Hi,

Please read these articles for preparation of nanoparticles. https://www.researchgate.net/publication/262843669_Gold_nanoparticles_various_methods_of_synthesis_and_antibacterial_applications

https://www.omicsonline.org/open-access/gold-and-silver-nanoparticles-synthesis-methods characterization routes-and-applications-towards-drugs-2161-0525-1000384.php?aid=76676

Good luck

Examples of AuNPs preparation without use of an additional reducing agent. Positively charged with AuNPs average size of 7-9 nm cab be prepared via heating or visible light irradiation of tetrachloroauric acid with chitosan solution. Also HEPES buffer can be used for negatively charged AuNPs. Cryogelation of chitosan using noble-metal ions: in situ formation of nanoparticles D Berillo, B Mattiasson, H Kirsebom Biomacromolecules 2014, 15 (6), 2246-2255.

There are many ways that you can synthesis metal nanoparticles by them. If you prefer to synthesis via precipitation methods you will need the salt of the metal such as chloroauric acid for gold nanoparticles synthesis, and a reducing agent such as citrate sodium. I think watching this movie can help you substantially.

https://www.youtube.com/watch?v=-rbz3uLZvPc

And if you want to synthesis nanoparticles with green methods our research articles could help you with this issue.

Article Green synthesis, characterization and physiological stabilit...

Article Creating Anti-HIV-Infection effect by Synthesis of AuNPs fro...