Advances in spin properties of plant leaf-derived graphene quantum dots from materials to applications.

Over the past decade, graphene quantum dots have gained an inexhaustible deal of attention due to their unique zero-dimensional and quantum confinement properties, which boosted their wide research implication and reliable applications. As one of the promising zero-dimensional member and rising star of the carbon family, plant leaf-derived graphene quantum dots have attracted significant attention from scholars working in different research fields. Owing to its novel photophysical properties including high photo-stability, plant leaf-derived graphene quantum dots have been increasingly utilized in the fabrication of optoelectronic devices. Their superior biocompatibility finds their use in biotechnology applications, while their fascinating spin and magnetic properties have maximized their utilization in spin-manipulation devices. In order to promote the applications of plant leaf-derived graphene quantum dots in different fields, several studies over the past decade have successfully utilized plant leaf as sustainable precursor and synthesized graphene quantum dots with various sizes using different chemical and physical methods. In this review, we summarize the Neem and Fenugreek leaves based methods of synthesis of plant leaf-derived graphene quantum dots, discussing their surface characteristics and photophysical. We highlight the size and wavelength dependent photoluminescence properties of plant leaf-derived graphene quantum dots towards their applications in optoelectronic devices such as white light-emitting diodes and photodetectors, as well as biotechnology applications such as in vivo imaging of apoptotic cells and spin related devices as magnetic storage medium. Finally, we particularly discuss possible ways of fine tuning the spin properties of plant leaf-derived graphene quantum dot clusters by incorporation with superconducting quantum interference device, followed by utilization of atomic force microscopy and magnetic force microscopy measurements for the construction of future spin-based magnetic storage media and spin manipulation quantum devices so as to provide an outlook on the future spin applications of plant leaf-derived graphene quantum dots.