Synthesis of “amphiphilic” carbon dots and their application for the analysis of iodine species (I2, I− and IO3−) in highly saline water

Abstract

“Amphiphilic” carbon dots (A-CDs) with a strong green fluorescence emission were synthesized by a simple and green method at room temperature. The characterization demonstrated that the synthesized A-CDs have both hydrophilic and hydrophobic properties and could be dispersed well in aqueous and organic solutions. As a fluorescent probe, the fluorescence of A-CDs could be obviously quenched in the presence of iodine (I₂) and the quenching rate is proportional to the concentration of I₂. Therefore, the A-CDs could be used as fluorophores for the detection of I₂ with higher selectivity and sensitivity, and the linear working range for the I₂ sensor is 80 nM–10 μM with a detection limit of 3.5 nM (S/N = 3). More interesting is that IO₃⁻ and I⁻ could be transformed to I₂ with different sample treatment processes, therefore, the I₂ sensor based on A-CDs could also be used for the analysis of iodine species (I₂, I⁻ and IO₃⁻) in samples. The possible mechanism has also been discussed in this work, and the high selectivity response to I₂ can be attributed to the amphiphilic properties of A-CDs, which bring I₂ closer to A-CDs and quench their fluorescence. The proposed I₂ sensor has been successfully used for the analysis of iodine species in highly saline water, and the satisfactory results of detection and analysis of iodine species in samples demonstrate that the developed I₂ sensor based on A-CDs has potential application in the fields of environment and clinical medicine.