• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.105.1-105.1
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• 2016

Many of the complex materials developed today derive their unique properties from the presence of multiple phases or from local variations in elemental concentration. Simply performing analysis of the bulk materials is not sufficient to achieve a true understanding of their physical and chemical natures. Secondary ion mass spectrometer (SIMS) has met with a great deal of success in material characterization. The basis of SIMS is the use of a focused ion beam to erode sample atoms from the selected region. The atoms undergo a charge exchange with their local environment, resulting in their conversion to positive and negative secondary ions. The mass spectrometric analysis of these secondary ions is a robust method capable of identifying elemental distribution from hydrogen to uranium with detectability of the parts per million (ppm) or parts per billion (ppb) in atomic range. Nano secondary ion mass spectrometer (Nano SIMS, Cameca Nano-SIMS 50) equipped with the reactive ion such as a cesium gun and duoplasmatron gun has a spatial resolution of 50 nm which is much smaller than other SIMS. Therefore, Nano SIMS is a very valuable tool to map the spatial distribution of elements on the surface of various materials In this talk, the surface imaging applications of Nano SIMS in KBSI will be presented.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.203-214
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• 2015

We have been developing a new label-free nanobio imaging platform using non-linear optics such as Coherent Anti-Stokes Raman Spectroscopy (CARS) and ion beam techniques based on sputtering and scattering such as Secondary Ion Mass Spectrometry (SIMS) and Medium Energy Ion Scattering Spectroscopy (MEIS), which have been widely used for atomic and molecular level analysis of semiconductors and nanomaterials. To apply techniques developed for semiconductors and nanomaterials for biomedical applications, the convergence of nano-analysis and biology were tried. Our activities on label-free nanobio imaging during the last decade are summarized in this review about non-linear optical 3D imaging, ellipsometric interface imaging, SIMS imaging, and TOF-MEIS nano analysis for cardiovascular tissues, collagen thin films, peptides on microarray, nanoparticles, and cell adhesion studies and finally the present snapshot of nanobio imaging and the future prospect are described.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.73-73
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• 2010

Various organic- and bio-conjugated nanoparticles have been studied extensively for biological applications in medical diagnoses and drug delivery systems. Gold nanoparticles (AuNP) and poly(ethylene glycol) (PEG) are known biocompatible materials to be used in vivo and are becoming increasingly important in biomedical applications. In this work, we investigated the stability of PEG-conjugated AuNPs, dialysis and centrifuge effects after synthesis or pegylation of AuNPs as a function of elapsed time by using ToF-SIMS imaging technique along with dynamic light scattering (DLS), UV-visible absorption spectroscopic and statistical analyses. Roughly 15-nm-sized AuNPs were synthesized in a citrate-conjugated form, and then converted into the thiol-terminated PEG (O-[2-(3-Mercaptopropionylamino)ethyl]-O'-methylpolyethyleneglycol, M.W.=5 kDa) form. Based on our data, we will show that ToF-SIMS imaging analysis along with DLS, UV-visible absorption and statistical analyses would be a useful method to evaluate stability of PEG-conjugated AuNPs in various environmental conditions.

• Bulletin of the Korean Chemical Society
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• v.34 no.3
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• pp.815-819
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• 2013

Micropatterns of streptavidin and human epidermal carcinoma A431 cells were successfully imaged, as received and without any labeling, using cluster $Au_3{^+}$ ion beam-based time-of-flight secondary ion mass spectrometry (TOF-SIMS) together with a principal component analysis (PCA). Three different analysis ion beams ($Ga^+$, $Au^+$ and $Au_3{^+}$) were compared to obtain label-free TOF-SIMS chemical images of micropatterns of streptavidin, which were subsequently used for generating cell patterns. The image of the total positive ions obtained by the $Au_3{^+}$ primary ion beam corresponded to the actual image of micropatterns of streptavidin, whereas the total positive-ion images by $Ga^+$ or $Au^+$ primary ion beams did not. A PCA of the TOF-SIMS spectra was initially performed to identify characteristic secondary ions of streptavidin. Chemical images of each characteristic ion were reconstructed from the raw data and used in the second PCA run, which resulted in a contrasted - and corrected - image of the micropatterns of streptavidin by the $Ga^+$ and $Au^+$ ion beams. The findings herein suggest that using cluster-ion analysis beams and multivariate data analysis for TOF-SIMS chemical imaging would be an effectual method for producing label-free chemical images of micropatterns of biomolecules, including proteins and cells.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.91-94
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• 2008

Newly developed Atom Probe Tomography (APT) technique can provide the highest available spatial resolution, 3D tomography imaging and quantitative chemical analysis in a sub-nm scale. As a complementary technique to APT, Nano-secondary ion Mass Spectroscopy (SIMS) also provides the boron distribution in micro-scale. Therefore, the exact behavior of boron at either grain boundary or grain interior in steels can be investigated by the combination of APT and SIMS techniques from the sub-nanometer scale to the micrometer scale. The results obtained by both APT and SIMS revealed that the boron atoms were mainly segregated to the grain boundaries rather than to the grain interior in the steels containing 50ppm and 100ppm boron. It also found that carbon atoms were segregated at the boron enriched regions, which were thought to be retained austenite phase due to the chemical composition of carbon atoms.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.355-355
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• 2016

There has been an explosive development of nanocrystal (NC) synthesis and application due to their composition-dependent specific properties. Despite the composition, shape, and size of NCs foremost determine their physicochemical properties, the surface state and molecule conjugation also drastically change their characteristics. To make practical use of NCs, it is a prerequisite to understand the NC surface state and the degree to which they have been modified because the reaction occurs on the interface between the NCs and the surrounding medium. We report in here an analysis method to identify conjugated ligands and their binding states on semiconductor nanocrystals based on their molecular information. Surface science techniques, such as time-of-flight secondary-ion mass spectrometry (ToF-SIMS) and FT-IR spectroscopy, are adopted based on the micro-aggregated sampling method. Typical trioctylphosphine oxide-based synthesis methods of CdSe/ZnS quantum dots (QDs) have been criticized because of the peculiar effects of impurities on the synthesis processes. Since the ToF-SIMS technique provides molecular composition evidence on the existence of certain ligands, we were able to clearly identify the n-octylphosphonic acid (OPA) as a surface ligand on CdSe/ZnS QDs. Furthermore, the complementary use of the ToF-SIMS technique with the FT-IR technique could reveals the OPA ligands' binding state as bidentate complexes.

• Proceedings of the Korean Vacuum Society Conference
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• 2009.02a
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• pp.231.2-231.2
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• 2009

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.275-275
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• 2013

Formation and characterization of self-assembled monolayers (SAMs) on various surfaces are the essential basis for many other applications, including molecular switches, biosensors, microfluidics, and fundamental studies in surfaces and interfaces. To improve the performance at these applications, it is a key to control the quantity of each molecule in various mixed SAMs on the surface. In this study, using mixed SAM of carbamate-based hydroquinone (HQ)-PhBr and11-mercaptoundecanol, the quantitative mass spectrometric method of mixed SAM was developed based on comparison study with XPS and FT-IR methods. In addition, our method was applied to another mixed SAM of biotinylated PEG alkane thiol and 11-mercaptoundecanol for verification purpose. Time-of-flight secondary mass spectrometry (ToF-SIMS) analysis was performed to identify and quantify each molecule of mixed SAM along with principal component analysis (PCA). Since there is no matrix effect in the X-ray photoelectron spectroscopy (XPS) and Fourier transform-infrared (FT-IR) techniques, we compared ToF-SIMS results with XPS and FT-IR results. Because PCA results from ToF-SIMS analysis are well matched with XPS and FT-IR results from both mixed SAMs, we are expecting that our method will be useful to identify and quantify each molecule in various mixed SAMs.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.230.1-230.1
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• 2015

One of the major problems of biological ToF-SIMS imaging is the lack of protein and peptide imaging. Most of biological story telling is mianly based on proteins. The biological implication of lipid ToF-SIMS imaging would be much higher if protein imaging is provided together. Utilizing high secondary ion yields of metals, proteins can be ToF-SIMS imaged with nanoparticle tagged proteins. Nanoparticles such as Fe3O4, SiO2, PbS were used for imaing NeuN, MCH, Orexin A, ${\alpha}$ synucline, TH(Tryosine Hydroxylase) in mouse tissues with a spatial resolution of ${\sim}2{\mu}m$ using a TOF-SIMS. Lipids and neurotransmitters images obtained simultaneously with protein images were overlayed for more deeper understanding of neurobiology, which is not allowed by any other bioimaging technqiues. The protein images from TOF-SIMS were compared with confocal fluorescence microscopy and NanoSIMS images. A new sample preparation method for imaging single cell membranes in a tissue using the vibrotome technique to prepare a tissue slice without any fixation and freeze drying will be also presented briefly for Hippocampus and Hypothalamus tissues.

• Proceedings of the Korean Vacuum Society Conference
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• 2002.06a
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• pp.187-187
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• 2002