Chemical Reduction Method

Chemical reduction method is not limited to synthesis of silver nanoparticle only, it is also useful to synthesis gold (Au) nanoparticles. The first reduction method was employed in the year 1957 where gold chloride was reduced by phosphorous in aqueous medium. Later citrate stabilized Au nanoparticles (~20 nm) were synthesized from gold tetra-chloroauric acid and using tri-sodium citrate as reducing agent. The synthesis reaction of Au nanoparticles using citrate is written in the following way:
2HAuCl4 + 3C6H8O7 2Au + 3C5H6O5 + 8HCl + 3CO2
In this context it may be stated that size of the Au nanoparticles could be varied by changing synthesis temperature, reagent concentration etc. Later, the role of citrate salt on the pH of

Later, Leff et al. reported the preparation of amine-stabilized Au nanoparticles by substituting the dodecanethiol with dodecyl amine or oleylamine and increase the diameter of the prepared Au nanoparticles up to 7 nm. In the ethanol-mediated method, alkyl amine is used as a stabilizer-cum-phase transfer agent and has distinctive advantage over Brust–Schiffrin. In this two-step approach, aqueous solution of metal ions is mixed with an equal volume of ethanol containing dodecyl amine and the mixture is stirred for few minutes. Then, toluene is added with continuous stirring before transferring the mixture to a separating funnel. The two immiscible layers formed within few minutes. The transfer of metal salts from the aqueous phase to toluene then completes where ethanol is found to be very important candidate without which metal ions would not be transferred to the organic phase by the direct mixing of an aqueous metal precursor solution with an organic solvent containing dodecyl amine. The fact that water and ethanol are miscible ensures the maximum contact between metal ions and dodecyl amine. A large number of commonly used popular methods, e.g., wet

Similar to silver or gold, platinum nanoparticles are also synthesized by method of reduction starting from precursor H2PtCl6 for platinum and NaBH4 as reducing agent. The reaction can be summarized