Fabrication of irregular-layer-free and diameter-tunable Ni–Ti–O nanopores by anodization of NiTi alloy

Ni–Ti–O nanopores (NPs) free of irregular surface layers and with tunable diameters are prepared by anodizing NiTi alloy in glycerol containing H₂O and NaCl. In an electrolyte composed of glycerol, 10 vol% H₂O and 0.6 M NaCl, NPs with diameters between 23 and 39 nm can be produced at anodization voltages between 20 and 80 V. In this electrolyte system, the irregular oxide layer on the surface can be completely removed chemically and/or mechanically during anodization. The resulting Ni–Ti–O NPs with tunable diameters should prove useful, for example, in energy, environmental and biomedical applications.