Dispositivos eletroquímicos baseados em nanomembranas

Author(s)

Letícia Mariê Minatogau Ferro

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2022-03-11

Examining board members

Carlos César Bof Bufon; William Reis de Araujo; Ivo Milton Raimundo Júnior; Neri Alves; Cecília de Carvalho Castro e Silva

• Advisor: Carlos César Bof Bufon

Abstract

Hollow structures have attracted the increasing attention of the scientific community due to their unique properties. Features such as low density, high surface-to-volume ratio, and short mass and charge transport length have made the hollow structures excellent candidates for several applications. The rolling origami technology is a controllable way to obtain these structures. In this approach, nanomembranes (NMs) composed of nanometric films are deposited, and these systems have a strain gradient between their surfaces. The deposition is carried out on a sacrificial layer (SL) that is subsequently removed in solution. Accordingly, the NM is released from the substrate as the SL is selectively removed, so the tension of the NM films begins to relax. This leads to the NM self-rolling to form a microtube. The hollow architecture confines the electrolyte and allows the performance of electrochemical analyses within it. Thus, the development of miniaturized electrochemical devices based on self-rolled NMs is proposed in this project, including electrochemical cells (ECs) and organic electrochemical transistors (OECTs). The devices were miniaturized by microfabrication processes and characterized by electrical and electrochemical measurements. In brief, the proposed devices had three electrical terminals, so-called working, pseudo-reference, and counter electrodes, when configured as ECs, or drain, source, and gate, when characterized as OECTs. In addition, an organic semiconductor thin film connected two terminals of the OECTs. Furthermore, two distinct architectures were patterned for each device (EC and OECT), and their performances were compared to each other. The first architecture was composed of planar electrodes and the second one had the electrodes patterned on the inner walls of the rolled-up NM. Thus, the main difference between the architectures was the confinement of the active region of ECs or OECTs provided by the NM, while planar devices could be considered open systems. The morphology of ECs and OECTs and the topography of their components were analyzed by optical, confocal laser, scanning electron, and atomic force microscopies. Despite the small dimensions of the tubular devices, they exhibited improved electrical and electrochemical responses than their planar counterparts. The confined environment allowed picoliter sampling volume analyses, intensified the system's electric field, the ion diffusion processes in ECs, and the intrinsic gain for the OECTs. Finally, due to such improvements, the self-rolled devices were applied as sensors for biomolecules nicotinamide adenine dinucleotide and dopamine in solution, which are biomarkers associated with human neurodegenerative diseases (AU)

• FAPESP's process: 17/21117-4 - Development and characterization of nanomembrane-based electrochemical cells for biosensor application
• Grantee: Letícia Mariê Minatogau Ferro
• Support Opportunities: Scholarships in Brazil - Doctorate