Nanosilver cotton swabs for highly sensitive and selective colorimetric detection of sulfide ions at nanomolar level

Herein, we report a simple and rapid method for the visual detection of sulfide ion in an aqueous environment with high sensitivity and specificity by using ciprofloxacin capped silver nanoparticles (Cip-AgNPs). The sensor system can be used to detect as low as 16 nM of S2- in aqueous environment by only naked-eye and 0.112 nM of S2- by absorption spectrophotometer. The visual detection limit of 16 nM is much lower than the maximum allowable level of S2- (15 mu M) in the drinking water defined by the world health organisation. The proposed sensor detects S2- at a wide range of pH and also demonstrated to sense S2- in tap water and river water, with good recovery. For portable use, we synthesized highly stable Cip-AgNPs on cotton and demonstrated good sensitivity against S2- ion. As prepared Cip-AgNPs embedded cotton detects S2- in an aqueous solution and S2- in a gaseous state, indicating that our sensor meets the requirement for on-site detection of S2- in the environment by only-naked eye. (C) 2017 Elsevier B.V. All rights reserved.