Sustainable synthesis of carbon dots from Ananas Comosus as renewable biomass: nanomolar level detection of glutathione

The adoption of green alternatives has become critically important for ensuring a sustainable environment in light of the state of our ecosystem. Biomass, being carbon-rich and environmentally benign, has garnered significant attention and has emerged as a viable solution. Herein, we report the synthesis of highly fluorescent intrinsic nitrogen-functionalized carbon dots using Ananas Comosus (AC-CQDs) juice as a renewable biomass precursor through a microwave-aided pyrolysis method utilizing only its natural ingredients. This approach was executed without the use of any chemical additive, underscoring its applicability as a green methodology. Besides, the as-prepared AC-CQDs exhibited high biocompatibility, water solubility, and photostability, and the synthesis protocol was also facile and cost effective. The surface state functionalization and nature of the synthesized AC-CQDs were characterized and confirmed by X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform-infrared and Raman spectroscopic analyses. The average size of the AC-CQDs was observed to be 2.25 nm via HR-TEM analysis. In order to ensure the stability of the AC-CQDs, the impact of pH variation, irradiation time, ionic strength, and storage duration were investigated. The as-prepared nanoprobe displayed a substantial PLQY value of ∼48% and, further, showed high selectivity and sensitivity for the label-free determination of Mn(vii) ions. The interaction of the synthesized AC-CQDs with Mn(vii) ions showed promising fluorescence turn-off quenching, and the sensitivity of AC-CQDs toward Mn(vii) ions was found to be up to the nanomolar range with a limit of detection of 14 nM. Furthermore, fluorescence restoration of the proposed nanosensor [AC-CQDs@Mn(vii)] was observed by the addition of glutathione (GSH). This fluorescence turn-on–off–on nanoprobe showed an appreciable detection limit up to the nanomolar range (8.8 nM) for GSH with a satisfactory linearity range between 0 and 250 nM. Various photophysical parameters of the AC-CQDs were thoroughly investigated in the presence of dual analytes to acquire a better understanding of the sensing mechanism. For ensuring the high precision of the dual analytes in the proposed nanosensor, a number of analytical parameters were also examined. In addition to this, the feasibility of the designed nanosensor was assessed through paper strip testing, and to gauge the viability of the detection approach, real sample analysis was undertaken, showcasing satisfactory recovery rates and relative standard deviations with respect to the developed probe. This study aligns well with the UN's Sustainable Development Goal 3 (good health and well-being) and 12 (responsible consumption and production). Thus, the nanosensor derived from biomass precursors will pave a path for the development of CQDs through a straightforward, swift, cost-effective and green approach.