A material capable of rapid, reversible molecular oxygen uptake at room temperature is desirable for gas separation and sensing, for technologies that require oxygen storage and oxygen splitting such as fuel cells (solid-oxide fuel cells in particular) and for catalytic applications that require reduced oxygen species (such as removal of organic pollutants in water and oil-spill remediation). To date, however, the lowest reported temperature for a reversible oxygen uptake material is in the range of 200-300 °C, achieved in the transition metal oxides SrCoOx (ref. 1) and LuFe₂O(4+x) (ref. 2) via thermal cycling. Here, we report rapid and reversible oxygen scavenging by Ti(2-x) nanotubes at room temperature. The uptake and release of oxygen is accomplished by an electrochemical rather than a standard thermal approach. We measure an oxygen uptake rate as high as 14 mmol O₂ g(-1) min(-1), ∼2,400 times greater than commercial, irreversible oxygen scavengers. Such a fast oxygen uptake at a remarkably low temperature suggests a non-typical mechanistic pathway for the re-oxidation of Ti(2-x). Modelling the diffusion of oxygen, we show that a likely pathway involves 'exceptionally mobile' interstitial oxygen produced by the oxygen adsorption and decomposition dynamics, recently observed on the surface of anatase.

Oxygen scavengers are commonly used in packaged foods and other oxygen sensitive goods because of the advantages they offer in maintaining quality and extending shelf life. The performance of oxygen scavengers can be influenced by several conditions, such as ambient temperature and relative humidity. We recently studied oxygen scavenging at room temperature using titanium oxide nanotubes (TONT). Prior work showed that TONTs can have oxygen uptake rates of up to three orders of magnitude higher compared with commercially available iron-based scavengers at room temperature. However, the effect of humidity was not established. This research investigates the potential of TONTs as oxygen scavengers in packaging applications such as modified atmosphere packaging as well as a colour indicator. As opposed to commercial scavengers that need water to be active, TONT performs at their best in dry conditions, making them a strong potential candidate for pharmaceutical and medical devices industries.

In the previous work we presented results demonstrating the ability of transmission mode terahertz time domain spectroscopy (THz-TDS) to detect doping profile differences and deviations in silicon. Here we report follow up work demonstrating doping profile measurement by first precisely removing a thin layer (currently ~ 20 nm) from the junction by anodization followed by selective oxide etching. The anodization-etching step is followed by measuring the terahertz transmission using THz-TDS. The anodization and terahertz measurement steps are then alternated. The doping profile can then be reconstructed using the resultant dataset. In this work we share results obtained on phosphorus doped silicon wafers. We find good agreement between the measured transmitted terahertz spectra and the simulated terahertz spectra for all etching cycles when the doping profile used in the simulations agrees with SIMS analysis. We conclude that anodization combined with THz-TDS can potentially be a high resolution destructive doping profile mapping method.