title: Free-Standing Networks of Core-Shell Metal and Metal Oxide Nanotubes for Glucose Sensing.
abstract: Nanotube assemblies represent an emerging class of advanced functional materials, whose utility is however hampered by intricate production processes. In this work, three classes of nanotube networks (monometallic, bimetallic, and metal oxide) are synthesized solely using facile redox reactions and commercially available ion track membranes. First, the disordered pores of an ion track membrane are widened by chemical etching, resulting in the formation of a strongly interconnected pore network. Replicating this template structure with electroless copper plating yields a monolithic film composed of crossing metal nanotubes. We show that the parent material can be easily transformed into bimetallic or oxidic derivatives by applying a second electroless plating or thermal oxidation step. These treatments retain the monolithic network structure but result in the formation of core-shell nanotubes of altered composition (thermal oxidation: Cu2O-CuO; electroless nickel coating: Cu-Ni). The obtained nanomaterials are applied in the enzyme-free electrochemical detection of glucose, showing very high sensitivities between 2.27 and 2.83 A M-1cm-2. Depending on the material composition, varying reactivities were observed: While copper oxidation reduces the response to glucose, it is increased in the case of nickel modification, albeit at the cost of decreased selectivity. The performance of the materials is explained by the network architecture, which combines the advantages of one-dimensional nano-objects (continuous conduction pathways, high surface area) with those of a self-supporting, open-porous superstructure (binder-free catalyst layer, efficient diffusion). In summary, this novel synthetic approach provides a fast, scalable, and flexible route toward free-standing nanotube arrays of high compositional complexity.
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Falk
authors.identifier: http://orcid.org/0000-0001-5279-0989
authors.initials: F
authors.lastname: Muench
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Luwan
authors.initials: L
authors.lastname: Sun
authors.affiliation: Department of Physical and Theoretical Chemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany.
authors.forename: Tintula
authors.initials: T
authors.lastname: Kottakkat
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Antoni
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Schaefer
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kunz
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Molina-Luna
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Duerrschnabel
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Kleebe
authors.affiliation: Science Faculty, Department of Chemistry, Dokuz Eylul University , Tinaztepe Kampusu, Buca, 35160 Izmir, Turkey.
authors.forename: Sevda
authors.initials: S
authors.lastname: Ayata
authors.affiliation: Department of Physical and Theoretical Chemistry, Freie Universität Berlin , Takustraße 3, 14195 Berlin, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Roth
authors.affiliation: Department of Materials and Earth Sciences, Technische Universität Darmstadt , Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ensinger
keywords: Kirkendall effect; core−shell nanostructures; electroless plating; enzyme-free glucose sensing; ion-track technology; metal nanotubes