Synthesis of carbon dots from polyurethane and natural rubber for metal ion sensing and energy storage applications

Carbon dots are a new class of carbon-based materials, having interesting chemical, physical and biological properties. Due to these unique properties, they have been used in many applications, for example, bio-imaging probes, drug and gene delivery, sensors, fluorescent ink, optoelectronic devices, and photocatalysis. In this thesis, the carbon dots were synthesized through pyrolysis and hydrothermal methods from polyurethane and natural rubber as carbon-based precursors. The prepared carbon dots from polyurethane and natural rubber were used for metal ion sensing because oftheir selective binding ability with selected metal ions. In addition, the carbon dots will be applied for supercapacitor application. Zinc oxide is a metal oxide that is a promising candidate as the electrode of supercapacitors via redox reaction and Faradaic processes. However, it still has the shortcomings of poor performance because of its slow faradicreaction and low electron transportability at high current. The carbon dots are pseudocapacitivematerials because of the presence of heteroatoms whereas zinc oxide can generate oxygen-containing groups to enhance the charge storage by redox reactions. Moreover, carbon dots were modified using gamma irradiation in the presence of ethylenediamine to introduce surface passivation by ammonium groups in the carbon dot structure. Therefore, the gamma-irradiated carbon dots and zinc oxide will be used to fabricate the composite electrodes in order to improve performances in supercapacitors. In summary, this thesis will demonstrate the versatility of carbon dots and their unique properties in various applications.