*Read the full article online at https://pubs.acs.org/doi/10.1021/acsomega.0c03465

*Read the full article in pdf at http://fluoridealert.org/wp-content/uploads/mukherjee-2020.pdf

Abstract

Higher levels of fluoride (F^–) in groundwater constitute a severe problem that affects more
than 200 million people spread over 25 countries. It is essential not only to detect but also
to accurately quantify aqueous F^– to ensure safety. The need of the hour is to develop
smart water quality testing systems that would be effective in location-based real-time
water quality data collection, devoid of professional expertise for handling. We report
a cheap, handheld, portable mobile device for colorimetric detection and rapid estimation
of F^– in water by the application of the synthesized core–shell nanoparticles
(near-cubic ceria@zirconia nanocages) and a chemoresponsive dye (xylenol orange).
The nanomaterial has been characterized thoroughly, and the mechanism of sensing
has been studied in detail. The sensor system is highly selective toward F^– and
shows unprecedented sensitivity in the range of 0.1–5 ppm of F^–, in field water samples,
which is the transition regime, where remedial measures may be needed. It addresses
multiple issues expressed by indicator-based metal complexes used to determine F^–
previously. Consistency in the performance of the sensing material has been tested
with synthetic F^– standards, water samples from F^– affected regions, and dental care
products like toothpastes and mouthwash using a smartphone attachment and by
the naked eye. The sensor performs better than what was reported by prior works on
aqueous F^– sensing.