Fabrication of glass-based analytical devices by immobilizing nanomaterials on glass substrate with a fluorescent glue for the highly sensitive determination of mercury ions.

A facile method is reported to develop glass-based analytical devices (GADs) based on immobilizing nanomaterials on a glass substrate with fluorescent glue. The fluorescent glue was first prepared by coupling bovine serum albumin (BSA)-protected Au nanoclusters (NCs) and sugars (i.e., ascorbic acid, AA). The glue was then used to immobilize carbon dots (C-dots) on glass substrates to fabricate the portable GADs. The liquid glue-C-dots mixture and probable GADs were developed for Hg detection. Under 365-nm excitation wavelength, the emission at 652 nm from the glue is gradually quenched with increasing concentrations of Hg. This quenching is explained in terms of the Stern-Volmer equation and is ascribed to static quenching. The fluorescent color of the glue and GADs gradually changes from pink to blue, with increasing concentrations of Hg. The limits of detection (LODs) for Hg determination by bare eyes are 1 nM both for the glue and GADs, suggesting an uncompromised sensing capability even after immobilization. The detection sensitivity of GADs shows a significant improvement compared with the same material-based papers (5 μM). A linear relationship is observed between the total Euclidean distances (EDs) and Hg concentration in the range 0-100 nM, providing the potential for Hg quantification using GADs. The LOD is estimated to be 0.84 nM. To show a potentially practical application, the GADs were used to detect Hg in certified reference material and lake water.