Abstract The electronic band gap of flame-formed carbon nanoparticles (CNPs) is determined for the first time using scanning tunneling spectroscopy (STS). Flame-formed CNPs are sampled from a laminar, burner-stabilized stagnation ethylene-air flame through in-situ insertion of gold-coated mica substrates, on which CNPs are collected as thin films. Optical band gap measurements using UV-vis absorption spectroscopy are also performed to compare with the STS measurements. The suitability of STS in measuring electronic band gaps is first demonstrated through measurements using reference materials: the electronic band gaps of naphthalene, pyrene, and coronene are found to be slightly larger than the respective optical band gaps, as expected, because of the over potential in the presence of a current. Flame-formed CNPs of three different particle size distributions were sampled and tested. The electronic band gap of each CNP shows a clear size-dependency that supports the earlier conclusion (Liu et al. Proc. Natl. Acad. Sci. U.S.A. 116 (2019) 12692-12697) that flame-formed CNPs exhibit apparent quantum confinement or quantum-dot behaviors. Furthermore, the measured electronic band gaps matches the respective optical results within the experimental uncertainty of 0.1-0.2 eV. The over potential observed in PAH samples is not present in CNP sampls, which may indicate stronger intermolecular interactions between the PAHs constituting the CNPs than those of crystalline PAHs.

Electronic Band Gap of Flame-Formed Carbon Nanoparticles by Scanning Tunneling Spectroscopy

Mario Commodo;Patrizia Minutolo;
2021

Abstract

Abstract The electronic band gap of flame-formed carbon nanoparticles (CNPs) is determined for the first time using scanning tunneling spectroscopy (STS). Flame-formed CNPs are sampled from a laminar, burner-stabilized stagnation ethylene-air flame through in-situ insertion of gold-coated mica substrates, on which CNPs are collected as thin films. Optical band gap measurements using UV-vis absorption spectroscopy are also performed to compare with the STS measurements. The suitability of STS in measuring electronic band gaps is first demonstrated through measurements using reference materials: the electronic band gaps of naphthalene, pyrene, and coronene are found to be slightly larger than the respective optical band gaps, as expected, because of the over potential in the presence of a current. Flame-formed CNPs of three different particle size distributions were sampled and tested. The electronic band gap of each CNP shows a clear size-dependency that supports the earlier conclusion (Liu et al. Proc. Natl. Acad. Sci. U.S.A. 116 (2019) 12692-12697) that flame-formed CNPs exhibit apparent quantum confinement or quantum-dot behaviors. Furthermore, the measured electronic band gaps matches the respective optical results within the experimental uncertainty of 0.1-0.2 eV. The over potential observed in PAH samples is not present in CNP sampls, which may indicate stronger intermolecular interactions between the PAHs constituting the CNPs than those of crystalline PAHs.
2021
Istituto di Ricerche sulla Combustione - IRC - Sede Napoli
Istituto di Scienze e Tecnologie per l'Energia e la Mobilità Sostenibili - STEMS
Scanning tunneling spectroscopy
Electronic band gap
Optical band gap
Soot particles
Polycyclic aromatic hydrocarbons
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/380698
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