ZnS nanoparticle decorated ZnO nanowall network: investigation through electron microscopy and secondary ion mass spectrometry

We report on the fabrication of ZnO nanowall networks decorated with ZnS nanostructures on aluminum substrates using simple chemical route. The structural features and elemental constituents of the ZnS/ZnO heterostructure systems have been extensively studied using electron microscopy and energy dispersive X‐ray spectroscopy. The light emission characteristics of the bare and heterostructured systems have been analyzed using room temperature photoluminescence spectroscopy. The decoration of ZnS nanostructures over ZnO nanowalls has been evidenced through secondary ion mass spectrometry (SIMS). The ‘matrix effect’ has been found to be prominent during SIMS analysis of the bare and heterostructured nanowalls indicating the presence of ZnS phase over ZnO surface. ‘MCs⁺‐SIMS’ has been employed to suppress the matrix effect and is found to be potentially effective in making a semi‐quantitative estimation of Zn and O surface–atom concentrations in both systems. The luminescence responses of the ZnS/ZnO heterostructures have been found to be strongly dependent on the extent of ZnS phase over ZnO. The higher luminescence responses in ZnS/ZnO heterostructures fabricated with smaller ZnS nanoparticles have been explained in terms of a mechanism of charge‐carrier transfer from ZnS to ZnO. Copyright © 2014 John Wiley & Sons, Ltd.     

Secondary ion mass spectrometry for characterizing antimony, arsenic and selenium on graphite surfaces modified with noble metals and used for hydride generation atomic absorption spectrometry

The surface and sub-surface distribution of noble metals (after electrodeposition of 600 μg or thermal reduction of 10 μg as modifiers), as well as Sb, As and Se (200 ng) as analytes after their deposition on the graphite surface was investigated using secondary ion mass spectrometry (SIMS) in the dynamic mode. This permitted simultaneous observation of the depth profile distribution of modifier and analyte with a depth resolution of down to approximately 25 nm, limited however, by the surface roughness of the samples. Hydride generation was intentionally used for this purpose because in this approach the investigated system: graphite–modifier with added analyte is free from matrix components. This was essential for the evaluation of this novel approach using SIMS for surface analysis. Investigations concerning the distribution of analytes were performed on the graphite surface modified with palladium, iridium or rhodium. It was found that after deposition at 400 °C, all analytes partially penetrated the graphite surface and their distribution overlaps the distribution pattern of the noble metals. The degree of penetration differs for each analyte and depends on the modifier used.     

Surface characteristics of glass fibres covered with an aluminum layer after a chemical modification process using secondary ion mass spectrometry (SIMS) and atomic force microscopy (AFM)

Results show investigations of surface of modified glass fibres (before and after chemical modification of their surface), which are candidates for future original matrix-less reference material for volatile ethene analytes (C₂H₄). Used analytical methods are secondary ion mass spectrometry and atomic force microscopy. The investigations were aimed at observation of changes and processes which occurred on the surface of glass fibres covered with an aluminum layer and constituting an ethane carrier.The paper describes the procedure of chemical modification of the surface of 3 cm segments of glass fibres covered with an aluminum layer (660/680 μm, external diameter of quartz/external Al diameter), a surfactant constituting a source of ethene. Ethene (a measured constituent) in a standard gas mixture is obtained during the process of controlled thermal decomposition of a surface compound in a stream of rarefied gas (such kind of mixture is called matrix-less reference material).     

Optimization of quadrupole ion storage mass spectrometric conditions for the analysis of selected polybrominated diphenyl ethers. Comparative approach with negative chemical ionization and electron impact mass spectrometry

Gas chromatography coupled to quadrupole ion storage mass spectrometry (QISTMS) operating in the non-resonant mode is presented as an innovative approach for the analysis of selected polybrominated diphenyl ethers (PBDEs). Although reductions in complexity and time needed for optimization are achieved in comparison with the resonant option, precise adjustment of the mass spectrometric conditions is required. Differences in isolation and fragmentation patterns of target species with degree of bromination were observed. The reliability of the method was confirmed by using standard solutions through the evaluation of certain quality parameters such as accuracy (92-108%), injection repeatability and reproducibility (coefficient of variation below 10% and 15%, respectively). Detection limits ranged from 62 to 621 fg, providing sensitivity similar to that of negative chemical ionisation (NCIMS) and greater than that of electron ionization mass spectrometry. The applicability of QISTMS method to real samples and matrix effects were evaluated through the analysis of some PBDE congeners in a sewage sludge sample from a Spanish waste-water treatment plant. Comparable results were obtained using QISTMS and NCIMS. According to these observations, QISTMS performed in the non-resonant mode may constitute a low-cost, rapid and reliable alternative to high-resolution devices for the analysis of selected PBDEs in environmental samples.     

Probing the surface chemical structure of some novel poly(ortho esters) prepared with N-methyl and N-phenyl ethanolamine by time-of-flight secondary ion mass spectrometry (ToF-SIMS)

The surface chemical structures of a series of novel poly(ortho ester) homopolymer and copolymer films prepared using N-methyl- and N-phenyl-ethanolamine (MDE and PDE) have been investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS). Systematic fragmentation patterns were observed within the ToF-SIMS spectra up to m/z = 1600, which were readily interpreted in terms of the polymer structures. Cations were detected which could be assigned to structures arising from the diols, the ortho ester species and diads, triads etc. of the monomer, from both the homopolymer and the random portion of the copolymer chains. The analysis of the proposed ion structures suggested two major mechanisms of fragmentation based on the cleavage of the ortho ester bonds involving either the exocyclic or the endocyclic alkoxy group. The Tof-SIMS peak area ratios for ions diagnostic of the diols and the ortho ester species reflected the bulk copolymer composition in a semi-quantitative fashion. The observation of such relationships for high mass cations (up to m/z = 500) is particularly noteworthy and has not been reported previously. These studies allow a dramatic insight into the surface chemical structure of these poly(ortho esters), information which has formed the foundation of current investigations on the mechanisms of the acid-catalysed surface degradation of these polymers.     

Modification of dipeptides by alkyl chloroformate—alkanol mixtures for analysis by gas chromatography/mass spectrometry with electron and chemical ionization and collisional activation: Differentiation of isomers

A possibility of dipeptide derivatization by alkyl chloroformate—alkanol (Alk = Me, Et, Pr, Bu) mixed reactants for their determination and differentiation of isomers in mixtures by gas chromatography/mass spectrometry with electron and chemical ionization and collisional activation was studied. Prospects for using derivatization by mixtures of methyl chloroformate with 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoropropanol, and 2,2,3,3,4,4,4-heptafluorobutanol were shown. Diagnostic ions that make it possible to determine the amino acid sequence in dipeptides and distinguish residues of isomeric leucine and isoleucine were revealed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2200–2204, December, 2006.     

Precipitation of lignin and extractives on kraft pulp: effect on surface chemistry, surface morphology and paper strength

The effect of pH on the formation of precipitates (lignin, extractives and metals) on kraft pulp surfaces was examined by electron spectroscopy for chemical analysis, time-of-flight secondary ion mass spectrometry and atomic force microscopy (AFM). A softwood kraft pulp slurry from an oxygen delignification stage was diluted to 3% consistency with water or an acidic Z filtrate. After heating to 70 °C the pH was lowered from 11 to 2–5, using sulphuric acid. Lignin and extractives precipitated at pH values below 6, and their amounts increased with decreasing pH. Most of the precipitated lignin was found on the pulp surface after sheet forming, whereas the main part of the precipitated extractives could be easily washed away with water. The layer of precipitated lignin was apparently thicker than the layer of extractives. AFM showed the precipitated material as a granular phase. Neither surface morphology nor surface coverage depended on the addition of Z filtrate. The amount of metals ID the pulp and on the pulp surface decreased when pH was lowered to 2. More metals, such as Ca and Mg, were detected ID the pulps as well as on the sheet surfaces when the pulp was diluted with Z filtrate. Strength and bonding properties of the pulp sheets were slightly impaired by the precipitated material. Acidification appears to be the main reason for the precipitation of both lignin and extractives on the pulp surfaces. This should be taken into account when filtrates are recycled ID the bleaching or washing of pulps.