Hollow SnS nanosensor for portable recognition, enrichment and detection of copper ions: a precision design based on the solubility product principle

• Hollow SnS nanoflowers were applied to selectively enrich and detect Cu 2+ ions. • After enriching Cu 2+ , HSnS NF has peroxidase-activity to recognize and detect Cu 2+ . • By coupling with RGB sensor, the HSnS NF nanosensor can detect 100 ng L −1 Cu 2+ . • HSnS NF enriching Cu 2+ undergoes formation of Cu 2 SnS 3 not by substitution reaction. • The solubility product principle can guide general and precision design. On-site, rapid and selective detection of trace heavy metal ions could provide real-time critical information for environment, health and safety concerns, but is yet a big challenge under state-of-the-art technologies. In the current work, hollow SnS nanoflowers (HSnS NF) were synthesized and applied for selective enrichment and detection of Cu 2+ ions. HSnS NF not only displays fast adsorption kinetics (reaching adsorption equilibrium in 15 min), but superior selectivity as well for Hg 2+ and Cu 2+ ions among multiple interfering metal ions. After enriching Cu 2+ , HSnS NF has peroxidase activity, rendering its ability to recognize and detect Cu 2+ among varied metal ions (even in presence of Hg 2+ ) over a wide concentration range of 50 ng L −1 to 200 μg L −1 in as short as 10 min. By coupling with a commercial RGB sensor (Red Green Blue value color sensor), the HSnS NF nanosensor can also achieve a detection limit as low as 100 ng L −1 with superior recovery, which may allow on-site detection of Cu 2+ ions. Mechanism studies indicate that HSnS NF enriching Cu 2+ undergoes formation of Cu 2 SnS 3 that possesses superior peroxidase-like activity instead of simple substitution reaction and the solubility product principle again plays a decisive role in achieving the excellent performance of HSnS NF towards Cu 2+ ions.