One-step green approach to synthesize highly fluorescent carbon quantum dots from banana juice for selective detection of copper ions

Green synthesis of carbon quantum dots (CQDs) from natural sources always remain an attraction due to their excellent optical properties. In present work, highly fluorescent N, S co-doped CQDs (NS-CQDs) were synthesized from banana (musa acuminata) juice using a simple one-step hydrothermal process, which not required any surface passivation, oxidizing agent or inorganic salt. Transmission electron microscopic images and X-ray diffraction analysis revealed spherical shaped NS-CQDs of an average size of 1.27 nm with poor crystallinity. The proposed method offers higher quantum yield (32 %) at an excitation wavelength of 330 nm as compared to other reported natural sources-derived CQD. These synthesized NS-CQDs utilized as a fluorescent probe for the detection of Cu (II) in the water sample. The fabricated fluorescent sensor displayed the detection of copper ions in the concentration range of 1−800 μg/mL with the LOD of 0.3 μg mL−1.