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Titanium oxide nanotube is a promising material for versatile applications. However, its structure and formation mechanism were quite confusedly reported. Therefore, it is essential to fully understand its structure, formation mechanism and stability. In this study, the structure, formation and stability of titanium oxide nanotube were studied in detail. New experimental findings on the morphology of titanium oxide nanotubes were reported, demonstrating close-opened nanotubes, cone-shaped nanotubes, twin and ternary nanotubes etc. A structural model of the titanium oxide nanotubes is proposed on the basis of cylinders of smoothly curved sheets of TiO₆ octahedra, among which H⁺ and H₃O⁺ are intercalated. The formation mechanism of titanium oxide nanotubes was deduced and discussed on the basis of their structural characteristics and chemical bonding behaviors of constituent atoms. The stability of the nanotubes was also studied under different conditions.

Single crystalline lithium nickel manganese oxide (LiNi_0.5Mn_1.5O₄) nanotubes have been prepared by a facile self-templating method from β-MnO₂ nanotubes. The wall thickness and hollow part of the nanotubes are around 250 nm and 200 nm, respectively. The tubular LiNi_0.5Mn_1.5O₄ exhibits good rate capability and high-rate cycling stability. At 10 C, it can yield a high discharge capacity of 99 mAh g^-1. After 550 cycles at 5 C, a discharge capacity of 85 mAh g^-1 can be kept, indicating a promising application in high-power Li-ion batteries.

NiO/Pt nanotubes were obtained by firstly preparing the NiO nanotube with self-sacrificial templating methods and subsequently loading Pt nanoparticles with microwave assistant procedures. The as-prepared NiO/Pt nanotubes sensors displayed better electrocatalytic activities for glucose oxidation. The detection limit and sensitivity for glucose detection are 0.3 $\mu$M and 418.28 $\mu$A⋅ mM${}^{-1}$⋅cm${}^{-2}$ in the range of 1 $\mu$M-4000 $\mu$M. In addition, the practicality of NiO/Pt nanotubes was also confirmed by determining the glucose in serum specimen.

Nanostructured thin-film electrode materials are proposed for supercapacitors due to their outstanding performance over bulk materials. In this work, we fabricated a TiO₂ nanotube film over a titanium foil using a top-down approach for supercapacitor electrodes. We noticed that the fabricated nanotubes are uniform and well aligned, confirmed by FESEM; the TiO₂ nanotube parameters were further simulated using COMSOL Multiphysics. Simulations show an areal capacitance of 1.19393 pF/cm² with oxidation and reduction peak currents of 6.18921×10${}^{-15}$ A and −6.0320×10${}^{-15}$ A, respectively, at 10 mV/s scan rate. The as-prepared nanotubes show a poor areal capacitance of 1.0193 F/cm², which is improved to 12.8764 F/cm² at a scan rate of 10 mV/s, that is approximately 12.63 times with oxidation and reduction peak currents of 0.129 mA/cm² and −0.105 mA/cm², respectively, by performing an electrochemical etching. Further, the surface roughness of both as-prepared and etched samples is studied to comment on their surface area changes. The effect of the etched sample is studied, compared and validated with simulation, which reveals that the etched TiO₂ nanotubes thin-film sample shows considerable similarity with the simulation results.

Here, we report investigations on the relative humidity (RH) sensing property of ZnO nanotubes synthesized via hydrothermal method. Grown nanotubes are formed with a hexagonal shape and possess a wurtzite crystal structure in conjunction with higher oxygen vacancies. ZnO nanotube-based RH sensor shows a small current increase in lower RH (<75% RH) region, due to the frozen motion of H${}^{+}$ ions, where electronic conduction dominates. The sensor conduction increases from 13 to 960 fold upon exposer of 65%–90% RH, respectively. The free motion of H${}^{+}$ ions steers the conduction mechanism to be protonic in higher level physisorbed water layer and is responsible for the observed sharp increase in response. The competitive adsorption and desorption of oxygen species and water molecules play a vital role in defining the conduction to be electronic or protonic during the experiment.

Nanostructured thin-film electrode materials are proposed for supercapacitors due to their outstanding performance over bulk materials. In this work, we fabricated a TiO₂ nanotube film over a titanium foil using a top-down approach for supercapacitor electrodes. We noticed that the fabricated nanotubes are uniform and well aligned, confirmed by FESEM; the TiO₂ nanotube parameters were further simulated using COMSOL Multiphysics. Simulations show an areal capacitance of 1.19393 pF/cm² with oxidation and reduction peak currents of 6.18921 × 10⁻¹⁵ A and −6.0320 × 10⁻¹⁵ A, respectively, at 10 mV/s scan rate. The as-prepared nanotubes show a poor areal capacitance of 1.0193 F/cm², which is improved to 12.8764 F/cm² at a scan rate of 10 mV/s, that is approximately 12.63 times with oxidation and reduction peak currents of 0.129 mA/cm² and −0.105 mA/cm², respectively, by performing an electrochemical etching. Further, the surface roughness of both as-prepared and etched samples is studied to comment on their surface area changes. The effect of the etched sample is studied, compared and validated with simulation, which reveals that the etched TiO₂ nanotubes thin-film sample shows considerable similarity with the simulation results.