Means eventually you are trying to go grafting, did you tried to give it an ultrasonigation treatment if not, Why don't you try it under ultrasonigation environment.

and yes the medium is also a big factor you may try various solvents generally for grafting DMF is used.

Yes surely grafting.. no i didnt do sonication.. what will be the advantage of sonication ?

Dear Wajiha Ahmad

Please read this article

Article Functionalized gold nanorods for nanomedicine: Past, present...

while we are talking about polymer the dispersion plays a good role as well it is necessary, ultra-sonication is found to be a very good Technic over simple mixing.

https://sciencing.com/sonication-work-5171302.html

follow this article it may be helpful to you, that why ultra sonication assisted mixing may be helpful for you.

thank you all for your answer.

I generally centrifuge the nanorods to remove the supernatant and place the solution for functionalization and leave under stirring at room temperature. It may be that the CTAB has not been removed enough for the thiolate binder to bind ...