Mechanistic elucidation of novel carbon quantum dots with high selectivity and sensitivity for picric acid detection

Background

Carbon quantum dots (CQDs) have evolved as promising alternatives to traditional semiconductor quantum dots due to their high photoluminescence, stability, tunable emission wavelengths, and diverse applications.

Methods

In this study, a novel precursor system composed of terephthalic acid and m-phenylenediamine was developed to synthesize CQDs. The as-prepared CQDs were characterized and applied for picric acid (PA) detection in various environmental samples. Moreover, the underlying sensing mechanism was thoroughly elucidated.

Significant findings

The CQDs exhibited excitation-independent green emission at 509 nm with a high quantum yield of 56.3 %. Characterizations confirmed that the green-emissive CQDs (G-CQDs) possessed a graphitic carbon framework and abundant surface functional groups, which contributed to excellent colloidal stability and robust photoluminescence across a wide range of pH values, ionic strengths, storage durations, and under prolonged UV irradiation. For PA sensing, the G-CQDs demonstrated high selectivity and sensitivity, achieving a low detection limit of 17 nM. This sensing capability was not affected by the presence of various cations and anions, and was successfully validated in real samples including sea, river, and tap waters. Mechanistic investigations revealed that the sensing process was primarily governed by the Inner Filter Effect (IFE), rather than by dynamic or static quenching pathways.