Phosphorescent Carbon Dots; Synthesis, Characterization, and Applications — 48a —Karolina Dobiecka, Weichao Liu

Bioimaging is a method that can visualize, isolate, and get deeper insights into targeted cellular tissue. Traditional bioimaging materials consist of optical nanomaterials that emit fluorescence. However, conventional fluorescent probes are limited by specific fluorescent emission, penetration depth, and the need for an excitation source. On the other hand, phosphorescent nanoparticles are promising materials for bioimaging due to the elimination of an excitation source. Notably, red phosphorescence presents advantages such as deeper tissue penetration and a longer emission window. However, typical phosphorescence materials have problems such as low biocompatibility, requiring extensive synthesis, and vulnerability to quenching. Carbon Dots have advantages such as biocompatible capability and size, synthesis methods that are less extensive or demanding, and the potential to show phosphorescence. Herein, we’ve developed a phosphorescent carbon nanodot, synthesized from ethylenediamine and phosphoric acid through a microwaved-assisted method (CDs). Subsequently, we embedded our carbon dots in a silica matrix via a Stöber process to prevent quenching (CDs@SiO2). We also explored the addition of three dyes into the silica matrix to achieve red emission through energy transfer. We first characterized all our CDs and CDs@SiO2 and verified their excitation and emission wavelengths for luminescence and phosphorescence. Then, throughout our research, we discovered that our CDs@SiO2 are less than 10 nm in size, retain a negative zeta potential, and are pH-responsive. Finally, our CDs exhibit luminescence and phosphorescence in the solid state exposed to air and alternative solvents. These results can further indicate the steps needed to develop a red phosphorescent nanomaterial that can be applied to future bioimaging or other possible applications.

University of South Dakota
Steven Wu