title: Breakdown into nanoscale of graphene oxide: confined hot spot atomic reduction and fragmentation.
abstract: Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedical applications due to its small size, intrinsic optical properties, large specific surface area, and easy to functionalize. To fully exploit nano-GO properties, a reproducible method for its production is of utmost importance. Herein we report, the study of the sequential fracture of GO sheets onto nano-GO with controllable lateral width, by a simple, and reproducible method based on a mechanism that we describe as a confined hot spot atomic fragmentation/reduction of GO promoted by ultrasonication. The chemical and structural changes on GO structure during the breakage were monitored by XPS, FTIR, Raman and HRTEM. We found that GO sheets starts breaking from the defects region and in a second phase through the disruption of carbon bonds while still maintaining crystalline carbon domains. The breaking of GO is accompanied by its own reduction, essentially by the elimination of carboxylic and carbonyl functional groups. Photoluminescence and photothermal studies using this nano-GO are also presented highlighting the potential of this nanomaterial as a unique imaging/therapy platform.
authors.affiliation: 1] TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Gil
authors.initials: G
authors.lastname: Gonçalves
authors.affiliation: 1] TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Vila
authors.affiliation: 1] TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Igor
authors.initials: I
authors.lastname: Bdikin
authors.affiliation: Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, E-28049 Madrid, Spain.
authors.forename: Alicia
authors.initials: A
authors.lastname: de Andrés
authors.affiliation: Department of Applied Physics and Mechanical Eng, Lulea University of Technology, Sweden.
authors.forename: Nazanin
authors.initials: N
authors.lastname: Emami
authors.affiliation: 1] Physics Department and CICECO, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Rute A S
authors.initials: RA
authors.lastname: Ferreira
authors.affiliation: 1] Physics Department and CICECO, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Luís D
authors.initials: LD
authors.lastname: Carlos
authors.affiliation: 1] TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Grácio
authors.affiliation: 1] TEMA-NRD, Mechanical Engineering Department, University of Aveiro, 3810-193 Aveiro, Portugal [2] Aveiro Institute of Nanotechnology, AIN, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Paula A A P
authors.initials: PA
authors.lastname: Marques