Banca de QUALIFICAÇÃO: THALITA MEDEIROS BARROS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : THALITA MEDEIROS BARROS
DATE: 24/11/2023
TIME: 09:00
LOCAL: VIRTUAL
TITLE:

Synthesis of graphite sheets by chemical vapor deposition and their application as an electrochemical sensor for pharmacological quantification

KEY WORDS:

Chemical vapor deposition, graphite sheets, caffeine

PAGES: 95
BIG AREA: Engenharias
AREA: Engenharia Química
SUBÁREA: Tecnologia Química
SUMMARY:

Graphite-based electrochemical sensors are widely applied in the most diverse fields of electrochemistry, such that innovations related to this material gain prominence in the scientific world. With this in mind, in order to obtain a disposable, utilitarian, green, and low-cost electrode, the synthesis of graphitic films on a micrometric scale was proposed through the pyrolysis of toluene, thus producing graphite microsheets. The chemical vapor deposition synthesis process is advantageous as it does not require the use of metal catalysts, substrates, vacuum, plasma, or hydrogen flow. In order to characterize the graphite microsheets as a working electrode, the morphological and physical-chemical characterization of the material was carried out using analytical techniques such as SEM, MET, FTIR, XRD, RAMAN, and contact angle. For a more in-depth characterization from an electrochemical point of view, the conformation of the electrode profile was evaluated in different redox probes (Hexacyanoferrate (III) and Hexamin Ruthenium (III), as well as their behavior in neutral,)alkaline, and acidic media. Furthermore, the electroactive area of the graphite microsheet electrode was evaluated, as was a study on its impedance, in order to compare it with the impedance of the glassy carbon electrode, already consolidated in the literature. Aiming to investigate the applicability of the graphite microsheet electrode in electroanalysis, the detection and quantification of caffeine in different types of commercial drinks were carried out. The results obtained clearly indicate that the graphite sensor presents a linear response over a wide range of caffeine concentrations (0.68-1477.26 µM), with R2 of 0.99. The limit of detection (LOD) estimated at 6.17 µM suggests greater sensitivity and reproducibility than the conventional graphite sensor. The low-cost disposable graphite microsheet electrode was successfully applied to determine caffeine in soft drinks, energy drinks, and black tea, presenting well-defined current signals in the analysis of real samples in the presence of 0.5M H2SO4 as an electrolyte. When comparing electrochemical determinations and high-performance liquid chromatography measurements, no significant differences were observed (standard deviation of about 4%), therefore, with these results, it is possible to highlight the potential use of this sensor as a new, disposable, portable analytical tool that is reliable, low-cost, and efficient to determine caffeine in different types of samples.

COMMITTEE MEMBERS:
Interna - 2275848 - ELISAMA VIEIRA DOS SANTOS
Interno - 2941160 - JOSE HERIBERTO OLIVEIRA DO NASCIMENTO
Interna - ***.673.134-** - JUSSARA CÂMARA CARDOZO - UFRN
Externo ao Programa - 1645110 - CARLOS ALBERTO MARTINEZ HUITLE - UFRN