Optical Properties and Photoactivity of Carbon Nanodots Synthesized from Olive Solid Wastes at Different Carbonization Temperatures

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Ameera Nasasreh, Ameera
Jitan, Madleen
Nasasreh, Majd
Salman, Maha
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Carbon nanodots (CNDs) have many fascinating properties such as optical properties (UV-Visible absorption and fluorescence emission), which nominate them to be good candidates in many applications such as photocatalysts for the degradation of several organic pollutants. This study aims to synthesize CNDs from olive solid wastes at different carbonization temperatures from 300 to 900 oC and study their effect on the optical properties of CNDs such UV-Vis, fluorescence, quantum yield, and energy bandgap in addition to their influence on the photoactivity of CNDs as photocatalysts for the degradation of methylene blue (M.B). CNDs were prepared from olive solid wastes (OSWs) by pyrolysis at different temperatures (300-900°C) to be converted to carbonized material, then oxidized chemically in the presence of hydrogen peroxide (H2O2). It was found that the increase in carbonization temperature of olive solid wastes leads to an increase of product yield with a maximum value at 500 °C and then decreased dramatically. On other hand, a decrease in fluorescence due to the diminishing of oxygen groups and destruction of the surface of CNDs was observed. The higher quantum yield (5.17%) and bandgap (2.77 eV) were achieved for CNDs prepared from OSWs carbonized at 300 oC. The rate and degradation efficiency of M.B were studied with different synthesized CNDs, finding that the increase in carbonization temperature leads to decreases in the rate and degradation efficiency of M.B realizes the highest values at 300 oC with a degradation rate of 0.0575 min-1 and degradation efficiency of 100% after 120 minutes of light irradiation.