Blue luminescent carbon quantum dots derived from diverse banana peels for selective sensing of Fe(III) ions

The eco-friendly production of carbon quantum dots (CQDs) from natural resources remains appealing owing to their superior optical properties. This work presents the synthesis of highly fluorescent CQDs from peels of different varieties of Musa (yellow, green, and red) through a straightforward one-step hydrothermal process, without needing a bit of metal salt or oxidizing agent. The proposed method resulted in quantum yields (QY) of 18.06 %, and 13.06 %, for CQDs from normal yellow banana and green banana, respectively compared to other CQDs derived from natural sources. The QY for the CQDs extracted from the small yellow banana was 7.72 %, while the red banana had a much lower value of 2.6 %. The optical properties of CQDs of different banana peels are also compared. All the CQDs produced a blue color upon exposure to 360 nm UV radiation, and the fluorescence was excitation-dependent. Moreover, each of the four types of CQDs is proven to be an efficient fluorescent probe capable of selectively detecting Fe³⁺ ions. The linear variation of fluorescence with the analyte amount allowed quantification of ions, with a limit of the detection value of 6 μM, across a concentration range of 37–277 μM. Above all, the real-world applications aimed at sensing Fe³⁺ ions in tap water achieved excellent recoveries ranging from 96 to 100 %. Therefore, these tuneable CQDs with good optical properties present an auspicious avenue for developing nano-sensors in real-time applications.