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.

Pressure is a powerful tool for tuning the magnetic properties of van der Waals magnets owing to their weak interlayer bonding. However, local magnetometry measurements under high pressure still remain elusive for this important class of emerging materials. Here we demonstrate magnetic imaging of a van der Waals magnet under high pressure with sub-micron spatial resolution, using a two-dimensional (2D) quantum sensing platform based on boron-vacancy () centers in hexagonal boron nitride (hBN). We first analyze the performances of centers in hBN for magnetic imaging under pressures up to few GPa, and we then use this 2D sensing platform to investigate the pressure-dependent magnetization in micrometer-sized flakes of 1T-CrTe2. Besides providing a new path for studying pressure-induced phase transitions in van der Waals magnets, this work also opens up interesting perspectives for exploring the physics of 2D superconductors under pressure via local measurements of the Meissner effect.

Brillouin spectroscopy is a non-invasive method technique for visualizing the mechanical properties of biological samples with sub-micrometer resolution. However, to obtain 2D or even 3D maps, a high-contrast spectrometer is required to effectively reject spurious signals and isolate the signal of interest. In this work, we present an optimized two-stage virtually imaged phased array-based Brillouin spectrometer capable of achieving a contrast of at least 80 dB thanks to a new single diffraction mask, and thus with an unprecedentedly high overall transmission. Numerical simulations of the electric field propagation through the spectrometer and dedicated experiments validate the increase in contrast. We have used the newly developed Brillouin spectrometer coupled to a confocal microscope to obtain 1 h high-resolution 2D images of about 104 spectra of transparent dental pulp stem cells near a MgF2 interface as well as of the much less transparent porcine dentin material, demonstrating its overall stability and reliability.