Highly Photoluminescent Carbon Dots Derived from Discarded Chewing Gum: toward Multiple Sensing of pH, Ferric Ion, and Adenosine Triphosphate

In this paper, we develop a sustainable strategy to reuse discarded chewing gum for low-cost synthesis of carbon dots (CDs) via a H2O2-assisted hydrothermal method. The as-prepared CDs have a large photoluminescence (PL) quantum yield (QY) of up to 25.7%, much higher than the most values of waste-derived CDs. Interestingly, the PL intensity of CDs increases linearly as pH rises from 1 to 6, demonstrating the possibility of CDs for accurate pH monitoring in acidic conditions. It is suggested that the pH-responsive PL feature is induced by the protonation and deprotonation of the surface oxygenous groups of CDs. Through the fluorescence quenching and recovery processes, the CDs can serve as a selective and sensitive sensor for sequential detection of ferric ion (Fe3+) and adenosine triphosphate (ATP) with limit of detection (LOD) as low as 0.028 and 0.003 mu M, respectively. A possible electron transfer process is proposed to elucidate the sensing mechanism. For real applications, the CD sensing platform is successfully employed to determinate pH in natural stream, Fe3+ in tap water, and ATP in erythrocyte sample.