Electrosynthesis and analytical characterization of PMMA coatings on titanium substrates as barriers against ion release

The performance of polyacrylic coatings as barrier films against corrosion of titanium-based orthopaedic implants was investigated. In particular, poly(methyl methacrylate) (PMMA) was electrosynthesized on titanium substrates by electro-reductive processes from aqueous monomer solutions. The obtained PMMA coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of an annealing treatment on the morphology of coatings with respect to uniformity and porosity of films was assessed by scanning electron microscopy (SEM). An inductively coupled plasma-mass spectrometry (ICP-MS) technique was used for ion concentration measurements in ion release tests performed on TiAlV sheets modified with PMMA coatings (annealed and unannealed). Results indicated that the annealing process produces coatings with considerable anticorrosion performances.Electronic Supplementary Material Supplementary material is available for this article at     

Chemical and structural characterization of carbon nanotube surfaces

To utilize carbon nanotubes (CNTs) in various commercial and scientific applications, the graphene sheets that comprise CNT surfaces are often modified to tailor properties, such as dispersion. In this article, we provide a critical review of the techniques used to explore the chemical and structural characteristics of CNTs modified by covalent surface modification strategies that involve the direct incorporation of specific elements and inorganic or organic functional groups into the graphene sidewalls. Using examples from the literature, we discuss not only the popular techniques such as TEM, XPS, IR, and Raman spectroscopy but also more specialized techniques such as chemical derivatization, Boehm titrations, EELS, NEXAFS, TPD, and TGA. The chemical or structural information provided by each technique discussed, as well as their strengths and limitations. Particular emphasis is placed on XPS and the application of chemical derivatization in conjunction with XPS to quantify functional groups on CNT surfaces in situations where spectral deconvolution of XPS lineshapes is ambiguous.      

Application of XPS and ToF-SIMS for surface chemical analysis of DNA microarrays and their substrates

The chemical composition of the functional surfaces of substrates used for microarrays is one of the important parameters that determine the quality of a microarray experiment. In addition to the commonly used contact angle measurements to determine the wettability of functionalized supports, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) are more specific methods to elucidate details about the chemical surface constitution. XPS yields information about the atomic composition of the surface, whereas from ToF-SIMS, information on the molecular species on the surface can be concluded. Applied on printed DNA microarrays, both techniques provide impressive chemical images down to the micrometer scale and can be utilized for label-free spot detection and characterization. Detailed information about the chemical constitution of single spots of microarrays can be obtained by high-resolution XPS imaging. Figure Eye-catching image for the graphical online abstract     

‘Gate effect’ in templated polyacrylamide membranes influences the electrotransport of proteins and finds applications in proteome analysis

Templating is an effective way for the structural modifications of a material and hence for altering its functional properties. Here protein imprinting was exploited to alter polymeric polyacrylamide (PAA) membranes. The sieving properties and selection abilities of the material formed were evaluated by studying the electrically driven transport of various proteins across templated PAA membranes. The sieving properties correlated with the templating process and depended on the quantity of template used during the polymerisation. For 1 mg/mL protein-templated membranes a ‘gate effect’ was shown, which induced a preferential migration of the template and of similar-size proteins. Such template preferential electrotransport was exploited for the selective removal of certain proteins in biological fluids prior to proteome analysis (depletion of albumin from human serum); the efficiency of the removal was demonstrated by analysing the serum proteome by two-dimensional electrophoresis experiments. Figure PAA templeted membrane for the electroremoval of serum albumin before proteome analysis     

Application of surface chemical analysis tools for characterization of nanoparticles

The important role that surface chemical analysis methods can and should play in the characterization of nanoparticles is described. The types of information that can be obtained from analysis of nanoparticles using Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary-ion mass spectrometry (TOF-SIMS), low-energy ion scattering (LEIS), and scanning-probe microscopy (SPM), including scanning tunneling microscopy (STM) and atomic force microscopy (AFM), are briefly summarized. Examples describing the characterization of engineered nanoparticles are provided. Specific analysis considerations and issues associated with using surface-analysis methods for the characterization of nanoparticles are discussed and summarized, with the impact that shape instability, environmentally induced changes, deliberate and accidental coating, etc., have on nanoparticle properties.      

SPME in environmental analysis

Recent advances in the use of solid-phase microextraction (SPME) in environmental analysis, including fiber coatings, derivatization techniques, and in-tube SPME, are reviewed in this article. Several calibration methods for SPME, including traditional calibration methods, the equilibrium extraction method, the exhaustive extraction method, and several diffusion-based calibration methods, are presented. Recent developed SPME devices for on-site sampling and several applications of SPME in environmental analysis are also introduced.      

Microstructural and chemical transformation of thin Ti/Pd and TiD<Subscript><Emphasis Type="BoldItalic">y</Emphasis></Subscript>/Pd bilayer films induced by vacuum annealing

Using a combination of scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction and X-ray photoelectron spectroscopy (XPS), we made a comparative study of the high-temperature annealing impact on thin titanium deuteride (TiD _y ) films covered by an ultrathin Pd layer, and on Ti/Pd bilayer films. The bilayer films were prepared under ultrahigh vacuum conditions and were in situ annealed using the same annealing procedure. It was found that the surface and the bulk morphology of both films undergo different annealing-induced transformations, leading to an extensive intermixing between the Ti and Pd layers and the formation of a new PdTi₂ bimetallic phase. Energy-filtered TEM imaging and energy-dispersive X-ray spectrometry analysis, as well as XPS depth profiling all provided evidence of a different distribution of Pd and Ti in the annealed TiD _y /Pd film compared with the annealed Ti/Pd film. Our results show that thermal decomposition of TiD _y , as a consequence of annealing the TiD _y /Pd film, modifies the intermixing process, thereby promoting Ti diffusion into the Pd-rich top layer of the TiD _y film and thus providing a more likely path for the formation of the PdTi₂ phase than in an annealed Ti/Pd film. Figure Figure Microstructural and chemical characterisation of thin TiDy/Pd film after annealing     

Effect of oxidation of nitride coatings on corrosion properties of Ti-6Al-4V alloy in 0.9% NaCl at 40°C

The corrosion properties of Ti-6Al-4V alloy with oxidized thermodiffusion nitride coatings were investigated in isotonic 0.9% solution of NaCl at temperature of 40°C. It was shown that modification of nitride coatings by oxygen leads to a deterioration of the protective properties of nitrided surface of Ti-6Al-4V alloy. The protective properties of the alloy with nitride coatings modified by oxygen are determined by the composition of formed surface oxynitride film.      

Octadecylsilane-modified silicas in the adsorption of toluene

A series of octadecylsilane-modified silicas were prepared by sol-gel and grafting methods. Carbon contents and octadecyl chain conformations were shown to depend on the preparative route. Grafting engenders a low carbon content and a liquid-like chain conformation, while the sol-gel method affords a much higher carbon content and a crystalline conformation. The relationships between the toluene adsorption of the hybrid silicas and their chain conformations, their carbon contents and their textural characteristics are discussed. These sorbents, when used in combination with ultraviolet diffuse reflectance spectroscopy (UV DRS), can be employed as a rapid screening method for detection of aromatic compounds in water and air environmental matrices. Figure Octadecylsilane-modified silicas in the adsorption of toluene     

Quasi in situ XPS investigations on intercalation mechanisms in Li-ion battery materials

New concepts for Li-ion batteries are of growing interest for high-performance applications. One aim is the search for new electrode materials with superior properties and their detailed characterization. We demonstrate the application of X-ray photoelectron spectroscopy (XPS) to investigate electrode materials (LiCoO₂, LiCrMnO₄) during electrochemical cycling. The optimization of a “quasi in situ” analysis, by transferring the samples with a transport chamber from the glove box to the XPS chamber, and the reliability of the experiments performed are shown. The behavior of characteristic chemical species at the electrodes and the changes in oxidation states of LiCrMnO₄ during cycling is discussed. The formation of Cr⁶⁺ is suspected as a possible reason for irreversible capacity loss during charging up to complete Li deintercalation (approximately 5.2 V). Figure Scheme of a quasi in situ XPS experiment on Li-ion battery electrode material     

Surface modification using a novel type I hydrophobin HGFI

Surface wettability conversion with hydrophobins is important for its applications in biodevices. In this work, the application of a type I hydrophobin HGFI in surface wettability conversion on mica, glass, and poly(dimethylsiloxane) (PDMS) was investigated. X-ray photoelectron spectroscopy (XPS) and water-contact-angle (WCA) measurements indicated that HGFI modification could efficiently change the surface wettability. Data also showed that self-assembled HGFI had better stability than type II hydrophobin HFBI. Protein patterning and the following immunoassay illustrated that surface modification with HGFI should be a feasible strategy for biosensor device fabrication. Figure A hydrophobin HGFI has been applied into surface wettability conversion for protein immobilization Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Electrochemical preparation of copper–dendrimer nanocomposites: picomolar detection of Cu<Superscript>2+</Superscript> ions

The present work describes, for the first time, in situ electrochemical preparation of dendrimer-encapsulated Cu nanoparticles using a self-assembled monolayer of fourth-generation amine-terminated polyamidoamine (PAMAM) dendrimer as the template. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) studies of the modified surface confirmed the presence of Cu nanoparticles entrapped in dendrimer film. Au electrode modified with a monolayer of the dendrimer enables preconcentration and subsequent voltammetric detection of Cu²⁺ at picomolar concentrations. Further, Cu nanoparticles in the dendrimer monolayer could be electrochemically derivatised to Cu hexacyanoferrate, which exhibits specific crystal planes, unlike the random distribution of crystal planes in bulk-formed Cu hexacyanoferrate, which is another catalytically active material for sensor applications. Figure Electrochemical preparation of copper–dendrimer nanocomposite     

Fourier transform ion cyclotron resonance mass spectrometry of covalent adducts of proteins and 4-hydroxy-2-nonenal, a reactive end-product of lipid peroxidation

Covalent adduction of the model protein apomyoglobin by 4-hydroxy-2-nonenal, a reactive end-product of lipid peroxidation, was characterized by nanoelectrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FTICR). The high mass resolving power and mass measurement accuracy of the instrument facilitated a detailed compositional analysis of the complex reaction product without the need for deconvolution and transformation to clearly show the pattern of adduction and component molecular weights. Our study has also demonstrated the value of electron capture dissociation over collision-induced dissociation for the tandem mass spectrometric determination of site modification for the 4-hydroxy-2-nonenal adduct of oxidized insulin B chain as an example. Figure FTICR allowed characterization of 4-hydroxy-2-nonenal (HNE)-modified apomyoglobin (an expanded spectrum of the +15 charge state is shown)     

A low perfusion rate microreactor for continuous monitoring of enzyme characteristics: application to glucose oxidase

This report describes a versatile and robust microreactor for bioactive proteins physically immobilized on a polyether sulfone filter. The potential of the reactor is illustrated with glucose oxidase immobilized on a filter with a cut-off value of 30 kDa. A flow-injection system was used to deliver the reactants and the device was linked on-line to an electrochemical detector. The microreactor was used for on-line preparation of apoglucose oxidase in strong acid and its subsequent reactivation with flavin adenine dinucleotide. In addition we describe a miniaturized version of the microreactor used to assess several characteristics of femtomole to attomole amounts of glucose oxidase. A low negative potential over the electrodes was used when ferrocene was the mediator in combination with horseradish peroxidase, ensuring the absence of oxidation of electro-active compounds in biological fluids. A low backpressure at very low flow rates is an advantage, which increases the sensitivity. A variety of further applications of the microreactor are suggested. Figure Preparation of apoGOx and restoration of enzyme activity using a soluton of FAD     

Electrochemical reduction of the iodinated contrast medium iomeprol: iodine mass balance and identification of transformation products

Potentiostatic-controlled electrochemical reduction of iomeprol was used to deiodinate iomeprol (IMP), a representative of the iodinated X-ray contrast media. The reduction process was followed by product analysis with liquid chromatography-electrospray ionization-tandem mass spectrometry and ion chromatography-inductively coupled plasma-mass spectrometry. The identification is mainly based on the interpretation of the mass fragmentation. The product analysis showed a rather selective deiodination process with the successive occurrence of IMP-I, IMP-2I, IMP-3I, and a transformation product (TP), respectively. The TP was formed from IMP-3I by a further cleavage of an amide bond and release of a (C = O)CHOH group from the side chain of IMP. The iodine mass balance on the basis of IMP and iodide showed a gap of about 26% at the beginning of the electrolysis process which could be completely closed by taking the intermediates IMP-I and IMP-2I into consideration. This means that the major intermediates and the TPs were considered and that the reduction process is a rather selective one to remove organically bound iodine from X-ray contrast media. An attractive application area would be the electrochemical deiodination of X-ray contrast media in urine of patients or hospital effluents.      

Iron fractionation for corrosion products from natural gas pipelines by continuous-flow sequential extraction

The forms and quantities of iron species in corrosion product samples from natural gas pipelines were examined, using a continuous-flow sequential extraction system. Sequential extraction consists of four steps that dissolve water soluble iron (FeSO₄), acid soluble iron (FeCO₃), reducible iron (Fe-(oxyhydr)oxides) and oxidisable iron (FeS₂) fractions, respectively. Selectivity of extracting reagents for particular iron species was evaluated by determination of co-extracted anions, using ion chromatography, and evolved CO₂, using indirect flame atomic absorption spectrometer (FAAS). Iron was found predominantly in the reducible fraction (61–99%), indicating that Fe-(oxyhydr)oxides are the major constituents of the corrosion products.      

Determination of the titanium content of human transferrin by inductively-coupled plasma-atomic-emission spectroscopy

We report a simple method that combines dialysis, as a purification method, with the multielement capability of ICP to determine the titanium-to-transferrin mole ratio at physiological pH, under buffer conditions. The method, by means of which titanium and transferrin are determined simultaneously, enabled us to assess the binding capacities of different titanocene complexes. Figure Titanocene dichloride     

TOF-S-SIMS molecular depth profiling of organic bilayers using mechanical wear test methodology

Recent publications on static secondary ion mass spectrometry (S-SIMS) focus on molecular depth profiling by using polyatomic or ultra-low energy monoatomic projectiles. Since their applicability depends on the relationship between the ion yield and the depth, which is hard to obtain without extensive studies, a combination of a wear test method with S-SIMS surface analysis was performed in the current study. Using this non-sputtering procedure, the relation between the signal intensity and the local concentration remains in principle the same as that at the surface (which is easy to determine). Mechanical erosion was successfully applied to expose sub-surface material from organic multilayers. Through surface analysis with S-SIMS on the gradually exposed deeper planes, molecular depth profiles could be obtained. The study was conducted on a model system relevant to offset printing, consisting of two polymer layers, containing dyes and a surfactant, cast on an Al substrate. Figure Concept of mechanical erosion followed by S-SIMS surface analysis to obtain molecular depth profiles     

Multiclass analysis of illicit drugs in plasma and oral fluids by LC-MS/MS

An analytical procedure for the simultaneous determination in human plasma and oral fluids of several illicit drugs belonging to different chemical and toxicological classes is presented. Amphetamine, methamphetamine, morphine, 6-monoacetylmorphine, methylenedioxyamphetamine, methylenedioxyethylamphetamine, methylenedioxymethamphetamine, cocaine, benzoylecgonine, tetrahydrocannabinol, carboxytetrahydrocannabinol, ketamine, and phencyclidine have been quantified in real samples using a very rapid sample treatment, basically a protein precipitation. The quantitative analysis was performed by liquid chromatography–tandem mass spectrometry and has been fully validated. All the analytes were detected in positive ionization mode using a TurboIonSpray source, except carboxytetrahydrocannabinol, which was detected in negative ionization mode. The use of a diverter valve between the column and the mass spectrometer allows the preservation of the ion source performances for high-throughput analysis. Figure Diverter system