No abstract

Titanium dioxide (TiO2) is an abundant metal oxide, widely used in food industry, cosmetics, medicine, water treatment and electronic devices. TiO2 is of interest for next-generation indium-free thin-film transistors and ion-gated transistors due to its tunable optoelectronic properties, ambient stability, and solution processability. In this work, we fabricated TiO2 films using a wet chemical approach and demonstrated their transistor behavior with room temperature ionic liquids and aqueous electrolytes. In addition, we demonstrated the pH sensing behavior of the TiO2 IGTs with a sensitivity of ∼48 mV/pH. Furthermore, we demonstrated a low temperature (120°C), solution processed TiO2-based IGTs on flexible polyethylene terephthalate (PET) substrates, which were stable under moderate tensile bending.

Titanium dioxide (TiO2) nanotube photocatalyst is highly desired for the photodegradation of dye in wastewater treatment. A series of titanium dioxide nanotube photocatalysts were successfully synthesized using methylamine as N-ligand via hydrothermal treatment at different hydrothermal temperatures and durations. The effect of these two parameters on the photocatalytic activity of synthesized materials were investigated. TEM micrographs and XRD analysis depicted methylamine assisted the transformation of anatase TiO2 nanoparticles to nanotube via the exfoliation of TiO2 crystallite into layered sheet and promoted the curling of layered sheet. Hydrothermal temperature up to 180°C was able to fully transform the morphology of anatase TiO2 nanoparticles into nanotube. The reaction duration was further modified. Fluorescence analysis showed that 24 h hydrothermal duration gave the slowest electron-hole recombination rate. DR-UV-Vis analysis indicated that the synthesized samples were active under UV region. The photocatalytic performance of the synthesized materials was tested in the photodegradation of Congo red under UV irradiation. The results suggested that among the materials synthesized, TiO2 nanotube synthesized at 180°C, under 24 h hydrothermal duration appeared to be the most superior photocatalyst which gave the highest photocatalytic activity of 77%. Possible mechanism of the TiO2 nanotube formation with methylamine as N-ligand is presented.

Titanium dioxide (TiO2) nanotubes (TNT) were successfully synthesized using different N-containing ligands via hydrothermal method. Methylamine, ethylenediamine and diethylenetriamine with different Ti/ligand molar ratios (1:1, 1:3, 1:5 and 1:8) were prepared. As-synthesized TiO2 without N-containing ligands were also prepared for comparison purpose. The X-Ray Diffraction patterns confirmed the presence of anatase phase of TiO2 in all the synthesized samples whereas the presence of sodium titanate was only detected in the samples containing N-containing ligands. The Transmission Electron Microscopy images also showed that the N-containing ligands promoted the formation of nanotubes in the anatase TiO2. Based on the Tauc Plot, the band gap energy of anatase TiO2 was shifted with the addition of methylamine, ethylenediamine and diethylenetriamine. The photoluminescence spectra also showed that with the addition of sufficient amount of N-containing ligands, the intensity of photoluminescence spectrum decreased, suggesting formation of more nanotube and reduction of electron hole recombination rate. The photocatalytic performance of all synthesized samples was determined through photodegradation of Congo red under UV light for 6 hours. The results suggested that among the synthesized materials, the sample which contained diethylenetriamine with molar ratio of 5 gave the highest photocatalytic activity of 76.71% which could be attributed to successful formation of nanotube, its higher surface rate reaction and low electron hole recombination. Diethylenetriamine showed higher efficiency in assisting the formation of TiO2 nanotubes compared to methylamine and ethylenediamine.

Copper modified titanium dioxide photocatalysts have been widely reported for their excellent performance in the wastewater treatment. However, there is lack of information on the effect of different synthesis methods towards the properties and catalytic activity of the photocatalyst. In this research, a series of copper-doped titanium dioxide (Cu-TiO2) photocatalysts were synthesized via three different methods of sonochemical, impregnation and physical mixing. Cu-TiO2 with varied molar ratios of Cu dopant to TiO2 TR595 (100:0, 99:1, 98:2, 97:3 and 96:4) were prepared. Comparison of physical-chemical properties and photocatalytic activity among the synthesized samples were made. X-ray diffraction analysis depicted the formation of TiO2 rutile phase in all samples. Besides, diffuse reflectance UV-visible analysis proved that the synthesized samples were active under visible light region. According to the Tauc plot and photoluminescence spectra, the band gap energies and recombination rate of electron-hole pairs of Cu-TiO2 samples decreased upon loading of Cu. Moreover, EDX analysis confirmed the existence of Ti and Cu in all the samples. The photocatalytic efficiencies of the synthesized samples were discovered through photodegradation of Rhodamine B organic dye under 6 hours of visible light irradiation. Amongst, Cu-TiO2 photocatalysts synthesized via sonochemical method with molar ratio of 98:2 produced the highest photocatalytic activity of 64.8% which attributed to the lowest recombination rate of photogenerated charge carriers and availability of large number of reactive oxidative species.