Presence of fluoride in water diminishes fast the SPR peak of silver nanocrystals showing large red shift with quick sedimentation - A fast sensing and fast removal case.

The medicinal use of fluoride is beneficial up to a low ppm level but regular ingestion at high doses show many adverse effects in human. Fluoride may get ingested through drinking water specially through ground water near the hilly regions, where fluoride content is huge. Hence, fluoride sensing and removal of it from water is very important as fluoride contaminated water is transparent and not easily detectable. Here, we have studied colorimetric and spectrophotometric techniques for sensing of fluoride along with its fast removal from water by using prepared saponin capped silver nanoparticles (AgNPs). Colorimetric study has confirmed the presence of fluoride ions in water samples above the colorimetric detection limit of 10 ppm. But spectroscopic sensing further provides more lower limit of sensing with the total removal of fluoride ions up to 1.2 ppm level. On repeating this this study 15 times, sensing and removal of fluoride is found to be well reproducible. The interaction of fluoride ions with silver nanoparticles has resulted in sedimentation of fluoride ions in the form of fluoride-nanoparticles complex and that interaction has been confirmed by FTIR spectral study of the sedimented part. EDX analysis has also provided the information of easy removal of the fluoride ions from water as presence of fluoride peak has been found in EDX spectra.