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Abstract Carbon quantum dots (CQDs), prepared by one-step hydrothermal treatment of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) and triethylamine (TEA), could be exfoliated or delaminated into single-layered graphene quantum dots (s-GQDs) with methanol for the first time, with fluorescence (FL) emission at 500 nm when excited at 417 nm. The s-GQDs, with more sufficient carboxyl groups on the surface than CQDs, could be induced to be aggregated by metal ion dysprosium (Dy3+), resulting in aggregation-induced emission quenching effect subsequently. However, the presence of phosphate (PO 4 3-) destroys the Dy3+-induced aggregates of s-GQDs owing to the strong coordination between Dy3+ and PO 4 3-, inducing the FL emission recovery of the s-GQDs and providing selective detection method of PO 4 3- in the artificial wetlands with the linear range of 0.2–30 μM and determination limit of 0.1 μM (3σ). Graphical abstract Carbon quantum dots (CQDs) was firstly reported to be exfoliated or delaminated into single-layered graphene quantum dots (s-GQDs) by mixing with methanol followed by evaporating. The s-GQDs with sufficient carboxyl groups on the surface could specifically be induced by metal ion dysprosium (Dy3+) to form aggregates, resulting in aggregation-induced emission quenching effect. However, the presence of phosphate (PO 4 3-) destroyed the Dy3+-induced aggregates of s-GQDs, inducing the FL emission recovery of the s-GQDs, which can be used for sensitive and selective detection of PO 4 3-. fx1 Highlights • Single-layered GQDs (s-GQDs) are easily obtained by exfoliating or delaminating the as-prepared CQDs with methanol. • The s-GQDs with more carboxyl groups on the surface than the CQDs can be induced to generate aggregation-induced emission quenching by Dy3+. • An off-on fluorescent strategy is successfully applied for the highly selective detection of PO43- by using s-GQDs-Dy3+ complex. [ABSTRACT FROM AUTHOR]