RESEARCH PAPER Patterning silver nanocubes in monolayers using phase separated lipids as templates Nur Ahamad • Daniel Prezgot • Anatoli Ianoul Received: 18 October 2011 / Accepted: 4 January 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Strategies for assembling silver nanocubes (NCs) into distinct 2D patterns on Langmuir–Blodgett (LB) films are demonstrated using two different lipid mixtures as vehicles: (1) raft mixtures containing 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), sphingomyelin (SPM), and cholesterol in different mole ratios (2:2:1 and 1:1:1) and (2) 1,2-dipalmitoyl-sn- glycero-3-phosphocholine (DPPC) and 1,2-dilauroyl- sn-glycero-3-phosphocholine (DLPC) at a 1:3 mol ratio. Atomic force microscopy was employed to unveil the mechanisms of such pattern formation in the LB film. The results demonstrate that aggregation of NCs into round-like pattern is governed by preferen- tial localization of NCs within the liquid condensed (LC) domains of DOPC/SPM/Cholesterol mixture. Cholesterol was found to govern the size and shape of the rounded islands. On the other hand, incorporation of NCs within the liquid expanded (LE) phase of DPPC/DLPC mixture produced linear-branched chains, oriented normal to the Langmuir film transfer direction. The as engineered patterns of silver NCs exhibited characteristic plasmonic signatures. Our results reveal the potential in assembling plasmonic metal nanoparticles into diverse patterns on solid substrates by exploiting their preferential localization either in LC or LE phase of appropriate lipid mixture in Langmuir film. Keywords Silver nanocubes Á Patterning Á Lipid mixture Á Liquid-expanded phase Á Liquid-condensed phase Introduction Langmuir–Blodgett (LB) technique was traditionally developed for investigating physicochemical behavior of amphiphilic molecules such as lipids and fatty acids in monolayers formed at air–water interface (Zasad- zinski et al. 1994). The advantage of the LB technique is that a water supported monolayer can be transferred onto a solid support for further investigation by various surface characterization techniques (Mogilev- sky et al. 2010). Presently, the LB technique has evolved as a powerful assembly approach for bottom- up fabrication of complex hierarchical structures consisting of various macromolecules to nanoscale building blocks with desired functional properties (Yang and Kim 2002). The technique is considered as a possible alternative for conventional lithographic techniques as it provides more flexibility in pattering complex 3D surfaces. Langmuir monolayers of lipids and colloidal hydrophobic metal nanoparticles have N. Ahamad Á D. Prezgot Á A. Ianoul (&) Department of Chemistry, Carleton University, 1125 Colonel By Dr., Ottawa, ON, Canada e-mail: anatoli_ianoul@carleton.ca 123 J Nanopart Res (2012) 14:724 DOI 10.1007/s11051-012-0724-9