Green synthesis of carbon dots from elm seeds via hydrothermal method for Fe3+ detection and cell imaging

• Carbon dots were synthesized by hydrothermal method using elm seed as carbon source. • The CDs were selectively quenched by Fe 3+ and can be used as sensitive Fe 3+ sensor. • The CDs were good biocompatible and could label HepG2 cells with blue fluorescence. Hydrothermal method to prepare biomass-based carbon dots (CDs) is environmentally-friendly and it can convert useless waste into valuable materials. In this work, we aimed to use natural siberian elm ( Ulmus pumila L.) seeds as carbon source to synthesize CDs by hydrothermal method. The obtained CDs were characterized by TEM, FTIR and XPS methods, founding they were near-spherical in shape with an average diameter of 3.83 nm. The CDs were mainly composed by carbon, nitrogen and oxygen, which formed the various hydrophilic functional carboxyl, hydroxyl, amino and amide groups on the surface. In addition, the CDs could emit bright blue fluorescence under ultraviolet illumination with excellent pH stability and photostability. Among various metal ions, the CDs could be selectively quenched by Fe 3+ . The degree of quenching was linearly related to the concentration of Fe 3+ , indicating they could be used for Fe 3+ detection. Finally, the CDs were proven to be good biocompatible by MTT assay and they could effectively label HepG2 cells with bright blue fluorescence. In summary, the CDs could be potentially applied as Fe 3+ sensors for water pollution detection and agents for cell imaging.