Aggregation-induced enhanced photoluminescence in magnetic graphene oxide quantum dots as a fluorescence probe for As(iii) sensing

Abstract

Clean drinking water is a basic need of human beings around the world. In the past few decades, many research groups have been trying different methods to exploit quantum dots (QDs) to decontaminate water but, due to either cost or cumbersome steps, they have been unsuccessful. We have tried exploiting graphene quantum dots (GQDs) for heavy metal ion detection, particularly for arsenic ions in contaminated water. Herein, we prepared highly sensitive and selective magnetic GQD (Fe-GQDs) based sensors for the “turn on” sensing of As³⁺ ions. Systematic characterization of the prepared magnetic GQDs was done using different spectroscopic techniques. Impressively, Fe-GQDs exhibited good selectivity for As³⁺ ions over a wide pH range. This “turn on” sensing of As³⁺ ions can be explained by the fact that Fe-GQDs aggregates were formed upon the addition of As³⁺ ions, which restricted the intra-molecular vibrational motion and consequently made the entire system emissive. A combination of techniques, such as time-correlated single-photon counting (TCSPC) experiments, Raman spectroscopy, XPS, DLS and zeta potential analysis, was employed to understand the aggregation-induced enhanced emission (AIEE) mechanism. The resultant limit of detection (LOD) value for as-prepared fluorescent Fe-GQDs was 5.1 ppb, which is well below the permissible limit for arsenic in drinking water. A reactive oxygen species (ROS) study in the presence and absence of UV light revealed the potential of the proposed quantum dots to act as an antibacterial agent. Overall, the low LOD value, the selectivity of Fe-GQDs over a wide pH range and the ROS study render our work of practical significance.