Sidewall hydrogenation impact on the structure and wettability of spaghetti MWCNTs
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Sidewall hydrogenation impact on the structure and wettability of spaghetti MWCNTs Asieh Sadat Kazemi1 · Zahra Ebrahim Nataj2 · Yaser Abdi2 Received: 26 May 2020 / Accepted: 4 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Carbonaceous and hydrophobic surfaces of carbon nanotubes require modification by functionalization to interact more efficiently with the surrounding medium such as air, water and bio-fluids. Two types of spaghetti MWCNTs, a less studied category of nanotubes, with the advantage of simpler incorporation with other materials, were fabricated, characterized and hydrogenated. The structural differences of the spaghetti types, mainly due to the structural differences of the substrates they were grown on, were reflected in FESEM and TEM images, XRD patterns and Raman spectra of the two samples. More interestingly, water contact angle measurements on initial hydrophobic structures showed a distinct wettability behavior in the two types with hydrogenation time, where one became even more hydrophobic and the other switched to hydrophilic. The inherent structural differences between the two types, the surface roughness, the increase in the hydrogen content on the sidewalls of the nanotubes and the interplay of repulsive Columbic and attractive van der Waals forces among the hydrogens and the nanotubes may have all played a role in this wettability behavior. However, the capability of switching surface wettability on demand is very useful for future environmental applications and may support unique devices in microfluidics, catalysis, and detection systems. Graphic abstract
Keywords Spaghetti · MWCNTs · Hydrogenation · Wettability
1 Introduction * Asieh Sadat Kazemi [email protected] 1
Department of Physics, Iran University of Science and Technology, Tehran, Iran
Department of Physics, University of Tehran, Tehran, Iran
2
Carbon nanotubes with many outstanding electrical, optical, thermal, and mechanical properties, are only carbonaceous surfaces and are usually hydrophobic [1, 2]. If modified by functionalization, the altered surface chemistry and
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wettability would allow the nanotubes to fully interact with the surrounding medium such as air, water and bio-fluids [3]. Among functionalization methods, covalent functionalization is more robust and generates important adjustments in multiwall carbon nanotube (MWCNT) properties [2], while non-covalent functionalization based on van der Waals interactions appears weaker [2, 4, 5]. In a covalent functionalization, there are two strategies: direct sidewall functionalization and defect group functionalization. The former installs the functional groups along the outer wall of the nanotubes and the latter, on the tips of the nanotubes [6]. Surface modification techniques are usually divided into physical and chemical methods. However, the chemical mutations are cost effective, have long operating time, and induce undesirable surface elements [7]. Albeit, phys
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