Self-assembly of ZnO nanoparticles to electrostatic coordination sites of functionalizedcarbon nanotubes

Abstract

We report the hierarchical self-assembly of ZnO nanoparticles on single-walled carbonnanotubes (SWCNT–ZnO) and multi-walled carbon nanotubes (MWCNT–ZnO) by utilizingan electrostatic coordination approach. The affinity for Zn atoms to the oxygen of theC = O in the carboxyl groups is utilized to decorate oxidized single-walled and multi-walledcarbon nanotubes with ZnO nanoparticles. The CNT–ZnO structures are indicative of thecarboxyl group distribution along the carbon nanotubes (CNTs). By this technique we haveachieved complex design architecture such as T- and Y-junctions that would be useful fordevice applications. The ZnO conjugation is a reversible process; that is, theZnO nanoparticles can be washed off from the CNTs by dissolving in NaOH orH2SO4. The conjugation leaves the suspension with carbon nanotubes of smaller lengthscompared to the average lengths of the material that we started with. Scanning andtransmission electron microscopy along with energy dispersive spectroscopy (EDS) wereused to characterize the conjugation.