XPS investigations of ink‐jet printed paper

Different ink‐jet printed paper materials were investigated using X‐ray photoelectron spectroscopy (XPS) yielding the elemental composition of the near‐surface region of the papers. We found significant differences with respect to the detected elements and their atomic concentrations in the different inks studied here. Two different groups of inks could be identified by means of a lower ratio of the O and C atomic concentrations and lower concentrations in specific trace elements like Mg, Na and Si. High‐resolution spectra of C 1s and O 1s core levels allowed a detailed determination of the chemical state of the respective elements. On the basis of a detailed deconvolution of these XPS signals, significant differences between all the investigated ink‐jet printed papers were found, thereby allowing their discrimination. The applicability of the measurements and, more generally, the XPS technique for forensic investigations of paper are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Comparison of the degradation behavior of cotton, linen, and kozo papers

The long term degradation behavior of cotton, linen, and kozo papers was studied to compare changes to the chemical and physical properties with time. The elemental composition, α-content, β-content, γ-content, and lignin content (K number) of the three unaged controls were determined. The papers were then degraded at 90 °C and 50 % relative humidity for several thousand hours. Changes to the pH, carbonyl content, yellowness index (YI), moisture content, molecular weight, and tensile strength with aging were monitored. The general trends in degradation behavior of linen and kozo papers were similar to cotton in that all three showed decreases in pH, molecular weight, and strength as well as increases in carbonyl content and YI during hydrolysis. However, the kinetics of degradation differed between the three papers. The cellulose component of all three papers dominated measured changes to the molecular weight while the presence of hemicellulose in the linen and kozo papers led to unique measured moisture contents, carbonyl group, and YI values relative to cotton after the same amount of degradation had occurred.     

Py/GC/MS characterisation of naturally and artificially aged inks and papers

A set of inks was analyzed using Py/GC/MS technique. They were prepared following some ancient Armenian recipes and then analyzed after being dried in air to obtain solid samples. A simple analytical procedure was adopted which excludes any treatment of the samples and consists in introducing the solid sample directly into the injector of the furnace pyrolyzer. Inks were also written on whatman paper by calamum and analyses of papers containing ink were carried out. A real sample analysis was reported. Comparing the pyrograms it was possible to discriminate fragments derived from ink, from that formed by the decomposition of paper by the influence of ink. In order to understand the origin of the fragments formed during the pyrolysis of inks the standard compounds used to prepare them were carried out, too.     

Iron gall ink-induced corrosion of cellulose: aging,degradation and stabilization. Part 2: application on historic sample material

Degradation of cellulose in historic paper by iron gall ink is a synergistic process of both, acid hydrolysis caused by acidic ink ingredients and oxidation catalyzed by free iron and/or copper ions. The interplay of both reactions was studied according to the CCOA method on historic paper samples. Only minute amounts (few mg) of the samples were required to obtain profiles of naturally present and oxidatively introduced carbonyl groups, which was done by group-selective fluorescence labeling in combination with determination of the molecular weight distribution by GPC-MALLS. In the present study naturally occurring degradation pathways in historic sample papers have been investigated. Different extents of oxidatitive degradation were shown for paper with and without ink. A typical pattern of the molecular weight distribution in naturally aged papers was identified, the peculiar feature being a distinctive shoulder in the region of low molecular weight, roughly between 25,000 and 5,000 g/mol corresponding to a DP between 150 and 30. This pattern was a typical attribute of degraded natural samples: any artificial aging procedures aimed at modeling natural aging processes must thus attempt to reproduce this feature. Although the historic samples had been more severely oxidized than model papers, the inhibition of further oxidation and hydrolysis by the calcium phytate/hydrogen carbonate treatment was evident and could be proven for the first time on the molecular level. Also on plain paper without ink application the oxidation was suppressed and the molecular weight was stabilized on a high level.     

Nano emulsion binders for paper coating synthesis and application

The key objectives of coating papers and paperboards are to improve their aesthetic appearance and printability. Coatings offer smoothness, gloss, brightness, and opacity to the base papers and provide them with enhanced printability, which requires resistance to ink splitting forces, smoothness, ink holdout and gloss, etc. Styrene acrylate latexes were synthesized, via emulsion polymerization, and were formulated as coats for white and brown recycled papers. Both processes were characterized specifically for offset printing. The prepared latexes showed enhanced solid content, viscosity, zeta potential and appropriate glass transition temperature for paper coating formulation. The porosity, gloss and Cobb60 values of coated papers increased with the increased addition of nano-emulsion modified latexes. The formulations afforded high printability (print gloss and print density) with local ground calcium carbonate compared with that of the imported pigment (kaolin). Furthermore, the synthesized binder had higher water resistance than the commercial one; which can tightly be correlated with print quality, printability and productivity and most significantly, permits usage of low viscous ink. Coated recycled brown base gave promising results with respect to print quality although offset printing was utilized. The novelty of this work was not only in employing the local alternative binder and local pigment but also in achieving compatibility with environmental regulations since oil-based inks and recycled papers were also used.     

X-ray fluorescence spectrometry on paper characterization: A case study on XVIII and XIX century documents

Paper documents from XVIII and XIX centuries were analyzed by energy dispersive X-ray fluorescence. The presence of Co (400 µg g^− 1), Ni (300 µg g^− 1), As (2000 µg g^− 1) and Bi (200 µg g^− 1) in Dutch papers and a Hespe watermarked paper allowed distinguishing them from the rest of the papers. The elemental composition of the ink present in these documents was also studied with the same technique and it was concluded that these elements could not be originated from ink dissemination. Strong positive Spearman correlations between Co, Ni, As and Bi were found in all Dutch and Hespe watermarked papers. Potassium and Ca are the predominant elements in all analyzed papers. Their concentration levels also allowed differentiating between Dutch and Hespe papers and the rest of the papers. Other elements such as Ti, Fe, Cu, Zn, Ba and Pb were also found. In this work a bibliographic research about the possible origin of each one of the mentioned elements present in the papers is also reported.     

Characterisation of organoclays and adsorption of p-nitrophenol: environmental application

Organoclays were synthesised through ion exchange of a single surfactant for sodium ions, and characterised by a range of method including X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). The change in surface properties of montmorillonite and organoclays intercalated with the surfactant, tetradecyltrimethylammonium bromide (TDTMA) were determined using XRD through the change in basal spacing and the expansion occurred by the adsorbed p-nitrophenol. The changes of interlayer spacing were observed in TEM. In addition, the surface measurement such as specific surface area and pore volume was measured and calculated using BET method, this suggested the loaded surfactant is highly important to determine the sorption mechanism onto organoclays. The collected results of XPS provided the chemical composition of montmorillonite and organoclays, and the high-resolution XPS spectra offered the chemical states of prepared organoclays with binding energy. Using TGA and FT-IR, the confirmation of intercalated surfactant was investigated. The collected data from various techniques enable an understanding of the changes in structure and surface properties. This study is of importance to provide mechanisms for the adsorption of organic molecules, especially in contaminated environmental sites and polluted waters.     

Studies on the degradation of blue gel pen dyes by ion-pairing high performance liquid chromatography and electrospray tandem mass spectrometry

Ion-pairing high performance liquid chromatography (IP-HPLC) was utilized to monitor the composition changes of blue gel pen ink entries on paper stored in different light conditions and natural environment. The chromatographic conditions were optimized by comparing the separation efficiencies of the blue gel pen inks using a series of ion-pairing reagents, including ammonium carbonate, ammonium acetate, triethylamine acetate, tributylamine acetate, tetrabutylammonium bromide and dihexylammonium acetate. It has been found that tributylamine acetate was a suitable ion-pairing reagent for separation of the inks on the common C18 column. The analysis results of the ink entries on paper in different aging conditions showed that the tendency of composition change in natural aging condition was similar with those in fluorescent light and UV light conditions, respectively. One main component dye of the blue gel pen ink, Acid Blue 9, and its degradation products were identified by ion-pairing high performance liquid chromatography coupled with electrospray tandem mass spectrometry. The results showed that the main degradation products originated from the Acid Blue 9. It gave a reasonable explanation for the changing rules of the relative content of the dyes in the blue gel pen ink. The results obtained can provide scientific evidences for dating of the blue gel pen ink entries on documents.     

Surface modification of carbon black by thiol-ene click reaction for improving dispersibility in aqueous phase

Carbon black (CB) particles were firstly encapsulated by γ-Methacryloxypropyltrimethoxysilane (MEMO) using a sol-gel method and then grafted with sodium 3-Mercapto-1-propanesulfonate (MPS) via thiol-ene click reaction. Morphology characterization reveals that modified CB particles have a core-shell structure. Element composition and chemical status derived from X-ray photoelectron spectroscopy (XPS) results prove the grafting of MPS molecules. Moreover, the crystal structure and thermal behavior of modified CB particles were characterized by Raman spectra and Thermogravimetric analysis (TGA) curves, respectively. The modified CB particles exhibit excellent self-dispersing ability in aqueous media and the dispersion has high thermal and centrifugal stability. This research provides a new insight into the preparation of inkjet printing ink with excellent stability.     

Iron gall ink-induced corrosion of cellulose: aging,degradation and stabilization. Part 1: model paper studies

Cellulose in historic paper documents is often damaged by the writing media used, especially iron gall ink or copper pigments. Degradation induced by iron gall ink is suggested to be a synergistic process comprising both hydrolytic and oxidative reactions. These processes were studied on very low sample amounts according to the CCOA and FDAM method, i.e. by fluorescence labeling of carbonyl and carboxyl groups in combination with GPC-MALLS, respectively. This study focused on preventive means to stop the deterioration induced by iron gall ink of cellulose and to prevent further damage, keeping in mind that a suitable conservation treatment has to hinder both, hydrolytic and oxidative processes, at the same time. A combination of the complexing agent calcium phytate and calcium hydrogencarbonate in aqueous solution was proved to give optimum results. To gain insight into long term stability, an aging step was performed after treatment and different ink modifications were tested. Recording the molecular weight distributions and the carbonyl group content over time GPC analysis verified for the first time the preventive effect of this treatment. This effect was not only seen for the ink-covered areas, but extended also to areas remote from the ink lines. Ink containing copper ions responded equally positively to the calcium phytate/hydrogencarbonate treatment as the iron gall ink papers did. Gelatine, sometimes used in a similar way due to an alleged cellulose-stabilizing effect did not have a beneficial influence on cellulose integrity when metal ions were present.     

Micro-spectrochemical analysis of document paper and gel inks by laser ablation inductively coupled plasma mass spectrometry and laser induced breakdown spectroscopy

Current methods used in document examinations are not suitable to associate or discriminate between sources of paper and gel inks with a high degree of certainty. Nearly non-destructive, laser-based methods using laser induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used to improve the forensic comparisons of gel inks, ballpoint inks and document papers based on similarities in elemental composition. Some of the advantages of these laser-based methods include minimum sample consumption/destruction, high sensitivity, high selectivity and excellent discrimination between samples from different origins. Figures of merit are reported including limits of detection, precision, homogeneity at a micro-scale and linear dynamic range. The variation of the elemental composition in paper was studied within a single sheet, between pages from the same ream, between papers produced by the same plant at different time intervals and between seventeen paper sources produced by ten different plants. The results show that elemental analysis of paper by LIBS and LA-ICP-MS provides excellent discrimination (> 98%) between different sources. Batches manufactured at weekly and monthly intervals in the same mill were also differentiated. The ink of more than 200 black pens was analyzed to determine the variation of the chemical composition of the ink within a single pen, between pens from the same package and between brands of gel inks and ballpoint inks. Homogeneity studies show smaller variation of elemental compositions within a single source than between different sources (i.e. brands and types). It was possible to discriminate between pen markings from different brands and between pen markings from the same brand but different model. Discrimination of ~ 96–99% was achieved for sets that otherwise would remain inseparable by conventional methods. The results show that elemental analysis, using either LA-ICP-MS or LIBS, provides an effective, practical and robust technique for the discrimination of document paper and gel inks with minimum mass removal (9–15 μg) and minimum damage to the document's substrate.     

Solid ink-printed filter paper as a green adsorbent material for the solid-phase extraction of UV filters from water samples

This work describes the development of a new green solid-phase extraction approach, which is based on the use of low-cost extraction discs composed of plain filter papers that are covered with a synthetic wax-like coating. The filter papers are printed in a commercial solid ink printer, which dispenses a synthetic wax-like ink on the surface of the paper, to cover the hydrophilic cellulose fibre matrix with an interface of lipophilic domains where non-polar analytes can partition through hydrophobic interactions. The modified paper filters were used to extract hydrophobic organic compounds from water samples following the customary procedure of solid-phase extraction without sorbent preconditioning and needless of high-vacuum sources. As a proof-of-concept application, a series of non-polar organic UV filters were used as model analytes to optimise the extraction parameters and evaluate the performance of the method in spiked water samples. Based on this principle, a new sample preparation platform with low environmental footprint has been developed that enables extraction to be carried out using low-cost, environmental benign and non-toxic conventional materials. The advantages and disadvantages of the method, alongside with its future prospects towards the development of custom-made ‘printed extraction kits’, are envisioned and discussed.     

Effect of atomization on surface oxide composition in 316L stainless steel powders for additive manufacturing

The initial oxide state of powder is essential to the robust additive manufacturing of metal components using powder bed fusion processes. However, the variation of the powder surface oxide composition as a function of the atomizing medium is not clear. This work summarizes a detailed surface characterization of three 316L powders, produced using water atomization (WA), vacuum melting inert gas atomization (VIGA), and nitrogen atomization (GA). X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy analyses were combined to characterize the surface state of the powders. The results showed that the surface oxides consisted of a thin (~4 nm) iron oxide (Fe₂O₃) layer with particulate oxide phases rich in Cr, Mn, and Si, with a varying composition. XPS analysis combined with depth-profiling showed that the VIGA powder had the lowest surface coverage of particulate compounds, followed by the GA powder, whereas the WA powder had the largest fraction of particulate surface oxides. The composition of the oxides was evaluated based on the XPS analysis of the oxide standards. Effects of Ar sputtering on the peak positions of the oxide standards were evaluated with the aim of providing an accurate analysis of the oxide characteristics at different etch depths.     

Liquid–paper interactions during liquid drop impact and recoil on paper surfaces

The spreading and recoiling of water drops on several flat and macroscopically smooth model surfaces and on sized paper surfaces were studied over a range of drop impaction velocities using a high-speed CCD camera. The water drop spreading and recoiling results on several model hydrophobic and hydrophilic surfaces were found to be in agreement with observations reported in the literature. The maximum drop spreading diameter for those model surfaces at impact was found to be dependent upon the initial drop kinetic energy and the degree of hydrophobicity/hydrophilicity of the surface. The extent of the maximum drop recoiling was found to be much weaker for hydrophilic substrates than for hydrophobic substrates. Sized papers, however, showed an interesting switch of behaviour in the process of water drop impaction. They behave like a hydrophobic substrate when a water drop impacts on it, but like a hydrophilic substrate when water drop recoils. Although the contact angle between water and hydrophilic or hydrophobic non-porous surfaces changes from advancing to receding as reported in literature, the change of contact angle during water impact on paper surface is unique in that the level of sizing was found to have a smaller than expected influence on the degree of recoil. Atomic force microscopy (AFM) was used to probe fibres on a sized filter paper surface under water. The AFM data showed that water interacted strongly with the fibre even though the paper was heavily sized. Implications of this phenomenon were discussed in the context of inkjet print quality and of the surface conditions of sized papers. Results of this study are very useful in the understanding of inkjet ink droplet impaction on paper surfaces which sets the initial condition for ink penetration into paper after impaction.     

Characterization of Carbohydrates in Paper and Paper Pulps Using Anion Exchange Chromatography and Principal Component Analysis

In the course of this investigation, a method for the characterization and differentiation of paper pulps was developed. After hydrolyzation of the papers and the respective raw pulps with trifluoroacetic acid, the hydrolyzates were analyzed with respect to their carbohydrate composition using ion exchange chromatography. The variations in carbohydrate composition mainly arise from the various hemicelluloses of the papers and pulps. The chromatographic results were then further processed using principal component analysis which allows correlating the various papers to different pulp materials.     

Surface modification of EPDM rubber by plasma treatment

The effect of argon, oxygen, and nitrogen plasma treatment of solvent cast EPDM rubber films has been investigated by means of atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and surface energy measurements. Plasma treatment leads to changes in the surface energy from 25 to 70 mN/m. Treatment conditions influenced both the changes in surface energy and the stability, and it became more difficult to obtain good contact angle measurements after longer (> ca. 4 min) treatment times, probably because of an increasingly uneven surface structure. XPS analyses revealed that up to 20 at. % oxygen can be easily incorporated and that variations of approximately 5% can be controlled by the plasma conditions. Oxygen was mainly found in hydroxyl groups, but also as carbonyl and carboxyl. XPS analyses showed more stable surfaces than expected from contact angles, probably because XPS analysis is less surface sensitive than contact angle measurements. AFM measurements revealed different surface structures with the three gases. The surface roughness increased generally with treatment time, and dramatic changes could be observed at longer times. At short times, surface energy changes were much faster than the changes in surface structure, showing that plasma treatment conditions can be utilized to tailor both surface energies and surface structure of EPDM rubber.     

Activation of PET Using an RF Atmospheric Plasma System

The plasma treatment of polymer surfaces is routinely used to enhance surface properties prior to adhesive bonding or biomolecule interaction. This study investigates the influence of plasma treatment conditions on the surface activation of polyethylene terephthalate (PET) using the SurFx Atomflo? 400L plasma source. In this study the effect of applied plasma power, processing speed, gas composition and plasma applicator nozzle to substrate distance were examined. The level of polymer surface activation was evaluated based on changes to the water contact angle (WCA) of PET samples after plasma treatment. PET surface properties were also monitored using surface energy and X-ray photoelectron spectroscopy (XPS) analysis. The heating effect of the plasma was monitored using thermal imaging and optical emission spectroscopy (OES) techniques. OES was also used as a diagnostic tool to monitor the change in atomic and molecular species intensity with changes in experimental conditions in both time and space. XPS analysis of the PET samples treated at different plasma powers indicated that increased oxygen content on samples surfaces accounted for the decreases observed in WCAs. For the first time a direct correlation was obtained between polymer WCA changes and the OES measurement of the atomic hydrogen Balmer H_α and molecular OH line emission intensities.     

Multitechnique characterization of thin films of immiscible polymer systems: PS–b‐PMMA diblock copolymers and PS–PMMA symmetric blends

Immiscible polymer systems are known to form various kinds of phase‐separated structures capable of producing self‐assembled patterns at the surface. In this study, different surface characterization methods were utilized to study the surface morphology and composition produced after annealing thin polymer films. Two different SIMS techniques—static time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and dynamic nano‐SIMS—were used, complemented by x‐ray photoelectron spectrometry (XPS) and atomic force microscopy (AFM). Thin films (spin‐coated onto silicon wafers) of polystyrene (PS)–poly(methyl methacrylate) (PMMA) symmetric blends and diblock copolymers of similar molecular weight were investigated. Surface enrichment by PS was found on all as‐cast samples. The samples were annealed at 160 °C for different time periods, after which the blend and the copolymer films exhibited opposite behaviour as seen by ToF‐SIMS and XPS. The annealed blend surface presented an increase in the PMMA concentration whereas that of copolymers showed a decrease in PMMA concentration compared with the as‐cast sample. For blends, the nano‐SIMS as well as AFM images revealed the formation of phase‐separated domains at the surface. The composition information obtained from ToF‐SIMS and XPS, as well as the surface mapping by nano‐SIMS and AFM, allowed us to conclude that PS formed phase separated droplet‐like domains on a thin PMMA matrix on annealing. The three‐dimensional nano‐SIMS images showed that the PS droplets were supported inside a rim of PMMA and that these droplets continued from the surface like columnar rods into the film until the substrate interface. In the case of annealed copolymer samples, the AFM images revealed topographical features resembling droplet‐like domains on the surface but there was no phase difference between the domains and the matrix. In the case of copolymers, owing to the covalent bonding between the blocks, complete phase separation was not possible. The three‐dimensional nano‐SIMS images showed domain structures in the form of striations inside the film, which were not continuous until the substrate interface. Information from the different techniques was required to gain an accurate view of the surface composition and topographical changes that have occurred under the annealing conditions. Copyright © 2005 John Wiley & Sons, Ltd.