Study on the synthesis of carbon dots via hydrothermal carbonization and evaluation towards biosystems

Author(s)

Mateus Batista Simões

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2014-07-17

Examining board members

Oswaldo Luiz Alves; Adley Forti Rubira; Juliano Alves Bonacin

• Advisor: Oswaldo Luiz Alves

Abstract

The differences in observed properties considering a material in its bulk state and its nanoscale are possibly the most striking and fascinating feature of nanotechnology. Carbon dots are carbon-based nanomaterials that present fluorescence when smaller than 10 nm, but may fluoresce after treatment of its surface considering particles of the order of until 100 nm. Interestingly, the wavelength at which the fluorescence occurs is dependent on the particle size. Thus, it is possible to modulate the fluorescence controlling the size of the carbon dots, which have great potential for application in photocatalysis, bioimage, optoelectronics and sensors, being possible to functionalize these materials, aiming an application in vivo, in order to increase its biocompatibility. The hydrothermal syntheses have attracted interest for obtaining the carbon dots, being a simple, cheap and efficient technique. Moreover, it is possible to obtain materials with high homogeneity and controlled morphology and size, factors that will influence the fluorescence. Thus, the present work aimed to study the influence of the conditions of hydrothermal synthesis in the fluorescence of carbon dots, perform the functionalization of this material and evaluate the ability to in vivo use of the material by hemolytic trials. Carbon dots were obtained by hydrothermal carbonization of glucose and the synthesis parameters were optimized by a factorial design of experiments. It was observed that higher temperature and time of synthesis and a lower initial concentration of the carbon source leads to nanoparticles with a higher quantum yield (varying between 3.3 and 5.8%). The carbon dots were characterized by infrared spectroscopy, ultraviolet-visible spectroscopy, transmission electron microscopy, beyond to have its fluorescence profile studied, and it was observed that the maximum excitation occurs at the ultraviolet range and the maximum emission at the blue range of the spectrum. Hemolytic trials were performed with the nanoparticles of highest quantum yield, and the results showed that no hemolysis was provoked, demonstrating that he material have a raised potential to in vivo applications. Lastly, with the optimized synthesis parameters, carbon dots were also obtained by hydrothermal carbonization of pectin, evidencing that the synthesis protocol is robust and effectual to alternatives carbon sources. The carbon dots of pectin presented a quantum yield of 3.6% and were characterized by the same techniques utilized to the carbon dots of glucose (AU)

• FAPESP's process: 12/22612-5 - Study on the synthesis of carbon dots via hydrothermal carbonization and evaluation toward biosystems
• Grantee: Mateus Batista Simões
• Support Opportunities: Scholarships in Brazil - Master