title: Direct Drawing Method of Graphite onto Paper for High-Performance Flexible Electrochemical Sensors.
abstract: A simple and fast fabrication method to create high-performance pencil-drawn electrochemical sensors is reported for the first time. The sluggish electron transfer observed on bare pencil-drawn surfaces was enhanced using two electrochemical steps: first oxidizing the surface and then reducing it in a subsequent step. The heterogeneous rate constant was found to be 5.1 × 10-3cm s-1, which is the highest value reported so far for pencil-drawn surfaces. We mapped the origin of such performance by atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Our results suggest that the oxidation process leads to chemical and structural transformations on the electrode surface. As a proof-of-concept, we modified the pencil-drawn surface with Meldola's blue to electrocatalytically detect nicotinamide adenine dinucleotide (NADH). The electrochemical device exhibited the highest catalytic constant (1.7 × 105L mol-1s-1) and the lowest detection potential for NADH reported so far in paper-based electrodes.
authors.affiliation: Brazilian Nanotechnology National Laboratory (LNNano), CNPEM , 13083-970 Campinas, Brazil.
authors.forename: Murilo
authors.identifier: http://orcid.org/0000-0002-9146-9677
authors.initials: M
authors.lastname: Santhiago
authors.affiliation: Brazilian Nanotechnology National Laboratory (LNNano), CNPEM , 13083-970 Campinas, Brazil.
authors.forename: Mathias
authors.identifier: http://orcid.org/0000-0003-0296-0956
authors.initials: M
authors.lastname: Strauss
authors.affiliation: Brazilian Nanotechnology National Laboratory (LNNano), CNPEM , 13083-970 Campinas, Brazil.
authors.forename: Mariane P
authors.initials: MP
authors.lastname: Pereira
authors.affiliation: Brazilian Nanotechnology National Laboratory (LNNano), CNPEM , 13083-970 Campinas, Brazil.
authors.forename: Andréia S
authors.initials: AS
authors.lastname: Chagas
authors.affiliation: Brazilian Nanotechnology National Laboratory (LNNano), CNPEM , 13083-970 Campinas, Brazil.|Institute of Chemistry (IQ), UNICAMP , 13083-970 Campinas, Brazil.|Institute of Physics "Gleb Wataghin" (IFGW), UNICAMP , 13083-859 Campinas, Brazil.
authors.forename: Carlos C B
authors.initials: CC
authors.lastname: Bufon
keywords: carbon electrodes; direct transfer method; electrocatalytic detection; nanodebris; paper-based devices