Interfacial Systems Chemistry: Out of the Vacuum—Through the Liquid—Into the Cell

Abstract

Received 6th January 2010, Accepted 2nd February 2010First published as an Advance Article on the web 24th February 2010DOI: 10.1039/c000304mWe report a two-step chemical vapor deposition (CVD) method for fabrication of hierarchicalpolymer-coated carbon nanotube (CNT) microstructures having tunable mechanical properties andaccessible chemical functionality. Diverse geometries of vertically aligned CNTs were grown fromlithographically patterned catalyst films, and the C NT microstructures were chemically functionalizedvia poly[4-trifluoroacetyl-p-xylylene-co-p-xylylene] made by chemical vapor deposition polymerization.The polymer coating conformally coated the individual CNTs and CNT bundles within the CNT‘‘forest’’. The chemical structure of the polymer films was verified by X-ray photoelectronspectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Simple control of themechanical properties of the nanocomposite structures can be achieved by adjusting the depositiontimes during CVD polymerization. Increasing the polymer film thickness from 10 nm to 27 nmresulted in a change of the Young’s modulus from 65 to 80 MPa. These values are substantiallyhigher than the 36 MPa measured for the as-grown CNTs without polymer coating. The effect of thepolymer coating in reinforcing the connectivity among CNTs within the structures has beenunderstood using an analytical model. Finally, chemical functionality of the CNT compositestructures after CVD polymerization was verified by a 4-fold fluorescence enhancement after bindingof a dye to the coated CNT microstructures. This technique can be adapted to a wide variety ofreactive coatings and facilitates attachment of chemical groups and functional nanostructures on thesurfaces of the CNTs; therefore, this material could serve as a tunable platform for couplingmechanical and chemical responses in materials for environmental and biological sensing.