Effect of synthesis conditions on Rheodiscolor leaf-derived carbon quantum dots as electrolytes for energy storage applications

Carbon Quantum Dots (CQDs) were synthesized from Rheodiscolor leaf extract using Soxhlet extraction followed by a hydrothermal process in four variants: S1 (raw CQDs), S2 (5 % ethanol-CQDs), S3, and S4. UV–Visible absorption bands at 211–339 nm and excitation-dependent photoluminescence (315–475 nm) confirmed moderate quantum confinement. FTIR spectra identified O–H (∼3400 cm⁻¹) and C O (∼1645 cm⁻¹) groups, with additional C–H and C C bands in S2–S4 enhancing solubility. Electrochemical characterization using GCD and cyclic voltammetry (CV) revealed contrasting outcomes: GCD showed reduced capacitance of GCE for all CQD variants compared to KOH, with S1 retaining 45–54 % and S4 only 20–38 %, whereas CV indicated strong, stable performance of GCE for CQDs (S1–S3) (∼80–88 % of KOH) and moderate retention for CQD (S4) (43–60 %). These findings suggest that Rheodiscolor leaf-derived CQDs, especially S1–S3, are promising, sustainable, and tunable electrolyte materials for energy storage applications, with properties strongly influenced by synthesis conditions. Carbon Quantum Dots from Rheodiscolor leaves • Rheodiscolor leaf extract via green Soxhlet–hydrothermal method produced CQDs. • CQDs show UV-Vis absorption at 211–339 nm and PL emission at 315–475 nm. • Best electrochemical stability and reversibility were observed in S1 and S2. • S1-S3 showed 45–54 % (GCD) and 80–88 % (CV) vs KOH; S4 retained less. • Rheodiscolor CQDs show low-cost, sustainable electrolytes for flexible supercapacitors.