Raman Spectra of Double-Wall Carbon Nanotubes under Extreme Uniaxial Stress

We investigated the pressure dependence of the Raman frequencies and intensities of the D and G bands of double-wall carbon nanotubes under strong uniaxial conditions. Using moissanite anvils, we observed for the first time the evolution of the D band under extreme stress/pressure conditions. We find that the difference between D and G frequencies remains constant over the whole stress range. In addition, we observe that double-wall carbon nanotubes behave elastically up to the maximum uniaxial stress reached in our experiments, which is estimated to be about 12 GPa

Morphological changes in carbon nanohorns under stress: a combined Raman spectroscopy and TEM study

In this work, we present the first study of highly compressed carbon nanohorns (CNHs).</p

Linear, Non-Conjugated Cyclic and Conjugated Cyclic Paraphenylene under Pressure

The n-paraphenylene family comprises chains of phenylene units linked together by C-C bonds that are between single- and double-bonded, and where n corresponds to the number of phenylene units. In this work, we compare the response of the optical properties of different phenylene arrangements. We study linear chains (LPP), cyclic systems (CPPs), and non-conjugated cyclic systems with two hydrogenated phenylenes (H4[n]CPP). Particularly, the systems of interest in this work are [6]LPP, [12]- and [6]CPP and H4[6]CPP. This work combines Raman and infrared spectroscopies with absorption and fluorescence (one- and two-photon excitations) measured as a function of pressure up to maximum of about 25 GPa. Unprecedented crystallographic pressure-dependent results are shown on H4[n]CPP, revealing intramolecular ¿-¿ interactions upon compression. These intramolecular interactions justify the H4[n]CPP singular optical properties with increasing fluorescence lifetime as a function of pressure

Pressure-Induced Conductivity in a Neutral Nonplanar Spin-Localized Radical

Souto, Manuel et al.There is a growing interest in the development of single-component molecular conductors based on neutral organic radicals that are mainly formed by delocalized planar radicals, such as phenalenyl or thiazolyl radicals. However, there are no examples of systems based on nonplanar and spin-localized C-centered radicals exhibiting electrical conductivity due to their large Coulomb energy (U) repulsion and narrow electronic bandwidth (W) that give rise to a Mott insulator behavior. Here we present a new type of nonplanar neutral radical conductor attained by linking a tetrathiafulvalene (TTF) donor unit to a neutral polychlorotriphenylmethyl radical (PTM) with the important feature that the TTF unit enhances the overlap between the radical molecules as a consequence of short intermolecular S···S interactions. This system becomes semiconducting upon the application of high pressure thanks to increased electronic bandwidth and charge reorganization opening the way to develop a new family of neutral radical conductors.This work was supported by the EU ITN iSwitch 642196 DGI grant (BeWell; CTQ2013-40480-R), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), and the Generalitat de Catalunya (grant 2014- SGR-17). This work has also been supported by MINECO through the projects CSD2007-00045, CTQ2012- 38599-C02- 02 and CTQ2013-48252-P. ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496). M.S. is grateful to Spanish Ministerio de Educación, Cultura y Deporte for a FPU grant and he is enrolled in the Material Science Ph.D. program of UAB. D.B. is grateful to the EC ITN Nano2fun grant no607721. M.P.A. is grateful to the Spanish Ministerio de Educación, Cultura y Deporte for an FPU grant. M.P.A. and V.G.B. thank the project CTQ2015-67755-C2-1-R. H.O. Jeschke, M. Tomic and R. Valenti thank the Deutsche Forschungsgemeinschaft (DFG) for funding through grant SFB/TRR49 and Steve Winter for useful discussions. We thank Carlos Goḿ ez-Garcıá (Univ. Valencia) for SQUID measurements as well as Xavier Fontrodona (Univ. Girona) for X-ray diffraction measurements and Mercedes Taravillo (UCM) for the support provided during the high pressure Raman measurements.Peer reviewe