this paper help you

https://web.uvic.ca/~agbrolo/jp404250q.pdf

Sodium azide is added to prevent the growth of microorganisms. Do not use it. Good luck using edc, it is a pain in the ass. Use edc in excessive amounts If you have no other options.

Ariadne Tuckmantel

Why 3 question marks in 'why sodium azide???'

Why 2 question marks in 'Can anyone help, please??'

Is one not enough?

Dear Ariadne Tuckmantel, apparently, sodium azide is a preservative for the gold nanoparticles. In this context, you might want to check out a related question on RG:

https://www.researchgate.net/post/How_can_sodium_azide_be_removed_from_a_gold_nanoparticle_solution

It is interesting to note that the original preparations (references [62], [66], and [67] in your protocol) all do not use sodium azide (see attached).

Dear Abdelkader Dehbi, this is the paper with the protocol that I follow. I couldn't find anywhere else the use of sodium azide before adding Nile blue to gold nanoparticles. And I tried without the azide but the Nile blue was not present whereas it worked with azide.

Dear Alan F Rawle,

sorry, I didn't mean to sound rude. The three question marks are because I am so puzzled, trying to find this answer that I got carried away trying to show it.

The "Can anyone help, please" is maybe because the only time I asked for help in Matlab forums no one answered, so I was double asking in hopes fr someone to answer. :) Next time I use this platform I will be sure to write in a better way. I am sorry.

Dear Frank T. Edelmann,

thank you for answering.

Yes, the original papers don't use the azide. What is intriguing is that I tried without azide and the Nile blue was not in the nanoparticle, whereas with azide I could see the Nile blue in the particle using Raman. For the only reference that uses dye, they don't show results for Nile blue, they show for another dye.

I think the azide is used to anchor somehow the Nile blue to the gold nanoparticle, but I can't find a reasonable explanation for how that may be.

I have seen that question that you sent me but the azide seems to aggregate their particle, which doesn't happen to me.

Dear Omar Gonzalez-Ortega,

yes, I would like not to use it, but I need to have Nile Blue in the gold nanoparticle and for some reason, the dye only adhered to the particle when I added this.

I am thinking in wash more times before trying to put the antibody, to eliminate this from the media after getting the Nile blue to stick to the particle.

Thank you for answering.

Ariadne Tuckmantel

Thank you for your politeness. It is much appreciated.

Dear Ariadne Tuckmantel

I think these two articles (related to such Au NPs) will be helpful to you. My Regards

Article A facile approach for the reduction of 4‑nitrophenol and deg...

Article Gold Modified Polydopamine Coated Mesoporous Silica Nano-Str...