Hi all.
Currently, I am synthesizing the gold-coated silica ( 0.5mm < d < 1mm) for GEM (gaseous elemental mercury) analysis. We have successfully synthesized the product that matches the physicochemical properties described in numerous preceded researches. Our work is mainly based on the paper I attach below.
The next intention of our group is to co-precipitate PtNPs (platinum nanoparticles) alongside with AuNPs to create a Pt-AuNPs coated silica product.
I myself have referred to the one-pot synthesis of Pt-AuNPs where they use ascorbic acid-meditated reduction for the [AuCl4]- and [PtCl6]2- mixture, and I will use the procedure for the nanoparticle synthesis. I'm just not so sure the newly-formed Pt-AuNPs would be grafted on the silica surface, using ATPMS ((3-aminopropyl)trimethoxysilane) 1% v/v in methanol as the adhesive.
I am looking to hearing your opinion and willing to respond to any answer.
Thank you so much in advance.
http://pubs.acs.org/doi/abs/10.1021/ac001207d
Dear Minh,
the adsorption of gold nanoparticles on aminosilanized surfaces is based on electrostatic attraction of negatively charged AuNP on a positively charged aminosilanized surface. Thus, if your AuPt-NP are as well negatively charged it should be no problem to deposit them on the aminosilanised silica. You could check the charge of the synthesized particles by measuring the zeta-potential of the NP-solution and then decide if adsorption would be successful.
Kind regards, Corinna
Dear Prof.Corinna.
Thank you for your kind answer.
I have read elsewhere in the literature that the zeta potentials of AuNPs solution (at pH above 5) are all negative. Another paper stated in their reference data that the zeta potential of PtNPs solution (at pH 5.5) is -33.3 mV. With those given values, I think the potency of using APTMS as an adhesive is undoubted. Thanks for your comment.
Actually, I followed one of your investigations ( DOI:10.1021/la404110y) and found out that you used modified AuNPs to graft on Pt surfaces. Since the intention of my research is to create the Pt base (a more rigid base) for Au deposit (therefore having better Au-Hg amalgamation), do you think this is a better approach than the use of Pt-AuNPs itself?
I have read that the Pt-AuNPs could be formed as various morphologies, of which Au core- Pt shell model is not what I expected.
I hope to hear more about your opinion on this aspect.
Thank you so much :D
Hi Minh,
It could be easier to deposit AuNP directly on a pristine Pt surface, because you obtain the Pt surface by sputtering or vapor deposition and you can subsequently deposit the functionalized AuNP. Additionally, I think a final plasma cleaning step is necessary to tether the AuNP irreversibly to the Pt underground and to remove the organic coating of the AuNP to permit amalgamation.
Best regards,
Corinna
Dear Prof.Corinna.
Unluckily, we could not afford sputtering or vapor deposition at the moment, due to the lack of instrumentation. Maybe I'll try to find a procedure that helps me to coat the PtNPs on the silica surface first through the road of an electrodeless deposit, following up by a AuNPs attachment.
Can we substitute the plasma cleaning step with any alternatives?
Looking to hearing your opinion
Best regards
Two options you might try: first, purely electrostatic. Take your silica, which is negatively charged, put some polylysine solution on it. Rinse the surface to remove excess PL with water, add your nanoparticles. If they are strongly negatively charged, they will adhere to this surface, which is now positively charged.
Second option is covalent, it will rely on the fact that thiol interacts with gold. Take some thiol triethoxysilane, (it is like APTES but with a thiol instead of amine), incubate with your silica surface to put thiol on it, wash away the excess. Add nanopartices; gold-thiol will firmly bind.
Best of luck with the experiment!
A.K.