This article shows the differentiation between water adsorbed outside of a single-walled carbon nanotube (CNT) and that confined inside. This distinction is made possible by tracking the electronic transport of a CNT-based field effect transistor constructed with an individual nanotube and exposed to controlled environments. The presence of water shifts the electrical neutrality point, indicating charge transfer between the nanotube and its environment. We identify three types of water molecules: (i) chemically adsorbed on the SiO2 surface, forming silanol groups, (ii) physically adsorbed outside the nanotube, and (iii) confined inside. The first type is eliminated only by high-temperature treatment under vacuum, while the latter two desorb at room temperature under moderate or high vacuum, i.e. 10−3 mbar. We observe that water confinement inside the nanotube is fast and thermodynamically favorable, with no qualitative influence from the metallicity of the nanotube.

Among the different methods to grow graphene on silicon carbide (SiC), the chemical vapor deposition (CVD) in a hydrogen atmosphere has several interesting features arising from the use of this gas. Despite its versatility and its ability to grow graphene with a quality allowing applications in electrical metrology, this synthesis method remains largely understudied. This work is specifically dedicated to this growth technique in conditions leading to the epitaxy of graphene on a buffer layer. We first show that hydrogen has several effects during the cooling down, possibly leading to hydrogen intercalation beneath graphene, or even to graphene etching. Then, we use a specific cooling under argon, allowing the suppression of hydrogen effects, to follow the successive phases of the graphene formation, from the nucleation of islands and ribbons to their coalescence on SiC. Finally, we demonstrate that graphene growth is, in our growth conditions, self-limited to a unique monolayer.

This study investigates the influence of interlayer cations on the thermodynamics and sorption mechanisms of water in a reference Wyoming montmorillonite. The behaviour of the montmorillonite exchanged with monovalent cations (Li + , Na + , K + , Rb + , Cs + ) or divalent cations (Mg 2+ , Ca 2+ , Ba 2+ ) is compared. The analysis combines X-ray diffraction (XRD), water sorption isotherms at various temperatures and mid-infrared spectroscopy. Li + , Mg 2+ and Ca 2+ promote greater water uptake and swelling, whereas K + , Rb + and Cs + significantly limit these processes. The behaviour of Na + and Ba 2+ stands out, demonstrating intermediate water uptake and high swelling. Mid-infrared spectral analysis supports these observations. It is shown that a cation’s effect on water uptake and swelling correlates best with the product of its elementary charge and ionic radius rather than with other properties such as the electrostatic potential, solvation enthalpy or chemical hardness. However, differences in isotherm shapes, hysteresis between adsorption and desorption and the variation of isosteric heat with water content suggest the presence of two distinct sorption mechanisms: one involving Li + , Cs + , Mg 2+ , Ca 2+ and Ba 2+ , and another involving Na + , K + and Rb + . These findings indicate that isotherm shape and swelling alone do not directly reflect water uptake capacity. These findings thus outline that the chaotropic (structure-breaking) or kosmotropic (structure-making) nature of the cations, along with the complex interplay between cation hydration and TOT layer attraction, may explain the complex observed differences.