Carbon Quantum Dots—A Sustainable Nanoplatform in Sensing and Energy Applications

significant interest for the development of novel applications in the physical and life sciences. This is especially true for luminescent nanoparticles, which have been investigated for the development of sensors, imaging/diagnostic probes, display and solar cell applications. Recently, a relatively new class of luminescent nanomaterials, namely carbon dots, has come to light. Carbon dots, sometimes known as carbongenic dots, are carbon, oxygen, nitrogen and hydrogen containing materials with the first two elements typically accounting for ~90% of their elemental composition. Moreover, they are water dispersible and can be prepared from an abundant number of inexpensive sources including small molecules such as citric acid, amino acids, sugars and even waste. While they are small in size (typically 1-10 nm), they can offer a high quantum yield of fluorescence, a process that is controlled through passivation of the surface with an organic reagent. Of particular interest are their optical properties, which can be tailored via careful selection of the starting precursors and the desired synthesis route resulting in the ability to generate fluorescence from the blue to the near infrared regions of the spectrum. In addition to their versatile optical properties, these carbon dots are generally known to have low cytotoxicity and good biocompatibility. Combined with their small size and versatile optical properties, developing carbon dots as a nanoplatform can be achieved as these nanodots lend themselves for integration in a myriad of applications most notably in sensing and catalysis, among others. Our work focuses on achieving a fundamental understanding of the synthesis of these carbon dots in order to control their size and achieve homogenous surface chemistry and optical properties. We take advantage of the large surface area to volume ratio and study their binding to heavy metals in water in an effort to develop novel environmental sensing tools. Finally, we exploit their surface chemistry and study their catalytic behaviour in the transformation of refined and waste oils to clean biofuel.