Tuning optical band gap by electrochemical reduction in TiO<sub>2</sub> nanorods for improving photocatalytic activities

Yun, Jong-Won; Ryu, Ki Yeon; Nguyen, Tri Khoa; Ullah, Farman; Park, Yun Chang

doi:10.1039/c6ra25274e

Cited by 29 publications

(19 citation statements)

References 56 publications

(64 reference statements)

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“…The first peak corresponds to hydroxyl groups on the surface of the micromotors, the second peak is assigned to the lattice oxygen in BiVO 4 crystal, and the latter peak can be attributed to a weak metal and oxygen binding at the material surface, respectively. 34,37 The star-shaped BiVO 4 micromotors show self-propulsion when irradiated under visible light. Figure 2A illustrates the motion mechanism, which is mainly due to the asymmetrical generation of chemical species on the surface of multifaceted BiVO 4 motors induced by light illumination.…”

Section: Resultsmentioning

confidence: 99%

“…The O 1s region shows three contributions at 531.0, 529.1, and 527.8 eV (Figure G). The first peak corresponds to hydroxyl groups on the surface of the micromotors, the second peak is assigned to the lattice oxygen in BiVO 4 crystal, and the latter peak can be attributed to a weak metal and oxygen binding at the material surface, respectively. , …”

Section: Resultsmentioning

confidence: 99%

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Visible-Light-Driven Single-Component BiVO₄ Micromotors with the Autonomous Ability for Capturing Microorganisms

et al. 2019

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Light-driven micro/nanomotors represent the next generation of automotive devices that can be easily actuated and controlled by using an external light source. As the field evolves, there is a need for developing more sophisticated micromachines that can fulfill diverse tasks in complex environments. Herein, we introduce single-component BiVO4 micromotors with well-defined micro/nanostructures that can swim both individually and as collectively assembled entities under visible-light irradiation. These devices can perform cargo loading and transport of passive particles as well as living microorganisms without any surface functionalization. Interestingly, after photoactivation, the BiVO4 micromotors exhibited an ability to seek and adhere to yeast cell walls, with the possibility to control their attachment/release by switching the light on/off, respectively. Taking advantage of the selective motor/fungal cells attachment, the fungicidal activity of BiVO4 micromotors under visible illumination was also demonstrated. The presented star-shaped BiVO4 micromotors, obtained by a hydrothermal synthesis, contribute to the potential large-scale fabrication of light-powered micromotors. Moreover, these multifunctional single-component micromachines with controlled self-propulsion, collective behavior, cargo transportation, and photocatalytic activity capabilities hold promising applications in sensing, biohybrids assembly, cargo delivery, and microbiological water pollution remediation.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Visible-Light-Driven Single-Component BiVO₄ Micromotors with the Autonomous Ability for Capturing Microorganisms

et al. 2019

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“…However, there are various methods to tune band gaps which could be employed in practice, such as impurity doping, introducing vacancies, elemental substitution, and creating heterostructures with other 2D building blocks. [70][71][72][73] Since defects can significantly influence the gap energies, the effect of oxygen vacancies on the electronic band structure was investigated. Monovacancies were created in a supercell containing 108 atoms by removing each of the two symmetrically distinct oxygen sites 6i and 2d.…”

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confidence: 99%

Two-Dimensional Hexagonal Sheet of TiO₂

et al. 2017

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We report on the ab initio discovery of a novel putative ground state for quasi two-dimensional TiO2 through a structural search using the minima hopping method with an artificial neural network potential. The structure is based on a honeycomb lattice and is energetically lower than the experimentally reported lepidocrocite sheet by 7 meV/atom, and merely 13 meV/atom higher in energy than the ground state rutile bulk structure. According to our calculations, the hexagonal sheet is stable against mechanical stress, it is chemically inert and can be deposited on various substrates without disrupting the structure. Its properties differ significantly from all known TiO2 bulk phases with a large gap of 5.05 eV that can be tuned through strain engineering. arXiv:1704.03983v1 [cond-mat.mtrl-sci]

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“…This can be determined from the secondary electron cutoffs of the annealed TNTs in Figure b, while their respective VB spectra are exhibited in Figure c. The φ here for each sample was calculated by subtracting the cutoff energy ( V cutoff ) from the energy of the incident He–I photons: φ = 21.22 – V cutoff . , Here, the secondary electron cutoffs for 500, 800, and 900 °C annealed TNTs are estimated to be 16.64, 16.94, and 16.96 eV, respectively [see Figure b]. With the above equation, the φ is found to be 4.57, 4.27, and 4.25 eV for 500, 800, and 900 °C annealed TNTs, respectively.…”

Section: Resultsmentioning

confidence: 99%

Unveiling Temperature-Mediated Dual-Band Edge in TiO₂ Nanotubes with Enhanced Photocatalytic Effect

et al. 2021

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An annealing temperature-driven appearance of a sharp dual-band edge in the ultraviolet−visible absorption spectrum of electrochemically anodized TiO 2 nanotubes (TNTs) and the corresponding impact on the photodegradation of organic dyes is reported based on the evolution of an anatase (A)/rutile (R) phase junction. Systematic X-ray diffraction followed by a micro-Raman analysis illustrates the impact of annealing between 500 and 900 °C in promoting the anatase-to-rutile phase transformation with a higher degree of crystallinity through an evolution of an intermediate mixed phase. X-ray photoelectron spectroscopy (XPS) further reveals a clear transition from the sub-stoichiometric to stoichiometric TNTs with increasing annealing temperature. Moreover, the valence band (VB) XPS along with the ultraviolet photoelectron spectroscopy (UPS) analysis suggests the possible band alignment at the A/R interface, whereas the X-ray absorption spectroscopy (XAS) at the Ti L-and O K-edges confirms a systematic change from an anatase to a rutile phase owing to the modification in local symmetry. To validate our experimental results, especially the formation of a dual-band edge at the A/R phase junction in TNTs, theoretical calculations using density functional theory (DFT) were also performed. Here, a one-to-one analysis of our theoretical and experimental results not only shows a good agreement to each other but also illustrates the microscopic origin behind the formation of a dual-band edge in mixed phase TNTs as well as the observed variation in Raman and XPS spectra with annealing temperature. Finally, an improved photocatalytic degradation of methylene blue aqueous solution is demonstrated in the presence of a mixed phase and explained in the framework of an efficient transfer of photogenerated electrons from the conduction band (CB) of R to the CB of A and holes from the VB of A to the VB of R across the phase junction in tube walls.

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Tuning optical band gap by electrochemical reduction in TiO₂ nanorods for improving photocatalytic activities

Abstract: Tuning of the optical band gap of TiO2 nanorods (TiO2 NRs) was investigated by electrochemical methods for improving their photocatalytic activities.

Cited by 29 publications

References 56 publications

Visible-Light-Driven Single-Component BiVO₄ Micromotors with the Autonomous Ability for Capturing Microorganisms

Visible-Light-Driven Single-Component BiVO₄ Micromotors with the Autonomous Ability for Capturing Microorganisms

Two-Dimensional Hexagonal Sheet of TiO₂

Unveiling Temperature-Mediated Dual-Band Edge in TiO₂ Nanotubes with Enhanced Photocatalytic Effect

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Tuning optical band gap by electrochemical reduction in TiO2 nanorods for improving photocatalytic activities

Abstract: Tuning of the optical band gap of TiO2 nanorods (TiO2 NRs) was investigated by electrochemical methods for improving their photocatalytic activities.

Cited by 29 publications

References 56 publications

Visible-Light-Driven Single-Component BiVO4 Micromotors with the Autonomous Ability for Capturing Microorganisms

Visible-Light-Driven Single-Component BiVO4 Micromotors with the Autonomous Ability for Capturing Microorganisms

Two-Dimensional Hexagonal Sheet of TiO2

Unveiling Temperature-Mediated Dual-Band Edge in TiO2 Nanotubes with Enhanced Photocatalytic Effect

Contact Info

Product

Resources

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Tuning optical band gap by electrochemical reduction in TiO₂ nanorods for improving photocatalytic activities

Visible-Light-Driven Single-Component BiVO₄ Micromotors with the Autonomous Ability for Capturing Microorganisms

Visible-Light-Driven Single-Component BiVO₄ Micromotors with the Autonomous Ability for Capturing Microorganisms

Two-Dimensional Hexagonal Sheet of TiO₂

Unveiling Temperature-Mediated Dual-Band Edge in TiO₂ Nanotubes with Enhanced Photocatalytic Effect