Fourier Transform Infrared Spectroscopy In Attenuated Total Reflection Research Articles

Unveiling Polychrome Printing Methods on Textiles: Preliminary Results from the Mariano Fortuny y Madrazo Collection in Venice

At the beginning of the 20th century, the eclectic artist Mariano Fortuny y Madrazo patented two innovative methods for polychrome printing on fabrics and textiles, giving life to Fortuny fabric production in Venice. The first patent was related to colour application, while the second to a special machine that allows continuous printing using cylindrical rollers. Despite the descriptions, the methodology and materials used remain a secret. In collaboration with the Fortuny Museum in Venice, this research aimed at studying and identifying the different steps of Fortuny printing methodologies. Printing matrices, fabrics and raw materials found in the artist’s studio were analysed in a multi-analytical campaign through digital microscopy, X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy in attenuated total reflectance (FTIR-ATR), μ-Raman spectroscopy and gas chromatography–mass spectrometry (GC–MS). Three main pigments were identified in paper samples: ivory black, a copper-based pigment, and a carbon black pigment with ultramarine for blues. The pigments were bound with linseed oil and colophony in varying proportions. Polychrome silk fabrics were dyed with a base colour, and then the coloured patterns were superimposed by continuous printing. Prussian blue was identified as one of the textile inks. Results provided a better understanding of printing methodology.

The effects of exogenous substances on the color of heated bones.

Burned bone coloration has been used for decades to help in the bioanthropological analysis of burned human bones. However, there is a variety of factors that can interfere with the coloration manifested by bones exposed to heat, resulting in colors that differ from the usual black to white gradient. In this study, we evaluated possible causes of unusual coloration changes and hues in burned bone. For that purpose, defleshed fresh pig (Sus scrofa) ribs as well as fresh and dry human clavicles were burned at four different temperatures (500, 700, 900 and 1100°C) in contact with different materials (CaO, Zn, Fe, Cu, Mn, and polyester cloth). Observable color changes were assessed through naked eye observation and description, Munsell color charts, and reflectance spectrophotometry. Additionally, chemical changes in bone were assessed using Fourier-transform infrared spectroscopy in attenuated total reflectance (FTIR-ATR) and x-ray fluorescence (XRF). Our results showed that some materials did affect usual burned bone coloration (Fe, Mn, Cu, Zn) and correspondent FTIR-ATR and XRF spectra. As for other materials, although no effect on visual bone coloration was observed, they still affected FTIR-ATR and XRF spectra (CaO and cloth). This study can contribute to the anthropological analysis of burned human remains, providing some answers to what can cause unusual types of heat-induced colorations.

Hydrophobic AlOx Surfaces by Adsorption of a SAM on Large Areas for Application in Solar Cell Metallization Patterning

A resist-free metallization of copper-plated contacts is attractive to replace screen-printed silver contacts and is demonstrated on large-area silicon heterojunction (SHJ) solar cells. In our approach, a self-passivated Al layer is used as a mask during the plating process. In this study, Al/AlOx or Al2O3 plating masks are further functionalized by a self-assembled monolayer (SAM) of octadecyl phosphonic acid (ODPA). The ODPA adsorption is characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy in attenuated total reflectance (FTIR-ATR) (in situ), and contact angle measurements to link the surface chemical composition to wetting properties. The SAM leads to homogeneous hydrophobic surfaces on large-area textured solar cells and planar flexible printed circuit boards (PCBs), which allows reproducible patterning of narrow lines by inkjet printing of an etchant. Selective copper plating is then performed to complete the metallization process and produce Cu contacts in the patterned areas. Silicon heterojunction (SHJ) solar cells metallized by the complete sequence reached up to 22.4% efficiency on a large area.

Multiscale connections between morphology and chemistry in crystalline, zinc-substituted hydroxyapatite nanofilms designed for biomedical applications

Hydroxyapatite (HA), Ca10(PO4)6(OH)2, is a key material used to manufacture thin, bioactive coatings on metal implants for hard tissue regeneration. Technical challenges in their fabrication include control of the coating structure and chemical composition, as well as managing surface activation via ionic substitution. In this study, 15 – 216 nm-thick zinc-doped HA (ZnHA) thin films were grown via magnetron sputtering at room temperature. The effect of substituting Zn2+ for Ca2+ on the ultrastructures of the HA films was analyzed during several stages of film growth. Infrared vibrational scattering scanning near-field optical microscopy (s-SNOM) using the ultra-broad-band IR beam from synchrotron radiation was compared with Fourier transform infrared spectroscopy in attenuated total reflectance (FTIR/ATR) to reveal the close relationships between local topography and the chemical compositions of the film surface and the bulk of the film. The energy delivered via ionic bombardment induced the formation of complex structures: island-shaped nanoparticles of amorphous zinc-doped calcium phosphate, coalescent islands, disordered non-stoichiometric ZnHA nanoparticles, and long-range structures of nearly stoichiometric and crystalline ZnHA. Grazing incidence X-ray diffraction (GIXRD) from synchrotron radiation, X-ray photoelectron spectroscopy (XPS), focusing ion beam (FIB), and high-resolution transmission electron microscopy (HRTEM) confirmed Zn substitution into the HA lattice. Zinc was distributed homogeneously within the film structure (1.6 at%) but its concentration increased slightly on the film surface. The bulk of the film consisted of crystalline, columnar ZnHA domains oriented perpendicular to the substrate surface while the regions near the film/substrate interface were preferentially disordered and non-stoichiometric.

Adsorption of chromate and cupric ions onto chitosan-coated cotton gauze

A chitosan-coated cotton gauze was prepared by UV-curing and tested as adsorbent to remove copper (II) and chromium (VI) ions from water solutions. The adsorbent characterization was carried out by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX) and Fourier Transform Infrared Spectroscopy in Attenuated Total Reflection (FTIR-ATR).Adsorption of copper and chromium ions onto the gauze was tested in batch process at different experimental conditions. The effects of pH, temperature, contact time and metal ion concentration were investigated. The optimum adsorption took place at pH 3 for Cr(VI) and pH 5 for Cu(II) ions respectively, while the temperature did not affect the adsorption process.Pseudo-first and pseudo-second order models were used to investigate the adsorption kinetics which was found very fast and better described by the pseudo-second order model for both metal ions. The adsorption of Cr(VI) ions was satisfactory described by the Langmuir isotherm, while that of Cu(II) ions showed a better agreement with the Freundlich model.

20th century artists’ oil paints: The case of the Olii by Lucio Fontana

During the 20th century, many innovative binders have been rapidly introduced to the art world and soon became popular as artists’ paints and pictorial media. However, despite the advantages that new synthetic materials presented, oil paints have never been entirely substituted. Indeed, this paper focuses on the results provided by the scientific analysis of a group works from the oeuvre of Lucio Fontana (1899–1968), all of which created between 1960 and 1964 using oil-based media, and aims to illustrate how oils contained in the pictorial media have influenced these works’ respective ageing and degradation processes. Despite the apparent coherence in the behaviour of many of Fontana's creations, some artworks revealed discrepancies in terms of the physical and mechanical behaviour of the pictorial films and in alterations resulting from degradation processes. Samples taken from case studies belonging to the Olii and Fine di Dio series were analysed using optical microscopy, X-Ray Fluorescence (XRF), Fourier-Transform Infrared Spectroscopy in attenuated total reflectance (FTIR-ATR) and Gas Chromatography-Mass Spectrometry (GC-MS) in order to study and identify the materials employed by the artist and the products of their degradation processes. These analyses gave unexpected but useful results (such as the presence of non-drying or slow-drying oils in the paint formulations) which not only provided us with new insight into the nature of the constituent materials, but also facilitated the elaboration of correct conservation measures and suitable restoration interventions.

Polyetherimide composites with gamma irradiated carbon fabric: Studies on abrasive wear

Abstract Interfacial adhesion between matrix and fiber is an important aspect in controlling performance properties of the composites. Carbon fibers are known for chemical inertness and hence limited wettability with the matrix and need prior surface treatment to improve its adhesion with the matrix. In this work, γ (gamma) irradiation technique with varying doses (0–300 kGy) was employed to the twill weave carbon fabric (CF) to develop composites with polyetherimide (PEI) matrix based on impregnation method followed by compression molding. Composites were characterized for interlaminar shear strength (ILSS) and abrasive wear performance. Improvement in the friction and wear properties was correlated with the improvement in ILSS as a result of CF treatment. Higher the treatment dose, higher was the ILSS and better was the tribo-performance. SEM studies on fibers indicated increased roughness of the surface as a consequence of treatment and dose. Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance (FTIR-ATR) mode indicated inclusion of functional groups (mainly carbonyl). Both these factors were responsible for enhancing the fiber–matrix interface. Various techniques such as adhesion test, fiber tension test and Raman spectroscopic analysis of CF were also exploited to analyze the influence of γ irradiation on CF.

Physicochemical characterization of coumestrol/β-cyclodextrins inclusion complexes by UV–vis and FTIR-ATR spectroscopies

The inlcusion behaviour of unsubstituted β-cyclodextrin (β-CyD) and (2-hydroxypropyl)-β-cyclodextrin (HP-β-CyD), in solution and solid state was studied with regards to a poorly water-soluble bioflavonoid, coumestrol (Coum), namely 7,12-dihydroxycoumestan, well-known for its anti-oxidant, anti-inflammatory, anti-fungal and anti-viral activities. Phase-solubility measurements were performed to evaluate in solution the complexation of the two cyclodextrins, i.e. β-CyD and HP-β-CyD. The stoichiometry and stability constants of the Coum/β-CyD and Coum/HP-β-CyD complexes were calculated by the phase-solubility method, after which drug–cyclodextrin solid systems were prepared by co-precipitation. In solid phase, the formation of inclusion complexes was confirmed by Fourier transform infrared spectroscopy in attenuated total reflectance (FTIR-ATR) geometry. In particular, complexation mechanisms were explained by the significant differences revealed in the FTIR-ATR spectra of physical mixtures with respect to those of the complexes; the use of deconvolution and curve fitting was determinant.

Polyelectrolyte Multilayers of Weak Polyacid and Cationic Copolymer: Competition of Hydrogen-Bonding and Electrostatic Interactions

We report on the competitive role of hydrogen bonding and electrostatic interactions in growth and stability of polyelectrolyte multilayers (PEMs) in a wide range of pH. The system was a cationic copolymer of acrylamide and dimethyldiallylammonium chloride (PAAm-DMDAAC) containing 50% cationic units and poly(methacrylic acid) (PMAA) as a polyacid. The amounts of polymers adsorbed and ionization of carboxylic groups within a film were quantified using in situ FTIR-ATR (Fourier transform infrared spectroscopy in attenuated total reflection). The results were contrasted with the stability of films formed from polyacrylamide (PAAm) and PMAA. In the PAAm/PMAA system, interlayer adhesion occurred through hydrogen-bonding interactions, and the multilayer decomposed at pH > 5.5. However, the PAAm-DMDAAC/PMAA multilayers produced at low pH could be stabilized at a pH as high as 8 with transition to electrostatic interactions. With films deposited at pH = 2 from low ionic strength solutions, asymmetric release of P...

Layered, Erasable Polymer Multilayers Formed by Hydrogen-Bonded Sequential Self-Assembly

Robust multilayers can be formed on solid surfaces, and subsequently destroyed by changing the environmental conditions, by the layer-by-layer sequential assembly of monomolecular films of a polyacid and polybase from aqueous solution. Interlayer hydrogen bonding produces stable multilayers up to the point where altered pH or other environmental stimulus introduces an unacceptably large electrical charge within them. This is demonstrated for the polyacids poly(acrylic acid), PAA, and poly(methacrylic acid), PMAA, and for the polybases poly(vinylpyrrolidone), PVPON, and poly(ethylene oxide), PEO, in D2O. The adsorption was quantified by Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The ratio between suppressed ionization of the carboxylic groups within the film and their ionization in solution, as directly measured by FTIR-ATR, was used to estimate the fraction of hydrogen-bonded carboxylic groups; this was ∼0.5 in PVPON/PMAA but only ∼0.1 in the PEO/PMAA system, though...

Adsorption of human serum albumin: Dependence on molecular architecture of the oppositely charged surface

We contrast the adsorption of human serum albumin (HSA) onto two solid substrates previously primed with the same polyelectrolyte of net opposite charge to form one of two alternative structures: randomly adsorbed polymer and the “brush” configuration. These structures were formed either by the adsorption of quaternized poly-4-vinylpyridine (QPVP) or by end-grafting QPVP chains of the same chemical makeup and the same molecular weight to surfaces onto which QPVP segments did not adsorb. The adsorption of HSA was quantified by using Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). The two substrates showed striking differences with regard to HSA adsorption. First, the brush substrate induced lesser perturbations in the secondary structure of the adsorbed HSA, reflecting easier conformational adjustment for longer free segments of polyelectrolyte upon binding with the protein. Second, the penetration of HSA into the brush substrate was kinetically retarded relative to the randomly adsorbed polymer, probably due to both pore size restriction and electrostatic sticking between charged groups of HSA and QPVP molecules. Third, release of HSA from the adsorbed layer, as the ionic strength was increased from a low level up to the high level of 1 M NaCl, was largely inhibited for the brush substrate, but occurred easily and rapidly for the substrate with statistically adsorbed QPVP chains. Finally, even after addition of a strong polymeric adsorption competitor (sodium polystyrene sulfonate), HSA remained trapped within a brush substrate though it desorbed slowly from the preadsorbed QPVP layer. This method to produce irreversible trapping of the protein within a brush substrate without major conformational change may find application in biosensor design.

Graft polymerization of methyl methacrylate onto radiation-peroxidized ultrahigh molecular weight polyethylene in the presence of metallic salt and acid

Using a radiation peroxide grafting technique, a ultrahigh molecular weight polyethylene (UHMWPE) stored at room temperature for 10 days after irradiation in air was graft copolymerized with methyl methacrylate (MMA) in the presence of metallic salt and acid. The MMA-grafted UHMWPE samples were analyzed by measuring Fourier transform infrared spectroscopy in attenuated total reflectance (FTIR–ATR) and by electron spectroscopy for chemical analysis (ESCA). The 1,1-diphenyl-2-picrylhydrzyl (DPPH) technique was utilized to evaluate the concentration of peroxide formed in the peroxidized UHMWPE samples by counting the quantity of DPPH consumed from the reaction of peroxide radicals with DPPH. It was shown that the inclusion of an FeSO4 ·7H2O and sulfuric acid in MMA grafting solutions was extremely beneficial and led to a most unusual synergistic effect in the radiation-peroxidized grafting. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 659–666, 1999

Kinetic regimes of polyelectrolyte exchange between the adsorbed state and free solution

We studied the exchange between the adsorbed state and free solution when polyelectrolyte chains, adsorbed to a solid surface of opposite charge, were displaced by chains of higher charge density. Metastable states of surface composition were extremely long-lived (>2–3 days). The system was a family of poly(1,4 vinyl)pyridines (PVP) with different fractions of charged segments (14%, 48%, and 98% quaternized and the same degree of polymerization); samples were exposed sequentially from aqueous D2O solution to a single silicon oxide substrate at pH where the surface carried a large negative charge (pH=9.2 or 10.5). Measurements were based on Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). As a first conclusion, we found charge of adsorbed polymer to be conserved during extended exchange times, suggesting that charge at the surface (not mass adsorbed) regulated the dynamics of adsorption and desorption. Except at the highest ionic strength charge of polymer at the surface during the displacement process considerably exceeded that for the initially-adsorbed layer, suggesting an intermediate state in which newly-adsorbed chains were more extended from the surface and not yet equilibrated in their conformations. Second, we concluded that desorption was the rate-limiting step in adsorption–desorption, since the desorption rate responded more to changes of ionic strength than did the adsorption rate onto previously-adsorbed polymer. Ionic strength appeared to modulate the intensity of sticking to the surface. Third, we found that the initial stages of desorption obeyed a simple functional form, exponential in the square root of elapsed time. This is conclusively slower than a first-order kinetic process and suggests that desorption in this polyelectrolyte system was diffusion-controlled during the initial stages. It is the same functional form observed for flexible polymers in nonpolar solvents. Fourth, we concluded that at relatively low concentration of salts desorption proceeded in two stages; one subpopulation of adsorbed chains desorbed relatively quickly, with a rate exponential in the square root of time, and a second subpopulation was so much slower to be desorb that it appeared to be kinetically frozen at the surface. The higher the ionic strength, the less the polymer was kinetically frozen and this effect disappeared entirely for the highest ionic strength. The interpretation that the kinetically-frozen states reflected conformational heterogeneities within the adsorbed layer was supported by direct measurements of the dichroic ratio of adsorbed pyridinium rings. Finally, a new kinetic regime was observed at the highest salt concentrations, in which the exchange was inhibited by worsened solubility of the displaced molecules. It is significant that this regime began at salt concentrations significantly below the point of bulk insolubility. Since most organic polyelectrolytes may be considered to be a copolymer of polar charged units and hydrophobic uncharged units, this effect is expected to be general.

Polyelectrolyte adsorption onto an initially-bare solid surface of opposite electrical charge

We contrast the adsorption, over a wide range of pH and ionic strength, of polyelectrolyte chains with different fractions of charged segments but similar degree of polymerization. The system was a cationic polymer, poly(1,4 vinyl)pyridine (PVP), with 14%, 48%, and 98% quaternized repeat units, adsorbed from aqueous solution (D2O or H2O) onto a single silicon oxide substrate at 25 °C. Measurements were based on Fourier transform infrared spectroscopy in attenuated total reflection (FTIR-ATR). In the first phase of this study, we varied the surface charge density by changing pH and showed that attraction of PVP to the surface was electrostatic. The amount adsorbed of charged (quaternized) PVP segments was nearly the same regardless of the overall fraction of charged segments in the chain. In addition, polymer adsorption appeared to enhance the dissociation of silanol groups on the solid surface. In a second phase of this study, the ionic strength was varied systematically under conditions of high negative surface charge density (high pH), focusing on 98% quaternized PVP. Strong chemical specificity was found; the polyelectrolyte was insoluble in KI above a low salt concentration, but soluble in NaCl, signifying that the anions, Cl− and I−, competed with the negatively-charged surface for association with the polyelectrolyte. At the same time, the cations, Na+ and K+, competed with the polyelectrolyte for access to the limited surface area. The mass adsorbed increased strongly with increasing salt concentration and, for polymer in aqueous NaCl, passed through a maximum with subsequent decrease, reflecting a greater abundance of loops and tails at intermediate ionic strength and ultimately complete desorption of the chains when the salt concentration was very high. The maximum in mass adsorbed occurred at very high ionic strength (1 molar NaCl), indicating competitive adsorption of Na+ with charged segments of the polymer. Direct measurements of the infrared dichroism of pyridinium rings of the adsorbed PVP confirmed the presence of a relatively flattened state at low ionic strength and nearly isotropic orientation otherwise. In the third phase of this study, we studied the competitive adsorption to surfaces of high negative charge of Na+ and a monomeric analog of the PVP repeat unit, the 1,4-dimethylpyridinium ion (P+). A tentative quantitative estimate of the effective surface sticking energy of P+ relative to Na+ ions indicated a decrease from 7kBT in low-ionic-strength buffer solution to 4.5kBT in 0.5 M NaCl. These numbers appear to exceed the weak-adsorption limit in which facile equilibration of the adsorbed layer should be expected.

Formation and Characterization of Covalently Bound Polyelectrolyte Brushes

Poly(4-vinylpyridine) (PVP), functionalized at one terminus with a styrenyl group, was end-grafted to vinyl-functionalized self-assembled monolayers by UV irradiation in 1-methyl-2-pyrrolidinone. In this solvent and with oxygen excluded, surface reactions appeared to be selectively limited to the polymer terminus. The dry film thickness was determined by ellipsometry and the grafted amount by FTIR-ATR (Fourier transform infrared spectroscopy in attenuated total reflection). Controlled amounts of positive charge were introduced into the grafted chains by alkylation with a 2.5% solution of CH3I in dimethylformamide (DMF). FTIR-ATR was used to quantify the extent of alkylation, from 10% to 96%. These polyelectrolyte brushes will comprise a model system for studying polyelectrolytes at surfaces.

Mass adsorbed and surface forces in ternary solution as nonsolvent was added to the point of precipitation: polystyrene in mixtures of cyclopentane and linear pentane

The influence of ternary solvent composition on mass adsorbed and on surface forces between adsorbed polystyrene layers was investigated. Polystyrene (M, = 500 000 and 3.84 X lo6) was adsorbed onto silicon oxide and mica from dilute solution (0.15 mg mL-1) in mixtures of cyclopentane and n-pentane at 23 OC. Simplicity was afforded by the fact that the two solvents were expected to mix nearly athermally. FTIR-ATR (Fourier transform infrared spectroscopy in attenuated total reflection) was used to measure mass adsorbed at the silicon oxide interface, and surface forces were measured between overlapping adsorbed layers at the muscovite mica interface. Three principal findings emerged. (1) The levels of adhesion and the thicknesses of the adsorbed polymer layers, measured in the surface force apparatus, increased significantly with the addition of nonsolvent, but there was a continuous transition between behavior in homogeneous solution and in phase-separated solution. (2) The mass of polystyrene adsorbed at the silicon oxide interface increased systematically with higher volume fraction, 43, of n-pentane. The relation Ar = 43*.13 (Ar is the mass adsorbed in excess of that adsorbed from undiluted cyclopentane) described this increase empirically, amounting to a factor of 2 before the point of precipitation. (3) Possibly contrary to intuition, there occurred no detectable (<0.1 mg m-2) depletion of the nonsolvent, n-pentane, from the adsorbed polymer layers (surface coverages 4 and 5.5 mg m-9. Two hypotheses are suggested; they pertain not only to polymers in ternary solution but also to polymer chains adsorbed from a single solvent. First, the adhesion in two-phase solution sets a resonable upper bound on the interfacial tension between a polymer-rich surface and a polymer-poor coexisting solution, y = 0.05 mJ/m2. Second, the large but still microscopic amount adsorbed just before phase separation is consistent with the expectation that adsorbed monolayers should broaden to form mul- tilayers containing chains, none of whose segments are located directly at the substrate surface.