Directed Assembly of Single-Walled Carbon Nanotubes via Drop-Casting onto a UV-Patterned Photosensitive Monolayer

Over the past decade, single-walled carbon nanotubes (SWCNTs) have emerged as a promising material for use in a variety of electronic applications due to their unique electrical and physical properties.¹ SWCNTs are cylindrical molecules that can be described as a rolled up graphene sheet; they can be either semiconducting or metallic depending on their diameter and helicity.¹ The versatility of SWCNTs yields an impressive range of potential applications, including sensors, transistors, flexible electronics, and photovoltaics. Semiconducting nanotubes, in particular, have attracted considerable attention because of their demonstrated performance in field-effect transistors.² However, the fabrication of such devices depends upon the ability to selectively place oriented SWCNTs. The concept of using heterogeneous surface wettability for selective deposition was explored using a multitude of systems,³ including the use of self-assembled monolayers to selectively deposit inorganics from a solution.^3a,4 The wettability of self-assembled monolayers was also utilized to selectively deposit organics, including polymers,^3b polymer microspheres,^3c and carbon nanotubes.^3d Previous work from this laboratory⁵ utilized end groups (i.e. phosphonic acid and hydroxamic acid) that selectively bind to basic oxide surfaces in order to prevent or enhance the adhesion of carbon nanotubes to certain regions of a patterned surface. In these studies, oxide surfaces were patterned lithographically to produce the regions to which the carbon nanotubes would bind. Here, we were able to bypass the need for complex lithography by utilizing a simple and scalable approach to solution-based, selective placement of SWCNTs based on photopatterning a photosensitive selfassembled monolayer.