Graphene-derived materials attract a great deal of attention because of the peculiar properties that make them suitable for a wide range of applications. Among such materials, nano-sized systems show very interesting behaviour and high reactivity. Often such materials have unpaired electrons that make them suitable for electron paramagnetic resonance (EPR) spectroscopy. In this work we study by continuous wave and pulse EPR spectroscopy undoped and nitrogen-doped graphene quantum dots (GQD) with a size of about 2 nm. The analysis of the spectra allows identifying different types of paramagnetic centers related to electrons localized on large graphenic flakes and molecular-like radicals. By hyperfine spectroscopies on nitrogen-doped samples, we determine the hyperfine coupling constant of paramagnetic centers (limited-size π-delocalized unpaired electrons) with dopant nitrogen atoms. The comparison of the experimental data with models obtained by density functional theory (DFT) calculations supports the interpretation of doping as due to the insertion of nitrogen atoms in the graphene lattice. The dimension of the delocalized regions in the flakes observed by pulse EPR is of about 20–25 carbon atoms; the nitrogen dopant can be classified as pyridinic or graphitic.

N-Doped Graphene Oxide Nanoparticles Studied by EPR

Tampieri, Francesco
Investigation
;
Tommasini, Matteo
Software
;
Agnoli, Stefano
Writing – Review & Editing
;
Favaro, Marco
Writing – Review & Editing
;
Barbon, Antonio
Supervision
2020

Abstract

Graphene-derived materials attract a great deal of attention because of the peculiar properties that make them suitable for a wide range of applications. Among such materials, nano-sized systems show very interesting behaviour and high reactivity. Often such materials have unpaired electrons that make them suitable for electron paramagnetic resonance (EPR) spectroscopy. In this work we study by continuous wave and pulse EPR spectroscopy undoped and nitrogen-doped graphene quantum dots (GQD) with a size of about 2 nm. The analysis of the spectra allows identifying different types of paramagnetic centers related to electrons localized on large graphenic flakes and molecular-like radicals. By hyperfine spectroscopies on nitrogen-doped samples, we determine the hyperfine coupling constant of paramagnetic centers (limited-size π-delocalized unpaired electrons) with dopant nitrogen atoms. The comparison of the experimental data with models obtained by density functional theory (DFT) calculations supports the interpretation of doping as due to the insertion of nitrogen atoms in the graphene lattice. The dimension of the delocalized regions in the flakes observed by pulse EPR is of about 20–25 carbon atoms; the nitrogen dopant can be classified as pyridinic or graphitic.
File in questo prodotto:
File Dimensione Formato  
AMR_GQD_Ndoped_accept.pdf

accesso aperto

Descrizione: open access
Tipologia: Published (publisher's version)
Licenza: Creative commons
Dimensione 1.03 MB
Formato Adobe PDF
1.03 MB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3355170
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 5
  • ???jsp.display-item.citation.isi??? 4
social impact