Simultaneous Synthesis of Au and Cu Nanoparticles in Pseudo-Core-Shell Type Arrangement Facilitated by DMPG and 12-6-12 Capping Agents Mandeep Singh Bakshi,* ,²,‡,§,# Fred Possmayer, ²,‡ and Nils O. Petersen ‡,§,| Department of Obstetrics and Gynaecology, Department of Biochemistry, and Department of Chemistry, UniVersity of Western Ontario, 339 Windermere Rd, London, ON, Canada N6A 5A5, National Institute for Nanotechnology, Edmonton, Alberta, Canada, and Department of Chemistry, Guru Nanak DeV UniVersity, Amritsar 143005, Punjab, India ReceiVed NoVember 20, 2006. ReVised Manuscript ReceiVed January 8, 2007 A seed-growth method has been applied to synthesize the gold (Au) nanoparticles (NP) in the presence of 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt) (DMPG) and hexamethylene- 1,6-bis(dodecyldimethylammonium bromide)(12-6-12) as capping agents at ambient conditions. The systematic addition of CuSO 4 leads to anisotropic growth of Au NP at low CuSO 4 concentration in the presence of DMPG while this was not observed in the case of 12-6-12 where mostly spherical Au NP were obtained. At high CuSO 4 concentration, small Cu NP appeared which arranged themselves around large Au NP in a typical pseudo-core-shell type arrangement. This was achieved by the fusion of lipid bilayers of lipid-capped Au and Cu NP. The cause of anisotropic growth of Au NP in the presence of DMPG has been discussed on the basis of its poor capping ability in comparison to 12-6-12. Introduction Recent advances in the synthesis of nanosized metallic morphologies have provided a variety of strategies to explore their vast applications in nanotechnology. 1 The shape and size-controlled synthesis of single-component nanoparticles (NP) such as Au, Ag, Ir, Pd, and Pt has generated immense interest in the field of nanoscience. 2 The synthesis of bimetallic NP is another very important branch of nano- science where different metallic substances can be put together to produce integrated morphologies in a controlled fashion. The overall shape and structure of a bimetallic NP can then be manipulated by adjusting the material parameters of individual components. As physical properties significantly depend on the size of NP at nanoscale, any change in the size upon mixing two components leads to a drastic change in the physical properties. It provides numerous possibilities for achieving new combinations. 3 The seed-mediated approach in producing shape-controlled Au NP in aqueous surfactant solutions has become increas- ingly popular recently. 4 Unlike the use of strong reducing agents, a controlled growth requires weak reducing condi- tions. Some studies have successfully lead to a controlled size distribution (typically 10-15%) in the range of 5-40 nm, and the size can be manipulated by varying the ratio of seed to metal salt. 5 Step-by-step size control is more effective than a single-step seeding method to avoid secondary nucleation. In seed-growth methods, small metal particles * To whom correspondence should be addressed. E-mail: ms_bakshi@yahoo.com. ² Department of Obstetrics and Gynaecology, University of Western Ontario. ‡ Department of Biochemistry, University of Western Ontario. § Department of Chemistry, University of Western Ontario. | National Institute for Nanotechnology. # Guru Nanak Dev University. 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Mater. 2007, 19, 1257-1266 10.1021/cm062771t CCC: $37.00 © 2007 American Chemical Society Published on Web 02/17/2007 Downloaded by CHANG GUNG UNIV on September 15, 2015 | http://pubs.acs.org Publication Date (Web): February 17, 2007 | doi: 10.1021/cm062771t