title: Facile synthesis of water-soluble carbon nano-onions under alkaline conditions.
abstract: Carbonization of tomatoes at 240 °C using 30% (w/v) NaOH as catalyst produced carbon onions (C-onions), while solely carbon dots (C-dots) were obtained at the same temperature in the absence of the catalyst. Other natural materials, such as carrots and tree leaves (acer saccharum), under the same temperature and alkaline conditions did not produce carbon onions. XRD, FTIR, HRTEM, UV-vis spectroscopy, and photoluminescence analyses were performed to characterize the as-synthesized carbon nanomaterials. Preliminary tests demonstrate a capability of the versatile materials for chemical sensing of metal ions. The high content of lycopene in tomatoes may explain the formation of C-onions in alkaline media and a possible formation mechanism for such structures was outlined.
authors.affiliation: Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, c/Julián Clavería, 8. Oviedo, 33006, Spain; Chemistry Department, Faculty of Science, Damanhour University, Damanhour, Egypt.
authors.forename: Gaber Hashem Gaber
authors.initials: GH
authors.lastname: Ahmed
authors.affiliation: Chemistry Department, Faculty of Science, Damanhour University, Damanhour, Egypt.
authors.forename: Rosana Badía
authors.initials: RB
authors.lastname: Laíño
authors.affiliation: Chemistry Department, Faculty of Science, Damanhour University, Damanhour, Egypt.
authors.forename: Josefa Angela García
authors.initials: JA
authors.lastname: Calzón
authors.affiliation: Chemistry Department, Faculty of Science, Damanhour University, Damanhour, Egypt.
authors.forename: Marta Elena Díaz
authors.initials: ME
authors.lastname: García
keywords: carbon dots; carbon onions; metal-ion sensing; photoluminescence; thermal carbonization