TiO2 nanotube sensor for online chemical oxygen demand determination in conjunction with flow injection technique

1D Titanium Dioxide: Achievements in Chemical Sensing

For the last two decades, titanium dioxide (TiO₂) has received wide attention in several areas such as in medicine, sensor technology and solar cell industries. TiO₂-based gas sensors have attracted significant attention in past decades due to their excellent physical/chemical properties, low cost and high abundance on Earth. In recent years, more and more efforts have been invested for the further improvement in sensing properties of TiO₂ by implementing new strategies such as growth of TiO₂ in different morphologies. Indeed, in the last five to seven years, 1D nanostructures and heterostructures of TiO₂ have been synthesized using different growth techniques and integrated in chemical/gas sensing. Thus, in this review article, we briefly summarize the most important contributions by different researchers within the last five to seven years in fabrication of 1D nanostructures of TiO₂-based chemical/gas sensors and the different strategies applied for the improvements of their performances. Moreover, the crystal structure of TiO₂, different fabrication techniques used for the growth of TiO₂-based 1D nanostructures, their chemical sensing mechanism and sensing performances towards reducing and oxidizing gases have been discussed in detail.

The Inhibition Effect of Tert-Butyl Alcohol on the TiO2 Nano Assays Photoelectrocatalytic Degradation of Different Organics and Its Mechanism

The inhibition effect of tert-butyl alcohol (TBA), identified as the •OH radical inhibitor, on the TiO2 nano assays (TNA) photoelectrocatalytic oxidation of different organics such as glucose and phthalate was reported. The adsorption performance of these organics on the TNA photoelectrode was investigated by using the instantaneous photocurrent value, and the degradation property was examined by using the exhausted reaction. The results showed that glucose exhibited the poor adsorption and easy degradation performance, phthalate showed the strong adsorption and hard-degradation, but TBA showed the weak adsorption and was the most difficult to be degraded. The degradation of both glucose and phthalate could be inhibited evidently by TBA. But the effect on glucose was more obvious. The different inhibition effects of TBA on different organics could be attributed to the differences in the adsorption and the degradation property. For instance, phthalate of the strong adsorption property could avoid from the capture of •OH radicals by TBA in TNA photoelectrocatalytic process.

The Promotion Effect and Mechanism of Methanoic Acid on the Photoelectrocatalytic Degradation of Fulvic Acid

A significant promotion effect of methanoic acid (MA) was proposed in the photoelectrocatalytic (PEC) degradation of fulvic acid (FA) and the degradation mechanism was also discussed. The PEC degradation property of FA and MA was investigated by an assembled thin-layer PEC reactor in which photoanode is TiO2nanotube arrays (TNAs) material. The result shows that only about 40% of FA was degraded, while MA could be completely degraded at the same condition. When mixing MA with FA, it shows a significant improvement in the degradation of FA. For instance, 50 mg/L FA mixed with 45 mg/L MA could achieve exhausted degradation. The results could be attributed to the promotion effect of MA that enhanced the generation of hydroxyl radicals, which maintain the continuous degradation of both FA and the intermediate products during the PEC process. This study proposed a new way of promoting the PEC degradation of FA as well as removing humus from the polluted water.

Visible light photoelectrochemical properties of a hydrogenated TiO2 nanorod film and its application in the detection of chemical oxygen demand

Hydrogenated TiO₂ nanorod arrays as a photoelectrochemical sensor exhibit good stability and reproducibility for online COD monitoring using visible light.