Carbon nanostructures are emerging sensing nanomaterials that have attracted interest from potential researchers owing to their merits such as small size, photostability, tunable fluorescence properties, and biocompatibility. Therefore, to gain further detailed insight, their formation was investigated from the spinach juice and extracts via hydrothermal treatment. In order to understand the role of different components of spinach on the optical properties of nanostructures, a serial extraction was performed using Soxhlet apparatus with different solvents such as ethanol, a mixture of ethanol and water (1:1), n-hexane, and chloroform. Such extracts and spinach juice were taken as starting carbon precursors and heated at 200 °C for 6 h, in a Teflon-lined stainless-steel vessel. Among all the prepared carbon nanostructures, spinach juice-derived particles were found to be in the size range of 3–4 nm, therefore could be termed carbon dots (CDs). Such nanostructures showcased the best optical properties, therefore, were employed for sensing Cr (III) ions. The limit of detection (LOD) and quantification (LOQ) were estimated to be 0.138 and 1.38 µM for Cr (III) ions respectively. Thus, such CDs could be promising candidates for sensing applications.

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