Banca de DEFESA: LEONARDO HIDEKI HASIMOTO
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.DISCENTE : LEONARDO HIDEKI HASIMOTO
DATA : 18/03/2022
HORA: 14:00
LOCAL: remota
TÍTULO:
Functionalization of paper-based electrochemical devices with polydopamine
PÁGINAS: 97
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Eletroanalítica
RESUMO:
Flexible devices based on paper and carbon have been applied in the development of electrochemical sensors and devices in the energy area and have gained notoriety due to their simplicity and ease of manufacture. However, although these devices have a wide range of application, they can be limited in some cases, requiring functionalization steps to ensure greater versatility, selectivity and stability, to name a few advantages. Since the discovery of polydopamine, this material has been widely explored in the area of materials science due to its great adhesive capacity, however, little attention has been given to the preparation of functionalized surfaces for the fabrication of flexible paper-based devices. In this work, the fabrication of flexible high-performance electrochemical devices made from cheap and common materials such as office paper and commercial pencil and their functionalization with polydopamine is presented. Initially, working electrodes were prepared using the direct transfer method (pencil-drawing) and were subjected to electrochemical treatment processes to improve the electron transfer kinetics. Then, polydopamine was formed on the surface of the working electrode using the chemical polymerization route. Polydopamine films (6 nm thickness) on carbon were characterized by contact angle, X-ray photoelectron spectroscopy, scanning electron microscopy, confocal microscopy, atomic force microscopy (topography and electrical measurements) and electrochemical techniques. After the functionalization process, it was observed that the presence of the polydopamine film introduces oxygen and nitrogen-rich chemical functionalities (such as R-NH2 and R-C=O) that decrease the contact angle from 72° to 48°. As verified by scanning electron microscopy and confocal microscopy, the electrochemical treatment process causes the formation of microcracks that increase the surface roughness. Topographic mapping by atomic force microscopy revealed a difficulty in obtaining contrast after polydopamine film formation due to the high roughness of the carbon surface and small thickness of the functionalizing film. Simultaneous capacitance gradient mapping, on the other hand, clearly revealed the presence of a film that hinders the capacitive coupling (approximately 50% decrease). However, as noted, the polydopamine film does not block heterogeneous electron transfer. In fact, one of the largest standard heterogeneous rate constants for paper-based electrodes (2.5 x 10-3 cm s-1) was observed, which is an essential parameter to obtain higher currents. In addition, the obtained results suggest that carbonyl functionalities are related to the electroactivity of the formed film. As a proof of concept, electro-oxidation of a biologically relevant molecule, nicotinamide adenine dinucleotide, showed remarkable features such as lower oxidation potential, electrocatalytic peak currents more than 30 times higher when compared to unmodified electrodes and electrocatalytic constant of 8.2 x 102 L mol-1 s-1.
MEMBROS DA BANCA:
Presidente - Interno ao Programa - 050.966.059-22 - MURILO SANTHIAGO - CNPEM
Membro Titular - Examinador(a) Interno ao Programa - 1544341 - WENDEL ANDRADE ALVES
Membro Titular - Examinador(a) Externo à Instituição - RODRIGO ALEJANDRO ABARZA MUNOZ - UFU
Membro Suplente - Examinador(a) Interno ao Programa - 2605463 - JOSE ANTONIO SOUZA
Membro Suplente - Examinador(a) Interno ao Programa - 007.041.553-62 - RENATO SOUSA LIMA - UNICAMP
Membro Suplente - Examinador(a) Externo à Instituição - MAURO BERTOTTI - USP
Membro Suplente - Examinador(a) Externo à Instituição - CAMILA MARCHETTI MARONEZE - UPM