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Ethanol-Assisted Alkanethiol Self-Assembled Monolayer Disruption by Mobile Siloxane Oligomers for Precise Galvanic
Yu-Ling Tu1, Chia-Li Liao1, Elmer Ismael Guerra1
1Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
None:
Siloxane oligomers with low molecular weights often exist in elastomeric polymers, e.g., polydimethylsiloxane, and can be troublesome chemical species when utilizing polymers due to their hard-to-control behavior and unpredictable mobility. For instance, the presence of these species can contaminate surfaces and affect molecular integrity when these polymers are applied in developing functional substrates. In this study, on the contrary, we provide an unconventional approach whereby siloxane oligomers originating from a polymerized matrix are transported to alkanethiol self-assembled monolayer (SAM)-functionalized Au through the mediation of ethanol pre-entrapped in the elastomer. Relying on the interface mobile environment provided by ethanol, siloxane oligomers controllably diffuse, transfer, and disrupt a preformed alkanethiol monolayer on Au during conformal contact sealing, which in turn promotes the detachment of Au-thiolates from the surface. Spectroscopic analyses, including sum frequency generation vibrational spectroscopy and X-ray photoelectron spectroscopy, confirm the disruption of SAMs and the detachment of Au-thiolates. Several key parameters, including conformal contact sealing duration, molecule backbone chain length, and terminal group functionality, are critical in this SAM disruption phenomenon. The produced disordered SAM environment enables the penetration of ions when placed in solutions and supports underlying metal oxidation for precise feature transfer. Furthermore, selective galvanic replacements between different metals can be triggered at SAM-disrupted regions to produce bimetallic substrates. These bimetallic interfaces selectively enhance fluorophore-dependent fluorescence emission by interparticle electric field promotion. By combining multiple spatial SAM disruption operations on the same substrate, the produced fluorescent assay, built with manifold internal standards, offers a reliable platform, supporting ratiometric treatments for further bioimaging analysis and detection.
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