Biosynthesis of silver nanoparticles: A colorimetric optical sensor for detection of hexavalent chromium and ammonia in aqueous solution

The current study is focussed on bio-fabrication of single step Durenta erecta (D. erecta) fruit extract synthesis of silver nanoparticles (Ag NPs). The prepared materials were examined through UV-Vis spectrophotometry due to localized surface plasmon resonance (SPR) and were found highly stable. X-ray diffraction (XRD) revealed face centered cubic (fcc) crystalline nature of Ag NPs. Morphologies and average size of Ag NPs was evaluated by field emission-scanning electron microscopy (FE-SEM), while elemental analysis was carried out by energy dispersive X-rays spectroscopy (EDS) and X-ray photo electron spectroscopy (XPS). Fourier transform infrared spectroscopy (FTIR) displayed the presence of the functional groups responsible for reducing as well as stabilizing of Ag NPs. The prepared Ag NPs were applied as colorimetric optical sensors for the detection of carcinogenic hexavalent chromium (Cr6+) and ammonia and the kinetic shift in lambda(max) and change in color for both Cr6+ and ammonia was found to be extremely fast and took a few seconds. Characteristic SPR, low-cost, high sensitivity, simplicity, lower detection limit up to 0.1 ppm and fast response time of Ag NPs are very useful for the colorimetric detection of Cr6+ and ammonia and can be used as an optical sensor for clinical diagnosis at room temperature.