Synthesis of carbon dots from organic waste as heavy metal ions detector sensor

The comparison between two different bottom-up synthetic techniques had been prepared in order to synthesis the carbon dots (CD) from organic waste, i.e. the hydrothermal (HT) and microwave irradiation (MI) techniques. The CD were extracted from two different sources, i.e. from watermelon rind (wet organic waste) and peanut skin (dry organic waste). All of the products were characterized using spectroscopy characterization to determine their optical characteristics. It was obtained that all of the CD absorbing light in the UV region (around 300 nm) and emitting light in the visible light region (around 500 nm) which is called as photoluminescence (PL). The time-resolved PL (TRPL) was also observed within all of the products, which shows that they have TRPL around 3 to 4 ns, thus those CD categorized as fluorescence. Then, both CD from watermelon rind (WR) and peanut skin (PS) were examined using FTIR and it was obtained that both CD has carboxyl group content. After that, both products were also compared based on their performance as Fe³⁺ and Pb²⁺ sensors (1 nM-10^-1 M with 10 interval). The best performance was achieved by PS CD, due to its consistency in optical characteristics degradations (negative degradation) due to PL-turn off sensor method with the regression of each optical characteristics (absorbance, PL, and TRPL) are 0.6542, 0.6567, and 0.6168.