Síntese de óxido de grafeno a partir da pirólise do ácido cítrico: estudo da morfologia da partícula
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Data
2022-11-22
Autores
Medeiros, Marcelo José de
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Universidade Estadual Paulista (Unesp)
Resumo
Durante os últimos anos tem se estabelecido uma busca por materiais que possam ser
utilizados na nanotecnologia. Paralelamente surge na comunidade científica um grande
interesse no grafeno por suas interessantes propriedades físico-químicas e por ser um
material com potenciais aplicações em várias áreas. Basicamente o grafeno é composto por
uma monocamada de átomos carbono com características excepcionais como alta
condutividade elétrica, resistência mecânica, dentre outras. Partículas denominadas Pontos
Quânticos de Carbono (Carbon Quantum Dots) e Pontos Quânticos de Grafeno (Graphene
Quantum Dots) e seus derivados como partículas de óxido de grafeno, apresentam
propriedades de emissão de luz como, por exemplo, fluorescência, tendo diversas
aplicações atraindo olhares da comunidade científica. A obtenção de óxidos de grafeno é
possível pela pirólise do ácido cítrico (C6H8O7), que é uma molécula orgânica de baixo
custo. Neste trabalho, amostras de óxido de grafeno foram obtidas a partir da pirólise do
ácido cítrico em atmosfera inerte de gás nitrogênio a temperaturas de 750 ºC por 3, 4, 6 e 8
horas. As amostras obtidas na forma de grânulos foram dispersas em água deionizada
(2mg/ml) e submetidas à fragmentação por ultrassom de alta potência (200W) para estudo
do tamanho e morfologia de partícula em função do tempo de ultrassom. O estudo do
tamanho e morfologia de partícula foi realizado via microscopia ótica, e as análises do
tamanho de partícula em função do tempo de ultrassom foi realizado via análise de imagens
com o programa ImageJ. Amostras preparadas a 750 ºC/3 h apresentaram tamanho médio
de partícula de 650 μm, e após 1 hora de ultrassom de alta potência apresentaram tamanho
de médio de 160 μm. As demais amostras preparadas a 750 ºC por 4 , 6, e 8 h,
apresentaram tamanho médio de partícula em torno de 500 μm, e após 1 hora de ultrassom
de alta potência apresentaram tamanho de médio de 340 μm. Partículas menores que 100
μm foram observadas nas amostras 750 ºC/4 h, 6 h, e 8 h e não apresentaram diminuição de
tamanho mesmo após 3 horas de ultrassom. A amostra 750 ºC/3 h apresentou partículas de
75 μm que diminuíram para 60 μm após 3 horas de fragmentação por ultrassom.
During the last few years, a search for materials that can be used in nanotechnology has been established. At the same time, in the scientific community there is a huge interest in graphene due to its interesting physicochemical properties and because it is a material with potential applications in several areas. Basically, graphene is composed of a monolayer of carbon atoms with exceptional characteristics such as high electrical conductivity, mechanical resistance, among others. Particles called Carbon Quantum Dots (CQD) and Graphene Quantum Dots (GQD) and their derivatives such as graphene oxide particles, present light emission properties such as, for example, fluorescence, having several applications attracting looks from the scientific community. Obtaining graphene oxides is possible by pyrolysis of citric acid (C6H8O7), which is a low-cost organic molecule. In this work, samples of graphene oxide were obtained from the pyrolysis of citric acid in an inert atmosphere of nitrogen gas at temperatures of 750 oC for 3, 4, 6 and 8 hours. The samples obtained in the form of granules were dispersed in deionized water (2mg/ml) and subjected to fragmentation by high power ultrasound (200W) to study particle size and morphology as a function of ultrasound time. The study of particle size and morphology was performed via optical microscopy, and the analysis of particle size as a function of ultrasound time was performed via image analysis with the ImageJ software. Samples prepared at 750 ºC/3 h showed an average particle size of 650 μm, and after 1 hour of high power ultrasound fragmentation they showed an average particle size of 160 μm. The other samples prepared at 750 oC for 4, 6, and 8 h, showed an average particle size of around 500 μm, and after 1 hour of ultrasound fragmentation, they showed an average particle size of 340 μm. Particles smaller than 100 μm were observed in the samples 750 ºC/4 h, 6 h, and 8 h and did not show a decrease in size even after 3 hours of ultrasound. The 750 ºC/3 h sample showed 75 μm particles that decreased to 60 μm after 3 hours of ultrasound fragmentation.
During the last few years, a search for materials that can be used in nanotechnology has been established. At the same time, in the scientific community there is a huge interest in graphene due to its interesting physicochemical properties and because it is a material with potential applications in several areas. Basically, graphene is composed of a monolayer of carbon atoms with exceptional characteristics such as high electrical conductivity, mechanical resistance, among others. Particles called Carbon Quantum Dots (CQD) and Graphene Quantum Dots (GQD) and their derivatives such as graphene oxide particles, present light emission properties such as, for example, fluorescence, having several applications attracting looks from the scientific community. Obtaining graphene oxides is possible by pyrolysis of citric acid (C6H8O7), which is a low-cost organic molecule. In this work, samples of graphene oxide were obtained from the pyrolysis of citric acid in an inert atmosphere of nitrogen gas at temperatures of 750 oC for 3, 4, 6 and 8 hours. The samples obtained in the form of granules were dispersed in deionized water (2mg/ml) and subjected to fragmentation by high power ultrasound (200W) to study particle size and morphology as a function of ultrasound time. The study of particle size and morphology was performed via optical microscopy, and the analysis of particle size as a function of ultrasound time was performed via image analysis with the ImageJ software. Samples prepared at 750 ºC/3 h showed an average particle size of 650 μm, and after 1 hour of high power ultrasound fragmentation they showed an average particle size of 160 μm. The other samples prepared at 750 oC for 4, 6, and 8 h, showed an average particle size of around 500 μm, and after 1 hour of ultrasound fragmentation, they showed an average particle size of 340 μm. Particles smaller than 100 μm were observed in the samples 750 ºC/4 h, 6 h, and 8 h and did not show a decrease in size even after 3 hours of ultrasound. The 750 ºC/3 h sample showed 75 μm particles that decreased to 60 μm after 3 hours of ultrasound fragmentation.
Descrição
Palavras-chave
Óxido de grafeno, Fragmentação ultrassônica, Morfologia de partícula, Tamanho de partícula, Microscopia óptica, Graphene oxide, Ultrasonic fragmentation, Particle morphology, Particle size, Optical microscopy