Synthesis of Banana Peel-based Carbon Dots using Citric Acid Pre-treatment via Hydrothermal Synthesis

Abstract

Agricultural wastes, such as banana peels, are being valorized in line with the United Nations Sustainable Development Goals, specifically SDG 12 (Responsible Consumption and Production) and SDG 13 (Climate Action). This study aims to sustainably convert these wastes into accessible, cost-effective materials via green synthesis. Carbon dots (CDs), fluorescent nanomaterials with bioimaging, drug delivery, and environmental monitoring applications, were synthesized using the autoclave hydrothermal method. To address challenges in efficient synthesis caused by incomplete biomass breakdown, pretreatment with 50% citric acid was applied. Characterization methods such as ATR-FTIR, UV-Vis, SEM, and fluorescence spectrometry are used to determine the properties and efficiency of the extraction of CDs. The pretreated sample obtained significant broad peaks at 3312 cm-1, 2872 cm-1, and 1680 cm-1 due to the presence of -OH, C=O, and C=C bonds, respectively. On the other hand, a maximum wavelength of 242 nm was obtained from the UV-Vis spectra, indicating a π → π* transition in correlation to the functional groups gathered from the IR spectra. The maximum wavelength obtained from the UV-Vis spectra was used to extrapolate the fluorescence spectra with a significant peak at around 388 nm, indicating a pH-dependent shift, as the pretreated sample is slightly more acidic than the untreated sample.