Identification of mono-and few- layer graphene: Raman study

International audienceIn this theoretical work, the Raman spectra were analyzed by considering the origin of the G peak, its shape, position and relative intensity as a function of the number of graphene layers. By using the spectral moment's method, the Raman spectra of mono, bi and few-layers of graphene are calculated and a good agreement was found with group theory concerning the number of the Raman-active modes and the Raman measurements. Our results provide a Raman analysis to evaluate the number of layers in multilayer graphene

Real Time Weed Detection using a Boosted Cascade of Simple Features

Weed detection is a crucial issue in precision agriculture. In computer vision, variety of techniques are developed to detect, identify and locate weeds in different cultures. In this article, we present a real-time new weed detection method, through an embedded monocular vision. Our approach is based on the use of a cascade of discriminative classifiers formed by the Haar-like features. The quality of the results determines the validity of our approach, and opens the way to new horizons in weed detection

Infrared-active phonons in carbon nanotubes

The aim of the present paper is to identify the main infrared vibrational features of carbon nanotubes. In this goal, infrared experiments have been performed on different well-characterized single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) as well as graphite and carbon aerogel. The comparison between the experimental spectra measured on these different samples allows us to identify the infrared-active modes of carbon nanotubes. In SWCNTs, the tangential modes are located around 1590 cm−1 and the radial mode around 860 cm−1. This latter mode vanishes in the infrared spectrum of DWCNTs. Finally, in the infrared spectra of all the carbon nanotubes investigated, a band around 1200 cm−1 is evidenced and assigned to the D-band (disorder-induced band)

Materials Materials and and Devices Devices CONFERENCE VOLUME (ISPDS2)

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Proceedings of the International Conference on Advanced Materials, Microscopy and Energy (ICAMME’19)

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Mechanical coupled vibrations in an individual double-walled carbon nanotube

In this paper we calculate the Raman spectra of different double-walled carbon nanotubes (DWCNTs) by using the spectral moments method. Using a convenient Lennard-Jones expression of the van der Waals intermolecular interaction between the inner and outer tubes, the optimized structures of DWCNT are derived. We found that the C-C bond length in DWCNT is depending on the metallic (M) or semiconducting (Sc) character of the inner and outer nanotubes. We show that the radial breathing-like modes (RBLM) of DWCNT are characterized by concerted inner and outer wall motions. Comparison with Raman spectra measurements is given

Structure and Raman Spectra of C60 and C70 Fullerenes Encased into Single-Walled Boron Nitride Nanotubes: A Theoretical Study

International audienceWe report the structures and the nonresonant Raman spectra of hybrid systems composed of carbon fullerenes (C60 and C70) encased within single walled boron nitride nanotube. The optimal structure of these systems are derived from total energy minimization using a convenient Lennard-Jones expression of the van derWaals intermolecular potential. The Raman spectra have been calculated as a function of nanotube diameter and fullerene concentration using the bond polarizability model combined with the spectral moment method. These results should be useful for the interpretation of the experimental Raman spectra of boron nitride nanotubes encasing C60 and C70 fullerenes

C60 Filling Rate in Carbon Peapods: A Nonresonant Raman Spectra Analysis

International audienceWe calculated the nonresonant Raman spectra of C60 peapods to determine the concentration of C60 fullerenes inside single-walled carbon nanotubes. We focus on peapods with large diameters for which C60 molecules can adopt a double helix configuration or a two-molecule layer configuration. Our calculations are performed within the framework of the bond-polarizability model combined with the spectral moment’s method. The changes in the Raman spectra as a function of C60 filling rate and the configuration of C60 molecules inside the nanotubes are identified and discussed. Our calculations support the experimental method proposed by Kuzmany to evaluate the concentration of C60 molecules inside nanotubes