Direct drawing method of graphite onto paper for high-performance flexible electrochemical sensors

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP-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: fiA 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 × 10−3 cm 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 × 105 L mol−1 s−1) and the lowest detection potential for NADH reported so far in paper-based electrodes.9131195911966CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP483550/2013-22009/54066-72013/22127-22014/25979-2The authors acknowledge CNPq (Project 483550/2013-2) and FAPESP (Project 2013/22127-2 and 2014/25979-2) for the financial support. We would like to thank the National Center for Research in Energy and Materials (CNPEM) and Brazilian Nanotechnology National Laboratory (LNNano). We also thank Davi H. S. de Camargo, Catia C. Correa, and Evandro M. Lanzoni (LCS) for their valuable help. The authors would like to thank the Laboratory of Advanced Optical Spectroscopy (LMEOA/IQ-UNICAMP/FAPESP Grant 2009/54066-7) for the Raman analysis. All authors contributed equally to this work