent and ligand-dependent differences, which highlight the intrinsic importance of distal steric effects within the heme pocket and their dynamic coupling with exterior solvent constraints. CO-photodissociation and O2-exchange experiments conducted on rapidly interconverting (coupled and fully hydrated) and noninterconverting (uncoupled and partially hydrated) Fe-CO conformers also suggest that the open linear-perpendicular mode corresponds to a more tightly bound form of CO than the axially distorted Fe-CO species; similar differences are not evident in Fe-O2, which already prefers a bent end-on geometry within the heme pocket. Control IR spectra aimed at monitoring the progressive effects of various denaturants on HbCO further indicate that this same open mode serves as a common precursor to any of a number of more highly disordered folding modes. The overall properties of the 1968-1967-cm-1 conformer are discussed in terms of (1) the possibility of its corresponding to an available relaxation mode capable of facilitating the dynamics of ligand entry-release events and (2) its potential additional significance as a native folding mode that exhibits a marked tendency to be destabilized by hydration.

SiH and SiOH electromodulation at SiSiO 2 interfaces in a multiple internal reflectance configuration

Electromodulation of SiH and SiOH vibrational bands at a hydrogen-implanted SiSiO 2 interface in a multiple-internal-reflectance configuration is reported. Dipole stregthening and Stark shifts are calculated and theoretical lineshapes derived from their combinations are compared with the experimental electromodulation curves.

The effects of oxygen diffusion on the surface photooxidation of polystyrene

AbstractThis paper further illustrates the applicability of multiple internal reflectance infrared spectroscopy to the analysis of near‐surface photooxidation. The results are compared with transmission infrared spectra to evaluate compositional gradients resulting from photooxidation and the influence of oxygen diffusion. The sample was a solvent‐cast film of atactic, narrow distribution polystyrene, Mw of 100,000, that had been drawn to a ratio of 3.0 at 110°C by solid state coextrusion. Irradiation of these thin films, ∼25μm thickness, was performed on exposure to air at 35°C for periods of up to 6 h using a mercury source emitting at 254 nm. On photooxidation, a board peak appears at 3200–3500 cm−1, attributable to hydroperoxide formation. The most dramatic increase in the infrared spectra is found for a carbonyl band at 1730 cm−1. It appears to result from an aromatic acid group since it is shifted to 1660 cm−1 on immersion of the oxidized polystyrene films in aqueous ammonium hydroxide. It is confirmed that the photooxidation of polystyrene occurs preferentially at the surface and that this reaction rate is greatly reduced in the drawn polystyrene film.