Banca de QUALIFICAÇÃO: LUCIO CESAR DANTAS DE MEDEIROS

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : LUCIO CESAR DANTAS DE MEDEIROS
DATE: 27/02/2023
TIME: 09:30
LOCAL: Auditório do Química III
TITLE:

Action of Eucalyptus pyroligneous acid on the ecologically correct synthesis of silver nanoparticles

KEY WORDS:

wood vinegar; noble nanoparticles; nanocellulose; bactericidal effect

PAGES: 99
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Físico-Química
SPECIALTY: Química do Estado Condensado
SUMMARY:

The interest in products derived from renewable natural resources has increased in recent years. Concerning nanotechnology, the goal is to employ low-toxicity chemicals resulting from environmentally benign processes. In the present study, we demonstrated for the first time that pyroligneous acid (PA), a compound obtained from the condensation of polluting gaseous emissions generated during the pyrolysis of biomass, functioned concomitantly as  reducing and stabilizing agents in the synthesis of silver nanoparticles (AgNPs). Furthermore, this methodology was also employed for the production of a nanocomposite consisting of AgNPs anchored in cellulose nanocrystals (AgNPs/NC). Through chromatographic analysis (GC-MS) and Raman spectroscopy, it was shown that in alkaline medium oxygenated species contained in PA reduced silver ions to their metallic form. Concomitantly, acetic acid, abundantly present in PA, adsorbed on the surface of AgNPs conferring them electrostatic stability. The AgNPs werespherical in shape with an average size of 16.42 ± 4.62 nanometers, being stable for at least 150 days (zeta potential = -56 mV). In the production of the AgNPs/NC nanocomposite, it was observed that the time for the total stabilization of the AgNPs was drastically shortened and   the average size substantially reduced (5.12 ± 1.59 nanometers). Thermogravimetric experiments demonstrated that the impregnation efficiency of AgNPs in cellulose nanocrystals was greater than 95%. Finally, AP showed activity against Escherichia coli and Staphylococcus aureus bacteria only at its original pH (pH ~ 2.8). However, upon neutralization (pH = 7.5) the bactericidal activity vanished completely. As demonstrated, the actual responsible for the bactericidal effect was acetic acid. When applied at neutral pH, AgNPs and AgNPs/NC showed bacteriostatic activities similar to those reported in the literature. Based on this information, it is concluded that the use of pyroligneous acid in the synthesis of silver nanomaterials is an interesting and promising approach.

COMMITTEE MEMBERS:
Interno - 1198847 - JOSE LUIS CARDOZO FONSECA
Presidente - 1958858 - LUIZ HENRIQUE DA SILVA GASPAROTTO
Externo ao Programa - 3304576 - RODOLFO LUIZ BEZERRA DE ARAÚJO MEDEIROS - null