Carbon nanotube are exceptional mechanical resonators. Indeed, they are extremely light, with masses in the range of ~ag (1 ag = 10-18g). In addition, as bottom-up materials, they do not suffer from surface defect as their top-down counterparts (MEMS etched from silicon or nitride substrates). From these 2 features stems their exquisite mass sensitivity as demonstrated by Chaste et al[1] with a sensitivity of 1.4 yg in a cryogenic environment. Yet, this sensitivity was reported to be much worse at room temperature, about 25 zg[2]. This has hindered the use of CNTs as sensors in real-life applications. In this work, we propose a unique set-up to track in real time the vibrations of a individual single-walled CNT (SWCNTs) at room temperature. It allows us to demonstrate a record mass sensitivity of 0.2 yg +/- 0.17 yg (1 yg = 10-24 g, the mass of a single proton).We carefully investigated the noise mechanisms that could be limiting the sensitivity: set-up noise, interaction with the gas phase and Brownian motion to name only the most important ones. We found that our device operates closely to the Brownian noise limit and is not limited by external sources of noise. Surprisingly, increasing the pressure up to 35 mbar (after which we could not detect the motion due to viscous damping) does not seem to degrade the sensitivity, which might be preserved up to ambient pressure. Finally, yet importantly, the exquisite sensitivity observed here is similar for several devices, making it a reliable and reproducible feature. This opens up the possibility to perform single-molecule sensing, in various contexts such as biological applications, mass spectrometry or surface science[1,3].[1] J. Chaste, A. Eichler, J. Moser, G. Ceballos, R. Rurali, A. Bachtold (2012). A nanomechanical mass sensor with yoctogram resolution, Nat. Nano, 7, 5, 301-304.[2] B. Lassagne, D. Garcia-Sanchez, A. Aguasca, A. Bachtold (2008). Ultrasensitive mass sensing with a nanotube electromechanical resonator, Nano. Let., 8, 11, 3735 – 3738.[3] P. Robin, L. Bocquet (2023). Nanofluidics at the crossroads, Soft Cond. Matt., preprint.

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.

Carbon nanotubes as nanomechanical resonators are very promising systems due to their small size and mass as well as their stiffness that grant them great sensitivity as a sensor. As a result, ample research [1][2] is oriented towards these devices in order to understand the sources of noise and reach better sensitivities. In this work, we are interested in the mass-sensing applications and will analyze their mechanics, both in the linear and nonlinear regimes. The treatment of nonlinearities is particularly challenging because there is no unique solution to the equation of motion. In addition, even if we do not perceive its characteristic bi-stability at room temperature, we still enter the nonlinear regime where the well-known models are no longer accurate. However, it is not easy to distinguish between the two regimes, since the linear model is only an approximation of the nonlinear model for small drives. The benefit of the nonlinear regime is that the received signal is stronger.There are several parameters to take into account (drive power, temperature,...), we studied some that affect the sensitivity to understand which are relevant for our system. We obtained a record-breaking sensitivity of 2x10⁻²⁵ g.We usually work at room temperature and cannot observe bi-stability, but we observed bi-stability when the temperature is lowered, which is in agreement with the theory that a small Q prevents hysteresis from appearing. With this in mind, it is interesting to have a low Q system at room temperature, as a sharper resonator would introduce additional noise due to bi-stability. We have therefore found a compromise between a large damping [3], which blocks hysteresis, and a sharp resonance, which gives precision.We achieved a record-breaking sensitivity at room temperature of 0.2 yg which is promising for future applications, given that the previous record sensitivity was reached in a cryostat [4].[1] K. L. Ekinci, M. L. Roukes. Nanoelectromechanical systems. Review of Scientific Instruments, (2005). https://doi.org/10.1063/1.1927327.[2] De Bonis, Sergio & Urgell, Carles & Yang, Wei & Samanta, C. & Noury, Adrien & Vergara-Cruz, J. & Dong, Quan & Jin, Yong & Bachtold, A.. (2018). Ultrasensitive Displacement Noise Measurement of Carbon Nanotube Mechanical Resonators. Nano Letters. 18. 10.1021/acs.nanolett.8b02437.[3] Swapan K. Roy et al. ,Improving mechanical sensor performance through larger damping.Science360,eaar5220(2018).DOI:10.1126/science.aar5220[4] Chaste, J., Eichler, A., Moser, J. et al. A nanomechanical mass sensor with yoctogram resolution. Nature Nanotech 7, 301–304 (2012). https://doi.org/10.1038/nnano.2012.42

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.

In this paper, we theoretically and experimentally investigate the specificities of single-walled carbon nanotubes (SWNTs) for field electron emission (FE) and field ion evaporation (FI). For FE, the small radii of curvature of these nanotubes lead to a significant widening of the tunnel barrier, and thus, for a given emission current, the fields at the surface of the SWNTs are significantly higher than commonly observed in standard large radius FE. For currents in the μA range, for example, fields ranging from 7–8 V/nm for large nanotubes to 17–18 V/nm for the thinnest are required. These strong fields, in turn, have repercussions on FI and electrostatic forces. The electric fields and longitudinal electrostatic forces during FE and FI as a function of nanotube radius are presented. The evolution of the nanotube during field evaporation was also studied in an environmental transmission electron microscope as a function of field strength and polarity. A strong dissymmetry between positive and negative polarity is observed. For negative polarity, the nanotubes can gradually shorten as the voltage is increased, whereas in positive polarity, they are almost systematically torn off before apex evaporation occurs. A model to explain this dissymmetry for our samples is presented. These results can be used to optimize nanotube cathode geometries.

Colloids are widely used as model systems to study the glass transition, with much research focused on hard or soft neutral colloids and their mixtures. However, the glass transition of soft-charged spherical colloids and its dynamic effects remain underexplored. This study assesses the glass transition of polymeric multiarm charged soft colloids using shear rheology, coarse-grained molecular dynamics (MD) simulations, and X-ray scattering. Strong particle-particle correlations, driven by electrostatic interarm repulsion, inhibit Newtonian behavior in the dilute regime. The liquid-to-glass transition occurs at just 0.25 wt %, marked by weak caging and minimal interdigitation of arms, as evidenced by particle contact analysis in MD simulations and the strong frequency dependence of the dynamic moduli. Particle shells interdigitate only well within the glassy regime, leading to a nearly frequency-independent rheological response. The weak volume fraction dependence of the yield stress sets these charged systems among the softest colloids reported in the literature.