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Nanostructures & Spectroscopie
(30) Production(s) de l'année 2021
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Raman resonance tuning of quaterthiophene in filled carbon nanotubes at high pressures
Auteur(s): Alencar R. S., Aguiar A. L., Ferreira R. S., Chambard R., Jousselme B., Bantignies J.-L., Weigel C., Clement S., Aznar R., Machon D., Souza Filho A. G., San-Miguel A., Alvarez L.
(Article) Publié:
Carbon, vol. 173 p.163-173 (2021)
Texte intégral en Openaccess :
Ref HAL: hal-03163018_v1
DOI: 10.1016/j.carbon.2020.10.083
WoS: WOS:000613132200003
Exporter : BibTex | endNote
Résumé: Filling carbon nanotubes with molecules is a route for the development of electronically modified one-dimensional hybrid structures for which the interplay between the electronic structure of molecules and nanotubes is a key factor. Tuning these energy levels with external parameters is an interesting strategy for the engineering of new devices and materials. Here we show that the hybrid system composed by quaterthiophene (4T) molecules confined in single-walled carbon nanotubes, presents a piezo-Raman-resonance of the molecule vibrational pattern. This behavior manifests as a rapid pressure induced enhancement of the 4T Raman mode intensities compared to the tubes G-band Raman modes. Density functional theory calculations allow to explain the spectral behaviour through the pressure-enhanced quaterthiophene resonance evolution. By increasing pressure, the tube cross-section deformation leads to a reduction of the intermolecular distance, to the splitting of the molecular levels and then to an increase of resonance channels. Calculations and experiments converge to the 4T piezo-resonance scenario associated with the pressure-induced nanotube radial collapse observed at about 0.8 GPa. Our findings offer possibilities for the development of pressure transducers based on molecule-filled carbon nanotubes.
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High-throughput screening of metal - Organic frameworks for CO2 and CH4 separation in the presence of water
Auteur(s): Rogacka J., Seremak Agnieszka, Luna-Triguero Azahara, Formalik F., Matito-Martos Ismael, Firlej L., Calero Sofia, Kuchta Bogdan
(Article) Publié:
Chemical Engineering Journal, vol. 403 p.126392 (2021)
Texte intégral en Openaccess :
Ref HAL: hal-03118302_v1
DOI: 10.1016/j.cej.2020.126392
WoS: WOS:000579752500109
Exporter : BibTex | endNote
Résumé: Competitive adsorption of water is an important issue in the adsorption-based industrial processes of bio- and flue gases separation. The dehumidification of gases prior to separation would increase process complexity and lower its economic interest. In this work, large-scale computational screening was applied to identify Metal-Organic Frameworks (MOFs) structures which exhibit high CO2/CH4 selectivity and total loading higher than 0.5 mol/kg (in the presence of water). High-throughput Grand Canonical Monte Carlo (GCMC) screening of nearly 3000 existing MOF materials was carried out. Initial selection assumed fixed values of pore limiting diameter (PLD) and Henry's constant for water and allowed one to preselect 764 structures. After GCMC simulations carried for 50/50 CO2/CH4 mixture, at ambient conditions (p = 1 bar, T = 298 K), and variable gas humidity (0%, 5%, 30% and 40%) the final selection revealed 13 most promising MOFs structures. We focused on analysis of the correlations between the properties of the selected MOFs and the separation selectivity. We show that the selectivity is a complex function of the porous materials characteristics and finding selective sorbent, performing well in dry and wet conditions requires careful analysis of available MOFs.
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