One-pot green synthesis of supramolecular Β-cyclodextrin functionalized gold nanoclusters and their application for highly selective and sensitive fluorescent detection of dopamine

We report here one-pot synthetic method for preparing gold nanoclusters (AuNCs) by employing pristine β-cyclodextrin (β-CD) as reducing-cum-stabilizing agent for the first time. The developed AuNCs were used as a selective and sensitive fluorescent probe for sensing dopamine (DA) based on β-CD supramolecular interaction and quenching effect. The as-synthesized β-CD protected gold nanoclusters (β-CD@AuNCs) showed good monodispersity with ultra-small size < 2.0 nm and exhibited strong fluorescence intensity at 450 nm β-CD@AuNCs have been systematically characterized by UV–vis absorption spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and dynamic light scattering. DA can trigger significant fluorescence quenching of β-CD@AuNCs on the basis of photo-induced electron transfer (PET) mechanism. Fluorescence lifetimes characterization of β-CD@AuNCs and DA/β-CD@AuNCs conjugate were performed to confirm the proposed PET process. A good linearity range (100.0 nM to 80.0 μM) for DA detection was obtained by applying the Stern-Volmer equation with lower LOD (3σ/s) of 20.0 nM, revealing the high sensitivity of the method. This fluorescent AuNCs sensing probe for DA demonstrates excellent selectivity among 24 biological interferents owing to the specificity of steric host-guest interactions between DA and the nanocavity of β-CD capped on AuNCs. The developed nanosensor was successfully applied in the detection of DA in human serum plasma and injection dosage forms, indicating its good practicability for DA detection in biological and pharmaceutical research.