Suchergebnisse

Antimonene, a novel group 15 two-dimensional material, is attracting great attention due to its outstanding physical and chemical properties. Despite its thermodynamic stability, the pronounced covalent character of the interlayer interactions imposes severe limitations on its exfoliation into mono- and few-layer. Here, we develop a systematic study of liquid phase exfoliation (LPE) with the aim to optimize antimonene production in terms of concentration and dimensional anisotropy, investigating the most relevant experimental factors affecting the exfoliation: pre-processing of pristine antimony, solvent selection based on Hansen solubility parameters and ultrasound conditions. Moreover, exhaustive characterization by means of turbidimetry, XRD, Raman spectroscopy, XPS, AFM, SEM, XEDS and TEM has been carried out. Indeed, we achieved concentration values of ca. 0.368 g L−1 (∼yield of 37 wt%), up to ∼30 times higher compared to the highest value so far reported, with ca. 50% of the nanolayers with heights between 2 and 10 nm and lateral dimensions in the 40–300 nm range. Furthermore, it has been demonstrated that the yield of the process can be enhanced up to ∼90 wt% by recycling the sediment to perform a maximum of 7 cycles. Moreover, we have illustrated the usefulness of this approach by characterizing the electrochemical behaviour of antimonene as a catalyst for the hydrogen evolution reaction (HER). This study provides important insights into the LPE and electrochemical properties of antimonene, allowing its large-scale production and paving the way for its application in fields of utmost importance such as energy storage and conversion or catalysis ; The work has been supported by the European Union (ERC-2018-StG 804110-2D-PnictoChem to G. A.) and the Spanish MICINN (MAT2016-77608-C3-1-P and PCI2018-093081) and MINECO (Structures of Excellence María de Maeztu MDM-2015-0538 and FIS2017-82415-R). G. A. acknowledges support from the Generalitat Valenciana (CIDEGENT/2018/001) and the Deutsche Forschungsgemeinschaft (DFG; FLAG-ERA AB694/2-1). R. S.-G. acknowledges the Spanish MINECO for an FPU fellowship. J. J. P. and W. S. P. acknowledge financial support from the Spanish MINECO through Grant FIS2016-80434-P, the Fundación Ramón Areces, and the European Union Seventh Framework Programme under FLAG-ERA agreement No. 604391. W. S. P. was funded by the CNPq Fellowship programme (Pós-doutorado júnior) under grant 405107/2017-0 and acknowledges the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madrid and the RES

Antimonene, a novel group 15 two-dimensional material, is functionalized with a tailormade perylene bisimide through strong van der Waals interactions. The functionalization process leads to a significant quenching of the perylene fluorescence, and surpasses that observed for either graphene or black phosphorus, thus allowing straightforward characterization of the flakes by scanning Raman microscopy. Furthermore, scanning photoelectron microscopy studies and theoretical calculations reveal a remarkable charge-transfer behavior, being twice that of black phosphorus. Moreover, the excellent stability under environmental conditions of pristine antimonene has been tackled, thus pointing towards the spontaneous formation of a sub-nanometric oxide passivation layer. DFT calculations revealed that the noncovalent functionalization of antimonene results in a charge-transfer band gap of 1.1 eV ; We thank the ESCA microscopy beamline team at Elettra for technical assistance with the scanning X‐ray photoelectron microscopy measurements. The research leading to these results has received partial funding from the European Union Seventh Framework Programme under grant agreement no. 604391 Graphene Flagship. We thank the Deutsche Forschungsgemeinschaft (DFG‐SFB 953 "Synthetic Carbon Allotropes", Projects A1 and C2), the Interdisciplinary Center for Molecular Materials (ICMM), and the Graduate School Molecular Science (GSMS) for financial support. We thank the MINECO (Spain) for financial support through the "María de Maeztu" Programme for Units of Excellence in R&D (MDM‐2014‐0377) and the projects: MAT2016‐77608‐C3‐1P and 3P, as well as MAT2014‐52477‐C5‐5 and MAT2015‐66888‐C3‐3‐R. Co‐funding from UE is also acknowledged. G.A. thanks the EU for a Marie Curie Fellowship (FP7/2013‐IEF‐627386), and the FAU for the Emerging Talents Initiative (ETI) grant #WS16‐17_Nat_04

Luminescent defects in hexagonal boron nitride (h-BN) have recently emerged as a promising platform for non-classical light emission. On-chip solutions, however, require techniques for controllable in-situ manipulation of quantum light. Here, we demonstrate the dynamic spectral and temporal tuning of the optical emission from h-BN via moving acousto-mechanical modulation induced by stimulated phonons. When perturbed by the propagating acoustic phonon, the optically probed radiative h-BN defects are periodically strained and their sharp emission lines are modulated by the deformation potential coupling. This results in an acoustically driven spectral tuning within a 2.5-meV bandwidth. Our findings, supported by first-principles theoretical calculations, reveal exceptionally high elasto-optic coupling in h-BN of ~50 meV/%. Temporal control of the emitted photons is achieved by combining the acoustically mediated fine-spectral tuning with spectral detection filtering. This study opens the door to the use of sound for scalable integration of h-BN emitters in nanophotonic and quantum information technologies ; This work was supported in part by the collaborative project "Single-Photon Generation in 2D Crystals for Quantum Information" (MDM-2014-0377) funded by the Condensed Matter Physics Center (IFIMAC) as well as by the Spanish MINECO under contracts MAT2014-53119-C2-1-R, MAT2016-77608-C3-1-P and MAT2017-83722-R. S.L. is a recipient of the Ramón and Cajal Research Grant (RyC-2011-09528) funded by the Spanish MINECO. J.J.P.B. acknowledges financial support from Spanish MINECO through Grant FIS2016-80434-P, the Fundación Ramón Areces, the Comunidad Autónoma de Madrid through MAD2D-CM Program (S2013/MIT-3007) and the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. W.S.P. was funded by the CNPq Fellowship programme (Pós-doutorado júnior) under grant 405107/2017-0 and acknowledges the computer resources at FinisTerrae2 and the technical support provided by Barcelona Supercomputing Center (RES-FI-2018-2-0036). We thank Eduardo J.H. Lee (UAM) for his help in sample preparation

2D materials have opened a new field in materials science with outstanding scientific and technological impact. A largely explored route for the preparation of 2D materials is the exfoliation of layered crystals with weak forces between their layers. However, its application to covalent crystals remains elusive. Herein, a further step is taken by introducing the exfoliation of germanium, a narrow-bandgap semiconductor presenting a 3D diamond-like structure with strong covalent bonds. Pure α-germanium is exfoliated following a simple one-step procedure assisted by wet ball-milling, allowing gram-scale fabrication of high-quality layers with large lateral dimensions and nanometer thicknesses. The generated flakes are thoroughly characterized by different techniques, giving evidence that the new 2D material exhibits bandgaps that depend on both the crystallographic direction and the number of layers. Besides potential technological applications, this work is also of interest for the search of 2D materials with new properties ; The authors acknowledge the financial support from the Spanish Ministry of Science and Innovation, through the "María de Maeztu" Programme for Units of Excellence in R&D (CEX2018-000805-M and CEX2019-000919-M) and MINECO-FEDER projects PID2019-111742GB-C31, PID2019-111742GB-C32, PCI2018-093081, PID2019-109539GB-C43, MAT2015-666888-C3-3R, MICINN projects FIS2017-82415-R, RTI2018- 097895-B-C43 and PID2019-111742GA-I00, the Comunidad Autónoma de Madrid through S2018/NMT-4321 (NanomagCOST-CM), the Generalitat Valenciana (CIDEGENT/2018/001 grant and iDiFEDER/2018/061 co-financed by FEDER) and the Deutsche Forschungsgemeinschaft (DFG, FLAG-ERA AB694/2-1), the European Union Seventh Framework Programme under Grant agreement No. 604391 Graphene Flagship. The authors thank the European Research Council (ERC Starting Grant 2D-PnictoChem 804110 to G.A.). W.S.P. acknowledges the computer resources and assistance provided by the Centro de Computación Científica of the Universidad Autónoma de Madrid and the computer resources at MareNostrum and technical support provided by Barcelona Supercomputing Center (FI-2019-2-0007)