How you are dissolving/adding MUA + MH to Au-NP solution 

Simply try to add ethanolic solution of  MUA + MH to Au-NP solution - it won't affect  pH of your solution 

Good luck to you

Hi Sir,

Thanks for the reply.I have been trying to dissolve MUA+MH using ethanol.But the nano particles were not stable in ethanol solution.That is why i was trying higher pH solutions

No need of increasing the pH. You simply dissolve MUA in EtOH. Then add in AuNPs for 40 mins at 10 ug/mL concentration. It will bind through Au-S covalent bonding.

No need to dissolve Au-NP in ethanol - just add ethanolic solution of MUA+MH to Au-NP solution 

Thanks for the suggestions Dr.Murugesan and Mr. Sudip