The exploration of novel fluorescent copper-cysteamine nanosheets for sequential detection of Fe³⁺and dopamine and fabrication of molecular logic circuits

Herein, newly emerged copper-cysteamine (Cu-Cy) nanosheets with red fluorescence and a good stability were explored as a new type of probe for Fe³⁺and dopamine detection. The sequential detection of Fe³⁺and dopamine by the use of Cu-Cy nanosheets isviaa fluorescence “ON-OFF-ON” mechanism and the Cu-Cy nanosheets showed highly selective and very sensitive detection for Fe³⁺with fluorescence quenching owing to the paramagnetic nature of Fe³⁺. Furthermore, this fluorescence quenching can be recovered upon the addition of dopamine, which can be used for the development of an “OFF-ON” fluorescence method for the detection of dopamine. The Cu-Cy provides a wider detection range (1-500 μM for Fe³⁺and 1-20 μM for dopamine) than most of the other fluorescent probes reported, owing to the large two-dimensional surface area and the high chemical reactivity of the Cu-Cy. Additionally, the sensing strategy was explored by designing molecular logic gates (NOT, XNOR, and NOR) and multiple-input logic circuits in order to convert the molecular information, such as metal ion chelation and oxidation, to detectable fluorescent signals.