3D Hydrogen Titanate Nanotubes on Ti Foil: A Carrier for Enzymatic Glucose Biosensor.

Glucose oxidase (GOx) based biosensors are commercialized and marketed for the high selectivity of GOx. Incorporation nanomaterials with GOx can increase the sensitivity performance. In this work, an enzyme glucose biosensor based on nanotubes was fabricated. By using Ti foil as a carrier, hydrogen titanate nanotubes (HTNTs), which present fine 3D structure with vast pores, were fabricated in-situ by the hydrothermal treatment. The multilayer nanotubes are open-ended with a diameter of 10 nm. Then glucose oxidase (GOx) was loaded on the nanotubes by cross-linking to form an electrode of the amperometric glucose biosensor (GOx/HTNTs/Ti electrode). The fabricated GOx/HTNTs/Ti electrode had a linear response to 1-10 mM glucose, and the response time was 1.5 s. The sensitivity of the biosensor was 1.541 µA·mM-1·cm-2, and the detection limit (S/N = 3) was 59 µM. Obtained results indicate that the in-situ fabrication and unique 3D structure of GOx/HTNTs/Ti electrode are beneficial for its sensitivity.

CdS-Modified TiO2 Nanotubes with Heterojunction Structure: A Photoelectrochemical Sensor for Glutathione.

The formation of heterojunction structures can effectively prevent the recombination of photogenerated electron-hole pairs in semiconductors and result in the enhancement of photoelectric properties. Using TiO2 nanotubes (prepared using the hydrothermal-impregnation method) as carriers, CdS-TiO2NTs were fabricated as a photoelectrochemical (PEC) sensor, which can be used under visible light and can exhibit good PEC performance due to the existence of the heterojunction structure. The experimental results show that the prepared CdS-TiO2NTs electrode had a linear response to 2-16 mM glutathione (GSH). The sensor's sensitivity and detection limit (LOD) were 102.9 µA·mM-1 cm-2 and 27.7 µM, respectively. Moreover, the biosensor had good stability, indicating the potential application of this kind of heterojunction PEC biosensor.

Platinum and Iridium Oxide Co-modified TiO2 Nanotubes Array Based Photoelectrochemical Sensors for Glutathione.

Oriented TiO2 nanotubes, which are fabricated by anodic oxidation method, are prospective in photoelectrochemical analysis and sensors. In this work, Pt and IrO2 co-modified TiO2 nanotubes array was prepared via a two-step deposition process involving the photoreductive deposition of Pt and chemical deposition of IrO2 on the oriented TiO2 nanotubes. Due to the improved separation of photo-generated electrons and holes, Pt-IrO2 co-modified TiO2 nanotubes presented significantly higher PEC activity than pure TiO2 nanotubes or mono-modified TiO2 nanotubes. The PEC sensitivity of Pt-IrO2 co-modified TiO2 nanotubes for glutathione was also monitored and good sensitivity was observed.