Hello,
We make self-assembled monolayers of gold nanoparticles on aminesilane glass substrate, and get pretty high quality monolayers. However, after we coat the gold particles in certain molecules, particularly hydrophobic molecules, the change in the surface of the gold allows for mobility in the aminated surface. This results in measurable aggregation of the nanoparticle film, and a degradation of quality of the sensor system that's using it.
I know that mercapto-silanes ought to give better nanoparticle adherence, but we've tried dozes of attempts and failed at getting a AuNPs on a thiol-silane film. We're trying to find other ways to ensure the nanoparticles are less mobile in the films, and wondered if maybe changing the nanoparticle size or surface coating prior to self-assembly might help. Is anyone aware of studies to control the aggregation of AuNP films.
Have a look
An electrochemical genosensor for Salmonella typhi on gold nanoparticles-mercaptosilane modified screen printed electrode, Journal of Biotechnology 188 (2014) 9–16
Metal nanoparticles immobilized on a solid substrate for sensing applications, http://shodhganga.inflibnet.ac.in:8080/jspui/bitstream/10603/2471/10/10_chapter%203.pdf
Try layer-by-layer deposition of polyelectrolytes. So, after depositing gold nps on amino-functionalized surface, coat it with e.g. polystyrene sulfonate (PSS). If this does not help enough to bind nps strong, then add layer of oppositely charged polyelectrolyte and so on, until you reach the desired adherence. Each layer will add something like 4-10 nm, and with each layer surface of nps will be less accessible.
As another solution - if you are using hydrophobic coating of nps then try hydrophobic coating of substrates too. Mercaptosilanes will not help with coated gold nps - they can only help with unmodified (or e.g. citrate stabilized) gold nps.
Has anyone ever tried covalent coupling between the aminated surface and a carboxymethlyated gold particle?
Our experience with the polyelectrolyte (peptides) as surface stabilizers of gold nanoparticles, deposited on various substrates (glass, mica, gold) shows that the fixing of gold nanoparticles occurs only upon the strong interaction with the surface of mica. For weak interactions with the inert substrate (glass) the aggregation of gold nanoparticles occurs. This process essentially depends on the ratio of positive and negative charges in the peptide molecule.
We can go through our following article which has been reported on “metal ion enriched multi-layer film with very good stability at any pH condition.
Langmuir 2012, 28, 8486−8495.
You can stabilize the Au NPs in membrane and control their mobility by taking 11-Mercaptoundecanoic acid stabilized gold nanoparticles, or polymer stabilized nanoparticles, like Polyethylene Glycol stabilized Au NPs. etc. u can also try with gold nanoparticle-block copolymer composites.
I have done that for 22nm gold nanospheres, but it doesn't actually improve their stability in an immobilized layer of aminated silanes. My solution is to try covalent linking first.
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