Directed Linking of Carbon Nanotubes with Single CdSe Quantum Dots

Metallic single-walled carbon nanotubes (SWNTs or NTs) are the ideal nanometer-scale wire, as they can withstand current densities up to 2 to 3 orders of magnitude higher than copper currently used in electronic chips [1]. These conductive NTs can be utilized as nano-electrodes to electrically contact another nanoscale object, such as a single semiconductor quantum dot (QD) or metallic nanoparticle (NP). We have designed a strategy for directed assembly of fabricated QD–SWNT devices. NTs were grown across patterned catalyst islands on a silicon wafer followed by electrode placement. After cutting the NTs, the resulting carboxyl group moieties found at the cut NT edges were used to covalently attach amine-functionalized cadmium selenium (CdSe) QDs or gold (Au) NPs. Electrostatic force microscopy (EFM) was used to monitor NT conductivity before and after cutting, as well as after NP attachment.