Three new dinuclear Co(II) complexes [Co 2 (L 1 ) 2 Cl 2 ](PF 6 ) 2 (1), [Co 2 L 2 (OAc) 2 (CH 3 OH) 4 ](ClO 4 ) 2 (2), and [Co 2 L 3 (OAc) 2 (CH 3 OH) 4 ](ClO 4 ) 2 (3) were synthesized and structurally determined by X-ray single-crystal diffraction analysis as well as IR, elemental analysis, and mass spectrometry. All complexes exhibit efficiently self-activated cleavage activity with hydrolytic mechanism, which was accurately proved by addition of regular radical scavengers, anaerobic cleavage experiment, and 2-thiobarbituric acid reaction. Complex 1 exhibited higher selective cytotoxicity against tumor cells than normal cells, which is significantly better than that of cisplatin. Hoechst 33342 staining, intracellular ROS generation and mitochondrial membrane potential were conducted to assess the apoptosis-inducing activity of 1. The effect of complex 1 on cell invasion was observed by Transwell assay and angiogenesis experiment, and the results demonstrated that 1 could inhibit the cell invasion and angiogenesis. K E Y W O R D S crystal structures, dinuclear Co(II) complexes, invasion, selective cytotoxicity, self-activating Yong-Po Zhang and Qing He contributed equally to this work.

This work describes two new colorimetric methods for smartphone-based point-of-care nanosensing of toxic Ag + ions. They were based on the analyte-triggered in situ "off-on" of Tyndall effect (TE) of non-plasmonic colloid or plasmonic metal nanoprobes. The first TE-inspired assay (TEA) focused on the initial analytical application of precipitation reactions where a non-plasmonic AgCl colloid could be formed once mixing the analyte with a NaCl solution. Such AgCl colloid displayed strong visual TE signals after their irradiation by a laser pointer pen, which unexpectedly achieved a detection limit of ~ 400 nM. The second TEA was further designed to reduce the limit down to ~ 78 nM using the analyte's oxidizability towards 3,3′,5,5′-tetramethylbenzidine molecules. The redox reaction could create positively charged products that could make negatively charged plasmonic gold nanoparticles aggregate through electrostatic interactions to remarkably amplify their TE responses. Both limits were lower than the minimum allowable Ag + level (~ 460 nM) in drinking water issued by the World Health Organization. The satisfactory recovery results for detecting Ag + ions in river, pond, tap, and drinking water additionally demonstrated good selectivity, accuracy and practicality of the proposed methods for potential point-of-need uses in environmental analysis, public health, water safety, etc.

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