Carbon quantum dots (CQDs) have received tremendous interest in the last decade and are widely used in many applications, especially in optoelectronic devices and bioimaging, due to their unique photoluminescence (PL) characteristics. Most of the CQDs are non-emissive in the aggregated or solid-state due to aggregation caused quenching (ACQ) effect, which limits their solid-state applications. Herein, we have synthesized nitrogen-doped carbon quantum dots (NCQDs) with bright solid-state emission from citric acid and m-phenylenediamine precursor by a facile one-pot solvothermal approach. The synthesized NCQDs exhibit excitation-dependent photoluminescence and solvatochromism phenomenon, which are not frequently observed in CQDs. The as-synthesized NCQDs show excellent solubility in common polar aprotic and protic solvents, which enables the possibility of studying photophysical properties by varying polarity of the solvents. We have extensively investigated the solvatochromism effect, which is observed in NCQDs and its PL mechanism. Our NCQDs exhibit multicolor PL emission across the entire visible region and their PL mechanism has also been studied in detail. Interestingly, we have observed a bright yellow emission of NCQDs in the solid powder form with the PL maxima centered at 583 nm ascribed to the presence of abundant surface functional groups. This helps to resist the p-p interaction between the CQDs and overcome the ACQ effect in the solid-state.

Multicolor emissive nitrogen-doped carbon quantum dots and their photophysical and solvatochromism studies

ACS Fall 2021

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