A Review on the Electrochemically Self-organized Titania Nanotube Arrays: Synthesis, Modifications, and Biomedical Applications

Table 1 TiO₂ nanotubes arrays fabricated through anodic oxidation in the three generations: electrolyte compositions, anodization conditions, and size of the resulting nanotubes

Generation	Electrolyte	Condition	Diameter	Thickness of layers	Ref
First generation	0.5 wt% HF in aqueous solution	20 V 20 min	60 nm	250 nm	[54]
second generation	0.1MKF+1MH₂SO₄+0.2Mcitric acid	25 V 20 h	115 nm (inner)	4.4 μm	[57]
second generation	1MNa₂SO₄+0.5wt%NaF	20 V 6 h	100 nm	2.4 μm	[58]
Third generation	0.5 wt% NH₄F	20 V	40 nm	7 μm	[59]
	In glycerol	13 h	40 nm	7 μm	[59]
	0.3 wt% NH₄F	60 V	100 nm	45 μm	[63]
	In ethylene glycol	18 h	100 nm	45 μm	[63]
	0.25 wt% NH₄F	60 V	160 nm	134 μm	[60]
	In ethylene glycol	17 h	160 nm	134 μm	[60]