Phytosynthesis of silver nanoparticles; naked eye cellulose filter paper dual mechanism sensor for mercury ions and ammonia in aqueous solution

In the present study, low cost novel cellulose filter paper based silver nanoparticles (CF-AgNPs) sensor was developed. AgNPs were synthesized via green approach using aqueous leaf extract of Convolvulus cneorum (C. cneorum). The prepared AgNPs were characterized by UV–visible spectroscopy, powder X-ray diffraction (XRD), field emission scanning electronic microscopy (FE-SEM) and energy dispersive X-ray spectroscopy (EDX). Fourier-transform infrared spectroscopy (FTIR) study revealed the role of C. cneorum metabolites in the reduction of Ag⁺ ions into AgNPs and their stabilization. Fast, low cost, single step and selective detection of carcinogenic heavy metals in the environmental sample is significant to take safety action. Prepared AgNPs showed a potential colorimetric detection limit for toxic mercury Hg^II around 5 ppb and Cr^VI up to 5 ppm. Addition of Hg^II, Cr^VI and ammonia showed marked blue shift in the surface plasmon resonance (SPR) peak of AgNPs. Of importance, this AgNPs probe was not only successfully applied for the detection of Hg^II, but also it could be used in the sensing of Cr^VI and aqueous ammonia. Thus, due to the distinctive localized SPR, high sensitivity, simplicity, lower detection limit at ppb level and rapid response time are the most useful for the colorimetric detection of aqueous ammonia and Hg^II at room temperature.