Carbon nanodots (CNDs) are a subset of the group of zero-dimensional carbon particles at size below 10 nm. CNDs contain a mixture of graphitic and diamond-like core surrounded with a variety of functional groups such as –OH, –CO, –COOH, –C=C, –NH<sub>2</sub> depending on the precursor materials and synthetic methods (bottom up or top-down). Since their discovery, there have been many proposed applications for CNDs including bioimaging, drug delivery, solar cells, electrocatalysis and so on, due to their superior solubility, biocompatibility, tunable photoluminescence, and flexibility for structure and composite manipulation. However, there are controversial debates on the understanding of the origins of optoelectronic properties such as the fluorescence, photocatalysis and antioxidation. This report presents our recent results of CNDs on the optoelectronic properties and in photoelectric and bio- applications. Firstly, a new combined fluorescence-electrochemical approach is used to investigate optoelectronic properties of CNDs. Optical and electrochemical measurements along with the Hückel level calculations are applied to study the energy gap of CNDs which explains the origin of excitation wavelength dependent fluorescence of CNDs. The wavelength dependence of the photocurrent generation of immobilized CNDs is examined to assess the potential application in photoelectric devices. Secondly, a variety types of CNDs, by doping the nitrogen and/or sulfur or modifying the surface functional groups, are synthesized to study the structure-function relations and bio-applications focusing on antioxidation capacity in radical scavenging. A few antioxidation assays, including photo-spectroscopy of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, electrochemistry of DPPH, and lucigenin-CL assay for reactive oxygen species (ROS) produced through the xanthine/xanthine oxidase (XO) reaction, are used for the antioxidant capacity evaluation. The reaction pathways of the antioxidation of CNDs are proposed correlating to the structures of CNDs in the radical scavenging reactions. These findings provide new perspectives and knowledge on the structure-properties of CNDs and should aid in their development for practical use in photoelectric devices and biomedicines.

Carbon nanodots (CNDs): Fundamentals of the optoelectronic properties and antioxidation

2019 Spring National Meeting

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