Abstract
For environmental applications, such as water and air purification utilizing photocatalysts, we synthesized patterned titanium dioxide (TiO2) thin films using polystyrene (PS) spheres. This was primarily done to enhance the surface area and photocatalytic activities. TiO2 thin films were deposited on silicon wafers attached to variously sized PS spheres via the spin coating method and were annealed at 600 °C. The processing step involved patterning and coating a TiO2 sol–gel. The photocatalytic performance was analyzed using an UV–visible spectrophotometer. Within 20 min, a high catalytic efficiency (98% removal) with a 20-time faster decomposition rate of the malachite green (MG) solution than that of the nonpatterned TiO2 was obtained from the patterned TiO2 with 400 nm sized PS due to the large surface area. In addition, the phenol in the water removed as much as 50% within 2 h with the same photocatalyst, which was expected to be one of the strong candidates to be applied to the next generation of photocatalysts for water purification.
Highlights
The degradation of toxic materials from the biosphere is a multibillion dollar industry [1]
The phenol in the water removed as much as 50% within 2 h with the same photocatalyst, which was expected to be one of the strong candidates to be applied to the generation of photocatalysts for water purification
TiO2 is an example of a solid state semiconductor, characterized by two “bands”of closely spaced electronic energy levels known as the valence and conduction bands, which are respectively analogous to the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO)
Summary
The degradation of toxic materials from the biosphere is a multibillion dollar industry [1]. The most common methods rely on the use of high temperatures to accomplish the degradation, but such processes are expensive and must be carefully controlled, and the removal of effluent gases is challenging [2,3,4,5]. In 1972, Fujishima and Honda demonstrated the potential of titanium dioxide (TiO2 ) semiconductor materials to split water into hydrogen and oxygen in a photoelectrochemical cell [10]. TiO2 is an example of a solid state semiconductor, characterized by two “bands”of closely spaced electronic energy levels known as the valence and conduction bands, which are respectively analogous to the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). When electrons are promoted from the valence band to the conduction band, they become delocalized, and the substrate can conduct electricity (Scheme 1)
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