Synthesis of Carbon Quantum Dot from Water Hyacinth Stalk by Radiation Processing

Abstract

Water hyacinth is a severe issue, resulting in river blocking in high flood risk areas like Pathum Thani province, Thailand. To reduce the amount of invasive water hyacinths, their stalks were used as carbon precursors for carbon dots (CDs) by one-pot gamma irradiation, which is a promising method for high-quality and large-scale production. Furthermore, this method was compared with the conventional hydrothermal method. This finding proved that the optical properties of as-prepared CDs from both methods were no significant differences. The CD solution had a pale yellow color and exhibited tuneable fluorescence emission. They are strongly absorbed in the UV region of 250-300 nm. An effect of ethanol pretreatment was also studied. It was found that the ethanol pretreatment has no substantial effect on the photophysical and chemical properties of as-prepared CDs, whereas it was crucially affected by the pH stability of CDs. The maximum fluorescence emission of CDs with (ECD-G) and without (CD-G) ethanol pretreatment were 443 nm (~2.5% of quantum yields) and 440 nm (~2.0% of quantum yields) with the excitation at 360 nm, respectively. The carboxyl groups were the primary functional group of CD-G and ECD-G, confirmed by the FTIR spectroscopy.