The content of magnesium ions (Mg2+) in drinking water is relatively high and the excessive Mg2+ ingestion may lead to pathological lesions in human body system. At present, the detection of Mg2+ still relies on costly devices or/and complex organic fluorescence probes. To solve this problem, this work proposed a NaBH4-mediated co-reduction strategy for the synthesis of glutathione-stabilized bimetallic AuAg nanoclusters (GSH@AuAg NCs) with recognition performance to Mg2+. The preparation of GSH@AuAg NCs was simple and rapid and could be performed at mild conditions. The reaction parameters and sampling orders were optimized to understand the formation mechanism of GSH@AuAg NCs. The GSH@AuAg NCs exhibited a sensitive “light-on” fluorescence response to Mg2+ due to the re-molding of the interfacial physicochemical environment following the Mg2+ coordination, which affected the surface charge transfer process, and thus led to a novel method for fluorescence detection of Mg2+ with admirable selectivity for Mg2+. The proposed method showed a detection limit of 0.2 μM, and its practical utility for the detection of Mg2+ in real sample of purified drinking water was also demonstrated, confirming its practicability in monitoring the Mg2+ concentration in drinking water.

Three monoruthenium complexes 1(PF6)23(PF6)2 bearing a N(CH3)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)2(L)](PF6)2, where L is a 2,5-di(N-methyl-N-(pyrid-2-yl)amino)pyrazine (dapz) derivative with various substituents and bpy is 2,2′-bipyridine. The photophyscial and electrochemical properties of these compounds have been examined. The solid-state structure of complex 3(PF6)2 is studied by single crystal X-ray analysis. These complexes show two well-separated emission bands centered at 451 and 646 nm (max = 195 nm) for 1(PF6)2, 465 and 627 nm (max = 162 nm) for 2(PF6)2, and 455 and 608 nm (max = 153 nm) for 3(PF6)2 in dilute acetonitrile solution, respectively. The emission maxima of the higher-energy emission bands of these complexes are similar, while the lower-energy emission bands are dependent on the electronic nature of substituents. These complexes display two consecutive redox couples owing to the stepwise oxidation of the N(CH3)-bridged ligand and ruthenium component. In addition, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to elucidate these experimental findings.