Molecular, Aromatic, and Amorphous Domains of N-Carbon Dots: Leading toward the Competitive Photoluminescence and Photocatalytic Properties

Carbon dots (CDs) have become one of most promising fluorescent materials in recent days, because of their promising photoluminescence and photocatalytic properties. However, the practical applicabilities for emissive and catalytic devices are still debatable, because of the lack of fundamental understanding behind the structure–property correlations. Herein, we have developed different types of nitrogen-doped CDs (N-CDs) by varying different nitrogen-containing precursors through a simple bottom-up based carbonization technique. Depending on the nature of nitrogen atom precursor, we are able to critically control the subpopulations of various intrinsic constituents of N-CDs, i.e., aromatic domains, amorphous domains, and small molecular fluorophores inside N-CDs. Detailed structural and elemental features have been correlated with the underpinning photophysical processes by means of steady-state and time-resolved fluorescence spectroscopy. In addition, the effect of temperature on overall photoluminescence properties has been corroborated with the internal structure of N-CDs. Finally, we have investigated the photocatalytic properties and the detailed photocatalysis mechanisms by scavenging the active species originated upon light irradiation. Results suggest that photocatalytic efficiency is maximum at a larger extent of amorphous domains and in the presence of nitrogen atoms specifically located at the edges, while photoluminescence intensity is higher at larger extent of molecular fluorophores and aromatic domains. Therefore, these fundamental investigations will open up new possibilities considering the optimizations of heteroatom functionalized CDs for their on-demand applicabilities in emitting as well as photocatalytic devices.