Formation and evolution of anodic TiO2 nanotube embryos

Abstract

Anodic TiO2 nanotubes (ATNTs) have been widely investigated for decades due to their interesting nanostructures and various applications. However, the formation mechanism of ATNTs still remains unclear. To date, most of researches focus on the tubular structure but neglect the formation process of initial nanotube embryos. Herein, polyethylene glycol (PEG) is added into the traditional electrolyte to moderate the transformation process from compact layer to porous layer. Based on ‘oxygen bubble mould’ and ‘plastic flow model’ theory, the formation and evolution process of nanotube embryo is clarified firstly. Results validate the effect of ‘oxygen bubble mould’ on the formation of nanotube embryo, which has a great effect on regulating the morphology of ATNT arrays. Besides, nanotubes prepared in electrolytes with PEG show shorter tube length with larger diameter than that prepared in traditional electrolytes. The addition of PEG can also effectively avoid the breakdown phenomenon.HighlightsTransformation from compact layer into porous layer is observed in PEG electrolyte.The effect of oxygen bubble mould is first demonstrated and observed.The formation process of TiO2 nanotube embryo is described systematically.TiO2 nanotubes prepared in PEG electrolyte show short length and large diameter.