Chip-Scale Electrochemical Differentiation of SAM-Coated Gold Features Using a Probe Array

Tencer, Michal; Olivieri, Anthony; Tezel, Bora; Nie, Heng–Yong; Berini, Pierre

doi:10.1149/2.087203jes

Cited by 7 publications

(5 citation statements)

References 19 publications

(43 reference statements)

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“…This distinctive difference was revealed by ToF-SIMS, thanks to its extremely high surface sensitivity and superb chemical selectivity. For example, for alkanethiol SAMs formed on gold, ions associated with both the alkanethiol molecule (whose molecular formula is represented by M) and gold were detected, including Au 2 M − and [Au 2 M 2 -H] + [30], M 2 Au + [31] and [M-H + Au 2 ] − [32]. Even though alkanethiol molecules are covalently bonded to the substrate via the Au-S linkage [2], the detection of molecular or pseudomolecular ions by ToF-SIMS is attributed to the lack of cross linking of the molecular headgroups themselves.…”

Section: Discussionmentioning

confidence: 99%

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Time-of-Flight Secondary Ion Mass Spectrometry Analyses of Self-Assembled Monolayers of Octadecyltrimethoxysilane on SiO2 Substrate

Nie

Jahangiri-Famenini²

2022

Applied Sciences

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The self-assembled monolayers (SAMs) of organosilanes formed on an oxide substrate are thought to have a polymerized –Si–O–Si– network due to the homocondensation of silanols of hydrolyzed silane headgroups, which is the most significant difference in the SAMs of organosilanes in comparison with those of alkanethoils and organophsosphonic acids. In order to explore the interface chemistry of organosilane SAMs, surface-sensitive time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to compare ion fragmentation differences between the SAMs of octadecyltrimethoxysilane (OTMS) formed on a SiO2 substrate and free OTMS molecules, as well as oxide substrate. The ability of ToF-SIMS to verify the hydrolysis of the methoxy groups of OTMS molecules and to assess the polymerized –Si–O–Si– network in their SAMs was demonstrated, which shows that ToF-SIMS provides unique information to help us understand the interface chemistry of OTMS SAMs formed on oxides.

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Section: Discussionmentioning

confidence: 99%

“…The superior chemicals selectivity of ToF-SIMS provides a unique opportunity to explore the interface chemistry of SAMs. ToF-SIMS has been widely applied to studying alkanethiol SAMs on coinage metals [30][31][32] and organophosphonic acid SAMs on oxides [33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Time-of-Flight Secondary Ion Mass Spectrometry Analyses of Self-Assembled Monolayers of Octadecyltrimethoxysilane on SiO2 Substrate

Nie

Jahangiri-Famenini²

2022

Applied Sciences

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“…A brief synopsis of the applicable theory [38][39][40][41] is given in the Appendices A.2 and A. 3 The current density passing through the electrode is given by the Butler-Volmer equation (Appendix A.2) [40]:…”

Section: Theoreticalmentioning

confidence: 99%

“…Small, closely spaced metallic features of dimensions and separation in the micrometer range are of interest in electrochemical device applications or for integration with optical biosensors, e.g., based on surface plasmon-polaritons (SPPs) [1][2][3]. Optical biosensors exploiting long-range surface plasmon-polariton (LRSPP) waveguides have solicited significant interest because they enable compactness in integrated architectures, and offer very high sensitivity in an arrayed format [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Performance of Lithographically-Defined Micro-Electrodes for Integration and Device Applications

et al. 2021

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Small; lithographically-defined and closely-spaced metallic features of dimensions and separation in the micrometer range are of strong interest as working and counter electrodes in compact electrochemical sensing devices. Such micro-electrode systems can be integrated with microfluidics and optical biosensors, such as surface plasmon waveguide biosensors, to enable multi-modal sensing strategies. We investigate lithographically-defined gold and platinum micro-electrodes experimentally, via cyclic voltammetry (CV) measurements obtained at various scan rates and concentrations of potassium ferricyanide as the redox species, in potassium nitrate as the supporting electrolyte. The magnitude of the double-layer capacitance is estimated using the voltammograms. Concentration curves for potassium ferricyanide are extracted from our CV measurements as a function of scan rate, and could be used as calibration curves from which an unknown concentration of potassium ferricyanide in the range of 0.5–5 mM can be determined. A blind test was done to confirm the validity of the calibration curve. The diffusion coefficient of potassium ferricyanide is also extracted from our CV measurements by fitting to the Randles–Sevcik equation (D = 4.18 × 10−10 m2/s). Our CV measurements were compared with measurements obtained using macroscopic commercial electrodes, yielding good agreement and verifying that the shape of our CV curves do not depend on micro-electrode geometry (only on area). We also compare our CV measurements with theoretical curves computed using the Butler–Volmer equation, achieving essentially perfect agreement while extracting the rate constant at zero potential for our redox species (ko = 10−6 m/s). Finally, we demonstrate the importance of burn-in to stabilize electrodes from the effects of electromigration and grain reorganization before use in CV measurements, by comparing with results obtained with as-deposited electrodes. Burn-in (or equivalently, annealing) of lithographic microelectrodes before use is of general importance to electrochemical sensing devices

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“…The study of self-assembled monolayers (SAMs) has focused on scientific questions regarding their formation, structure, and properties, , as well as on technological applications such as their use to control wetting properties, , create biocompatible surfaces, , impart chemical resistance, and fabricate sensors. − Many of these applications require the formation of SAMs in specific patterns, and although the application of patterned SAMs on uniform substrates is relatively straightforward, the regioselective formation of SAMs on specific features on a complex substrate remains challenging. − Even more challenging is the production of a chemically diverse set of SAMs on such a substrate while maintaining the purity of each monolayer.…”

Section: Introductionmentioning

confidence: 99%

Spatially Selective Formation of Hydrocarbon, Fluorocarbon, and Hydroxyl-Terminated Monolayers on a Microelectrode Array

2013

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A protection-deprotection strategy, using gold oxide as a passivating layer, was used to direct the self-assembly of monolayers (SAMs) selectively at individual gold microelectrodes in an array. This approach allowed the formation of hydroxyl-terminated monolayers, without side reactions, in addition to hydrocarbon and fluorocarbon SAMs. Fluorescence microscopy was used to visualize selective dewetting of hydrophobic monolayers by an aqueous dye solution, and spatially resolved X-ray photoelectron spectroscopy was used to demonstrate a lack of cross-contamination on neighboring microelectrodes in the array.

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Chip-Scale Electrochemical Differentiation of SAM-Coated Gold Features Using a Probe Array

Cited by 7 publications

References 19 publications

Time-of-Flight Secondary Ion Mass Spectrometry Analyses of Self-Assembled Monolayers of Octadecyltrimethoxysilane on SiO2 Substrate

Time-of-Flight Secondary Ion Mass Spectrometry Analyses of Self-Assembled Monolayers of Octadecyltrimethoxysilane on SiO2 Substrate

Electrochemical Performance of Lithographically-Defined Micro-Electrodes for Integration and Device Applications

Spatially Selective Formation of Hydrocarbon, Fluorocarbon, and Hydroxyl-Terminated Monolayers on a Microelectrode Array

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