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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 S 2− in aqueous environment by only naked-eye and 0.112 nM of S 2− by absorption spectrophotometer. The visual detection limit of 16 nM is much lower than the maximum allowable level of S 2− (15 μM) in the drinking water defined by the world health organisation. The proposed sensor detects S 2− at a wide range of pH and also demonstrated to sense S 2− 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 S 2− ion. As prepared Cip-AgNPs embedded cotton detects S 2− in an aqueous solution and S 2− in a gaseous state, indicating that our sensor meets the requirement for on-site detection of S 2− in the environment by only-naked eye. [ABSTRACT FROM AUTHOR]

Chromium is recognized as a serious environmental pollutant because of high toxicity and carcinogenic properties. In this paper, we have developed cadmium sulfide quantum dots (CdS QDs) based fluorescence sensor for sensitive and selective detection of chromium ions. CdS QDs were synthesized by wet chemical method using pectin biopolymer as capping agent and taurine as an antioxidant. The fluorescence emission intensity of CdS QDs at 450 nm was selectively quenched by chromium ions, whereas other cations and anions showed negligible changes. The fluorescence intensity of CdS QDs is linearly proportional to the chromium concentration from 0.016 to 0.260 μM with a detection limit of 16 × 10 −9 M. The proposed sensor recognizes chromium ion at a wide range of pH from 4 to 10. In addition, CdS QDs were also used to detect chromium ions in biological fluid, sewage water, pond water and tap water samples, with low interference. [ABSTRACT FROM AUTHOR]

Herein, we report a facile method to synthesis copper nanoparticles (CuNPs) using fatty acid amide, N -lauryltyramine (NLTA) and hydrazine as capping and reducing agent, respectively. As prepared CuNPs aqueous solution appears brown in color and shows intense surface plasmon resonance (SPR) band at 580 nm. In presence of amino acid, cysteine (Cys), the brown CuNPs solution turned to olive green with concomitant change in SPR maximum, while other amino acids show negligible change in the color and UV–vis spectra of CuNPs. The spectrophotometry detection limit of the proposed sensor is 0.10 μM, whereas naked eye limit of detection was estimated to 20 μM. FTIR studies revealed that Cys forms layer on the surface of the CuNPs, which was further supported by electrochemical studies. The proposed method has been successfully validated by detecting Cys in blood plasma and tap water samples. [ABSTRACT FROM AUTHOR]