Spin communication over 30 μ\mum long channels of chemical vapor deposited graphene on SiO2_2

We demonstrate a high-yield fabrication of non-local spin valve devices with room-temperature spin lifetimes of up to 3 ns and spin relaxation lengths as long as 9 $\mu$m in platinum-based chemical vapor deposition (Pt-CVD) synthesized single-layer graphene on SiO$_2$/Si substrates. The spin-lifetime systematically presents a marked minimum at the charge neutrality point, as typically observed in pristine exfoliated graphene. However, by studying the carrier density dependence beyond n ~ 5 x 10$^{12}$ cm$^{-2}$, via electrostatic gating, it is found that the spin lifetime reaches a maximum and then starts decreasing, a behavior that is reminiscent of that predicted when the spin-relaxation is driven by spin-orbit interaction. The spin lifetimes and relaxation lengths compare well with state-of-the-art results using exfoliated graphene on SiO$_2$/Si, being a factor two-to-three larger than the best values reported at room temperature using the same substrate. As a result, the spin signal can be readily measured across 30 $\mu$m long graphene channels. These observations indicate that Pt-CVD graphene is a promising material for large-scale spin-based logic-in-memory applications

Mechanical detection of carbon nanotube resonator vibrations

Bending-mode vibrations of carbon nanotube resonator devices were mechanically detected in air at atmospheric pressure by means of a novel scanning force microscopy method. The fundamental and higher order bending eigenmodes were imaged at up to 3.1GHz with sub-nanometer resolution in vibration amplitude. The resonance frequency and the eigenmode shape of multi-wall nanotubes are consistent with the elastic beam theory for a doubly clamped beam. For single-wall nanotubes, however, resonance frequencies are significantly shifted, which is attributed to fabrication generating, for example, slack. The effect of slack is studied by pulling down the tube with the tip, which drastically reduces the resonance frequency

From radial to unidirectional water pumping in zeta-potential modulated Nafion nanostructures

Chemically propelled micropumps are promising wireless systems to autonomously drive fluid flows for many applications. However, many of these systems are activated by nocuous chemical fuels, cannot operate at high salt concentrations, or have difficulty for controlling flow directionality. In this work we report on a self-driven polymer micropump fueled by salt which can trigger both radial and unidirectional fluid flows. The micropump is based on the cation-exchanger Nafion, which produces chemical gradients and local electric fields capable to trigger interfacial electroosmotic flows. Unidirectional pumping is predicted by simulations and achieved experimentally by nanostructuring Nafion into microarrays with a fine tune modulation of surrounding surface zeta potentials. Nafion micropumps work in a wide range of salt concentrations, are reusable, and can be fueled by different salt cations. We demonstrate that they work with the common water-contaminant cadmium, using the own capture of this ion as fuel to drive fluid pumping. Thus, this system has potential for efficient and fast water purification strategies for environmental remediation. Unidirectional Nafion pumps also hold promise for effective analyte delivery or preconcentration for (bio)sensing assays

Exciton tuning and strain imaging in WS2supported on PDMS micropillars

Since the raise of 2D materials, significant research has been dedicated to their strain-dependent electronic and mechanical properties. In this work, we studied exciton energies and low-frequency phonon modes in CVD-grown mono- and few-layer WS2 transferred on PDMS micropillars. The modification of the band structure under strain was investigated by photoluminescence (PL) spectroscopy at room temperature. Machine learning (ML) methods were used to analyze the PL spatial maps and facilitate the spectral deconvolution. For monolayer (1L) WS2, red shift in the exciton energy was detected as a function of the position, which was ascribed to the presence of residual strain. For three-layer (3L) strained WS2, a significant increase in the PL intensity corresponding to direct (K-K) band transition together with a change of exciton energy was observed. From the PL spectra, strain distribution maps were extracted for both studied samples, which strongly resembled the ML clustering results. Finally, the low-frequency Raman modes of WS2 were studied on both Si/SiO2 and PDMS substrates and no significant change of their frequency was observed for the 3L-WS2

Ultrasensitive force detection with a nanotube mechanical resonator

Since the advent of atomic force microscopy, mechanical resonators have been used to study a wide variety of phenomena, such as the dynamics of individual electron spins, persistent currents in normal metal rings, and the Casimir force. Key to these experiments is the ability to measure weak forces. Here, we report on force sensing experiments with a sensitivity of 12 zN Hz^(-1/2) at a temperature of 1.2 K using a resonator made of a carbon nanotube. An ultra-sensitive method based on cross-correlated electrical noise measurements, in combination with parametric downconversion, is used to detect the low-amplitude vibrations of the nanotube induced by weak forces. The force sensitivity is quantified by applying a known capacitive force. This detection method also allows us to measure the Brownian vibrations of the nanotube down to cryogenic temperatures. Force sensing with nanotube resonators offers new opportunities for detecting and manipulating individual nuclear spins as well as for magnetometry measurements.Comment: Early version. To be published in Nature Nanotechnolog

ESPAI GEA: A new platform for promoting Geology in Catalonia

X Congreso Geológico de España, 5-7 Julio 2021, Vitoria - GasteizESPAI GEA es una comunidad abierta que nace con el objetivo de promover las Ciencias de la Tierra y divulgar la importancia del conocimiento geológico entre la ciudadanía. La voluntad de ESPAI GEA es la de conectar a todas las instituciones, asociaciones, entidades, museos, centros de interpretación, etc., que realizan actividades relacionadas con las Ciencias de la Tierra y la Geología en el territorio catalán. La primera acción que se está llevando a cabo desde ESPAI GEA es la de crear una agenda con el objetivo de centralizar las actividades de divulgación en una única plataforma que sirva al mismo tiempo de escaparate y altavoz. Con estas premisas se está implementando la agenda en un visor web, en el que se mostrarán principalmente dos tipos de información: i) por una parte, actividades y eventos de carácter temporal, y ii) por otra parte, la geolocalización de información geológica disponible permanentemente (paneles informativos, itinerarios geológicos, área geográfica de las guías publicadas, centros de interpretación, museos, centros de investigación, u otras instalaciones singulares relacionadas) así como otra información de interés complementaria. ESPAI GEA también quiere incidir de una manera muy especial en la comunidad educativa, realizando actividades formativas, proporcionando recursos didácticos y favoreciendo la actualización científica del profesorado.ESPAI GEA is an open community that is born with the aim of promoting Earth Sciences and to disseminate the importance of geological knowledge among citizens. The goal of ESPAI GEA is to connect all the institutions, associations, entities, museums, interpretation centres, etc., that carry out activities related to Earth Sciences and Geology in the Catalan territory. The first action undertaken within ESPAI GEA is to create an agenda to assemble all the dissemination activities in a common platform that works both as a showcase and as amplifier of the activities. Under these premises, the agenda is being implemented into a web viewer, this will display two main types of data; i) on the one hand, temporary activities and events, and ii) on the other hand, the location of existing permanent geological data (information boards, geological itineraries, geographical areas of published guides, interpretation centres, museums, research centres, etc.) along with other information. ESPAI GEA wants to pay special attention to the educational community, carrying out training activities, providing instructional resources and promoting continuing education in Geology for teacher community.Peer reviewe