Banca de DEFESA: LUANA CAROLINE DE OLIVEIRA LIMA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : LUANA CAROLINE DE OLIVEIRA LIMA
DATE: 01/03/2024
TIME: 14:00
LOCAL: On-line
TITLE:

Synthesis, characterization and biological and ecotoxicological evaluation of Carbon Dots from Coffee Grounds.

KEY WORDS:

Carbon dots. Spent Coffee Grounds. Design of Experiments. Toxicity

PAGES: 118
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Inorgânica
SPECIALTY: Química Bio-Inorgânica
SUMMARY:

It is well known in the literature the need to obtain more sustainable materials for technological applications that are less aggressive to the environment, through the transformation of rejects and residues into new products. In this same face of challenge, nanotechnology of carbonaceous materials has been an attractive resource in the transformation and redefinition of disused materials. This is because, many of these rejects and residues are mostly composed of carbon, oxygen and hydrogen, whose composition is the basis to produce carbon dot nanomaterials. However, nanometric materials have become worrying, as, due to their size, they can cause toxicity to human health and the environment. Therefore, to unify these three aspects, the present work aimed to synthesize carbon dots from spent coffee grounds – (SCG) – and evaluate their toxicological potential. To this end, the CD_SCG was synthesized via pyrolysis, under an oxidizing atmosphere, temperature of 400°C for 3h, and compared under the same conditions to a standard chemical formula: Tartaric Acid (AT). The synthetic parameters (temperature and time) were studied through a factorial experiment design (Design of Experiments – DoE), considering the average relative intensity as a determining factor in choosing the optimal working condition. As a characterization of CD_SCG, particles with two emission centers were obtained, the most intense with excitation at 310 nm and quantum yield of 6%. Thermogravimetry, energy dispersive spectroscopy and X-ray analyzes showed that the material obtained presented leachable metals, typical of the nutritional composition of coffee. Both in-vitro and in-vivo toxicity tests in mice showed no toxic effect at the highest concentration 160 µg/L and 2000 mg/kg, respectively, in 24h. However, BC4 showed toxicity in the test with zebrafish embryos, in which it exhibited teratogenic effects at 250 µg/L and a harmful effect at concentrations of 500 µg/L. Based on these results, spent coffee grounds is as a promising precursor for the synthesis of carbon dots and can be used safely once biological and ecotoxicological evaluations indicated very low or no toxicity of BC4.

BANKING MEMBERS:
Presidente - 1443844 - MARCO ANTONIO SCHIAVON
Interno - 1527524 - WAGNER SOUZA MACHADO
Externo ao Programa - 2141553 - PAULO HENRIQUE DE ALMEIDA CAMPOS JUNIOR
Externa à Instituição - ELLEN RAPHAEL - UEA