Applied Surface Science 258 (2011) 1519–1524 Contents lists available at SciVerse ScienceDirect Applied Surface Science j our nal ho me p age: www.elsevier.com/loc ate/apsusc Assembly of single-walled carbon nanotubes on patterns of Au nanoparticles Saleem G. Rao a,b,∗ , Ling Huang a,1 , Jennifer Murray a a Department of Physics and Center for Material Research and Technology, Florida State University, Tallahassee, FL 32306, USA b Laser Research Group, Department of Physics, King Fahd University of Petroleum and Minerals, Dhahran 31262, Saudi Arabia a r t i c l e i n f o Article history: Received 8 June 2011 Received in revised form 18 August 2011 Accepted 26 September 2011 Available online 2 October 2011 Keywords: Carbon nanotube Gold nanoparticles Patterned hybrid thin films Metal deposition on SAMs a b s t r a c t We report on the assembly of single-walled carbon nanotubes (SWNTs) and gold nanoparticles (NPs) hybrid structure without any surface modification of SWNTs on patterns of Au nanoparticles (NPs). Microscale Au NP patterns were created on composite self-assembled monolayer (SAM) templates of octadecanethiol (ODT) and octanedithiol (OD) through self-assembly of Au NPs via the thiol-Au chemi- cal bond onto the OD region. On such templates, we observed extensive adhesion and strong affinity of SWNTs on the Au NPs and no SWNT on ODT. We also examined systematically the adhesion of SWNTs on ODT with varying coverage of vapour-deposited Au. We observed little SWNT attachment even when there are high-density of Au clusters on the ODT SAM. Extensive adhesion of SWNTs is observed only when the coverage of ODT by Au is almost complete. Dynamic contact angle measurements of dichlorobenzene on the ODT/Au substrates revealed a direct correlation between the surface wettability and the SWNT assembly on a molecular template. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The outstanding electrical properties of single-walled carbon nanotubes (SWNTs) allow us to envision a new class of nanoscale high-performance electronic devices [1–7]. Devices based on individual SWNTs have demonstrated superior electronic char- acteristics compared to those of conventional semiconductors [8,9], which promises wide-ranging applications in micro/nano- electronics and as ultra-sensitive chemical and biological sensors. However, significant obstacles remain in the realization of these application potentials. The extreme inert nature of the surface has largely prevented effective non-invasive biofunctionalization of carbon nanotubes (CNTs) and consequently their use in biomolec- ular sensing. On the other hand, a major bottleneck for large-scale electronics applications of the SWNTs is the lack of an effective method to integrate such individual devices into high-density func- tioning circuits. High quality SWNTs are usually synthesized in powder form and individual SWNTs are dispersed randomly onto a substrate to build functional devices: typically an individual SWNT is located via atomic force microscopy (AFM) and electrical contacts are made using electron beam lithography [10,11]. Such methods, ∗ Corresponding author at: Department of Physics, Laser Research Group, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia. Tel.: +966 3 860 1675; fax: +966 3 860 2293. E-mail address: saleemg@kfupm.edu.sa (S.G. Rao). 1 Current address: Division of Bioengineering, School of Chemical and Biomedical Engineering, Nanyang Technical University, Singapore. derived from traditional microelectronics fabrication technology, are obviously not amenable to the production of large-scale SWNT- based circuits. An alternative strategy is to grow SWNTs from prepatterned catalyst particles or electrodes via chemical vapor deposition (CVD) [12–15]. However, CVD tends to produce large- diameter, small bandgap nanotubes, and the high-temperatures involved in the growth process are detrimental to integration with pre-existing circuit structures. Moreover, it is difficult to control the growth direction and number of individual SWNTs bridging the electrodes in this scheme. Molecular recognition is a promising route for large-scale bottom-up assembly of a variety of metallic and semiconduc- tor nanocomponents [16–18]. Although SWNTs are highly inert chemically, precise large-scale directed assembly of SWNTs using molecular functionalization and/or molecular templates has been demonstrated [19–24]. Two different approaches have been taken. The first scheme involves biological [19,20] or chemical [21] functionalization of CNTs and subsequent assembly of the func- tionalized CNTs through molecular recognition. This method was utilized to fabricate SWNT-based field-effect transistors (FETs). In this scheme, the nanotube functionalization often produces defects on the CNTs. Moreover, in the assembled devices either the elec- tron transport must go through the template molecules, or the molecules have to be removed using high temperature anneal- ing. An alternative method involves large-scale parallel assembly of SWNTs onto a molecular template without any nanotube func- tionalization. It was demonstrated [23] that successful alignment and assembly of millions of individual SWNTs and SWNT-based integrated circuit junctions can be achieved on suitable substrate 0169-4332/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.09.122