ToF SIMS Research Articles

Redistribution of Cav2.1 channels and calcium ions in nerve terminals following end-to-side neurorrhaphy: ionic imaging analysis by TOF–SIMS

The P/Q-type voltage-dependent calcium channel (Cav2.1) in the presynaptic membranes of motor nerve terminals plays an important role in regulating Ca2+ transport, resulting in transmitter release within the nervous system. The recovery of Ca2+-dependent signal transduction on motor end plates (MEPs) and innervated muscle may directly reflect nerve regeneration following peripheral nerve injury. Although the functional significance of calcium channels and the levels of Ca2+ signalling in nerve regeneration are well documented, little is known about calcium channel expression and its relation with the dynamic Ca2+ ion distribution at regenerating MEPs. In the present study, end-to-side neurorrhaphy (ESN) was performed as an in vivo model of peripheral nerve injury. The distribution of Ca2+ at regenerating MEPs following ESN was first detected by time-of-flight secondary ion mass spectrometry, and the specific localization and expression of Cav2.1 channels were examined by confocal microscopy and western blotting. Compared with other fundamental ions, such as Na+ and K+, dramatic changes in the Ca2+ distribution were detected along with the progression of MEP regeneration. The re-establishment of Ca2+ distribution and intensity were correlated with the functional recovery of muscle in ESN rats. Furthermore, the re-clustering of Cav2.1 channels after ESN at the nerve terminals corresponded with changes in the Ca2+ distribution. These results indicated that renewal of the Cav2.1 distribution within the presynaptic nerve terminals may be necessary for initiating a proper Ca2+ influx and shortening the latency of muscle contraction during nerve regeneration.

Protocol of single cells preparation for time of flight secondary ion mass spectrometry

There are several techniques like time of flight secondary ion mass spectrometry (ToF SIMS) that require a special protocol for preparation of biological samples, in particular, those containing single cells due to high vacuum conditions that must be kept during the experiment. Frequently, preparation methodology involves liquid nitrogen freezing what is not always convenient. In our studies, we propose and validate a protocol for preparation of single cells. It consists of four steps: (i) paraformaldehyde fixation, (ii) salt removal, (iii) dehydrating, and (iv) sample drying under ambient conditions. The protocol was applied to samples with single melanoma cells i.e. WM115 and WM266-4 characterized by similar morphology. The surface and internal structures of cells were monitored using atomic force, scanning electron and fluorescent microscopes, used to follow any potential protocol-induced alterations. To validate the proposed methodology for sample preparation, ToF SIMS experiments were carried out using C60+ cluster ion beam. The applied principal component analysis (PCA) revealed that chemical changes on cell surface of melanoma cells were large enough to differentiate between primary and secondary tumor sites.Subject category: Mass spectrometry.

Passivity breakdown of 316L stainless steel during potentiodynamic polarization in NaCl solution

Time-of-flight secondary ion mass spectroscopy (ToF SIMS) analysis was performed on 316L stainless steel polarized potentiodynamically up to different potentials in NaCl solution. The surface film thickness increased with the ending potential of the potentiodynamic polarization, when estimated by the oxygen ion depth profiles. The chloride ion intensities at the film/metal interface were correlated with the ending potentials during the potentiodynamic polarization and cumulative anodic charge densities that govern the pit initiation. The results and analysis support the passivity breakdown mechanisms considering the role of chloride ions at the metal/film interface, rather than at the film/solution interface.

Combined Effect of Phosphate Ester and OBCS on Tribochemical Decomposition of Hydrocarbon Oil on Nascent Steel Surfaces

Combined effect of additives, over-based calcium sulfonate (OBCS) and phosphate ester were investigated on the decomposition of multi-alkylated cyclopentane (MAC). The decomposition processes of the lubricants on the nascent surface of bearing steel AISI52100 were investigated using a ball-on-disk friction tester in a vacuum chamber with a quadrupole mass spectrometer. According to our previous report, the decomposition reaction can be deactivated by the effect of lubricant additives such as organic sulfides and organic phosphates. In this report, the order of efficiency in decreasing the decomposition rate was: OBCS < phosphate ester < phosphate ester + OBCS. The mixed additive was more effective and stable for suppression of the tribochemical decomposition under severe contact conditions of high load and high sliding speed. The critical load for the decomposition which is the lowest load to detect the gas evolution due to the decomposition increased with the mixed additive. XPS and TOF–SIMS analysis revealed that additive molecules competitively chemisorbed on the steel surface and reaction occurred by the formation of calcium phosphate, which covered the steel surface and deactivated the catalytic activity of active sites leading to deactivation. As a result, decomposition of MAC decreased significantly by the combined effect of the additives.

Synthesis of novel zwitterionic cellulose beads by oxidation and coupling chemistry in water

The design and synthesis of polysaccharide-based materials utilizing a systematic approach is essential to develop sustainable and biodegradable value added products. In this work, new zwitterionic cellulose beads of desired size range were prepared via spin drop atomization followed by sol gel transition technique. Carboxylic acid (COOH) and carbonyl (C=O) moieties were generated using NaClO2/NaClO/TEMPO mediated oxidation system under heterogenous reaction conditions. Coupling reaction between carboxymethyl trimethylammonium chloride hydrazide (Girard’s reagent T) and carbonyl functionalities on cellulose resulted in the formation of stable hydrazone groups. A variation in molar ratio of NaClO2, NaClO and TEMPO were studied to understand the effect of each reagent on the generation of oxidized products. COOH and C=O content was determined by conductometric titrations and oximation with hydroxylamine hydrochloride followed by elemental analysis, respectively. Evidence of functionalization was obtained with ATR-FTIR, Raman, solid state 13C NMR spectroscopic studies and ToF–SIMS analysis. Morphological changes were studied by FE-SEM. The increased porosity and hydrophilicity of zwitterionic beads provides a platform for the future application of these beads in separation of biomolecules, chiral molecules, immobilization of proteins and enzymes and encapsulation of zwitterionic drugs.

Comparing surface properties of melanoma cells using time of flight secondary ions mass spectrometry.

Various techniques have been already reported to differentiate between normal (non-malignant) and cancerous cells based on their physico-chemical properties. This is relatively simple when studied cancerous cells originate from distant stages of cancer progression. Here, studies on chemical properties of two closely related human melanoma cell lines are presented: WM115 melanoma cells were taken from the vertical growth phase while WM266-4 from the skin metastatic site of the same patient. Their chemical properties were studied by two techniques, namely time-of-flight secondary ion mass spectra (ToF SIMS) and photothermal microspectroscopy (PTMS), used to record mass and photothermal spectra of cells, respectively. In our approach, independently of the spectra type, its full range, i.e. masses and wavenumbers within the range 0-500 kDa and 500-4000 cm-1, underwent a similar methodology for principal component analysis (PCA). PCA outcome shows results groupped depending on the sample type (either WM115 or WM266-4 cells). The results are independent of the method applied to study chemical properties of melanoma cells, indicating that cancer-related changes are large enough to be identified with these techniques and to differentiate between cells originating from vertical growth phase and skin metastatis.

Correlating the magnetism and gas sensing properties of Mn-doped ZnO films enhanced by UV irradiation

Schematic diagram showing the 2D TOF SIMS overlays of Si+, Mn+and Zn+. The insert corresponds to the correlation between the sensing response and FMR signal as a function of Mn concentration when exposed to various gases.

Electrochemical detection of anti-tau antibodies binding to tau protein and inhibition of GSK-3β-catalyzed phosphorylation

Tau protein hyperphosphorylation triggers tau aggregation and its toxicity, leading to neuronal death and cell-to-cell toxicity. Hence, inhibition of protein kinases is a viable tool toward reduction of tau toxicity. By targeting various epitopes of Tau441 protein immobilized on Au surface, the protein kinase inhibition by anti-tau antibodies was measured by surface electrochemistry. The electrochemical impedance spectroscopy was used to measure the charge transfer resistance (Rct) of nonphosphorylated tau–Au film (nTau–Au) and compared with the phosphorylated tau–Au film (pTau–Au). The pTau–Au films were characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF–SIMS), which indicated high phosphorus content. The Rct factor was used as the measure of inhibition efficacies by anti-tau antibodies (D8, A10, P262, and Tau46) in addition to antibody formulation intravenous immunoglobulin (IVIG). The Rct factor for pTau–Au in the absence of antibodies was 0.25 ± 0.08, indicating a dramatic decrease in Rct on phosphorylation. The Rct factors for Tau46 and A10 were 0.57 ± 0.22 and 0.65 ± 0.26, respectively, indicating phosphorylation inhibition. All antibodies exhibited similar binding to nTau–Au. The proposed electrochemical assay may be used for detection of other posttranslational modifications.

Orthogonal chemical functionalization of patterned gold on silica surfaces.

Single-step orthogonal chemical functionalization procedures have been developed with patterned gold on silica surfaces. Different combinations of a silane and a thiol were simultaneously deposited on a gold/silica heterogeneous substrate. The orthogonality of the functionalization (i.e., selective grafting of the thiol on the gold areas and the silane on the silica) was demonstrated by X-ray photoelectron spectroscopy (XPS) as well as time-of-flight secondary ion mass spectrometry (ToF–SIMS) mapping. The orthogonal functionalization was used to immobilize proteins onto gold nanostructures on a silica substrate, as demonstrated by atomic force microscopy (AFM). These results are especially promising in the development of future biosensors where the selective anchoring of target molecules onto nanostructured transducers (e.g., nanoplasmonic biosensors) is a major challenge.

ToF-SIMS imaging of molecular-level alteration mechanisms in Le Bonheur de vivre by Henri Matisse.

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has recently been shown to be a valuable tool for cultural heritage studies, especially when used in conjunction with established analytical techniques in the field. The ability of ToF-SIMS to simultaneously image inorganic and organic species within a paint cross section at micrometer-level spatial resolution makes it a uniquely qualified analytical technique to aid in further understanding the processes of pigment and binder alteration, as well as pigment-binder interactions. In this study, ToF-SIMS was used to detect and image both molecular and elemental species related to CdS pigment and binding medium alteration on the painting Le Bonheur de vivre (1905-1906, The Barnes Foundation) by Henri Matisse. Three categories of inorganic and organic components were found throughout Le Bonheur de vivre and co-localized in cross-sectional samples using high spatial resolution ToF-SIMS analysis: (1) species relating to the preparation and photo-induced oxidation of CdS yellow pigments (2) varying amounts of long-chain fatty acids present in both the paint and primary ground layer and (3) specific amino acid fragments, possibly relating to the painting's complex restoration history. ToF-SIMS's ability to discern both organic and inorganic species via cross-sectional imaging was used to compare samples collected from Le Bonheur de vivre to artificially aged reference paints in an effort to gather mechanistic information relating to alteration processes that have been previously explored using μXANES, SR-μXRF, SEM-EDX, and SR-FTIR. The relatively high sensitivity offered by ToF-SIMS imaging coupled to the high spatial resolution allowed for the positive identification of degradation products (such as cadmium oxalate) in specific paint regions that have before been unobserved. The imaging of organic materials has provided an insight into the extent of destruction of the original binding medium, as well as identifying unexpected organic materials in specific paint layers.

Characterization Of Oxide Layers Produced On The AISI 321 Stainless Steel After Annealing

Abstract In this study, the structure, chemical composition and topography of oxide layers produced on the surface of the AISI 321 austenitic steel in the annealing process were analyzed. Heat treatment was done at 980°C temperature for 1 hour time in different conditions. The annealing was done in a ceramic furnace in oxidation atmosphere and in vacuum furnaces with cylindrical molybdenum and graphite chambers. The analysis was carried out using the following methods: a scanning electron microscope (SEM) equipped with an energy-dispersive X-ray spectrometer (EDX), a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray spectrometer (EDX), an X-ray diffractometer (XRD), a secondary ion mass spectrometer with time-of-flight mass analyzer (TOF SIMS) and an atomic force microscope (AFM). The oxide layer formed during annealing of the AISI 321 steel at 980°C consisted of sub-layers, diversified in the chemical composition. The thickness of the oxidized layer is depended on the annealing conditions. In a ceramic furnace in oxidation atmosphere, the thickness of the oxide layer was of 300-500 nm, in a vacuum furnace with molybdenum and graphite heating chambers, it ranged from 40 to 300 nm and from a few to 50 nm, respectively. TOF SIMS method allows to get average (for the surface of 100 μm × 100 μm) depth profiles of concentration of particular elements and elements combined with oxygen. In oxide layers formed in vacuum furnaces there are no iron oxides. Titanium, apart from being bounded with carbon in carbides, is a component of the oxide layer formed on the surface of the AISI 321 steel.

Coprecipitation of nickel zinc malonate: A facile and reproducible synthesis route for Ni1−xZnxO nanoparticles and Ni1−xZnxO/ZnO nanocomposites via pyrolysis

Nanoparticles of Ni1−xZnxO and Ni1−xZnxO/ZnO, which can be good candidates for selective gas sensors, were successfully obtained via a two-step synthetic route, in which the nickel zinc malonate precursor was first synthesized by co-precipitation from an aqueous solution, followed by pyrolysis in air at a relatively low temperature (~500°C). The precursor was characterized by ICP-AES, FTIR and TG and the results indicate the molecular structure of the precursor to be compatible with Ni1−xZnx(OOCCH2COO)·2H2O. The decomposition product, characterized using various techniques (FTIR, XRD, ToF-SIMS, SEM, TEM and XPS), was established to be a doped nickel oxide (Ni1−xZnxO for 0.01≤x≤0.1) and a composite material (Ni1−xZnxO/ZnO for 0.2≤x≤0.5). To elucidate the form in which the Zn is present in the NiO structure, three analytical techniques were employed: ToF-SIMS, XRD and XPS. While ToF SIMS provided a direct evidence of the presence of Zn in the NiO crystal structure, XRD showed that Zn actually substitutes Ni in the structure and XPS is a bit more specific by indicating that the Zn is present in the form of Zn2+ ions.

Potash-lime-silica glass: protection from weathering

Potash-lime silica glass was used for window panels in Europe north of the Alps in the medieval era. The high potassium and low silica content of this glass influences its chemical stability. When exposed to atmospheric conditions as well as acidic aqueous solutions, this type of glass can become hazy, foggy and/or flake phenomena can occur, which modify the original appearance of the artworks can occur. For proper conservation it is therefore necessary to understand the mechanisms of corrosion allowing for the selection of better conditions and treatments to slow down or avoid degradation. In previous works the applicability and the protective effect of a sol–gel silica coating on potash-lime-silica glass was tested in aqueous acidic solutions. With this work the previous results are integrated, investigating the protective effect against weathering and accelerated ageing. SEM analyses were performed to monitor the surface of the glass after accelerated ageing, in particular to detect the presence of corrosion products; moreover, ToF–SIMS analysis was performed to visualize the ion distribution as a function of depth and the presence of any changes due to the weathering treatment. The analyses showed that the formation of weathering products on the surface was slowed down significantly compared to the areas of the sample that were not coated with sol–gel. Different results were obtained depending on the glass composition.

TOF SIMS analysis, structure and photoluminescence properties of pulsed laser deposited CaS:Eu2+ thin films

CaS:Eu2+ thin films were deposited on Si (100) substrates using the pulsed laser deposition technique to investigate the effect of argon (Ar), oxygen (O2), and vacuum deposition atmospheres on the structural, morphological and photoluminescence properties of the thin films. The phosphor target was ablated using a 266nm Nd: YAG laser. X-ray diffraction, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray, fluorescence spectrophotometry and time-of-flight secondary ion mass spectrometry were used to characterize the thin films. The thin films prepared in oxygen were essentially amorphous, while those prepared in argon and vacuum showed some degree of crystallinity. The film deposited in Ar showed better photoluminescence intensity than those deposited in an O2 and vacuum. The emission observed at around 650nm for all the films is attributed to the transitions from the excited 4f6[F07]5d1(t2g) state to the ground state 4f7(S7/28) of the Eu2+ ions. The emission at 618nm, which is more prominent in the film prepared in O2, is ascribed to the D5→0F27transitions in Eu3+, suggesting that Eu2+ was unintentionally oxidized to Eu3+. The atomic force microscopy data showed that the film prepared in argon was rougher than those prepared in oxygen and vacuum.

A new approach to express ToF SIMS depth profiling

We propose a new approach to express SIMS depth profiling on a TOF.SIMS‐5 time‐of‐flight mass spectrometer. The approach is based on the instrument capability to independently perform raster scans of sputter and probe ion beams. The probed area can be much smaller than the diameter of a sputter ion beam, like in the AES depth profiling method. This circumstance alleviates limitations on the sputter beam–raster size relation, which are critical in other types of SIMS, and enables analysis on a curved‐bottomed sputter crater. By considerably reducing the raster size, it is possible to increase the depth profiling speed by an order of magnitude without radically degrading the depth resolution. A technique is proposed for successive improvement of depth resolution through profile recovery with account for the developing curvature of the sputtered crater bottom in the probed area. Experimental study of the crater bottom form resulted in implementing a method to include contribution of the instrumental artifacts in a nonstationary depth resolution function within the Hofmann's mixing–roughness–information depth model. The real‐structure experiment has shown that the analysis technique combining reduction of a raster size with a successive nonstationary recovery ensures high speed of profiling at ~100 µm/h while maintaining the depth resolution of about 30 nm at a 5 µm depth. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Nanolayer atmospheric pressure plasma graft polymerization of durable repellent finishes on cotton

High-density, non-thermal, glow-discharge atmospheric-pressure plasma was used for graft polymerization of a vapor deposited fluorocarbon mixture of 1,1,2,2-tetrahydroperfluorodecyl acrylate and 1,1,2,2-tetrahydroperfluorododecyl acrylate on undyed cotton fabrics, which furnished a highly durable nanolayer water and oil repellent finish. In this study, monomer vapor was deposited onto cotton fabrics on single and double sides of the fabrics. The influence of monomer flow rate and plasma preactivation was studied. The surface of the cotton treated with fluorocarbons is evaluated using the standard AATCC Test Methods. Surface chemistry and morphology of the treated cotton were characterized using FTIR, XPS, SEM, and TOF–SIMS. Plasma-assisted graft polymerization of fluorocarbon in the presence of the crosslinker pentaerythritol triacrylate (10:1 molar ratio of monomer: crosslinker) resulted in a polyfluorocarbon nanolayer on cotton, which was hydrophobic and durable to one accelerated laundering, which is equivalent to 10 home launderings.

Optical properties and chemical composition analyses of mixed rare earth oxyorthosilicate (R2SiO5, R=La, Gd and Y) doped Dy3+ phosphors prepared by urea-assisted solution combustion method

Dysprosium (Dy3+) doped lanthanum gadolinium oxyorthosilicate (LaGdSiO5), lanthanum yttrium oxyorthosilicate (LaYSiO5) and gadolinium yttrium oxyorthosilicate (GdYSiO5) phosphors (in powder form) were synthesized by urea-assisted combustion method. The X-ray diffractometer analysis confirmed that the LaGdSiO5, LaYSiO5 and GdYSiO5 crystalized in monoclinic phases. The chemical composition of the phosphors was analyzed by measuring the atomic and molecular ionic species using the time of flight secondary ion mass spectroscopy (ToF SIMS). In addition, ToF SIMS imaging technique was used to determine the distribution of the Dy3+ dopant ions on the surface on the phosphors. The average crystallite sizes and lattice strains of the phosphor were increased by Dy3+ doping. The field emission scanning electron microscope images showed that the powders were made up of an agglomeration of particles with no regular shape. The photoluminescence data showed narrow line emission peaks at the wavelengths of 485nm (minor emission) and 573nm (major emission) associated with the f→f transitions of Dy3+. The photoluminescence (PL) measurements showed that the emission peak of LaGdSiO5:Dy3+ was ~3× more intense than those of LaYSiO5:Dy3+ and GdYSiO5:Dy3+ when excited using monochromatic xenon lamp with a wavelength of 241nm. However, when the powders were excited using a 325nm He–Cd laser, the highest PL emission intensity was observed from GdYSiO5:Dy3+.

Influence of surface roughening of Titanium substrate in the electrochemical activity of Manganese oxide thin film electrode in anodic oxidation of dye-containing solutions

Previous work has verified the possibility to obtain mechanically, chemically and electrically stable electrodes based on manganese oxide (MnOx) thin films for anodic oxidation of solutions containing the Reactive Violet 5 (RV5) azo dye. To improve the morphological and electrochemical properties of these materials, in this study, a surface modification of the titanium support has been presented. Chemically modified surfaces were obtained by etching titanium substrates in hydrocloridric acid at high temperature. Untreated and modified electrodes were coated sequentially with a RuOx film, as interlayer and a MnOx film obtained by adopting three different techniques including anodic electrodeposition, cathodic electrodeposition and thermal decomposition. Surface morphology, topography and composition of all the electrodes were investigated by profilometric and TOF–SIMS analysis. The electrochemical activity of anodes were first determined by cyclic voltammetry, and then in the treatment of solutions containing the RV5 azo dye, as model pollutant, in undivided cell under galvanostatic conditions. The results show that the surface microstructure modifies substantially the electrochemical response of selected electrodes.

Lipid incorporation in soft contact lenses: XPS, ToF SIMS and TEM analysis

Lipid incorporation in soft contact lenses: XPS, ToF SIMS and TEM analysis

TOF SIMS analysis of fatty acid outgassing from wafer boxes adsorbed on wafers

Surface cleanness is crucial for reducing defect density of the semiconductor wafers. Organic contamination or residue on the wafer surface will lead to unintentional hydrophobization changes and haze formation and thus the performance of the subsequent wafer processes, such as film deposition or etching. Fatty acid salt is a common anionic surfactant. The residue of fatty acid salt will result in uneven etch of silicon and silicon nitride, which eventually causes particle issues. Time‐of‐flight SIMS was employed in this work to detect fatty acid residue on silicon, silicon oxide and silicon nitride wafers. The outgassing of the wafer container has been found to contribute to the fatty acid residue on the wafer surface. The outgassing of three different brands of wafer boxes was compared by investigating the adsorption on the wafers after fresh wafers were stored in boxes for a series of time duration. Different wafers also showed varied ability to absorb fatty acid, which can be attributed to electric dipole strength and concentration on the wafer surface. Time‐of‐flight SIMS and Fourier transform infrared spectroscopy analysis results showed that the difference in outgassing performance of different wafer boxes were due to the release agent residue on inner surface of the wafer boxes. More reliable results of fatty acid salt have been obtained on the wafers kept in the boxes with less outgassing. Copyright © 2014 John Wiley &amp; Sons, Ltd.