Structural Elucidation of Photoluminescent Carbon Nanodots through Quenching Kinetics with Molecular Electron Donors and Acceptors

Photoluminescence (PL) quenching mechanism and dynamics of carbon nanodots (CNDs) with molecular electron donors and acceptors are investigated by means of time-resolved emission spectroscopy. CNDs are prepared by direct pyrolysis from two different precursors, di-ammonium citrate and tri-ammonium citrate, at two different temperatures, 150 °C and 180 °C, for 40 hours under ambient conditions. Despite the small changes in the pyrolysis temperature, rather significant differences are observed in the structure, PL quantum yield, and hence observation of the important characteristics of PL quenching kinetics in the presence of benzophenone (BP) and dimethoxybenzene (DMB) as an electron acceptor and donor, respectively. Molecular dynamic simulations of CNDs in the presence of molecular quenchers support the spectroscopic data and the photophysical behavior of CNDs, and the distinct PL quenching dynamics are attributed to the hydrogen bonding interaction in the case of BP and the π π-stacking interaction in the case of DMB as PL quenchers.