N-CDs are synthesized by an outright green method and employed as a selective fluorescent probe for Au ³⁺ ions and is also used as a reducing agent to synthesize AuNPs.

Amidothiourea linked acridinedione derivatives selectively detect Hg²⁺ in unbuffered aqueous solution under broad pH range with both single- and two-photon excitation. The observed linear fluorescence intensity change allows the quantitative detection of Hg²⁺ in the concentration range of 22 nM–0.33 μM with the lower detection limit of 2 nM.