Bimetallic copper-cerium nanoclusters: Assembly-induced aggregation into nanowire network and cysteine-triggered strong red fluorescence turn-on for highly sensitive and selective cysteine sensing

Supramolecular self-assemblies enabled to obtain architectures with amusing properties for various applications including optical device, biosensing and bioimaging. Herein, bimetallic copper-cerium nanoclusters (Cu/Ce NCs) spheres dispersed in isopropanol (IPA)/phosphate buffer (PB, 10 mM, pH7.0) mixed solution can be aggregated to form non-fluorescent nanowire network through self-assembly. Interestingly, the non-fluorescent Cu/Ce NCs nanowire network can be further aggregated blocky structure in the presence of cysteine (Cys), with a strong red fluorescence turn-on. Moreover, the Cys-induced turn-on efficiency of Cu/Ce NCs dispersed in 60% (v/v) IPA/PB mixed solution is 2.7-times that value in PB solution. The Cys-triggered red fluorescence turn-on of Cu/Ce NCs presumably due to the solvent-caused aggregation-induced emission, given rise to by the strong coordination interaction of Ce with carboxyl groups of Cys, and Cu with Cys via the thiol group to link with Cu/Ce NCs by CuS bonding. Additionally, it was found that the Cu/Ce NCs dispersed in 60% IPA/PB mixed solution exhibited good storage stability and repeatability. Then, based on Cys-triggered red fluorescence turning on, fluorimetric sensing Cys was developed with a wide linear range of 10–32,000 nM and detection limit of 3 nM (S/N = 3). The other common species didn’t affect Cys detection. Furthermore, the as-proposed assay can be applied to measure Cys in actual samples accurately and reproducibly. Thereafter, featured by the solvent-induced self-assembly of metal NCs, which is envisioned to cast broad potential applications in designing luminescent materials, biosensing, clinical diagnosis and optoelectronic device.