LAUSR

The evaluation of intracellular reactive oxygen species (ROS) would greatly deepen the understanding of cell metabolism/proliferation and tumour detection. However, current long-acting level tracking techniques for intracellular ROS remain unsuited to practical application. To solve this problem, we synthesized cyclotriphosphazene doped graphene quantum dots (C-GQDs) whose quantum yield is highly sensitive to ROS (increased by 400% from 0.12 to 0.63). Electron cloud polarisation of oxidized cyclotriphosphazene rings in C-GQDs is confirmed to account for this novel optical property by density functional theory calculation and experimental results. In combination with excellent biological stability, C-GQDs achieve a long-acting evaluation of intracellular ROS level (more than 72 h) with an accuracy of 98.3%. In addition, recognition rates exceeding 90% are demonstrated to be feasible for eight kinds of tumour cell lines cultured with C-GQDs, which can also be expanded to in vivo detection. C-GQDs also show a high recognition rate (82.33%) and sensitivity (79.65%) for tumour cells in blood samples.