Influence of Solvent in Modulating Optoelectronic and Sensing Properties of Carbon Nanodots

Carbon nanodots (CNDs), boasting biocompatibility, structural versatility, and tuneable photoluminescence, are promising candidates in luminescent materials. This study demonstrates how the optical properties of N, S co-doped carbon nanodots can be effectively tuned through variation in solvents. Drastic change is noted in the physico-chemical features of CNDs achieved using sulphuric acid and water through solvothermal route. A red shift in emission is noted in system achieved using sulfuric acid medium. The synthesized CNDs are explored for light emitting diode (LED) application. CNDs achieved using hydrothermal method (MCDs) lead to pure white light (CIE coordinates: 0.33, 0.38) emitting LEDs, and sulfuric acid modification (SMCD) produces LEDs emitting in yellowish-orange light (CIE coordinates: 0.57, 0.42), due to enhanced oxidation of carbon core. Further, the difference in solvents is also reflected in the response of these CNDS toward external analytes. Picric acid induced luminescence quenching of SMCDs enabled selective detection of the analyte among 11 nitroaromatic compounds, highlighting the impact of surface functionalization in tuning the response toward external environments. The sensing mechanism, involving the inner filter effect and static quenching, as well as the selective response to picric acid, was confirmed through optical characterization and frontier molecular orbital (FMO) analysis.