The evolution of well-aligned amorphous carbon nanotubes and porous ZnO/C core–shell nanorod arrays for photosensor applications

Well-aligned amorphous carbon nanotube (a-CNT) and porous ZnO/C core-shell nanorod (NR) arrays were fabricated for the first time by a proposed deposition-etching-evaporation (DEE) route. The arrays were prepared by deposition of carbon on the surface of well-aligned ZnO NR arrays by thermal decomposition of acetone followed by spontaneous etching and evaporation of core-ZnO. By utilizing the decomposition of acetone as well as distinct degrees of interaction between intermediate products and ZnO, well-aligned nonporous ZnO/C core-shell NR, porous ZnO/C core-shell NR, and a-CNT arrays were separately prepared by varying the working temperature from 400 to 700 °C. Scanning electron microscopy and high-resolution transmission electron microscopy show that the thickness of carbon shells increases from 3 to 10 nm with the increase in working temperature. Raman spectra demonstrate slight sp(2) bonds of carbon, indicating small graphite regions embedded in amorphous carbon nanoshells. The E(2) peaks of ZnO reduce with the increase in substrate temperature. Photoresponse measurements of ZnO/C NR arrays shows enhancement of both photoresponsivity and response velocity, and the interference of humidity with regard to photosensing is effectively reduced by the capping of carbon nanoshells. The work not only provides an effective route to improve the photosensing of semiconductor nanomaterials for practical applications, but also sheds light on preparing various hollow carbon and porous ZnO/C core-shell nanostructures with distinct morphologies by employing the routes presented in the paper on diverse ZnO nanostructures for optoelectrochemical applications.