Molecular Sensor for Fluoride

Fluoride in proper amounts can make teeth stronger and aid in the treatment of osteoporosis, but in excessive amounts can be a killer - a carcinogen that causes bone, lung, and bladder cancers.

"1 part per million (ppm) of fuoride ions is acceptable in drinking water, but above 2 ppm is consider a serious health risk," said Sourav Saha, an assistant professor in FSU's Department of Chemistry and Biochemistry and its Integrative NanoScience Institute. "because fluoride is carcinogenic even at such small doses, a sensor is needed to detect fluoride selectively at very low concentrations and in the presence of other naturally occurring and biologically important ions."

Working with a team of graduate students and postdoctoral researchers, Saha was able to develop just such a sensor. His research team discovered that a compound called naphthalene diimide (NDI) interacts with fluoride ions in a uniquely colorful way.

NDIs are a family of neutral (albeit electron-deficient) aromatic compounds that are colorless until fluoride is added," Saha said. "A small amount of fluoride will quickly turn the sample orange, while a larger amount will turn it pink. In this manner, it becomes very easy to determine not only the presence of fluoride in water, but at what levels."

Although they can detect fluoride, they cannot accurately measure the levels of fluoride," Saha said. "Naked-eye detection of fluoride at different concentration levels is an advantage of NDI-based sensors. Our sensor relies on an electron transfer event from a fluoride ion to the NDI receptor for generating a visible response or signal, which in this case is color change. The electron transfer process can be reversed, and the sensor can be regenerated and reused over and over again."

 

Excessive fluoride over a length of time has also been linked to the development of osteosarcoma - a malignant and potentially fatal bone cancer - as well as cancers of the lungs and bladder. For those reasons and others, fluoride has not been formally approved by the Food and Drug Administration for the treatment of osteoporosis in the United States. 

Source:
Sourav Saha
Florida State University