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 Hg2+ detection. Under 365-nm excitation wavelength, the emission at 652 nm from the glue is gradually quenched with increasing concentrations of Hg2+. 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 Hg2+. The limits of detection (LODs) for Hg2+ 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 Hg2+ concentration in the range 0-100 nM, providing the potential for Hg2+ quantification using GADs. The LOD is estimated to be 0.84 nM. To show a potentially practical application, the GADs were used to detect Hg2+ in certified reference material and lake water.

Silica-templated photonic crystal sensors for specific detection of Cu2.

Responsive photonic crystals have attracted extensive attention due to their features of transforming external stimuli into a variation of optical signals or structural colors. In recent years, the accumulation of heavy metal ions has become a serious threat to human health and the environment. Thus, a simple and rapid method for the accurate detection of metal ions is of great importance. Herein, an imidazole-based-silica inverse opal photonic crystal (IOPC) sensor is prepared. Three different particle sizes of SiO2 photonic crystals were used as templates for the preparation of an IOPC. The results show that the template presents a high specific surface area and interconnected nanopores. When the nanopores adsorb copper ions, the functional monomer imidazole will chelate with copper ions to form a flat quadrilateral structure. Then the nanopores of the IOPC shrink, which will result in the red shifting of the diffraction peak to complete the visual response sensing. When immersed in different concentrations of metal ions, the structural color of the IOPC changes, making it a visual sensor. In addition, it is proved that the imidazole-modified IOPC is specifically responsive to Cu2+, and the structural color of the sensor will shift from green to yellow after sensing. The detection limit is as low as 1 × 10-6 mol L-1, and the maximum offset of the diffraction peak can reach 50 nm. Therefore, the IOPC prepared here provides an ideal platform for the fast and high selective detection of Cu2+, and it has potential applications in the rapid detection of other heavy metal ions.

Effective Recognition of Different Types of Amino Groups: From Aminobenzenesulfonamides to Amino-(N-alkyl)benzenesulfonamides via Iridium-Catalyzed N-Alkylation with Alcohols.

A simple, highly efficient, and general strategy for the direct synthesis of amino-(N-alkyl)benzenesulfonamides has been accomplished via direct N-alkylation of aminobenzenesulfonamides bearing both different types of amino groups with alcohols as alkylating agents. Notably, this research exhibited the potential for the recognition of different types of amino groups in the N-alkylation of complex molecules with alcohols, facilitating the progress of the transition-metal-catalyzed "hydrogen autotransfer (or hydrogen-borrowing) process."