Banca de QUALIFICAÇÃO: ANDERSON FERNANDO MAGALHÃES DOS SANTOS
Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.DISCENTE: ANDERSON FERNANDO MAGALHÃES DOS SANTOS
DATA: 06/03/2023
HORA: 08:30
LOCAL: forma híbrida: Auditório do PPGQ e link: meet.google.com/vcz-ahia-kpi
TÍTULO: Investigation of the effect of surface modification with organosilane on the multi-redox electrochemical behavior of Co3[Co(CN)6]2 nanocubes
PALAVRAS-CHAVES: cobalt, prussian blue analogue, silica, multi-redox, surface modification
PÁGINAS: 43
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Inorgânica
ESPECIALIDADE: Físico Química Inorgânica
RESUMO:
This work reports the successful synthesis of a new nanomaterial formed from a cobalt Prussian blue analogue, Co3[Co(CN)6]2,and an external amorphous layer (@SiO2-NH2) originated from the addition of organosilanes as tetraethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APTMS). The amount of tetraethyl orthosilicate (TEOS) (0.22, 0.33, 0.44, 0.55 and 0.67 nmol) used to prepare SiO2 NPs was varied to assess its impact in the properties of the nanomaterial. XRD analyses were consistent with the pattern for Co3[Co(CN)6]2. FTIR measurements confirmed the modification of Co3[Co(CN)6]2 nanocubes surface by the formation of SiO2, and the attachment of NH2 groups after the APTMS addition was confirmed by the ninhydrin test, since the UV-VIS analysis showed a band around 576 nm, typical of a Ruherman’s purple. TEM images showed Co3[Co(CN)6]2 nanocubes with averaging size around 110 nm, and a amorphous SiO2 layer around 15 nm thick after modification by TEOS and APTMS. The zeta potential analyses showed that the isoelectric point of Co3[Co(CN)6]2 moves to higher pH values and lower zeta potential values as the Co3[Co(CN)6]2 surface is modified by SiO2 and NH2. The Cyclic Voltammetry analyses of Co3[Co(CN)6]2@SiO2-NH2 nanomaterials showed the appearance of two redox processes as the surface of Co3[Co(CN)6]2 is modified byTEOS and APTMS, and a third oxidation process is evidenced in lower scan rates (10 mv to 50mV) as the amount of TEOS added to form the silica layer in the nanomaterial is higher than 125 μL. Co3[Co(CN)6]2@SiO2-NH2-75 μL showed the best parameters for increase in faradaic current, reversibility, surface coverage and film thickness and showed that the charge transfer process changes from a predominantly adsorptive process at low scan rates to a predominantly diffusive process at high scan rates.
MEMBROS DA BANCA:
Interno - 1714193 - JOSE MILTON ELIAS DE MATOS
Externo à Instituição - LUCYANO JEFFERSON ALVES DE MACEDO - LNLS
Interno - 2406262 - ROBERTO ALVES DE SOUSA LUZ
Presidente - 1508806 - WELTER CANTANHEDE DA SILVA