@article{7d72d7734c4c497cb75fe710c41c4832,
title = "Gas bubble formation of filaments from sedimented graphene oxide",
abstract = "Gas bubbles that were generated in freshly prepared graphene oxide (GO) solution were found to float up as oblate shapes and travelled in the same way as they would when created in water. Gas bubbles, that were produced from the sediment of GO solution that was stood for 120 h, however, floated upward with a fine filament present in their wake while still retaining the oblate form. With bubbles that were 5 and 10 μL in volume, their average vertical speeds of 0.4 m/s could be maintained via significantly lower lateral displacements compared with similar sized gas bubbles created in water, notwithstanding that the shape aspect ratio fluctuations remained throughout. This behavior could be accounted for by a proposed mechanistic model in which the superhydrophilic and conversely superaerophobic GO particles (with contact angles of 4° ± 0.8°), that began encapsulating the liquid-gas interface as soon as the bubble was formed at the tip, prevented a typical pinch-off from occurring. This produced a thin filament with elastic properties brought along by the upward floating bubble. Rising gas bubbles, released from sedimented GO that was mixed with iron powder were found to create, under the influence of a magnet, fine structures that attached to the side of a container. These structures have the potential to be applied for environmental remediation.",
keywords = "Aggregation, Buoyancy, Flotation, String, Superaerophobic, Suspension",
author = "Zhixiong Song and Lin, {Eric Shen} and Abid, {Hassan Ali} and Ong, {Jian Wern} and Ng, {Tuck Wah}",
note = "Funding Information: The WCA of the drops dispensed on substrates I and II were found to be 66° ± 7° and 25° ± 4° respectively. These values were consistent with earlier findings which showed that the deposition of GO on the PVC substrates would not result in superhydrophilicity (WCA < 10°) despite tending to lower the WCA. The WCA values of the drops dispensed on substrates III, IV and V alternatively were found to be 96° ± 8°, 22° ± 3.5° and 4° ± 0.8° respectively (see Fig. 2A–C). That the WCA of substrate III closely matched that of substrate I imputed that the supernatant had significantly low amounts of GO particles present. The significant difference in the WCA measured in substrates IV and V can be accounted for by first considering that the chemical exfoliation process during preparation would result in GO sheets with different characteristics. It has been previously contended that those sheets that had larger carbon layer spacing (d-spacing) would allow more water molecules to enter into the interlayers and thus improve the degrees of hydration [14]. This would then lower their densities and thus also the tendency to sediment. The results obtained here show that the stronger sedimented GO particles render the substrates coated with it to exhibit superhydrophilicity. This seemingly contradicting finding can be reconciled by the fact that the GO flakes are by themselves strongly hydrophilic in nature. The sedimented GO that is extracted from the bottom of the solution and left to stand would have a higher density (concentration) of these flakes, which when spread over the substrate by coating, would contain higher numbers of flake particles per unit area on the surface for water molecules (from the dispensed drop) to come in contact with, resulting in the superhydrophilic characteristic. It should also be noted that the lower WCA with substrate IV compared with substrate II further supports this thesis. Publisher Copyright: {\textcopyright} 2023 The Authors",
year = "2023",
month = nov,
day = "1",
doi = "10.1016/j.matchemphys.2023.128325",
language = "English",
volume = "309",
journal = "Materials Chemistry and Physics",
issn = "0254-0584",
publisher = "Elsevier",
}