Hexagonal nanotubes of ZnS by chemical conversion of monocrystalline ZnO columns

Monocrystalline ZnO columns grown in electrodeposition were converted to ZnS using ion exchange reactions in ${\mathrm{H}}_2\mathrm{S}$ or S vapor. At ∼400 °C the reaction with ${\mathrm{H}}_2\mathrm{S}$ only affects a thin layer of 10–30 nm thickness at the surface of the ZnO crystallites, and ZnS-coated ZnO columns are produced. Exploiting the large difference in etch resistance between ZnS and ZnO, the ZnO core of the columns can be removed, and a tubular structure of ZnS can be prepared. Typical dimensions of the ZnS tubes are a length of 1–3 μm, a diameter of 100–300 nm, and a wall thickness of 10–30 nm. The ZnS tubes have the same distribution, alignment, and surface morphology as the original ZnO columns. The reaction in S vapor is suitable to produce solid ZnS columns.