To date, a strong -and almost exclusive -focus has been giving to glycerol for such RT SF colloidal synthesis of Au NPs . The glycerol-mediated synthesis is fast and lead to relatively small size NPs in the range 5-10 nm over a wide range of conditions, e.g. different concentrations of base and/or alcohol contents . The synthesis using glycerol is also less sensitive to the light environment. The glycerolmediated synthesis is therefore overall more robust, which probably accounts for its popularity to date. However, a major drawback of the glycerol-mediated synthesis is the use of a relatively viscous solvent. The high viscosity of polyols prevent a simple and direct use of the Au NPs . Ethylene glycol is a possible alternative to glycerol , but is still a viscous solvent with similar pros and cons .