Coating carbon nanotubes with metal oxides in a supercritical carbon dioxide–ethanol solution

Metal oxide films, including Ce2O3 and/or CeO2, Al2O3, La2O3, were deposited on the outer surfaces of carbon nanotubes (CNTs) through the decomposition of metal nitrate precursors in supercritical CO2 modified with ethanol. Transmission electron microscopy showed that CNTs could be coated with metal oxide layers that were nominally complete and uniform. The thickness of the coating could be readily tailored by tuning the ratio of the initial mass of precursors to CNTs. The as-prepared CeO2–CNT composites showed high sensitivity and selectivity to acetone on the basis of chemiluminescence detection.