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Wang SK, Chang HY, Chu YH, Kao WL, Wu CY, Lee YW, You YW, Chu KJ, Hung SH, Shyue JJ. Effect of energy per atom (E/n) on the Ar gas cluster ion beam (Ar-GCIB) and O 2+ cosputter process. Analyst 2019; 144:3323-3333. [PMID: 30968864 DOI: 10.1039/c8an02452a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Gas cluster ion beam (GCIB) is a promising technique for preserving molecular structures during ion sputtering and successfully profiling biological and soft materials. However, although GCIB yields lower damage accumulation compared with C60+ and monoatomic ion beams, the inevitable alteration of the chemical structure can introduce artifacts into the resulting depth profile. To enhance the ionization yield and further mask damage, a low-energy O2+ (200-500 V) cosputter can be applied. While the energy per atom (E/n) of GCIB is known to be an important factor influencing the sputter process, the manner through which E/n affects the GCIB-O2+ cosputter process remains unclear. In this study, poly(ethylene terephthalate) (PET) was used as a model material to investigate the sputter process of 10-20 kV Ar1000-4000+ (E/n = 2.5-20 eV per atom) with and without O2+ cosputter at different energies and currents. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) with Bi32+ as the primary ion was used to examine surfaces sputtered at different fluences. The sputter craters were also measured by alpha-step and atomic force microscopy in quantitative imaging mode. The SIMS results showed that the steady-state cannot be obtained with E/n values of less than 5 eV per atom due to damage accumulation using single GCIB sputtering. With a moderate E/n value of 5-15 eV per atom, the steady-state can be obtained, but the ∼50% decay in intensity indicated that damage cannot be masked completely despite the higher sputter yield. Furthermore, the surface Young's modulus decreased with increasing E/n, suggesting that depolymerization occurred. At an E/n value of 20 eV per atom, a failed profile was obtained with rapidly decreased sputter rate and secondary ion intensity due to the ion-induced crosslink. With O2+ cosputtering and a moderate E/n value, the oxidized species generated by O2+ enhanced the ionization yield, which led to a higher ion intensity at steady-state in general. Because higher kinetic energy or current density of O2+ led to a larger interaction volume and more structural damage that suppressed molecular ion intensity, the enhancement from O2+ was most apparent with low-energy-high-current (200 V, 80 μA cm-2) or high-energy-low-current (500 V, 5 μA cm-2) O2+ cosputtering with 0.5 μA cm-2 GCIBs. In these cases, little or no intensity drop was observed at the steady-state.
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Affiliation(s)
- Shin-Kung Wang
- Department of Materials Science and Engineering, National Taiwan University, Taipei 106, Taiwan.
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Mahmoud AM, Tang T, Harrison DJ, Lee WE, Jemere AB. A regenerating self-assembled gold nanoparticle-containing electrochemical impedance sensor. Biosens Bioelectron 2014; 56:328-33. [PMID: 24530834 DOI: 10.1016/j.bios.2014.01.019] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/02/2014] [Accepted: 01/13/2014] [Indexed: 02/01/2023]
Abstract
We report on the development of an electrochemical reductive desorption protocol for repeated regeneration of gold electrodes modified with multi-layers of self-assembled surfaces for use in electrochemical sensing. The gold electrodes were first modified with 1,6-hexanedithiol to which gold nanoparticles were attached in a subsequent modification step. Attachment of thiolated single-stranded nucleic acid oligomers to the gold nanoparticles completed the electrochemical sensor. The changes of electrode behavior after each assembly and desorption processes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy techniques. The self-assembled sensor showed a wide dynamic range (0.1-100 nM), a low detection limit (20 pM) and high reproducibility (4.4% RSD) for complementary nucleic acid target molecules, along with reusability. On a single gold electrode, the complete sensor-target structure could be assembled and disassembled at least four times with 90% of its original signal intact.
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Affiliation(s)
- Amr M Mahmoud
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada T6G 2G2
| | - Thompson Tang
- Defence Research & Development Canada-Suffield Research Centre, Medicine Hat, AB, Canada T1A 8K6
| | - D Jed Harrison
- Department of Chemistry, University of Alberta, Edmonton, AB, Canada T6G 2G2; National Institute for Nanotechnology, National Research Council Canada, 11421 Saskatchewan Drive, Edmonton, AB, Canada T6G 2M9
| | - William E Lee
- Defence Research & Development Canada-Suffield Research Centre, Medicine Hat, AB, Canada T1A 8K6
| | - Abebaw B Jemere
- National Institute for Nanotechnology, National Research Council Canada, 11421 Saskatchewan Drive, Edmonton, AB, Canada T6G 2M9.
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Gooding JJ, Ciampi S. The molecular level modification of surfaces: from self-assembled monolayers to complex molecular assemblies. Chem Soc Rev 2011; 40:2704-18. [DOI: 10.1039/c0cs00139b] [Citation(s) in RCA: 390] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Negri P, Marotta NE, Bottomley LA, Dluhy RA. Removal of surface contamination and self-assembled monolayers (SAMs) from silver (Ag) nanorod substrates by plasma cleaning with argon. APPLIED SPECTROSCOPY 2011; 65:66-74. [PMID: 21211156 DOI: 10.1366/10-06037] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Surface contamination of surface-enhanced Raman (SERS)-active metallic substrates has been a limitation to the utility of SERS as an analytical technique, potentially affecting surface coverage, spectral reproducibility, and analytical limits of detection. We have developed a simple and versatile cleaning method for SERS-active Ag nanorod arrays that consists of a short (4 min) exposure of the substrate to an Ar(+) plasma in a low-pressure environment. The findings presented here demonstrate that this cleaning procedure essentially eliminates organic background contamination. This procedure works equally well for self-assembled monolayers of thiolates that strongly adsorb onto Au and Ag surfaces. For SERS-active surfaces composed of arrays of Ag nanorods prepared by oblique-angle vapor deposition, we investigated the (1) Raman band intensities, (2) nanorod morphology via scanning electron microscopy, and (3) surface hydrophobicity via static contact angle measurements, as a function of exposure time of the Ag nanorods to the Ar(+) plasma. Short (4 min) exposure to Ar(+) plasma eliminated background contamination but decreased the observed SERS intensity for re-adsorbed analytes by approximately a factor of 2 while leaving the nanorod morphology essentially unchanged. Prolonged exposure to Ar(+) plasma (>10 min) resulted in substantial morphological changes of the Ag nanorod lattice and led to a decrease in the observed SERS intensities by a factor of 10. The results presented here suggest that Ar(+) plasma cleaning is an efficient process for removing carbonaceous and organic contamination as well as thiolate monolayers from SERS-active Ag surfaces, as long as the plasma conditions and exposure times are carefully monitored.
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Affiliation(s)
- Pierre Negri
- Department of Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA
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Yuan M, Zhan S, Zhou X, Liu Y, Feng L, Lin Y, Zhang Z, Hu J. A method for removing self-assembled monolayers on gold. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:8707-10. [PMID: 18582131 DOI: 10.1021/la800287e] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Self-assembled monolayers (SAMs) have been widely used in studying interfacial phenomena, biological processes, electrochemistry, photoelectrochemistry, photoactivity and molecular interaction. Much research has been carried out in fabricating and removing SAMs on different substrates. In this work, we report for the first time, to our knowledge, that SAMs of thiolates on gold can be removed by immersing SAMs in 0.5 M NaBH 4 solution for 10 min. The procedure of removing thiolates was very convenient. Cyclic voltammetry, surface-enhanced Raman spectroscopy, and X-ray photoelectron spectroscopy were used to characterize this process. The results indicated that the SAMs of thiolates on gold can be removed efficiently by NaBH 4.
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Affiliation(s)
- Mingquan Yuan
- College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, People's Republic of China
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Liu TX, Li XZ, Li FB. AgNO3-lnduced photocatalytic degradation of odorous methyl mercaptan in gaseous phase: mechanism of chemisorption and photocatalytic reaction. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2008; 42:4540-4545. [PMID: 18605583 DOI: 10.1021/es7031345] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
In this study, AgNO3 films prepared by a simple dip-coating method were used to remove gaseous methyl mercaptan (CH3SH) for odor control. The AgNO3 films were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy/energy-dispersive X-ray spectrometry(SEM/EDX), and X-ray photoelectron spectroscopy (XPS) before and after the reaction, and as- obtained products were identified by means of gas chromatography/mass spectrometry (GC/MS) and ion chromatography. The experiments demonstrated that the AgNO3 film can induce a quick chemisorption of gaseous CH3SH to form AgSCH3 and other intermediate products such as alpha-Ag2S, Ag4S2, and AgSH on its surface. Under UVA illumination, these sulfur products can be photocatalytically oxidized to AgSO3CH3 and Ag2SO4. Then AgSO3CH3 and Ag2SO4 will continue the chemisorption of gaseous CH3SH, similar to AgNO3, to form AgSCH3 again and release two final products, HSO3CH3 and H2SO4. Hence it is a AgNO3-induced photocatalytic reaction for odorous CH3SH degradation in gaseous phase. This fundamental research about the mechanism of chemisorption and photocatalytic reaction provides essential knowledge with potential to further develop a new process for gaseous CH3SH degradation in odor control.
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Affiliation(s)
- Tong-Xu Liu
- Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
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Gooding J. Advances in Interfacial Design for Electrochemical Biosensors and Sensors: Aryl Diazonium Salts for Modifying Carbon and Metal Electrodes. ELECTROANAL 2008. [DOI: 10.1002/elan.200704124] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Love JC, Estroff LA, Kriebel JK, Nuzzo RG, Whitesides GM. Self-Assembled Monolayers of Thiolates on Metals as a Form of Nanotechnology. Chem Rev 2005; 105:1103-69. [PMID: 15826011 DOI: 10.1021/cr0300789] [Citation(s) in RCA: 4698] [Impact Index Per Article: 247.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- J Christopher Love
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA
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Yang W, Zhang R, Willett GD, Hibbert DB, Gooding JJ. Analysis of Self-Assembled Monolayer Interfaces by Electrospray Mass Spectrometry: A Gentle Approach. Anal Chem 2003; 75:6741-4. [PMID: 14640755 DOI: 10.1021/ac0345897] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A general mass spectrometry technique for the characterization of alkanethiol-modified surfaces is presented. Alkanethiol self-assembled onto a gold surface (in this case, peptides were attached to the gold surface via a thiolate bond) was reductively desorbed in 0.05 M KOH in the presence of octadecyl-derivatized silica gel. The peptide adsorbed onto the silica gel, whereupon it could be filtered, washed to remove any salts, and then eluted using a mixture of 4:1 v/v methanol/water. The eluant containing the peptide was injected into a Fourier transform ion-cyclotron resonance mass spectrometer (FTICR/MS) via electrospray ionization. The spectrum showed no fragmentation of the peptide, demonstrating the gentleness of the technique. This simple procedure is not limited to FTICR/MS and could be adapted to other mass spectrometers.
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Affiliation(s)
- Wenrong Yang
- School of Chemical Sciences, The University of New South Wales, Sydney, NSW 2052, Australia
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Senkevich JJ, Yang GR, Lu TM. Thermal stability of mercaptan terminated self-assembled multilayer films on SiO2 surfaces. Colloids Surf A Physicochem Eng Asp 2002. [DOI: 10.1016/s0927-7757(02)00074-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Current literature in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2001; 36:446-457. [PMID: 11333450 DOI: 10.1002/jms.91] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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