Banca de QUALIFICAÇÃO: THALITA MEDEIROS BARROS

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : THALITA MEDEIROS BARROS
DATE: 30/01/2024
TIME: 14:00
LOCAL: VIRTUAL
TITLE:

DEVELOPMENT, CHARACTERIZATION AND APPLICATION OF A NEW GRAPHITE SHEET ELECTRODE OBTAINED BY CHEMICAL STEAM DEPOSITION FOR ELECTROCHEMICAL DETERMINATION OF CAFFEINE

KEY WORDS:

Electrochemistry, caffeine, electrode characterization, graphite, graphene.

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, versatile, environmentally friendly and low-cost electrode, the synthesis of graphitic films on a micrometric scale was proposed through the pyrolysis of Toluene. The Chemical Vapor Deposition (CVD) synthesis process applied in this work is advantageous as it does not require the use of metal catalysts, substrates, vacuum, plasma or hydrogen flow, which are necessary when it comes to traditional CVD synthesis. In order to characterize the graphite microsheets as a working electrode, morphological and physical-chemical characterizations of the material were carried out using techniques such as: Scanning Electron Microscopy, Transmission Electron Microscopy, Fourier Transform Infrared Spectroscopy, Energy Dispersive X-rays, X-ray Diffraction, Raman Spectroscopy and Contact Angle (Θ = 95.69°). For a more in-depth characterization from an electrochemical point of view, the electrochemical behavior was evaluated in the presence of 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, estimated at 0.083 cm2. Electrochemical Impedance Spectroscopy was carried out with the aim of evaluating the resistance to charge transfer that the electrode offers. Aiming to investigate the applicability of the graphite microsheet electrode in electroanalysis, the detection and quantification of caffeine in different types of commercial drinks was carried out. The results obtained clearly indicate that the graphite foil electrode 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) is estimated at 0.68 µM, which suggests greater sensitivity and reproducibility than other conventional sensors, such as Glassy Carbon, Boron-doped Diamond Electrodes, for example. The low-cost disposable graphite sheet electrode was successfully applied to the determination of 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 electrolyte. When comparing electrochemical determinations and high-performance liquid chromatography measurements, it was observed the absence of discrepant values between both techniques. With these results, it is possible to highlight the potential use of this sensor as an analytical tool, disposable, portable, reliable, low-cost and high efficiency to determine caffeine in different types of samples.

COMMITTEE MEMBERS:
Presidente - 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