I want to create a densely packed, amine-terminated, self-assembled monolayer (SAM) on a silicon wafer to react with a second molecule via an NHS linkage. Piranha activation followed by APTES functionalization is the traditional method, but the drawbacks are the use of harsh solvents and the need for careful control of atmosphere (e.g. oxygen and humidity), which is challenging due to a lack of facilities.
I also have the option of doing e-beam evaporation of ultrathin gold and reacting with an aminothiol (e.g. cysteamine). This seems like the simplest method to achieve my goal. I just started reading about SAMs on gold. Are there drawbacks to this method I should be aware of, such as functional group density, instability in organic solvents or at higher temperature, or bond strength?
The APTES functionalization surely is more stable. The Si-O-Si bond is stronger than the Au-S bond. Moreover, the siloxanes form a - if done well 2D - network which makes them even more stable.
The treatment with the Piranha solution solution is done in order to remove organic adsobates and to form silanol groups for the reaction with APTES. The same effect can be achieved with plasma treatments. The Piranha treatment can be performed in any chem or bio lab. For the plasma treatment a special equipment is required.
Piranha sol'n is necessary only if there is organic contamination on the substrate. Normally dilute HCl followed by DI after is sufficient to activate the substrate. Also, for gold Si-H chemistry behaves like S-H. Please see the link: https://www.gelest.com/themencode-pdf-viewer/?file=https://www.gelest.com/wp-content/uploads/Goods-PDF-brochures-couplingagents.pdf
Kyle Michelson Can you post the protocol used for APTES incl. atmosphere considerations (if done in glove box) since it is very tricky to get it right?
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