Modulating the H-bond strength by varying the temperature for the high pressure synthesis of nitrogen rich carbon nanothreads

Year: 2020

Authors: Fanetti S.; Santoro M.; Alabarse F.; Enrico B.; Bini R.

Autors Affiliation: European Lab Nonlinear Spect, LENS, Via N Carrara 1, I-50019 Florence, Italy; Ist Chim Composti OrganoMetallici, ICCOM, Via Madonna del Piano 10, I-50019 Florence, Italy; CNR, INO, Via Nello Carrara 1, I-50019 Sesto Fiorentino, FI, Italy; Elettra Sincrotrone Trieste SCpA, ELETTRA, AREA Sci Pk, I-34149 Trieste, Italy; Univ Firenze, Dipartimento Chim Ugo Schiff, Via Lastruccia 3, I-50019 Sesto Fiorentino, Italy.

Abstract: Carbon nanothreads are among the most attractive new materials produced under high pressure conditions. Their synthesis can be achieved by compressing the crystals of aromatic molecules exploiting both the anisotropic stress produced by the unidirectional applied force and that intrinsic to the crystal arrangement. We explored here the transformation of pyridine into a nitrogen rich carbon nanothread crystal by varying the pressure and temperature conditions with the twofold purpose of disclosing the microscopic mechanism of transformation and optimizing the yield and quality of the produced crystalline nanothreads. The best conditions for the synthesis were identified in the 14-18 GPa range at temperatures between 400 and 500 K with a product yield greater than 30%. The comparison of experiments performed under different P-T conditions allowed us to understand the role of high temperature, which is necessary to weaken or even destroy the complex H-bond network characterizing the pyridine crystal and preventing the correct approach of the aromatic rings for nanothread formation. X-ray diffraction data confirm the excellent 2D hexagonal packing of the nanothreads over several tens of microns, whereas the sharp absorption lines observed in the IR spectrum strongly support a substantial order along the threads. Diffraction results suggest a polytwistane structure of the threads derived from a Diels-Alder [4 + 2] polymerization involving molecules arranged in a slipped parallel configuration along the pyridine crystal a and b axes. Electron microscopy evidences an arrangement of the nanothreads in bundles of tens of nanometers.

Journal/Review: NANOSCALE

Volume: 12 (8)      Pages from: 5233  to: 5242

More Information: We thank the European Laboratory for Nonlinear Spectroscopy (LENS) for hosting the research, and the Deep Carbon Observatory and the “Fondazione CR Firenze” for their strong support. The research has been supported by the following grants: Extreme Physics and Chemistry of Carbon: Forms, Transformations, and Movements in Planetary Interiors funded by the Alfred P. Sloan Foundation; Fondazione Cassa di Risparmio di Firenze under the project “Utilizzo dellŽanisotropia strutturale nella sintesi di nanofili di carbonio diamond-like ad alta pressione”. We also thank MIUR-Italy (“Progetto Dipartimenti di Eccellenza 2018-2022” allocated to Department of Chemistry “Ugo Schiff”); “Ente cassa di risparmio di Firenze” and Regione Toscana for the project FELIX (POR FESR 2014-2020, grant number no. 6455), for their financial support given for the acquisition of the TESCAN GAIA3 electron microscope and the Elettra Italian synchrotron for hosting our experiment under the proposal number 20185087.
KeyWords: Absorption spectroscopy, Carbon, Crystal structure, Crystals, High pressure engineering, Molecules
DOI: 10.1039/c9nr10716a

ImpactFactor: 7.790
Citations: 24
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