Green Synthesized Graphene Quantum Dots: Optical Properties and Potential Applications

In this work, plant-derived precursors from the leaves and flowers of Hibiscus and Hamelian plants were effectively used to create graphene quantum dots (GQDs). UV-visible absorption spectroscopy and photoluminescence (PL) spectroscopy were used to examine the optical characteristics of the produced samples. The Tauc plot method was used to measure the samples' optical band gap. The stated band gap values for graphene quantum dots are compatible with the computed band gap values, which vary from 3.5 eV to 4.98 eV. The creation of nanoscale carbon domains with significant quantum confinement effects is confirmed by the high band gap values. Hamelian leaf (new) and Hibiscus leaf samples had the largest band gap (4.98 eV) of all the samples, suggesting better quantum confinement and smaller particle sizes. The Hibiscus flower (3.5 eV) and Hamelian flower (3.6 eV) samples, on the other hand, exhibit considerably lower band gap values, which might be explained by bigger particle sizes or a higher density of surface defects. After 60 days, there is a modest decrease in the band gap between Hamelian leaf new (4.98 eV) and Hamelian leaf old (4.6 eV). This might be due to structural changes, quantum dot aggregation, or surface functional group mutation over time. This finding implies that the optical characteristics of GQDs generated from plants can change over time. Overall, the findings show that the optical characteristics and band gap of the produced graphene quantum dots are strongly influenced by the plant source, plant portion (leaf or flower), and storage duration.