TOF-SIMS analysis of sea salt particles: imaging and depth profiling in the discovery of an unrecognized mechanism for pH buffering

Gaspar, Daniel J.; Laskin, Alexander; Wang, Weihong; Hunt, S. W.; Finlayson-Pitts, Barbara J.

doi:10.1016/j.apsusc.2004.03.046

Cited by 24 publications

(21 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This has been demonstrated in the Fe-oxide nanoparticle system. [47] The impact of ions on nanostructured objects will be influenced by object size, [36] shape (due to angle of impact effects), [48,49] as well as other physical characteristic effects such as how the objects are supported [51] or if they are porous. [50] The two latter characteristics may lead to environmental effects as objects suspended in space respond differently to an ion beam than when they are supported on a substrate, and a porous structure may adsorb and retain ambient gases or solvents for considerable time in vacuum.…”

Section: Probe Effectsmentioning

confidence: 99%

Characterization challenges for nanomaterials

Baer

Amonette

Engelhard

et al. 2008

Surface & Interface Analysis

122

View full text Add to dashboard Cite

Nanostructured materials are increasingly subject to nearly every type of chemical and physical analysis possible. Due to their small sizes, there is a significant focus on tools with high spatial resolution. It is also natural to characterize nanomaterials using tools designed to analyze surfaces, because of their high surface area. Regardless of the approach, nanostructured materials present a variety of obstacles to adequate, useful, and needed analysis. Case studies of measurements on ceria and iron metal-core/oxide-shell nanoparticles are used to introduce some of the issues that frequently need to be addressed during analysis of nanostructured materials. We use a combination of tools for routine analysis including X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and x-ray diffraction (XRD) and apply several other methods as needed to obtain essential information. The examples provide an introduction to other issues and complications associated with the analysis of nanostructured materials including particle stability, probe effects, environmental effects, specimen handling, surface coating, contamination, and time.

show abstract

Section: Probe Effectsmentioning

confidence: 99%

Characterization challenges for nanomaterials

Baer

Amonette

Engelhard

et al. 2008

Surface & Interface Analysis

122

View full text Add to dashboard Cite

show abstract

“…Some of the discrepancy between the expected sputter rate based on that of vitreous C and the apparent sputter rate inferred from the SEM images may be due to differential sputter rates between organic C and vitreous C, but increased removal of material from sputtered particles in comparison to bulk samples has been noted before. For example, Gaspar et al (9) noted an approximately 40-fold increase in sputter rate from NaCl particles over that of bulk NaCl and hypothesized that much of the difference may have been due to the effects of reduced redeposition of sputtered material along with increased surface area exposed to the primary ion beam. Finally, it is apparent that the secondary ion signal obtained from such topography is not only an integration of all inner and outer layers of the spores, but also that different individual spores contribute various relative components of inner and outer spore materials to the signal.…”

Section: Resultsmentioning

confidence: 99%

Differentiation of Spores of Bacillus subtilis Grown in Different Media by Elemental Characterization Using Time-of-Flight Secondary Ion Mass Spectrometry

Cliff

Jarman

Valentine

et al. 2005

Appl Environ Microbiol

View full text Add to dashboard Cite

We demonstrate the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) in a forensics application to distinguish Bacillus subtilis spores grown in various media based on the elemental signatures of the spores. Triplicate cultures grown in each of four different media were analyzed to obtain TOF-SIMS signatures comprised of 16 elemental intensities. Analysis of variance was unable to distinguish growth medium types based on 40 Ca-normalized signatures of any single normalized element. Principal component analysis proved successful in separating the spores into groups consistent with the media in which they were prepared. Confusion matrices constructed using nearest-neighbor classification of the PCA scores confirmed the predictive utility of TOF-SIMS elemental signatures in identifying sporulation medium. Theoretical calculations based on the number and density of spores in an analysis area indicate an analytical sample size of about 1 ng, making this technique an attractive method for bioforensics applications.The 2001 anthrax attacks in the United States have increased interest in developing analytical methods for determining the source of biological materials. In this regard, there is clear evidence that the chemistry of bacterial spores reflects their growth history. Whiteaker et al. (34) were able to distinguish spores grown on blood agar by detecting heme groups on the spore surfaces by matrix-assisted laser desorption ionization mass spectrometry. Horita and Vass (13) and KreuzerMartin et al. (16,17) have shown that the stable isotope signatures of bacteria reflect those of the medium in which they grew. Here we explore a method capable of distinguishing the growth media in which spores of the Bacillus anthracis surrogate Bacillus subtilis were prepared based on the elemental signature of the dried spores.Metals associate with bacteria in several fundamental ways. Major constituents of the culture medium can be incorporated into cells to maintain osmotic and ionic balance, and trace metals can be assimilated as part of enzymatic cofactors. Metals may also be adsorbed to surfaces of cells during any part of an organism's growth history (3, 6) or be precipitated as a consequence of bacterial metabolism (4). In addition, B. anthracis and other spore-forming bacteria accumulate metals in the spore core, complexed to dipicolinic acid, during the sporulation process (21,29,30). This process is apparently correlated to heat resistance (10,15,26), and this phenomenon has led to interest in the metal content of bacterial spores related to food safety, general survivability in the environment, and astrobiology (1,15,18,(20)(21)(22)(23).The first report directly indicating that Bacillus spore metal content could be altered by the metal content of the growth medium dates back to 1959 (27). Under normal conditions, Ca is by far the most abundant metal found associated with the spore, potentially making up more than 3% of the spore weight (21). It is localized primarily in the spore core and to a lesser ext...

show abstract

“…4. The trio of peaks seen in the spectra of the unrinsed samples between 2850 and 2970 cm 1 are generally attributed to C-H stretching modes in alkanes. 6 These peaks are replaced by a single peak near 2970 cm 1 that is attributed to isopropanol.…”

Section: Film Processingmentioning

confidence: 96%

“…6 These peaks are replaced by a single peak near 2970 cm 1 that is attributed to isopropanol. 7 Second, the isopropanol appears to have removed adsorbed water within the pores as shown by the disappearance of the water mode near 1700 cm 1 . The electronics-grade isopropanol used is very dry and it displaces and/or removes the water that is adsorbed into the hydrophilic film after contact with the plasma.…”

Section: Film Processingmentioning

confidence: 98%

Erosion rate variations during XPS sputter depth profiling of nanoporous films

Gaspar

Engelhard

Henry

et al. 2005

Surface & Interface Analysis

View full text Add to dashboard Cite

Sputter depth profiling is commonly used to obtain valuable information regarding the three dimensional distribution of elements within a sample, and is one of the best ways to measure the composition of a buried interface or the uniformity of a thin film. X-ray photoelectron spectroscopy (XPS) is one of the analysis tools often used in conjunction with ion beam erosion to obtain sputter depth profiles. However, to obtain accurate depth information it is often necessary to understand better the sputtering process for a specific materials system. Artifacts such as differential sputtering, varying sputter rates and ion beam-induced chemistry are well known. Here, however, we present evidence from experiments on a porous thin film deposited on an Si wafer that relatively small chemical and/or structural changes in a nanoporous film can affect the rate of erosion measured during sputter depth profiling. Reproducible variations in sputter rate are found with chemical modification leading to compositional changes of the nanoporous thin film. The origin of the sputter rate changes is discussed with the aid of results obtained using Fourier transform infrared spectroscopy, profilometry, nuclear reaction analysis, electron microscopy and XPS-based depth profiling.

show abstract

TOF-SIMS analysis of sea salt particles: imaging and depth profiling in the discovery of an unrecognized mechanism for pH buffering

Cited by 24 publications

References 6 publications

Characterization challenges for nanomaterials

Characterization challenges for nanomaterials

Differentiation of Spores of Bacillus subtilis Grown in Different Media by Elemental Characterization Using Time-of-Flight Secondary Ion Mass Spectrometry

Erosion rate variations during XPS sputter depth profiling of nanoporous films

Contact Info

Product

Resources

About