Novel dual ligand co-functionalized fluorescent gold nanoclusters as a versatile probe for sensitive analysis of Hg2+ and oxytetracycline

In this work, we present a direct one-step strategy for rapidly preparing dual ligand co-functionalized fluorescent Au nanoclusters (NCs) by using threonine (Thr) and 11-mercaptoundecanoic acid (MUA) as assorted reductants and capping agents in aqueous solution at room temperature. Fluorescence spectra, high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), and infrared (IR) spectroscopy were performed to demonstrate the optical properties and chemical composition of the as-prepared AuNCs. They possess many attractive features such as near-infrared emission (lambda(em) = 606 nm), a large Stoke's shift (> 300 nm), high colloidal stability (pH, temperature, salt, and time stability), and water dispersibility. Subsequently, the as-prepared AuNCs were used as a versatile probe for turn off sensing of Hg2+ based on aggregation-induced fluorescence quenching and for turn-on sensing of oxytetracycline (OTC). This assay provided good linearity ranging from 37.5 to 3750 nM for Hg2+ and from 0.375 to 12.5 mu M for OTC, with detection limits of 8.6 nM and 0.15 mu M, respectively. Moreover, the practical application of this assay was further validated by detecting OTC in human serum samples.