A ternary sensor system based on pyrene derivative-SDS assemblies-Cu2+ displaying dual responsive signals for fast detection of arginine and lysine in aqueous solution

• A pyrene derivative-SDS assemblies-Cu2+ based ternary sensor system was built.
• The ternary system is highly sensitive to arginine and lysine in aqueous solution.
• The sensor shows the lowest detection limits of Arg (5.2 nM) and Lys (14.6 nM).
• The sensor displays dual responsive signals of “excimer-off” and “monomer-on”.
• Two different mechanisms occur to sensing different concentrated amino acids.

A new cationic pyrene derivative-based fluorescent probe (IPy) was designed and synthesized. This cationic fluorophore with two imidazolium groups can be well-dissolved in aqueous solution and exhibits only monomer emission. The anionic surfactant SDS assemblies can modulate its fluorescence emission and enable both monomer and excimer emission by controlling SDS concentration. The selected IPy/SDS system shows turn-off responses to Cu2+, however, the quenching effect of Cu2+ can be increased by amino acids with high pI values such as arginine (Arg) and lysine (Lys). Therefore, the optimized ternary system based on IPy/SDS/Cu2+ can function as a highly sensitive and selective fluorescent sensor for these two amino acids, displaying detection limits of 5.2 nM and 14.6 nM for Arg and Lys, respectively. Moreover, this sensor system displays dual responsive signals of “excimer emission off” to low concentrated amino acids (smaller than 10 μM), and “monomer emission on” to high concentrated amino acids (larger than 10 μM). It turns out that low concentrated basic amino acids binds with negative SDS assemblies and facilitate fluorescence quenching of the cationic fluorophore by Cu2+, however, the high concentrated basic amino acids induce disassembly of SDS aggregates and lead to leak of the fluorophore back into aqueous environment, which gives rise to monomer emission.

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