Electrochemical route to the preparation of highly dispersed composites of ZnO/carbon nanotubes with significantly enhanced electrochemiluminescence from ZnO

ZnO nanostructures were electrochemically deposited on the surfaces of carbon nanotubes (CNTs) supported on a Zn foil cathode, leading to the facile formation of ZnO/CNT composites with uniform mixing, high dispersion and high-quality interfaces. The electrochemical deposition method circumvents the need for bridging molecules to bring together the two phases and has the key advantage of controllability. By increasing the deposition time, the individual CNTs were first fully covered with ZnO and then the morphology of the deposited ZnO nanostructures was gradually changed from spherical nanoparticles to lily-like nanoflowers. The lily-like structures of ZnO/CNT nanocomposites showed enhanced electrochemiluminescence (ECL). Significantly, the ECL intensity of the lily-like structure of ZnO/CNT nanocomposites was almost an order of magnitude larger than that of pure ZnO nanoflowers, and the ECL starting voltage shifts positively from -1.06 to -0.41 V. These have been attributed to the presence of CNTs which decrease the barriers of ZnO reduction during the ECL process and the special structure of ZnO on the surface of CNTs as well. This work has demonstrated a new strategy to directly coat CNTs with oxides, probably many other inorganic materials, with tunable coverage and nanostructure. Furthermore, the significantly enhanced ECL of ZnO by interfacing with the CNTs highlights the importance and potential utility of such nanostructuring in the development of optoelectronic and biomedical devices.