Preparation of stable copper nanostructures and their direct phase transfer using mercaptosuccinic acid

This work aims at synthesis and phase transfer of highly stable oxidation resistant copper nanostructures (large nanoparticles, nanorods and nanosheets) using simple reduction of Cu(OH)(4)(2-) with hydrazine hydrate in the presence of cetyltrimethylammonium bromide (CTAB) as a surfactant. Different copper nanostructures were synthesized by varying the concentration of copper salt (CuCl2 center dot 2H(2)O), surfactant (CTAB) and reducing agent (hydrazine hydrate). The morphology of copper nanostructures is found to be dependent on the concentration of Cu(OH)(4)(2-). The synthesized copper nanostructures are stable against aggregation for at least 6 months. These copper nanostructures were also successfully transferred to organic solvents like toluene and hexane from aqueous surfactant solution using a protocol used for transferring gold nanorods. In this protocol, mercaptosuccinic acid (MSA) was successfully used to replace the existing CTAB molecules with negatively charge MSA molecules. It has been confirmed that an optimum concentration of MSA (30 mM) is very essential to promote the phase transfer from aqueous phase to toluene/hexane phase containing tetraoctylammonium bromide (TOAB). The morphology of copper nanostructures is also preserved even after phase transfer. Other simpler phase transfer techniques have also been tried but it has been observed that such methods failed to transfer these nanostructures to organic solvents.