What is outer coverage

Citrate and CTAB  are not  suitable for your work

Try coating PEG - it'll help to prevent aggregation and stability - for procedures check literature

Thank you your answer Dr. Muthu, yes ı know what you say but when ı tried to solve gold nanorods in buffer , gold nanorod is aggregated bottom of the tube , ı dont want to any aggregation , so which buffer or which pH range that ı use

Dear Aytaç Gül, I am working in Prof Tony Cass research group. Vigorous research activity is going on our group about nanoparticles, nanorods and nanostars. Even-though the procedure is simple,  available in the literature, I can't write much here.  Better you can write to Prof Tony Cass 

https://www.researchgate.net/profile/Tony_Cass

add some surfactants，such as CTAB, Tween 20, 40,40,80.

Here are some recent progresses on highly dispersible Au NRs:

http://www.ncbi.nlm.nih.gov/pubmed/25016644

http://pubs.rsc.org/en/content/articlehtml/2015/CC/C5CC01489A

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3643678/

Thank you your answer Prof Jeong-Hwan Kim, these articles seem to be very useful, I begin to analyze paper that you suggest