title: The effect of the degree of oxidation on broadband nonlinear absorption and ferromagnetic ordering in graphene oxide.
abstract: We report on the effect of the degree of oxidation on the broadband non-linear optical response and magnetic behavior of graphene oxide, as well as on a route for obtaining reduced graphene oxide with enhanced optical properties without sacrificing the high dispersibility of the parent graphene oxide. As more sp(3) states evolved with the rise in oxidation degree, it turned out that the sp(2)/sp(3) fraction and sp(2) clustering are crucial parameters for tuning the broadband non-linear optical absorption over a wide range from ps to ns laser pulses for both visible and infrared laser irradiation. This was clearly confirmed by two different approaches, namely by a synthetic route through the gradual oxidation of graphene oxide from 1 to 3 oxidizing cycles, and reversely by in situ reduction of graphene oxide by UV laser irradiation. Furthermore, as the sp(3) states carry localized magnetic moments, ferromagnetic ordering is observed at low temperatures. The magnetization and temperature at which ferromagnetic ordering evolves are found to increase on increasing the oxidation degree. The tuning of non-linear optical and magnetic properties of graphene oxide by oxidation/reduction thus provides an easy way to endow graphene oxide with tunable physical features highly required in both optoelectronics and spintronics applications.
authors.affiliation: Department of Physics, University of Patras, 26504 Patras, Greece. couris@physics.upatras.gr and Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1414, Patras 26504, Greece.
authors.forename: Nikos
authors.initials: N
authors.lastname: Liaros
authors.affiliation: Regional Centre of Advanced Technologies & Materials, Departments of Physical Chemistry and Experimental Physics, Faculty of Science, Palacky University, 17, listopadu 1192/12, 771 46 Olomouc, Czech Republic. radek.zboril@upol.cz.
authors.forename: Jiri
authors.initials: J
authors.lastname: Tucek
authors.affiliation: Department of Materials Science and Engineering, University of Ioannina, 45110, Ioannina, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Dimos
authors.affiliation: Regional Centre of Advanced Technologies & Materials, Departments of Physical Chemistry and Experimental Physics, Faculty of Science, Palacky University, 17, listopadu 1192/12, 771 46 Olomouc, Czech Republic. radek.zboril@upol.cz and Department of Materials Science, University of Patras, 26504 Patras, Greece.
authors.forename: Aristides
authors.initials: A
authors.lastname: Bakandritsos
authors.affiliation: Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1414, Patras 26504, Greece and Department of Materials Science, University of Patras, 26504 Patras, Greece.
authors.forename: Konstantinos S
authors.initials: KS
authors.lastname: Andrikopoulos
authors.affiliation: Department of Materials Science and Engineering, University of Ioannina, 45110, Ioannina, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Gournis
authors.affiliation: Regional Centre of Advanced Technologies & Materials, Departments of Physical Chemistry and Experimental Physics, Faculty of Science, Palacky University, 17, listopadu 1192/12, 771 46 Olomouc, Czech Republic. radek.zboril@upol.cz.
authors.forename: Radek
authors.initials: R
authors.lastname: Zboril
authors.affiliation: Department of Physics, University of Patras, 26504 Patras, Greece. couris@physics.upatras.gr and Institute of Chemical Engineering Sciences (ICE-HT), Foundation for Research and Technology-Hellas (FORTH), P.O. Box 1414, Patras 26504, Greece.
authors.forename: Stelios
authors.initials: S
authors.lastname: Couris