| Abstract
| - Gold (Au) nanowires (NW) have been synthesized by using mixtures of l-α-dipalmitoylphosphatidylcholine(DPPC) and various conventional surfactants (CS) of different polarities. The capping ability of the surfactantmixture has been quantitatively evaluated by using UV−vis, TEM, XPS, FTIR, and XRD studies. The synthesishas been carried out by using a total [DPPC+CS] in the range of 0.125 to 0.5 mM. The results clearlydemonstrate a surfactant selective synthesis that significantly depends on the polarity of the CS head group.An anionic surfactant like sodium dodecylsulfate (SDS) along with DPPC leads to a network of NW formationwith ≈50 nm thickness at different total surfactant concentrations while cationic surfactant, cetyltrimethylammonium bromide (CTAB), predominantly controls the spherical Au nanoparticle (NP) formation at highconcentration. At low [DPPC+CTAB], the NW is achieved by end-to-end fusion of spindle shaped Au NPwith an aspect ratio of ≈2.15. The chemical composition of the adsorbed capping surfactant on the Au surfaceand the alignment of the molecules were confirmed from XPS and FTIR studies. XPS results indicate that asmall amount of DPPC+SDS caps the Au NW in comparison to that of DPPC+CTAB. FTIR results furthersupport this and indicate even a smaller amount of DPPC is adsorbed in comparison to that of SDS, whichis attributed to a stable micellar phase formation in the case of the DPPC+SDS mixture in comparison toDPPC+CTAB. This leaves a small amount of surfactant for capping action in the former case and causesanisotropic growth of Au NP to NW formation. Interestingly, no Au NW formation is observed if no DPPCis used. All pure CS lead to the formation of spherical Au NP of different dimensions. This fact suggests thatone can control the morphology of Au NP by using DPPC along with different CS and thus one can designbiofriendly nanomaterials for bioengineering applications.
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