You probably can use Ethylene Glycol as capping agent. I havn't try that, have a good read before trying: http://pubs.acs.org/doi/pdf/10.1021/cg100740e
Thanks Mobin. Ethylene Glycol is able to reduce metal ions without reduction agent? Indeed, I want to, maybe I scared, use hydrothermal method without any gas generation during synthesis of metal nano particles.
Don't know what exactly you mean but EG is a relatively strong reducing agent and it has been used to synthesis metal (zero charge) NPs through hydrothermal process.