Propriedades ópticas de óxidos de grafeno obtidos a partir da carbonização de moléculas orgânicas em diferentes atmosferas
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Data
2022-11-18
Autores
Moretti, Alessandro Maciel
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Devido a crescente busca de novos materiais para o desenvolvimento
tecnológico, os materiais a base de carbono como nanotubos de carbono e o grafeno
tem despertado grande curiosidade nas últimas décadas. Mais especificamente, os
pontos quânticos de carbono (PQC) vem gerando grande interesse pelas suas
propriedades ópticas e elétricas, com aplicações em nanomateriais, transistores,
computadores quânticos e biomedicina. Além do interesse de suas propriedades
físicas, o impulso em seu estudo e futura aplicação nas tecnologias cotidianas se deve
ao seu baixo custo, facilidade de síntese e apresentar baixa toxidade para o ambiente.
Nesse trabalho foram estudadas as propriedades ópticas de pontos quânticos de óxido
de grafeno (PQOG), formado a partir do tratamento térmico do ácido cítrico anidro
(C₆H₈O₇) em atmosfera aberta de ar com temperaturas entre 250 °C até 500 °C, e em
tempos de 2 horas até 4 horas. Foram preparados pontos quânticos de óxido de
grafeno através de um processo bottom-up de degradação térmica, e através da
espectroscopia foram analisadas suas propriedades de absorção e emissão óptica UV-
VIS. As amostras feitas até 300 °C apresentaram uma intensidade alta de
luminescência no comprimento de onda entre 450 nm e 500 nm, porém conforme o
aumento de tempo ou de temperatura a emissão óptica diminuía. Posteriormente foi
feito um novo tratamento térmico de pirólise em atmosfera de nitrogênio gasoso puro a
temperatura de 750 °C e duração de 6 horas para ocorrer uma degradação lenta das
cadeias moleculares a fim de reduzir a amostra e consolidar a estrutura de grafeno.
Através da espectroscopia Raman foi confirmada a formação de partículas de carbono
com estrutura de óxido de grafeno nesse processo de redução. Assim como as
amostras feitas em atmosfera aberta, as propriedades ópticas dessa nova amostra
foram estudadas, apresentando uma forte luminescência azul na faixa dos 430 nm.
Due to the crescent search for new materials for technological development, carbon-based materials such as carbon nanotubes and graphene have triggered great curiosity in the last decades. Specifically, carbon quantum dots (CQD) are of significant interest for their optical and electrical properties and applications such as nanomaterials, transistors, quantum computers, and biomedicine. In addition to the interest of its intrinsical physical properties, low cost, easy synthesis, and presenting low toxicity to the environment provided an impetus in its study and future application in everyday technologies. The objective of this study was to explore the optical properties of graphene oxide quantum dots (GOQD) that was sinthesized by performing a heat treatment of anhydrous citric acid (C₆H₈O₇) in an open atmosphere with temperatures between 250 °C to 500 °C, and variating time from 2 to 4 hours. Graphene oxide quantum dots were prepared through a bottom-up thermical degradation process, and their UV-VIS absorption and optical emission properties were analyzed by spectroscopy. Samples prepared up to 300 °C showed a high intensity of luminescence at the wavelength between 450 nm and 500 nm, but with increasing time or temperature, the optical emission decreased. Subsequently, a new pyrolisys heat treatment was carried out in a nitrogen atmosphere at a temperature of 750 °C for 6 hours to have a slow degradation of the molecular chains and reduce the sample to a graphene structure. The formation of graphene oxide in this process was confirmed by Raman spectroscopy, and, as well as the samples synthesized in an open atmosphere and moderate temperature, the optical properties of this new sample were studied, showing a robust blue luminescence in the range of 430 nm.
Due to the crescent search for new materials for technological development, carbon-based materials such as carbon nanotubes and graphene have triggered great curiosity in the last decades. Specifically, carbon quantum dots (CQD) are of significant interest for their optical and electrical properties and applications such as nanomaterials, transistors, quantum computers, and biomedicine. In addition to the interest of its intrinsical physical properties, low cost, easy synthesis, and presenting low toxicity to the environment provided an impetus in its study and future application in everyday technologies. The objective of this study was to explore the optical properties of graphene oxide quantum dots (GOQD) that was sinthesized by performing a heat treatment of anhydrous citric acid (C₆H₈O₇) in an open atmosphere with temperatures between 250 °C to 500 °C, and variating time from 2 to 4 hours. Graphene oxide quantum dots were prepared through a bottom-up thermical degradation process, and their UV-VIS absorption and optical emission properties were analyzed by spectroscopy. Samples prepared up to 300 °C showed a high intensity of luminescence at the wavelength between 450 nm and 500 nm, but with increasing time or temperature, the optical emission decreased. Subsequently, a new pyrolisys heat treatment was carried out in a nitrogen atmosphere at a temperature of 750 °C for 6 hours to have a slow degradation of the molecular chains and reduce the sample to a graphene structure. The formation of graphene oxide in this process was confirmed by Raman spectroscopy, and, as well as the samples synthesized in an open atmosphere and moderate temperature, the optical properties of this new sample were studied, showing a robust blue luminescence in the range of 430 nm.
Descrição
Palavras-chave
Pontos quânticos de carbono, Ácido cítrico, Grafeno, Óxido de grafeno, Pirólise, Luminescência, Nanomateriais, Espectroscopia óptica, Física, Nanopartículas, Carbon quantum dots, Citric acid, Graphene, Graphene oxide, Pyrolisys, Luminescence, Optical spectroscopy