I am looking to control the surface deposition of AuNP's onto a glass surface by controlling the mixing density of amine-reactive silanes with non-reactive silanes. The idea is that by reducing the surface coverage of reactive silanes, we can control the coverage of AuNPs binding to the surface. For an amine-reactive silane, we found the ideal molecule to be:
trimethoxysilyl propyl diethylenetriamine (TMDSE)
And for non-reactive silanes, we tried:
ethyltrimethoxysilane (ETMS) and propyltrimethoxysilane (PTMS)
Our results showed that AuNPs bound signficantly, regardless of the mixing ratio (even at 1:10000). These results were corroborated by literature that showed that when AuNPs are deposited on a surface of reactive amines-silanes mixed with non-reactive silanes, the hydrophobic interaction somehow is enhanced and a great deal of nanoparticle aggregation occurs. The model for this interaction is complex, but basically, the exposed hydrophobic regions of the ETMS are causing unwanted effects.
Therefore, I'm interested in reducing this hydrophobic effect. Can you recommend a methoxysilane that has a headgroup that would give the surface a hydrophillic property? A colleague recommended using a molecule with a carboxyl headgroup, and said this would give it a hydrophillic property. Being bad at chemistry, I don't fully understand this, and hoped you may have some insights as to other molecules we can try out?
APTES any help? It's got an amine group, which is certainly polar. I do think it has a tendency to hydrolyze, though.
Can you react something like a PEG chain to a silane to reduce coverage?
We used APTMS in the past and found that it didn't give as nice monolayers of AuNPs as TMSDE. Never tried APTES. We have a paper; however, that shows APTMS, when mixed with the non-reactive silanes (ETMS) yieled identical results to what we're seeing (IE hydrophobic clustering), so it's unlikely that it would make a difference.
Aw bummer. Sorry I can't be of much greater help. Anything about decorating the silanes with some kind of non-specific binding inhibitor to break things up? You could mix the populations, although you might get subdomains of each type.
Just a quick google found a silane-PEG-silane. Maybe that'd work as part of your mix?
http://www.laysanbio.com/index.php?src=directory&view=products&refno=356&srctype=products_detail
We deposited AuNPs in silanized ITO glass slide without causing the nanoparticles to aggregate.The silane used was APTES. Please see the attached file for the exact protocol.
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