No abstract

Plasmonic Au nanoparticles-decorated TiO2 hollow fibers with enhanced visible-light photocatalytic activity have been successfully prepared by a two-step process: (i) template method using kapok and (ii) solution plasma process.

Vast quantities of marigold flowers are often discarded as waste at sacred places and temples after religious ceremonies in Thailand. This has motivated us to examine the utilization of waste marigold flowers as a precursor for the synthesis of porous carbons by hydrothermal carbonization (HTC) and pyrolysis. Waste marigold flowers were hydrothermally treated at 180 °C for 2, 12, and 24 h. The resultant hydrochars were subsequently pyrolyzed at 800 °C under argon (Ar) atmosphere. Based on X-ray diffraction and Raman spectroscopy analyses, the samples exhibited an amorphous phase regardless of HTC time. With increasing HTC time, the marigold surface became rougher and more ruptured. This resulted in the development of a porous structure, thereby increasing surface area. The specific surface area of carbon samples increased from 118 to 281 m2/g with HTC increasing from 2 to 24 h, respectively. Increase of specific surface area mainly resulted from the development of a microporous structure at longer HTC times. Our results offer guidelines to control surface area and porosity through the adjustment of HTC conditions.

Fe-doped TiO2 hollow fibers (Fe-THF) were prepared using a template replication method with kapok as the template. The Fe concentration was varied by adjusting the amount of iron (III) nitrate from 0 to 5 mol%. The effect of Fe doping on morphology, crystal structure, bandgap energy, and photocatalytic activity was investigated and discussed. Based on the characterization results, it was found that all samples possessed a hollow structure with anatase as the main crystalline phase. The rutile phase began to be observed with high-level doping. Bandgap energy decreased significantly from 3.02 to 2.12 eV as the Fe concentration increased, owing to the formation of intermediate energy level. The photocatalytic activity was probed using the degradation of methylene blue under light-emitting diode (LED) irradiation. We found that the photocatalytic activity of Fe-THF was inferior to undoped THF and decreased with increasing Fe concentration. This result indicated that Fe dopant could act as the recombination centers in the lattice system, thus inhibiting the photocatalytic activity of THF.