A sustainable synthesis of green carbon quantum dot (CQD) from Catharanthus roseus (white flowering plant) leaves and investigation of its dual fluorescence responsive behavior in multi-ion detection and biological applications

Abstract In this work, we have presented a facile, efficient and green strategy to prepare fluorescence CQD for multi ion sensing and bio imaging application. Hydrothermal carbonization technique was adopted as one-pot synthetic method to prepare CQD, using Catharanthus roseus (white) leaves as carbon source without any passivating and oxidizing agent. The as-synthesized carbon hold significant advantages such as high fluorescence (FL) emission, high aqueous solubility, stability and non-toxicity etc. Fourier transform infrared spectroscopy (FTIR) and Energy-dispersive X-ray spectroscopy (EDX) confirmed CQD's surfaces enriched with oxygen and nitrogen composition. Transmission electron microscopy (TEM) revealed that average of size of CQD was around 5 nm. The maximum quantum yield of as prepared CQD was 28.2% at excitation wavelength of 330 nm. The influence of different pH affecting on fluorescence behavior of CQD was systematically studied. In multi ions sensing, FL enhancement and quenching was identified as dual FL responsive mechanism in selective and sensitive detection of Al3+ (Linear range (LR) = 0–6 μM and Limit of Detection (LOD) = 0.5 μM) and Fe3+ (Linear range (LR) = 0–6 μM and Limit of Detection (LOD) = 0.3 μM) ions, respectively. Additionally, CQD exhibited its antioxidant activity and its potential to be used in bio imaging against MCF-7 cells. MTT assay showed good biocompatibility results. Finally, the proposed Catharanthus roseus (white) leaves derived CQD may exhibit great promise as sensing probe for cancer diagnosis and treatment and also multi- ions (Al3+ and Fe3+) in field of environmental water analysis.